VARIATIONS AMONG TEN YAM (Dioscorea spp.) GENOTYPES IN GROWTH 

AND TUBER YIELD AT DIFFERENT NITROGEN LEVELS 

 

 

 

 

BY 

 

 

 

 

BIDEMI AGBOZUADU 

B. Agric. (UNIBEN), M.Sc. Agric. Technology (GREECE) 

Matriculation Number: 225935 

 

 

 

 

A PROJECT REPORT IN THE DEPARTMENT OF CROP AND 

HORTICULTURAL SCIENCES SUBMITTED TO THE FACULTY OF 

AGRICULTURE IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR 

THE DEGREE OF 

 

 

MASTER OF SCIENCE 

 

 

 

of the 

 

 

UNIVERSITY OF IBADAN 

 

 

 

 

 

 

 

 

 

MAY, 2025



 
 
 
 

ii 

 

CERTIFICATION 

We certify that this research was carried out by Ms. Bidemi AGBOZUADU under our supervision 

in the Department of Crop and Horticultural Sciences, University of Ibadan, Nigeria. 

 

 

 

 

            

 

 

 

 

 

 

 

 

………………………….   

Dr. B. Olasanmi    
B.Sc., M.Sc., Ph.D. (Ibadan) 
Department of Crop and Horticultural Sciences, 
University of Ibadan, 
Ibadan, Nigeria. 
 

………………………….. 

Dr. Ryo Matsumoto 
Agronomist, 
Yam Breeding Unit, 
International Institute of Tropical 
Agriculture,  
Ibadan, Nigeria. 
 

     

  



 
 
 
 

iii 

 

DEDICATION 

This project is dedicated to the God of the Universe for charting the course of my life and 

for his innumerable blessings, and to my Parents, Mr. O. O. Agbozuadu and Mrs. Bosede 

Magaret Agbozuadu, for their guidance. 

  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 



 
 
 
 

iv 

 

ACKNOWLEDGEMENTS 

My sincere appreciation goes to God Almighty, the author and finisher of my faith who 

charts the course of my life and has guided me throughout this study. I sincerely thank Dr. 

B. Olasanmi for his excellent supervision, mentoring, and guidance. Throughout this work, 

I learned so much from your expertise. Words will fail me to express my profound gratitude 

to you, but I pray that your good works shall be greatly rewarded by the heavens. I am also 

grateful for the opportunity given to me by Dr. Ryo Matsumoto to conduct this research at 

the International Institute of Tropical Agriculture (IITA) as a Graduate Research Fellow 

under his supervision and for funding my research. I want to extend my appreciation to all 

staff of the Yam Improvement Programme at the International Institute of Tropical 

Agriculture for their valuable input towards the success of this research. I pray God will 

grant all your heart desires in Jesus Christ's mighty name.  I am equally grateful to the entire 

staff (academic and non-academic) of the Department of Crop and Horticultural Science 

and Faculty of Agriculture, University of Ibadan for their immense contribution to making 

me who I am today. 

I am grateful to God for the gift of my parents, Mr. O. O. Agbozuadu and Mrs. Magaret 

Bosede Agbozuadu for the love, parental guidance, financial, spiritual, moral, and 

emotional support they gave throughout my study. I pray that you will prosper in all your 

ways and your joy will be continually full.  

My gratitude also goes to Mrs. Ekine Blessing, Agbozuadu Godwin, Mrs. Mercy J. Ighalo, 

and Mary Agbozuadu, thanks for your support - you are the best siblings I could ever wish 

for. I pray we shall all fulfill our purpose in Jesus name. I am thankful to my sponsors; Dr. 

Peter Aghimien, Esme Stuart, and Mr. Sam Itegboje for their immense financial support 

during my study and also for mentoring me during daunting moments. May the good Lord 

bless you richly. 

Finally, I appreciate my friends who contributed to the accomplishment of this study, Tunde 

Akanbi Lanre, for providing me support in analyzing my data, Gillian, Amie, and Siira, for 

their encouragement, and to those names I cannot mention, you are indeed precious gifts to 



 
 
 
 

v 

 

me. I greatly appreciate and recognize every support and contribution given throughout my 

study; may the Almighty God bless you all. Amen. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 



 
 
 
 

vi 

 

ABSTRACT 

Yam is an essential food crop with high economic importance in Nigeria and West Africa. 

However, yam production has declined greatly because farmers lack knowledge of yam 

nutrient requirements for optimal yield. Semi-Autotrophic Hydroponics (SAH), a licensed 

propagation technique, enables year-round yam cultivation under controlled conditions and 

has been successfully adopted at the International Institute of Tropical Agriculture (IITA). 

Although previous studies have investigated adequate nutrient application and timing in 

yam, the overall scope of research remains limited. This limitation is partly attributable to 

the different sources of nutrients and genotypic variation in response to nutrient application 

by yam accessions. Also, no information exists on yam nutrient studies using the SAH 

technique. This study was therefore conducted to evaluate the variability in the response of 

yam to different nitrogen levels. 

Ten Dioscorea rotundata accessions (DRS002, DRS027, DRS044, DRS074, DRS104, R-

031, TDr93-31, TDr8902665, Meccakusa, TDr9519177) were screened under four nutrient 

regimes within a Semi- Autotrophic Hydroponics setup. A Randomized Complete Block 

Design (RCBD) with ten replicates per treatment was used. The nutrient regimes used were 

ALL-N (15.08 g N, 21.06 g K, 2.80 g P, 10.74 g Ca, 4.28 g Na, 3.25 g Mg, and 2 g Fe), 

Half-N (7.55 g N, 31.64 g K, 2.80 g P, 5.37 g Ca, 4.28 g Na, 3.25 g Mg, and 2 g Fe), - N (0 

g N, 21.11 g of K, 2.80 g P, 10.8g Ca, 21.55 g Na, 3.25 g Mg, and 2 g Fe), and Water (as 

control). 

Growth and yield parameters, including number of leaves (NL), leaf chlorophyll content 

(SPAD), leaf fresh weight (LFW), shoot fresh and dry weights (SFW, SDW), tuber fresh 

and dry weights (TFW, TDW), were recorded at 50 and 150 days after treatment (DAT). 

Amongst the accessions, TDr8902665 demonstrated significantly superior growth and yield 

(p > 0.001) under Half-N and ALL-N conditions compared to - N and Control treatments, 

with the highest TDW (0.69 g) recorded under the Half-N regime. 

These results indicate that Half-N concentrations can sustain comparable performance to 

full nutrient levels in certain yam genotypes under SAH. TDr8902665 is recommended for 

breeding programs and commercial propagation targeting improved nutrient efficiency 

under semi-autotrophic hydroponic systems. 

Keywords: Semi-Autotrophic Hydroponics, genetic gain, nitrogen, screening, breeding 

Word Count: 362 

 

 



 
 
 
 

vii 

 

TABLE OF CONTENTS 

Contents  Page 

Title Page i 

Certification ii 

Dedication  iii 

Acknowledgments iv 

Abstract vi 

Table of Contents vii 

List of Tables  x 

List of Figure xi 

CHAPTER 1: INTRODUCTION 1 

CHAPTER 2: LITERATURE REVIEW 6 

2.1: Origin and distribution of yam 6 

2.2: Botany of yam 7 

2.3: Propagation methods of yam 7 

2.4: Semi-Autotrophic Hydroponics technique for yam propagation  8 

2.5: Yam Genetic Resources 9 

2.6: Importance and Uses of Yam  9 

2.7: Constraints to Yam Production 10 

2.8: Soil Fertility 11 

2.9: Soil Nutrient Management 12 

CHAPTER 3: MATERIALS AND METHODS 13 

3.1: Experimental Site 13 



 
 
 
 

viii 

 

3.2: Source of yam genetic material and equipment used 13 

3.3.0: Semi-Autotrophic Hydroponics Procedure 13 

3.3.1: Preparation of growth media 13 

3.3.2: Experimental Design 17 

3.3.3: Establishing plants in the laboratory and transplanting yam plants to the                

 screenhouse 

17 

3.3.4: Growth conditions in the laboratory 19 

3.3.5: Watering and Nutrient application in the SAH laboratory 19 

3.3.6: Acclimatization and transplanting of yam plantlets in the screenhouse 19 

3.3.7: Watering and Nutrient application in the screenhouse 20 

3.4: Data Collection 20 

3.5: Imaging of the plants and tubers in the screenhouse 21 

3.6: Data Analysis 21 

CHAPTER 4: RESULTS  

4.1: Mean squares of growth and yield variables of ten white guinea yam 

accessions evaluated in IITA, Ibadan in 2021/2022 

4.2: Effect of Nutrient Level on the Leaf Chlorophyll content (SPAD value) of 

the 10 white guinea yam genotypes evaluated in 2021/2022 

21 

 

 

22 

 

4.3: Effect of Nutrient Level on Tuber Fresh Weight (TFW) of 10 white guinea 

yam genotypes at 50 Days after Transplanting (DAT) in 2021/2022 

25 

4.4: Effect of Nutrient Level on Tuber Fresh Weight (TFW) of 10 white guinea 

yam genotypes at 150 Days after Transplanting (DAT) in 2021/2022 

25 

4.5: Effect of Nutrient Level on the Shoot Dry Weight (SDW) of the 10 white 

guinea yam genotypes evaluated in 2021/2022 

28 

4.6: Genotypic response to growth and yield performance across four nutrient 

levels evaluated in 2021/2022 

28 



 
 
 
 

ix 

 

4.7: Nutrient response to genotypic variation in growth and yield across ten 

yam accessions evaluated in IITA, in 2021/2022 

31 

CHAPTER 5: DISCUSSION   33 

CHAPTER 6: SUMMARY AND CONCLUSIONS  36 

REFERENCES 37 

APPENDIX 45 

  

  

 

    

 

 

 

 

 

 

 

 

 

 

 



 
 
 
 

x 

 

LIST OF TABLES 

Table

  

Title Page 

3.1 Yam genotypes evaluated in Ibadan in 2021 for micropropagation at 

different nitrogen levels 

15 

3.2 Concentration of the four different nutrient levels used for the study 16 

3.3 Experimental layout of the plants and treatments at the screenhouse 18 

4.1 Mean squares for growth and yield variables in ten white yam accessions 

evaluated in IITA, Ibadan in the 2021/2022 season 

23 

4.2 Effect of Nutrient Level on the Leaf Chlorophyll Content (SPAD) of the 

10 white guinea yam genotypes evaluated in 2021/2022. 

24 

4.3 Effect of Nutrient Level on the Tuber Fresh Weight of the 10 white guinea 

yam genotypes evaluated in 2021/2022 at 50 Days after transplanting 

(DAT) 

26 

4.4 Effect of Nutrient Level on the Tuber Fresh Weight of the 10 white guinea 

yam genotypes evaluated in 2021/2022 at 150 Days after transplanting 

(DAT). 

27 

4.5 Effect of Nutrient Level on the Shoot Dry Weight of the 10 white guinea 

yam genotypes evaluated in 2021/2022 

29 

4.6 Genotypic response to growth and yield across four nutrient levels 

evaluated in IITA in 2021/2022 

30 

4.7 Nutrient response to growth and yield across ten yam accessions 

evaluated in IITA, in 2021/2022 

32 

   

 

 

 

 



 
 
 
 

xi 

 

 

LIST OF FIGURES 

 

Figure Title Page 

3.1 Map of the International Institute of Tropical Agriculture showing 

study site coordinates 

14 

   

   

   

   

   

   



 
 
 
 

1 

 

 

CHAPTER 1 

INTRODUCTION 

Yam is a tropical root crop cultivated predominantly for its edible starchy tubers, which 

are consumed as staple foods in West Africa, South America, the Caribbean, Asia, and 

Oceania (FAO, 2021). There are over 600 species of yams, of which six are socially and 

economically cultivated for food, income, and medicine (IITA, 2009). Approximately 

50 other species are consumed as food in times of scarcity and as wild-harvested staples 

(Padhan and Panda, 2020; Elliott et al., 2016), and a few are grown on a small scale as 

medicinal plants. 

Yam performance is affected by the agronomic quality of the soil. Unlike other root and 

tuber crops such as potatoes and cassava, which survive in marginal soils, yam require 

pulverized and well-drained, nutrient-rich soil with high soil organic matter content, 

which aids tuber penetration and development. Yam is grown in tropical areas and 

mostly produced in the savannah region of West Africa, where the climatic condition is 

classified into rainy and dry seasons. Yam requires an even rainfall distribution during 

its active growth period for vine and leaf development, tuber maturation, and bulking 

(Adifon et al., 2020). An annual rainfall of 1000–1200 mm, particularly when spread 

over 6-7 months cropping season, is adequate for vegetative growth and tuber 

development (Andres et al., 2017; Gweyi- Onyango et al., 2021).  Plant growth could 

be stalled during long periods of drought (Asiedu, 2003). In regions experiencing 

irregular rainfall, supplemental irrigation may be necessary to maintain soil moisture 

and avoid yield reduction, as water stress has been shown to induce leaf yellowing, 

senescence, and early leaf drop, reducing the crop’s photosynthetic capacity and leaf 

area index (Agre et al., 2022a). 

Yam production is majorly concentrated in Africa as it accounts for 98 percent of global 

production, with West Africa contributing 95 percent between 2020 and 2022 (FA0, 

2024). Within the same period, Nigeria contributed 71 percent, Ghana 11 percent, Côte 

d'Ivoire 9 percent, Benin 4 percent, and Togo 1 percent to Africa’s yam production. In 



 
 
 
 

2 

 

2023, the total area of land harvested in Nigeria was about 7.5 million hectares with a 

total production of about 61.9 million tonnes (FAOSTAT, 2024).   

Despite the importance of yam in Africa and other parts of the world, with Nigeria being 

the largest producer (Yaw et al., 2024) there has been a decline or stagnation in yam 

production with some farmers getting 10 tonnes per hectare compared to a potential yield 

of 50 tonnes per hectare (Neina, 2021).  According to Kalu (2023), farmers were 

interviewed across the farming belts of Nigeria, and it was identified that pest and 

disease attacks, climate change, high cost of seed yams, insecurity, lack of improved 

seeds, low sprouts, low yields, and high labour cost were the major causes of this decline. 

However, the three most prevalent problems faced by farmers in the South-South region 

of Nigeria are pest and disease attacks (50%), high cost of farm inputs (18.8%), and low 

soil fertility (17.5%). Yam yield in Nigeria declined from 9.4 tons per hectare in 1988 to 

an estimated value of 8.2 tons per hectare in 2023 (FAOSTAT, 2024). Scarcity of quality 

seed yams may ultimately lead to a further reduction in yam production. 

Yam is traditionally grown as the first crop after clearing in many parts of West Africa 

due to its high nutrient demand (Danquah et al., 2022a). Yam has been reported to 

respond to fertilizer application under various agronomic conditions (Hgaza et al., 

2010a). Studies have shown that the most critical yield-limiting factor in yam production 

is nitrogen availability (Hgaza et al., 2012b; Cornet et al., 2022). Yam is particularly 

sensitive to soil nutrient status, and its productivity is closely tied to nitrogen uptake 

during early growth stages (Oberson et al., 2020). Nitrogen is an essential nutrient not 

only for plants but also for the environment. Yet, yam production in West Africa often 

occurs on nutrient-depleted soils due to shortened fallow periods and continuous 

cropping systems, reducing natural nitrogen replenishment (Pouya et al., 2022; Danquah 

et al., 2022a). Multiple recent studies (2021-2023) across diverse agroecological zones 

in West Africa involving soil fertility management confirm a strong positive correlation 

between fallow duration and yam tuber yield (Pouya et al., 2023; Danquah et al., 2022b). 

This relationship holds due to the important role fallow plays in the restoration of soil 

structure, nitrogen cycling, and beneficial microorganisms (Heller et al., 2022; Maliki 

et al., 2022). However, the interaction between fallow history, cover crop species, soil 

type, and fertilizer application introduces significant variation in yam response to 



 
 
 
 

3 

 

nitrogen, emphasizing the need for site-specific and genotype-specific recommendations 

(Agre et al., 2022b) 

Moreover, while nitrogen is widely acknowledged as a critical macronutrient for yam, 

there remains no clear consensus on the optimal nitrogen requirements for different yam 

species. Empirical studies have shown that yam response to nitrogen varies significantly 

across genotypes, soil types, and environmental conditions, leading to conflicting 

fertilizer recommendations (Oberson et al., 2020; Tokpa et al., 2020; Cornet et al., 2022). 

The discrepancies underscore the importance of quantifying nutrient use efficiency 

(NUE) across yam genotypes, which could inform precision nutrient management and 

breeding programs. A good knowledge of the nitrogen requirement of plants, especially 

under controlled propagation systems, where nutrient delivery can be precisely 

managed, is key to improving yam yield. Therefore, it is important to develop efficient 

phenotyping protocols for yam nutrient use efficiency. 

In response to the persistent limitations in yam seed systems, particularly the low 

multiplication rate, high susceptibility to diseases, and reliance on bulky tuber 

propagation, numerous innovative propagation technologies have been developed. 

These include tissue culture, vine cutting, aeroponics, temporary immersion bioreactors 

(TIBs), minisett techniques, and, more recently, Semi-Autotrophic Hydroponics (SAH). 

These methods have been tested and documented by research institutions such as the 

International Institute of Tropical Agriculture (IITA) in Ibadan, Nigeria (Aighewi et al., 

2015a; Balogun et al., 2021). 

Among these tissue culture techniques have gained significant attention for their 

potential to generate disease-free planting materials, conserve genetic resources, and 

accelerate multiplication under controlled environments (Agrodemy website: Yam 

Minisett: A Guide with Tissue Culture Micropropagation 2023 – Agrodemy 

Technologies and services; Balogun, 2014; Aighewi et al., 2021a). This method of 

propagation provides effective solutions to several limitations of conventional 

propagation methods, particularly by enabling the production of disease-free planting 

materials, ensuring year-round availability of high-quality seed yams, and facilitating 

the conservation of valuable genetic resources. Recent studies have validated the use of 



 
 
 
 

4 

 

tissue culture, including meristem culture and micropropagation, as scalable options to 

reduce the transmission of pathogens, enhance multiplication rates, and maintain genetic 

stability in elite yam genotypes (Uyoh et al., 2022; Ossai et al., 2024; Deubel, 2023). 

Although tissue culture systems are effective, they are often costly and technically 

demanding, especially for decentralized or rural propagation centers. In contrast, SAH 

systems, which allow yam propagation in semi-controlled, nutrient-enriched 

environments without soil, offer a cost-effective and scalable alternative (Cornet et al., 

2022; Maroya et al., 2020). SAH combines the efficiency of hydroponics with reduced 

input costs, enabling continuous monitoring of nutrient uptake and facilitating genotype 

screening. 

Despite their potential, most propagation techniques, including SAH, have not been 

optimized for specific nutrient regimes, particularly for nitrogen, which has been 

consistently identified as the most limiting nutrient in yam production (Hgaza et al., 

2012b; Oberson et al., 2020). Moreover, the response of yam genotypes to different 

nitrogen levels under SAH remains poorly characterized, resulting in a knowledge gap 

that limits the effective deployment of this technique for seed system development and 

breeding support. Addressing this gap is essential for improving Nitrogen Use Efficiency 

(NUE), shortening the yam breeding cycle, and developing a standardized, genotype-

responsive SAH protocol. 

Furthermore, integrating nutrient screening within SAH platforms allows researchers to 

select high-performing genotypes under low-input conditions, making it highly relevant 

for resource-constrained farmers. By establishing nutrient-efficient genotypes and 

optimized in vitro nutrient regimes, this study aims to support seed yam innovation and 

breeding programs with broader implications for food security and sustainable 

intensification in yam-based systems across West Africa. 

The objectives of this study were therefore to: 

i. investigate the effect of different nitrogen levels on the growth and yield of yam 

using the Semi-Autotrophic Hydroponics technique, thereby defining optimal 

nutrient regimes for in-vitro propagation. 



 
 
 
 

5 

 

ii. assess genotypic variation in nitrogen use efficiency, with the goal of identifying 

nutrient-efficient yam genotypes. 

iii. establish a stable seed system that shortens the breeding cycle of yam using Semi-

Autotrophic Hydroponics protocols. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 



 
 
 
 

6 

 

CHAPTER 2 

LITERATURE REVIEW 

2.1. Origin and distribution of yam 

Yam is a common name for various species belonging to the family Dioscoreaceae and 

genus Dioscorea with varying origins and distributions in the tropic, sub-tropic, and 

temperate regions (Darkwa et al., 2020). There are over 600 species of yam with only 

six species that are of economic importance as foods. These include D. rotundata (white 

yam), D. alata (water yam), D. cayenensis (yellow yam), D. esculenta (lesser yam), D. 

dumeterum (bitter yam), and D. bulbifera (aerial yam). The white yam, water yam, and 

yellow yam are the most important together making up about 90% of the world's food 

yam production. 

Yam species have different sources of origin. White yam is closely related to yellow 

yam, another domesticated yam widely consumed in West Africa. They were both 

derived from the wild progenitor Dioscorea praehensilis (Scarcelli et al., 2019). 

Dioscorea alata (purple yam or "ube") was first cultivated somewhere in Southeast Asia. 

It has the largest distribution worldwide as it is grown in Asia, the Pacific islands, Africa, 

and the West Indies (Mignouna, 2003). Water yam has also become an invasive species 

in some southern states of the United States of America. Meanwhile, aerial yams are 

found both in Africa and Asia. All edible yams are cultivated for their tuber except D. 

bulbifera which are produced for their bulbils or aerial growing tubers. Although D. 

bulbifera produces underground tubers, the bubils are the more important food products 

(Ambayeba, 2018). Dioscorea dumetorum is like D. hispida, it is popular in some parts 

of West Africa and D. esculenta is of Asian origin. However, most of these species are 

spread across continents and can be found in many parts of the world. 

Yams were successfully grown in Europe to mitigate the effects of the potato famine in 

1840’s. Although yam is cultivated in Asia and America, more than 96% of the world’s 

yam is grown in Africa, and its high starch content makes it an important food crop 

(FAO, 2016). History has it that yams were taken to America by pre-colonial Portuguese 

and Spanish on the borders of Brazil and Guyana. They were later dispersed throughout 

the Caribbean. Yams are produced mainly in West and Central Africa, New Guinea, 

Islands of the pacific, and some parts of South-East Asia (Dumont and Vernier, 2000). 

 



 
 
 
 

7 

 

2.2 Botany of Yam 

Yams are monocotyledonous herbaceous climbing plants that coil readily around a stake. 

They are perennial crops that can grow and produce over several years through their root 

system but are grown as annual crops within a single growing season (Dumet et al., 

2008). It takes about six to eight months to complete its growth cycle comprising five 

distinct stages which vary according to species, genotypes, and environmental 

conditions. These stages are tuber sprouting, foliage development, tuber bulking, foliage 

senescence, and dormancy. Tuber sprouting can take up to six weeks. It normally begins 

during storage, in the absence of light, soil and water (Frederik et al., 2013).  

Yams are large plants, with their twining vines growing as long as 10 to 20 m (33-39. 

ft). The direction of twining may vary with species. The three most important edible yam 

species, D. rotundata, D. alata, and D. cayenensis are characterized by vines that twine 

to the right, in a clockwise direction (Bhattacharjee et al., 2011). Yam vines can grow 

up to several meters long if a rigid support is provided and their length varies among 

species. Yam leaves grow on long petioles and could be simple, cordate, or acuminate 

but are usually lobed or palmate in some species. Dioscorea rotundata bears simple 

cordate leaves which have an opposite arrangement (Okonkwo, 1985). The tip of the 

leaf is usually green (Rodriguez and Montero, 2007) except in young leaves of D. alata 

cultivars in which anthocyanin pigment may mask the green color of the leaves 

(O’Sullivan 2010). The petiole is long with a swollen base and D. rotundata is capable 

of twisting in such a way that it exposes its lamina to a maximal amount of sunlight. 

2.3 Propagation Methods of Yam 

Traditionally, seed yams are used for propagation. A portion of seed yam from the 

previous harvest is reserved for planting in the next season (Nweke et al., 2011); 

otherwise, tuber setts could be used as practiced in West Africa. The most important 

traditional method of propagation in the yam belt of West Africa is ‘milking’ whereby a 

plant is harvested twice. The first harvest is done carefully 4 to 5 months after shoot 

emergence while the shoot is still green. The multiplication ratio is 1:4 to 1:6 (Aighewi, 

2015b). The minisetts technique is a modern method of yam propagation developed by 

the National Root Crops Research Institute (NRCRI), Umudike, Nigeria (IITA, 1985). 

This technique makes use of healthy seed yams cut into discs of about 2 cm, which are 



 
 
 
 

8 

 

further cut into segments and then treated with wood ash or fungicides and insecticides 

and spread out to dry for 1-2 days before planting. Minisetts are usually 20–25 g in size 

and are used to produce planting material or seed yams, which are in turn used for ware 

yam production (Pelemo, 2012). The multiplication ratio of the minisetts technique is 

1:30. The vine cutting technique is fast replacing seed yam production and has a higher 

multiplication ratio (1:300) when compared to methods such as milking and minisetts 

techniques, thereby reducing the cost of the planting material (IITA, 2014., Aighewi et 

al., 2021b). The vine-cutting technique is advantageous because it makes year-round 

production of yams possible. Other techniques for propagating yam include the use of 

botanical seeds for seed yam propagation, plant tissue culture, aeroponics system, 

Temporary immersion bioreactor system, semi-autotrophic Hydroponics, etc. 

2.4 Semi-Autotrophic Hydroponics Technique for Yam Propagation 

Semi-autotrophic hydroponics (SAH) is a licensed technology targeted at the high ratio 

propagation of true-to-type virus-free plants of tissue culture origin. It is a low-cost and 

easy-to-adapt technique that is suitable for commercial seed production and enhanced 

multiplication in breeding programme. This technology has been used for seed 

production in clonal crops, such as potato, cassava (Legg et al., 2022), and recently, yam 

(IITA, 2018). Semi-autotrophic hydroponics facility for yam started in Ibadan in April 

2017 to expand the scope of technologies targeted at overcoming seed yam production 

challenges (IITA, 2018).  

This technology produces plants at an efficient rate to meet the seed needs of yam 

growers. Semi-Autotrophic Hydroponics is useful for arrays of activities within the 

research communities. These uses include, but are not limited to, high ratio propagation 

of virus-free yam seedlings for seed yam tuber production and reintroduction into tissue 

culture, shortening of breeding cycle and scale testing scheme to accelerate yam 

breeding gain, acclimatization of in vitro plantlets for onward transplanting into the 

field, efficient viral and microbial inoculation, viral indexing, and adequate symptom 

expression and data capture.  

Plants, like other living organisms, require nutrients for growth and survival. These 

nutrient forms have been grouped into plant hormones and macro and micronutrients. 

Nutrient supply in vivo depends on soil type and use, as well as some edaphic factors, 



 
 
 
 

9 

 

while for in vitro propagation, growth factors, including nutrient supply, can be 

manipulated to suit the aim. Nutrients significantly influence the growth rate and 

physiological development of tissue culture plantlets, with mineral elements like 

nitrogen, phosphorus, potassium, and micronutrients being essential for proper 

morphogenesis, shoot elongation, and root development in vitro (Arteta et al., 2022; 

Munthali et al., 2022). Moreover, plant species and even genotypes within the same 

species display distinct responses to nutrient availability, with significant variation in 

sensitivity to nutrient deficiencies and ion concentrations (Kumar et al., 2023; Manokari 

et al., 2022). 

Over the years, the semi-autotrophic hydroponics technique on seed yam propagation 

has been very productive and economically beneficial. The performance in terms of the 

growth and development of yams using this technique has been attributed to several 

factors, including the variety and its adaptation in vivo.  

2.5 Yam Genetic Resources  

The largest world collection of yams is maintained by the International Institute of 

Tropical Agriculture (IITA), Ibadan, which accounts for over 3,000 accessions mainly 

of West African origin. The collection comprised eight species: D. rotundata (67%), D. 

alata (25%), D. cayenensis (2%), D. bulbifera (2%), D. dumetorum (1.6%), D. 

mangenotiana (0.25%), D. esculenta (0.7%), and D. praehensilis (0.3%). The passport 

data and characterization information on these accessions are maintained in databases 

accessible at http://genebank.iita. org/. On request, these germplasm accessions are 

distributed following Standard Material Transfer Agreements (SMTA). As with many 

other crops, the request for gene bank accessions has been low for use in national and 

international yam improvement programmes. Of a total of 3170 accessions maintained 

at IITA as of 2012, only 1077 accessions had been distributed over the preceding decade 

(Lopez et al., 2012). 

2.6 Importance and Uses of Yam 

Yam is among the most important root crops worldwide, alongside other root and tuber 

crops such as cassava (Manihot esculenta), potato (Solanum tuberosum), and sweet 

potato (Ipomoea batatas Lam). These crops rank among the top ten foods grown in 



 
 
 
 

10 

 

developing countries. (Scott et al., 2000). Yam is a major food security crop for millions 

of resource-poor farmers in West Africa (Matsumoto et al., 2021). Yam falls into a wide 

range of root and tuber crops, which contributes to food diversification and plays an 

important role in the annual food cycle by acting as a safety net in sustaining food 

availability to households across Africa, even at times of general scarcity.  

Yams contain riboflavin, thiamin, pantothenic acid, folic acid, and niacin. Dioscorea 

alata is rich in vitamins, minerals, fibers, and carbohydrates (Baah et al., 2009). Yams 

are used in Japanese, Korean, and Chinese medicine because they contain allantoin, 

which accelerates the healing process when applied as a poultice to abscesses and boils 

(Wang et al., 2023). Yam contains diosgenin, which is a hormone that is believed to 

affect hormonal patterns by producing steroids, such as progesterone and estrogen. It 

helps reduce the symptoms of menopause in women (Mustapha et al., 2018). 

Yam can be boiled, fried, roasted, grilled, sliced, mashed, chipped, and flaked. Fresh 

tubers can be peeled, chipped, dried, milled into flour, and pounded into paste with hot 

water that is eaten with soup (Condé et al., 2024). However, it is most popularly eaten 

as pounded yam in its growing belt in West Africa. Yam could also be used as feed for 

livestock, especially the peels. Yam is used in fertility and marriage ceremonies, and an 

annual festival is held to celebrate its harvest (Condé et al., 2024).  

2.7 Constraints to Yam Production 

Studies by Ayanwuyi et al. (2011a) and Kleih et al. (2012) showed that low soil fertility, 

lack of improved yam varieties, poor road networks, high cost of labour, and lack of 

finance to carry out necessary farming activities are constraints to productivity. Yam 

cultivation, like many other crops in Nigeria, requires a significant amount of labour. 

The demand and cost of labour have been major constraints in the production of yams. 

Smallholder farmers’ production is hampered by the high cost of labour (Ayanwuyi et 

al., 2011b; Migap and Audu, 2012). Labour accounts for a substantial share of the yam 

production costs, with planting alone contributing more than half the costs of total 

variable expenses in some regions (Ariyo and Adebayo, 2020). In a bid to cut labour 

costs, most family members practically perform all production and marketing activities 

themselves (Ike and Inoni, 2006). Okeoghene et al. (2013) confirmed that over 65% of 

smallholder farmers used family labour in Delta State, Nigeria. A study by the Food and 



 
 
 
 

11 

 

Agriculture Organization (FAOSTAT, 2022) on the decline in yam yield in Nigeria found 

that the average yield dropped from 9.4 tonnes per hectare in 1988 to 7.94 tonnes per 

hectare in 2020, resulting in an annual loss of between 10% and 20% over the period. 

The country recorded its highest yam loss in 2006 with over 3.7 million metric tons 

(Verter and Bečvářová, 2015). Inadequate preservation, storage, and processing 

facilities, marketing, and market access to yam products are responsible for yam waste 

and loss in the country. This partly dissuades rural farmers from fully participating in 

their cultivation (Verter and Bečvářová, 2015). Pest-related issues such as parasitic 

nematodes, insects such as leaf and tuber beetles, fungi such as leaf spot, tuber rot, and 

other viruses such as Yam mosaic virus (Aighewi et al., 2025) have also been identified 

as major constraints to yam production.  

In developing countries like Nigeria, Ghana, Cote d’Ivoire, Benin, and Togo, insufficient 

farm inputs and lack of modern technologies also act as constraints to yam production 

(Verter and Bečvářová, 2015). As a result, the majority of smallholder farmers still use 

traditional farming methods, such as hand hoes, axes, wood, and cutlasses, as opposed 

to machines and tractors for farm-related activities. In addition, there is the problem of 

insufficient chemical and fertilizer applications and the resulting decline in soil fertility, 

which has affected output in recent times (Verter and Bečvářová, 2015). Financial 

resources are another major constraint to production, as farmers are poor and suffer from 

limited access to credit facilities. This impedes productivity and output (Izekor and 

Olumese, 2010). The lack of adequate provision for agricultural loans from financial 

institutions to farmers has constrained sustainable yam cultivation in Nigeria. This can 

be attributed to factors such as the risk involved in yam production, the difficulty in 

estimating returns on investment, and the inability of many yam producers to provide 

the required collateral securities (Migap and Audu, 2012). The lack of political will by 

the government regarding policies related to yam production in the country also 

constrains yam production in Nigeria. 

2.8 Soil Fertility 

Yam performed better in deep, well-drained loamy soils. They are nutrient-demanding 

plants, explaining why after the land is left to fallow, yams are cultivated first in a 

rotation system. Low soil resulted in a low yield of 8 tonnes per hectare, where its 



 
 
 
 

12 

 

potential yield was estimated at approximately 30 tonnes per hectare (Andres et al., 

2017). Farmers' inability to purchase fertilizers due to limited financial resources and 

lack of access has worsened the situation, compelling them to integrate soil fertility 

management practices. These include crop rotation or intercropping, conservation 

tillage, maintenance of organic matter content through direct applications of manures or 

compost, and soil cover maintenance before planting to enhance soil fertility and 

structure in yam-based cropping systems. (Andres et al., 2017) 

2.9 Soil Nutrient Management 

Several soil nutrient management technologies that enhance crop productivity have been 

developed, tested, and promoted in Africa’s low-input farming systems (Kihara et al., 

2020). However, little information is available on yams’ input intensification 

technologies (Enesi et al., 2017). Intensification of yam production through soil 

amendments, improved cultivars, and other inputs could increase the yield per unit area. 

Cultivars that are tolerant to low soil nutrients and responsive to external nutrient inputs 

are the most efficient and practical approach for improving productivity in low-input, 

smallholder farming systems (Matsumoto et al., 2021). Tolerance to low soil nutrients 

promotes sustainable production by reducing input costs and environmental impact, 

while responsiveness to mineral fertilizers enables crop intensification and higher yields. 

Combining these traits in crop breeding and management strategies holds promise for 

sustainable, resilient, and productive agricultural systems. 

 

 

 

 

 

 

 

 

 

https://www.frontiersin.org/articles/10.3389/fpls.2021.629762/full#B30
https://www.frontiersin.org/articles/10.3389/fpls.2021.629762/full#B30
https://www.frontiersin.org/articles/10.3389/fpls.2021.629762/full#B17


 
 
 
 

13 

 

CHAPTER 3 

MATERIALS AND METHODS 

3.1. Experimental Site 

The experiment was carried out at the Semi-Autotrophic Hydroponics (SAH) laboratory and 

screenhouses of the Yam breeding unit of the International Institute of Tropical Agriculture, 

Ibadan (IITA) on longitude 3° 89ʹE; latitude: 7° 49ʹN; and at an altitude of 239.34m above 

sea level as shown in Figure 3.1. 

3.2. Source of Yam Genetic Materials and Equipment Used 

Ten genotypes of white yam were obtained from the Yam Semi-Autotrophic Hydroponics 

(SAH) laboratory, Ibadan, Nigeria. The genetic material and concentrations of the four 

different nutrient levels are presented in Tables 3.1 and 3.2, respectively. 

The equipment used in this experiment includes SAH culture boxes, weighing balance, 

polyethylene pots, steel stakes, sphagnum peat (Klassman TS3 media), Konica Minolta 

SPAD-502 Chlorophyll meter, forceps, surgical blades, aluminum foil, paper towel, beakers, 

measuring cylinder, oven, autoclave, water bath, Mettler toledo pH meter, Magnetic stirrer, 

opaque bottles, Tween 20, thermometer, micropipette, crates, sprinklers. 

3.3.0. SAH Procedure 

3.3.1. Preparation of Growth Media and Nutrient Solution 

The SAH boxes were carefully perforated with four holes at the top using a soldering iron. 

This process was performed to allow aeration. The Growth medium used in this study was 

Klasmann TS3. In each box, 500 mL of Klasmann TS3 was directly measured in a beaker. 

It was then compressed with a rectangular-shaped container and moistened with SAH-

prepared nutrient solution. The SAH nutrient solution was prepared by dissolving all 

essential nutrients provided as chemical compounds in distilled water in a beaker. The 

solution was stirred using a magnetic stirrer. The pH of the nutrients was checked using a 

Metler Toledo, and when necessary, the pH was raised or reduced to 5.7. This was then made 

up to mark in a 20 L water dispenser, and benzyl amino purine was added. Fifteen planting 

holes were then created in the substrate-filled SAH box, and the single-node vine cuttings 

were subcultured from the older boxes. 

 

 



 
 
 
 

14 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 3.1: Map of the International Institute of Agriculture (IITA) showing the 

longitude and latitude. 



 
 
 
 

15 

 

Table 3.1: Yam genotypes evaluated in Ibadan in 2021 for micropropagation at 

different nitrogen levels 

 

Origin Specie Genotype ID 

DrDRS* Dioscorea rotundata DRS002 

DrDRS Dioscorea rotundata DRS027 

DrDRS Dioscorea rotundata DRS044 

DrDRS Dioscorea rotundata DRS074 

DrDRS Dioscorea rotundata DRS104 

Breeding line Dioscorea rotundata TDr8902665 

Breeding line Dioscorea rotundata TDr9519177 

Breeding line Dioscorea rotundata R-031 

Landrace Dioscorea rotundata TDr93-31 

Landrace Dioscorea rotundata Meccakusa 

* Dioscorea rotundata diversity research set 

Source: Jircas Research Highlights, 2020. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 



 
 
 
 

16 

 

Table 3.2: Concentration of the four different nutrient levels used for the study 

 ALL-N (g/20L) 1/2N (g/20L) -N (g/20L) Control (l) 

KNO3 54.43 27.22 0 0 

CaNO3.4H2O 63.17 31.58 0 0 

CaSO4.2H2O 0 0 46.37 0 

MgSO4.7H2O 32.93g 32.93 32.93 0 

NaH2PO4.2H2O 14.11g 14.11 14.11 0 

K2SO4 

Iron solution 

(mL) 

 

Water 

0 

200 

 

- 

47.04 

200 

 

- 

47.04 

200 

 

- 

0 

0 

 

20 

  

 

 

 

 

 



 
 
 
 

17 

 

3.3.2 Experimental Design 

The experiment was set up in a 10×4 factorial randomized complete block design 

(RCBD). The experiment was arranged in two blocks, with the first five genotypes under 

each nutrient and the last five genotypes, based on the variable growth of plants. The 

experimental layout is presented in Table 3.3, which shows the arrangement of the plants 

in the screenhouse. The same layout was replicated for genotypes 6 - 10. Each treatment 

combination consisted of 10 plants (one plant per pot as a replicate). The stakes were 

inserted into pots for vine training and climbing. The temperature ranged between 21 

and 39°C during the study period. The median between transplanting the first and last 

five genotypes was selected as the transplantation date. Plants were randomly arranged 

within each block. Each block included four nutrients: Half-N, ALL-N, Control, and - 

N. Nitrogen was applied to the Half-N and ALL-N nutrient solution in the form of 

calcium nitrate tetrahydrate (Ca(NO3)2·4H2O and Potassium nitrate KNO3. The control 

treatment consisted only of distilled water, with no added nutrients or fertilizers, while 

the -N treatment received all nutrients except nitrogen. Additionally, each nutrient 

(except control) contained sufficient levels of phosphorus (NAH2PO4)2H2O, potassium 

(K2SO4), magnesium, calcium, sulfur (CaSO4)2·2H2O, (MgSO4) · 7H2O, and iron 

solution (Fe-acetate) was added to the nutrient solution. Both Phosphorus and Sodium 

were added as sodium dihydrogen phosphate dihydrate [(NaH₂PO₄)₂·2H₂O], potassium 

as potassium sulfate (K₂SO₄), calcium as calcium sulfate dihydrate (CaSO₄·2H₂O), 

magnesium as magnesium sulfate heptahydrate (MgSO₄·7H₂O), and iron in the form of 

iron-acetate solution. ALL-N contained 54.43 g of potassium nitrate (KNO3) and 63.17 

g of calcium nitrate tetrahydrate (CaNO3.4H2O), which is equivalent to 15.08 g 

Nitrogen, 21.06 g Potassium, 2.80 g Phosphorus, 10.74 g Calcium, 4.28 g Sodium, 3.25 

g Magnesium, and 2 g Iron. Similarly, Half-N contained 27.22 g of KNO3 and 31.58 g 

(CaNO3)2·4H2O, which contains 7.55 g of nitrogen, 31.64 g Potassium, 2.80 g 

Phosphorus, 5.37 g Calcium, 4.28 g Sodium, 3.25 g Magnesium, and 2 g Iron), - N 

excluded nitrogen sources, but included all other nutrients, 21.11 g of Potassium, 2.80 g 

Phosphorus, 10.8g Calcium, 21.55 g Sodium, 3.25 g Magnesium, and 2 g Iron), and 

Water (as control). 

3.3.3 Establishing Plants in the Laboratory  

Yam vines were established in the SAH laboratory in October 2021. They were dissected 

at one nodal cutting, and 15 vines were planted inside each SAH box filled with an 

appropriate amount of Klasmann TS3. The boxes were kept closed for the first 14 days 

to reduce transpiration and allow for the formation of new shoots. The temperature for 

the plants was maintained at 25±2°C. Ten boxes, each containing 15 plants, were 

established in the laboratory for each of the ten genotypes. SAH plants were transferred 

to the screenhouse in two batches. The first five genotypes were transplanted on the 8th 



 
 
 
 

18 

 

Table 3.3: Experimental layout of the plants and treatments at the screenhouse 

ALL-N CNTRL (Water) ½ Nitrogen Minus N (-N) 

G1P

1 

G2P

8 

G3P

8 

G4P

2 

G5P

1 

G1P

1 

G2P

8 

G3P

8 

G4P

2 

G5P

1 

G1P

1 

G2P

8 

G3P

8 

G4P

2 

G5P

1 

G1P

1 

G2P

8 

G3P

8 

G4P

2 

G5P

1 

G1P

3 

G2P

4 

G3P

1 

G4P

5 

G5P

3 

G1P

3 

G2P

4 

G3P

1 

G4P

5 

G5P

3 

G1P

3 

G2P

4 

G3P

1 

G4P

5 

G5P

3 

G1P

3 

G2P

4 

G3P

1 

G4P

5 

G5P

3 

G1P

5 

G2P

5 

G3P

3 

G4P

3 

G5P

7 

G1P

5 

G2P

5 

G3P

3 

G4P

3 

G5P

7 

G1P

5 

G2P

5 

G3P

3 

G4P

3 

G5P

7 

G1P

5 

G2P

5 

G3P

3 

G4P

3 

G5P

7 

G1P

7 

G2P

3 

G3P

2 

G4P

7 

G5P

9 

G1P

7 

G2P

3 

G3P

2 

G4P

7 

G5P

9 

G1P

7 

G2P

3 

G3P

2 

G4P

7 

G5P

9 

G1P

7 

G2P

3 

G3P

2 

G4P

7 

G5P

9 

G1P

8 

G2P

2 

G3P

10 

G4P

9 

G5P

8 

G1P

8 

G2P

2 

G3P

10 

G4P

9 

G5P

8 

G1P

8 

G2P

2 

G3P

10 

G4P

9 

G5P

8 

G1P

8 

G2P

2 

G3P

10 

G4P

9 

G5P

8 

G1P

2 

G2P

10 

G3P

9 

G4P

8 

G5P

2 

G1P

2 

G2P

10 

G3P

9 

G4P

8 

G5P

2 

G1P

2 

G2P

10 

G3P

9 

G4P

8 

G5P

2 

G1P

2 

G2P

10 

G3P

9 

G4P

8 

G5P

2 

G1P

10 

G2P

1 

G3P

6 

G4P

10 

G5P

10 

G1P

10 

G2P

1 

G3P

6 

G4P

10 

G5P

10 

G1P

10 

G2P

1 

G3P

6 

G4P

10 

G5P

10 

G1P

10 

G2P

1 

G3P

6 

G4P

10 

G5P

10 

G1P

4 

G2P

7 

G3P

4 

G4P

4 

G5P

5 

G1P

4 

G2P

7 

G3P

4 

G4P

4 

G5P

5 

G1P

4 

G2P

7 

G3P

4 

G4P

4 

G5P

5 

G1P

4 

G2P

7 

G3P

4 

G4P

4 

G5P

5 

G1P

9 

G2P

6 

G1P

5 

G4P

1 

G5P

4 

G1P

9 

G2P

6 

G1P

5 

G4P

1 

G5P

4 

G1P

9 

G2P

6 

G1P

5 

G4P

1 

G5P

4 

G1P

9 

G2P

6 

G1P

5 

G4P

1 

G5P

4 

G1P

6 

G2P

9 

G3P

7 

G4P

6 

G5P

6 

G1P

6 

G2P

9 

G3P

7 

G4P

6 

G5P

6 

G1P

6 

G2P

9 

G3P

7 

G4P

6 

G5P

6 

G1P

6 

G2P

9 

G3P

7 

G4P

6 

G5P

6 

G = Genotype, P= Plant  



 
 
 
 

19 

 

of December 2021, while the last five genotypes were transplanted into pots at the 

screenhouse on the 16th of December 2021 because the growth rate was slower for the 

last five genotypes. 

3.3.4 Growth Conditions in the Laboratory 

Fifteen plantlets were subcultured from the mother plants into new SAH boxes filled 

with 500 mL of substrate and established in the laboratory for approximately 8 weeks. 

The average temperature was between 25-27°C at the laboratory and up to 38.9°C at the 

greenhouse. The source of lighting in the laboratory was LED fluorescent bulbs, with 

two on each plate on a shelf and central lighting. The LED fluorescent bulbs were 

programmed to operate on a 12-hour photoperiod using a timer. After eight weeks, the 

plants were moved to the screenhouse, allowed to acclimatize for a week, and then 

transplanted into polyethylene pots. 

3.3.5.   Watering and Nutrient application in the laboratory 

Watering was performed biweekly using a nutrient solution at the yam semi-autotrophic 

hydroponics laboratory. The nutrient solution comprised solutions A and B. Solution A 

contained 47.2 g of calcium nitrate, while Solution B contained potassium nitrate (20.20 

g), potassium phosphate (5.44 g), magnesium sulfate (19.2 g), iron stock (200 mL), and 

benzyl aminopurine (6 mL). Solutions (A and B) were diluted separately in 20 L of water. 

Thereafter, 500 mL of each stock solution (A and B) was combined and diluted with 

water to a final volume of 20 L to prepare the nutrient solution. This water was used to 

water the plants during the period of establishment in the laboratory. 

3.3.6. Acclimatization and Transplanting Yam Plantlets into Pots in the 

 Screenhouse 

The plants were grown in the laboratory for 8 weeks. By week 9, they were moved to 

the screenhouse to allow the plants to acclimate to changes in the environment, such as 

temperature and humidity. After a week of moving the plantlets from the laboratory to 

the screenhouse, they were transplanted into polyethylene pots. Before transplanting, 

each pot was filled with 90 g Klasmann TS3 substrate and moistened with distilled water. 

The plants were shaken. The average daily temperature in the screenhouse ranged from 

22°C to 35 °C throughout the growth period. 



 
 
 
 

20 

 

3.3.7.   Watering and Nutrient Application in the Screenhouse 

All the plants were watered twice weekly with the respective nutrients, as described in 

Table 3.2. However, distilled water was applied to pots that showed excess dryness at 

midweek to avoid wilting before the next treatment day. 

3.4 Data Collection  

Destructive sampling was conducted on five of the ten plants. All plants were gently 

removed from the soil after SPAD measurements. The petioles and leaves were detached 

from the vines and the number of leaves and fresh shoot biomass were measured. The 

total fresh shoot biomass (vine, petiole, and leaves) was measured. Leaves, shoots, and 

tubers were sampled after SPAD measurement and dried at 80 °C for three days to obtain 

the total shoot dry weight. SPAD values were measured for the first five plants in 

February 2022, while the last five plants were allowed to continue tuber development 

and were harvested in June of the same year. Measurements were taken by placing 

individual leaves into the receptor window, repeating the procedure for three different 

leaves, and then pressing the average button to record the mean value. The SPAD unit 

was then recorded from the reading on the display 50 days after the commencement of 

the treatments. Based on the average growth rate, pictures of one of the remaining five 

plants were captured to represent each genotype/treatment. All five plants had senesced 

by 150 days after transplanting (DAT), at which point tubers were harvested and 

weighed. 

Data were collected on the following quantitative traits to assess the assessment of ten 

yam genotypes. 

Number of Leaves per plant (NL, g Leave-1): The number of visible leaves were cut 

off from the vine and carefully counted manually with the eye. 

Chlorophyll Content of the Leaves (SPAD): The SPAD value or chlorophyll content 

of the leaves was measured using a Konica Minolta SPAD-502 plus a chlorophyll meter. 

Chlorophyll content was measured by selecting three different leaves per plant (targeting 

the leaves closer to the top of the plants), and the average of the three data points was 

calculated. 



 
 
 
 

21 

 

Shoot Fresh Weight (SFW, g Plant-1): A weighing scale was used to measure the shoot 

weight (including the vine, petioles, and leaves). 

Leave Fresh Weight (LFW, g Plant-1): The weight of the leaves was measured using a 

weighing scale. 

Tuber Fresh Weight (TFW, g Plant-1): All the soil was carefully washed off, and the 

weight of the tubers was measured using a weighing scale. 

Shoot Dry Weight (SDW, g Plant-1) and Tuber Dry Weight (TFW, g Plant-1): The 

shoots and tubers were dried at 100°C for three days and weighed afterward using a 

weighing scale. 

3.5 Imaging of Plants and Tubers in the Screenhouse 

Images of entire plants and tubers were taken in the screenhouse with a custom-made 

indoor imaging system comprising a blue and white background, white paper meter rule, 

and Field Book App on a Samsung tablet. Both the blue plastic plates and white 

background were installed vertically and horizontally, respectively, and positioned in a 

solid iron frame to provide support. Each pot was placed in a black mark on a white 

horizontal plate, and the plant was placed in front of a blue background. Images of the 

plants were taken at 50 days after transplanting (DAT) and for the tuber at 150 DAT (See 

Appendix 2-6). 

3.6 Data Analysis 

Analysis of variance (ANOVA) was performed using the generalized linear model 

(GLM) procedure for a Randomized Complete Block Design in R-studio software 

(4.4.2). Tukey’s Honest Significant Difference (HSD) test for post-hoc comparisons at a 

95% confidence level. The level of significance was fixed at an alpha of 5%. 

 

 

 

 

 



 
 
 
 

22 

 

CHAPTER 4 

RESULTS 

4.1 Mean Squares of Growth and Yield Variables of Ten White Guinea Yam 

 Accessions Evaluated in IITA, Ibadan in 2021/2022 

The analysis of variance revealed highly significant differences among the ten yam 

accessions for all quantitative traits measured after 50 days of transplanting and the 

interaction between the accessions and nutrients was significant (Table 4.1) in specific 

traits such as leaf chlorophyll content (SPAD), Shoot Dry weight (SDW), and Tuber 

Fresh weight (TFW). 

4.2 Effect of Nutrient Level on Leaf Chlorophyll Content (SPAD Value) of Ten 

 White Guinea Yam Genotypes Evaluated in 2021/2022 

The leaf chlorophyll content of the ten yam genotypes in each of the four nutrient levels 

used in this study is shown in Table 4.2. In Half-N, DRS104 had the highest mean SPAD 

value of 39.1 and consistently high means across all treatments. Genotypes DRS044, 

TDr9519177, and DRS074 closely followed with mean SPAD Values of 35.9, 35.5, and 

35.3, respectively, under the same treatment. In contrast, DRS002 had the lowest mean 

SPAD value of 29.0, and the second lowest mean SPAD value of 29.4 was recorded in 

genotype DRS027 under the Half-N treatment. 

For ALL-N, R-031 had the best performance, with a mean SPAD value of 35.4, followed 

by DRS044 and TDr9519177, with mean SPAD values of 34.5 and 34.4, respectively. 

The lowest SPAD value of 25.6 under ALL-N was observed in TDr93-31. In the Control 

treatment, DRS104 had the highest SPAD value of 36.1, followed by TDr9519177, with 

an SPAD value of 34.3. Genotype DRS044 had the lowest mean value of 18.4 under the 

control treatment. 

In the - N treatment, TDr93-31 emerged as the genotype with the highest SPAD value 

of 33.6, followed by R-031 and TDr9519177 with mean SPAD values of 31.2 and 31.0, 

respectively. In contrast, DRS44 had the lowest mean SPAD value of 18.8, whereas 

Meccakusa had the second-lowest SPAD value (21.2). Genotypes DRS002 and DRS074 

had a SPAD value of 22.5.  



 
 
 
 

23 

 

Table 4.1: Mean squares for growth and yield variables in ten white yam accessions evaluated in IITA, Ibadan 

       in the 2021/2022 season. 

Source of 

Variation 

DF NL SPAD LFW  

(g Plant-1) 

SFW  

(g Plant-1) 

SDW  

(g Plant-1) 

TFW  

(g Plant-1) 

TDW  

(g Plant-1) 

Accession 9 342.020*** 162.880*** 5.836*** 5.203*** 0.234*** 6.642*** 0.395*** 

Nutrient 3 447.160*** 851.380*** 18.764*** 16.857*** 0.608*** 8.432*** 0.090 

Acc × Nut 27 44.300 74.430*** 1.490 1.431 0.0541* 1.273* 0.056 

*, **, *** = significant at p < 0.05, p < 0.01, and p < 0.001 respectively, DF = Degree of Freedom; SPAD = Leaf Chlorophyll content, LFW 

= Leaf Fresh Weight, SFW = Shoot Fresh Weight, SDW = Shoot Dry Weight, TFW = Tuber Fresh Weight, and TDW = Tuber 

Dry Weight. 

 

 

 

 

 

 

 

 

 

 

 

 

 



 
 
 
 

24 

 

Table 4.2: Effect of Nutrient Level on the Leaf Chlorophyll Content (SPAD) of ten 

white guinea yam genotypes evaluated for growth and yield in 2021/2022 season 

ACCESSION Half-N ALL-N Control - N 

DRS002 29.0a 33.5a 23.1abc 22.5abc 

DRS027 29.4a 32.7a 21.1ab 29.2abc 

DRS044 35.9ab 34.5a 18.4a 18.8a 

DRS074 35.3ab 32.9a 24.9abc 22.5abc 

DRS104 39.1b 33.6a 36.1c 30.2bc 

Meccakusa 30.5a 28.7a 24.2abc 21.2ab 

R-031 32.2a 35.4a 21.9abc 31.2bc 

TDr8902665 35.2ab 32.6a 25.4abc 24.2abc 

TDr93-31 33.6ab 25.6a 24.5abc 33.6c 

TDr9519177 35.5ab 34.4a 34.3abc 31.0bc 

Means followed by the same letter within a row are not significantly different at 5% 

probability level 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 



 
 
 
 

25 

 

 

 

4.3 Effect of nutrient level on Tuber Fresh Weight (TFW) of ten white guinea 

yam  genotypes at 50 Days after Transplanting (DAT) in the 2021/2022 

season 

At 50 DAT, the highest TFW of 4.37 g and 3.74 g were observed in DRS044 in Half-N 

and ALL-N (Table 4.3). For Half-N, R-031 had the lowest TFW of 1.17 g. Genotype R-

031 also had consistently low TFW under ALL-N and - N, weighing 1.310 g and 1.30 g, 

respectively. However, under the Control treatment, R-031 displayed a slight increase in 

TFW, reaching 1.60 g. 

In the - N treatment, it was observed that most accessions showed the lowest tuber 

weight when compared with Half-N and ALL-N, except for TDr8902665. Genotype 

TDr8902665 showed quite stable performance across all four nutrient treatments, 

including - N, where it had the highest TFW of 3.02 g. Meccakusa had TFW of 3.57 g 

and 3.59 g under Half-N and ALL-N treatments, respectively, but its TFW dropped under 

- N to 1.75 g. 

Across all four nutrient treatments, TDr9519177 maintained relatively stable tuber yield 

(2.52 g, 2.17 g, 2.40 g, and 2.13 g). In the Half-N treatment, DRS027 had the highest 

tuber yield of 3.15 g and dropped significantly across the other nutrient levels, with the 

lowest weight observed in the control treatment. Under the ALL-N treatment, genotypes 

DRS104 and Meccakusa exhibited high tuber yields of 2.69 g and 3.59 g, respectively. 

Genotype TDr93-31 also had the highest tuber fresh weight of 2.29 g in ALL-N. 

Meccakusa had the lowest weight of 1.71 g at 50 DAT in - N. 

4.4 Effect of nutrient level on tuber fresh weight (TFW) of 10 white guinea yam 

 genotypes at  150 Days after Transplanting (DAT) in 2021/2022 season 

Genotype TDr8902665 had the highest tuber fresh weight of 11.07 g in Half-N and 9.97 

g in ALL-N at 150 DAT (Table 4.4). It also demonstrated relatively stable performance, 

maintaining the highest TFW under both the Control (6.91 g) and - N (6.49 g) treatments, 

as shown in Appendix 2. Genotype DRS044 followed closely after TDr8902665, 

maintaining the second highest value of 8.21 g and 6.62 g in Half-N and ALL-N, 

respectively (See Appendix 3).  

 



 
 
 
 

26 

 

 

Table 4.3: Effect of nutrient level on tuber fresh weight at 50 days after 

      transplanting of ten white guinea yam genotypes in 2021/2022 season 

Accession Half-N ALL-N Control - N 

DRS002 2.67abc 2.09abc 2.00a 1.51ab 

DRS027 3.15abc 1.93abc 1.20a 1.76ab 

DRS044 4.37c 3.74c 2.11a 2.10ab 

DRS074 2.12ab 1.57ab 1.57a 1.51ab 

DRS104 2.23ab 2.69abc 1.97a 1.26a 

Meccakusa 3.57bc 3.59bc 2.65a 1.75ab 

R-031 1.17a 1.31a 1.60a 1.33a 

TDr8902665 3.73bc 3.13abc 2.18a 3.02b 

TDr93-31 1.69ab 2.29abc 1.99a 2.10ab 

TDr9519177 2.52abc 2.17abc 2.40a 2.13ab 

Means followed by the same letter within a row are not significantly different at 5% 

probability level 

  



 
 
 
 

27 

 

Table 4.4: Effect of nutrient level on tuber fresh weight at 150 Days after 

transplanting of ten white guinea yam genotypes in 2021/2022 

Accession Half-N ALL-N Control - N 

DRS002 6.71bcd 4.68ab 2.64a 2.58a 

DRS027 3.80ab 4.12ab 2.49a 3.53a 

DRS044 8.21cd 6.62bc 3.79ab 4.82ab 

DRS074 4.69abc 1.82a 2.00a 2.98a 

DRS104 1.91a 2.66ab 1.99a 2.73a 

Meccakusa 5.78abc 2.06a 2.64c 3.48a 

R-031 3.60ab 2.86ab 3.10ab 3.24a 

TDr8902665 11.070d 9.97c 6.91c 6.49b 

TDr93-31 3.56ab 2.66a 2.44a 3.41a 

TDr9519177 4.02abc 5.69abc 5.17bc 3.56a 

Means followed by the same letter within a row are not significantly different at 5% 

probability level 

 
  



 
 
 
 

28 

 

In Half-N, DRS104 had the lowest tuber fresh weight of 1.91 g, while DRS074 had the 

lowest TFW of 1.82 g in the ALL-N treatment. In the Control, DRS104 showed the 

lowest TFW of 1.99 g. However, DRS104 had a higher tuber biomass of 2.73 g under - 

N, whereas DRS002 had the lowest tuber biomass of 2.58 g. Genotype R-031 had a 

relatively low tuber biomass of 2.86 g under the ALL-N treatment, compared to 3.60 g 

under Half N and higher values under the Control and - N treatments.  

4.5 Effect of nutrient level on Shoot Dry Weight (SDW) of ten white guinea 

 yam genotypes evaluated in 2021/2022 

In Half-N, TDr8902665 had the highest shoot dry weight (0.786 g), whereas the lowest 

SDW (0.076 g) was recorded in DRS104 (Table 4.5). Similarly, under ALL-N, 

TDr8902665 had the highest shoot dry weight of 0.636 g compared to other accessions. 

Genotype R-031 had the lowest SDW under ALL-N. Under the control treatment, 

DRS044 had the highest SDW of 0.298 g, while DRS104 had the lowest SDW of 0.044 

g. In the - N treatment, TDr8902665 again recorded the highest shoot dry weight (0.270 

g), showing strong adaptability to varying nitrogen levels. The lowest SDW (0.064 g) 

under the - N treatment was recorded for DRS104. 

4.6 Growth and yield performance of ten yam genotypes under four nutrient 

 levels during the 2021/2022 season 

TDr8902665 had the best performance for all traits evaluated under varying nutrient 

levels (Table 4.6).  

Number of Leaves per Plant (NL): The highest number of leaves (15.25) was observed 

for TDr8902665. Genotype DRS027 had a mean NL of 14.30, whereas DRS074 had a 

mean NL of 12.65. The lowest number of leaves (4.15) was recorded in genotype R-031, 

whereas DRS104 and TDr93-31 had 4.70 and 5.05 mean NL, respectively. Meccakusa 

(9.10) and DRS044 (8.35) had an intermediate number of leaves (Table 4.6). 

Leaf Fresh Weight (LFW) 

Genotype TDr8902665 had the highest leaf fresh weight (2.547 g), and DRS044 had the 

second-highest LFW of 1.707 g (Table 4.6). Genotype DRS104 had the lowest LFW of 

0.621 g followed by R-031 with a leaf fresh weight of 0.865 g. Genotypes DRS027, 

DRS074, and TDr93-31 all had LFW values close to 1.0 g. Meccakusa (1.563 g) and 

DRS044 (1.707 g) showed moderate performance. 



 
 
 
 

29 

 

Table 4.5: Effect of Nutrient Level on the Shoot Dry Weight of the 10 white guinea 

      yam genotypes evaluated in 2021/2022 

ACCESSION Half-N ALL-N Control - N 

DRS002 0.492ab 0.340a 0.192ab 0.138ab 

DRS027 0.350ab 0.242a 0.228ab 0.258b 

DRS044 0.460ab 0.458a 0.298b 0.220ab 

DRS074 0.282a 0.300a 0.172ab 0.148ab 

DRS104 0.076a 0.246a 0.044a 0.064a 

Meccakusa 0.516ab 0.514a 0.222ab 0.204ab 

R-031 0.180a 0.138a 0.116a 0.124ab 

TDr8902665 0.786b 0.636a 0.160ab 0.270b 

TDr93-31 0.354ab 0.222a 0.108a 0.136ab 

TDr9519177 0.134a 0.492a 0.158ab 0.138ab 

Means with the same letter are not significantly different at 5% probability level 

 

 

 

 

 

 

 

 

 

 

 

 



 
 
 
 

30 

 

Table 4.6: Genotypic response to growth and yield across four nutrient levels 

       evaluated in IITA in 2021/2022 

 

ACCESSION NL LFW SFW TDW 

DRS002 12.050bcd 1.661ab 2.156ab 0.429ab 

DRS027 14.300cd 1.216a 1.780ab 0.437abc 

DRS044 8.350abc 1.707ab 2.347ab 0.641cd 

DRS074 12.650bcd 1.317a 1.739ab 0.386b 

DRS104 4.700a 0.621a 0.842a 0.400ab 

Meccakusa 9.100abcd 1.563ab 2.215ab 0.684d 

R-031 4.150a 0.865a 1.098a 0.267a 

TDr8902665 15.250d 2.547b 3.219b 0.695d 

TDr93-31 5.050a 1.000a 1.382a 0.502bcd 

TDr9519177 6.450ab 1.215a 1.643a 0.511bcd 

NL = Number of Leaves per plant; LFW = Leaf Fresh Weight; SFW = Shoot Fresh 

Weight; TDW = Tuber Dry Weight 

Means followed by the same letter within a column are not significantly different at 5% 

probability level 

 

  



 
 
 
 

31 

 

Shoot Fresh Weight (SFW) 

Genotype TDr8902665 had the highest SFW of 3.219 g while DRS044, Meccakusa, and 

DRS002 had an SFW of 2.347 g. 2.215 g and 2.156 g, respectively. Genotype DRS104 

had the lowest SFW of 0.842 g, while R-031 had a value of 1.098 g (Table 4.6).  

Tuber Dry Weight (TDW) 

Genotypes TDr8902665 and Meccakusa had the highest TDW, measuring 0.695 g and 

0.684 g, respectively. Genotype DRS044 also had a relatively high TDW of 0.641 g. 

Genotype R-031 had the lowest TDW (0.267 g).  Genotypes DRS027, DRS074, and 

DRS104 all had relatively low TDW (Table 4.6).  

4.7 Variation among ten yam genotypes for growth and yield at different 

 nutrient levels 

 

The ten yam genotypes performed best under the Half-N treatment. The highest values 

of 12.02, 33.60, 1.933, and 2.560 g were recorded for NL, SPAD, LFW, and SFW, 

respectively, under the treatment. The values for all traits measured across the ten 

genotypes under Half-N were comparable to ALL-N, but significantly different from 

control and - N (Table 4.7). The same trend was observed for all other measured 

quantitative traits.  

The lowest number of leaves was observed under control (6.32), but was comparable to 

that of - N (6.94). Similarly, the Control treatment recorded the lowest leaf chlorophyll 

content (SPAD value) of 25.4 recorded across the genotypes, compared closely with - N 

with a value of 26.4. A similar trend was observed for LFW across the genotypes. Half 

N resulted in the highest LFW of 1.933 g, comparable to the ALL-N at 1.869 g. Under 

control, LFW was lowest with a value of 1.13 g, while LFW was 1.21 g under - N.  There 

was significant variation in SDW and TFW among the genotypes at both 50 and 150 

DAT across the four nutrient treatments. In contrast, TDW showed no significant 

differences in TDW among the four nutrient treatments.  

  



 
 
 
 

32 

 

Table 4.7: Nutrient response to growth and yield across ten yam accessions 

evaluated in IITA, in 2021/2022 

NUTRIENT 

NL SPAD LFW SFW SDW TFW 

50DAT 

TDW 

50DAT 

TFW 

150DAT 

Half-N 12.02b 33.6b 1.933b 2.56b 0.363b 2.72c 0.535a 5.34b 

ALL- N 11.54b 32.4b 1.869b 2.47b 0.359b 2.46bc 0.524a 4.72ab 

Control 6.32a 25.4a 0.837a 1.13a 0.170a 1.97ab 0.481a 3.70a 

- N 6.94a 26.4a 0.845a 1.21a 0.170a 1.85a 0.442a 3.70a 

Means with the same letter are not significantly different at 5% probability level 

NL =Number of Leaves per plant; SPAD = Leaf Chlorophyll content value; LFW = Leaf 

Fresh Weight; SFW = Shoot Fresh Weight; SDW = Shoot Dry Weight; TFW 50DAT= 

Tuber Fresh Weight at 50 Days after Transplanting; TDW = Tuber Dry Weight; TFW 

150DAT=Tuber Fresh Weight at 150 Days after Transplanting; DAT = Days after 

Transplanting 

 

  



 
 
 
 

33 

 

CHAPTER 5 

DISCUSSION 

Screening yam genotypes for their responses to varying nutrients that are essential for 

growth and yield is crucial for yam propagation. This process facilitates the selection of 

high-yielding genotypes that are tolerant to low-nutrient conditions and suitable for case-

specific production when considering scarce resources. Land preparation, cost of 

planting materials, staking, weeding, and harvesting are capital-intensive; therefore, it is 

beneficial to reduce the costs of fertilizers. Selecting yam genotypes that are highly 

responsive to nutrients can greatly accelerate genetic gains for breeding programmes, 

considering the reduced cost of production, especially in developing countries such as 

Nigeria, where fertilizers are often imported.  

In this study, ten yam genotypes were assessed for their growth and yield response to 

four different nutrient levels (Half-N, ALL-N, - N, and Control) at the Yam Rapid 

Multiplication Laboratory and screenhouse of the International Institute of Tropical 

Agriculture (IITA), using a semi-autotrophic hydroponic technique during the 

2021/2022 growing season. 

The significant effect of nitrogen levels and genotype observed in this study suggests 

that different yam accessions exhibit varying capacities for nitrogen uptake and 

utilization. The significant differences among the genotypes and nutrients for the number 

of leaves, leaf fresh weight, shoot fresh weight, and tuber dry weight imply that adequate 

nutrient treatment required for each yam genotype should be identified and used to 

propagate the genotype.   

According to the Konica Minolta manual, chlorophyll content, which is represented by 

the SPAD value, increases in proportion to the amount of nitrogen present in the leaf. 

For most species, a higher SPAD value indicates healthier plants and better yield. In the 

present study, genotypes generally exhibited higher SPAD values when supplied with 

ALL-N or Half-N, indicating optimal chlorophyll content under sufficient fertilization. 

The results of this study are in agreement with those of the glasshouse study conducted 

by Müller (2018), which showed that the fixed indoor phenotyping station yielded 

results that robustly reflected the impact of N fertilization rates on early plant growth, 

leaf SPAD values, and N content. 



 
 
 
 

34 

 

The low SPAD values recorded in the Control and - N treatments demonstrate how 

nutrient deficiencies impact leaf chlorophyll content, reflecting suboptimal plant health. 

Genotype DRS104 with the highest SPAD value under Half-N with strong chlorophyll 

retention despite reduced nitrogen input also agrees with the report by Ringger (2017), 

who showed significant relations between SPAD values and N leaf content and between 

TGI values and N leaf content for the cultivar raja ala. The highest SPAD value recorded 

for the genotype TDr93-31 under - N suggests its potential ability to maintain 

chlorophyll levels, even under nitrogen-deficient conditions. 

The highest TFW under Half-N and ALL-N at 50DAT recorded for DRS044 showed a 

high response to the treatments.  

Generally, moderate nitrogen availability (Half-N) resulted in increased tuber weight 

compared to water and - N treatments, confirming the positive role of nitrogen in 

chlorophyll content as indicated by SPAD values, shoot, and tuber development. The 

observations from this study are consistent with the findings of Law-Ogbomo and 

Remison (2008), who conducted two field trials and reported maximum yield at a 

fertilizer dosage of 300 kg/ha NPK. However, this contrasts with a study by Shiwachi et 

al. (2015), which stated that the role of the application of NPK fertilizer was unclear in 

tropical yam species and did not influence the yield of water yams despite the application 

of varying quantities. At 50 days after transplanting (DAT), genotype TDr8902665 

recorded the highest shoot dry weight (SDW) under the Half-N treatment, while 

Meccakusa exhibited the highest SDW under the same treatment, suggesting efficient 

nitrogen utilization by both genotypes. In addition, the observed lowest shoot biomass 

across all treatments reported for genotype DRS104 indicates the possible susceptibility 

of the genotype to nitrogen stress. R-031 also had a consistently low SDW across 

treatments and weak adaptability to nitrogen fluctuations, as shown in the plant image 

on Appendix 4. Takada et al. (2017) also suggested that water yams absorb nitrogen from 

the air, which may account for the high shoot fresh/dry weight recorded for genotype 

TDr8902665 in this study. 

In addition, it was observed that the optimal nutrient for yam propagation using the semi-

autotrophic hydroponics method of propagation was Half-N because it was significantly 

better than the Control and - N. However, Half-N and ALL-N were not significantly 



 
 
 
 

35 

 

different. Meanwhile, the findings of Akom et al. (2024) on the effect of biochar and 

organic fertilizer on yam production in Ghana observed no significant differences in the 

response of soil parameters to treatment, except for total nitrogen, where a decline was 

observed compared to the control. The same study reported that biochar and organic 

fertilizers had no significant effect on the vegetative growth of yam plants. However, 

dry matter production increased significantly, suggesting that later dates and higher rates 

of biochar application will be useful for yam production. 

 

  



 
 
 
 

36 

 

CHAPTER 6 

CONCLUSIONS AND RECOMMENDATIONS 

The production of yams in Nigeria and Africa faces diverse challenges, one of which is a 

decline in yield due to the high cost of farm inputs and fertilizers. This has led to a gap in 

supply, as yam production fails to meet the demands of Africa’s teeming population. To curb 

this and avoid food insecurity in Africa, there is a need to adopt innovative solutions that 

increase seed production strategies and foster research advancements in genetic gain.  

This study was conducted to investigate the effectiveness of the semi-autotrophic 

hydroponics technique in screening yam genotypes for their response to different nutrient 

levels (ALL-N, Half-N, control, and - N) using chemical solutions. The experiment was 

conducted for 150 days, and the first data collection took place 50 days after the plants were 

transplanted into pots in the screenhouse.  

It was confirmed that the choice of genotype and nutrient concentration are important factors 

for improving yam productivity using the SAH technique. Among the growth and yield 

variables assessed, a significant interaction between the genotypes and nutrients was 

revealed for Leaf Chlorophyll content (indicated by the SPAD Value), shoot dry weight, and 

tuber fresh weight.  

The recommended nutrient level for yam SAH production based on the results of this study 

is Half-N, and the best yam genotype based on this study is TDr8902665. It was stable across 

all treatments, making it a promising genotype in different nitrogen environments. Semi-

autotrophic hydroponics should be further exploited to complement yam seed production to 

shorten the breeding cycle and increase the yam seed multiplication rate. This system will 

also aid in the production of disease-free propagules. 

The inherent potential of semi-autotrophic hydroponics for identifying genetic variation in 

nutrient utilization among yam genotypes was demonstrated in this study. 

 

 

 

 



 
 
 
 

37 

 

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APPENDIX 

 

Appendix 1: Experimental layout of the plants and nutrient treatments at the 

screenhouse. 

  



 
 
 
 

46 

 

 

 

Appendix 2: TDr8902665 tubers growth differences at 150DAT across all four different 

nutrient levels 

 

 

 



 
 
 
 

47 

 

 

 
Appendix 3: DRS044 tubers growth differences at 150DAT across all four different 

nutrient levels   



 
 
 
 

48 

 

 

 

 

Appendix 4: Plant growth differences in R-031 at 50DAT across all four different 

nutrient levels 

R031 ALL 
R031 Half N 

R031 CNTRL R031 Minus N 


	51ac28256a1f028332a10b854a7fc96a579b74c0d43ed22faac9b220d4fe54c3.pdf
	Bidemi_Thesis_Final+RM
	51ac28256a1f028332a10b854a7fc96a579b74c0d43ed22faac9b220d4fe54c3.pdf