Eliminating Hunger: Yam for Improved
Income and Food Security in West Africa
Beatrice Aighewi, Norbert Maroya, Robert Asiedu, Djana Mignouna,
Morufat Balogun and P. Lava Kumar
1. Introduction
Yam is a monocotyledonous tuber crop in the family Dioscoreaceae. The genus
includes more than 600 species worldwide (Mondo et al. 2020), but only a few are
cultivated. Dioscorea rotundata is the most valuable and widely cultivated species in
West Africa, followed by D. alata. D. cayenensis, D. dumetorum, and D. esculenta,
which are also cultivated in limited quantities in the region. Yam is a crop of
great value in many communities in West Africa, and it is mainly cultivated for its
underground tubers, although some species also produce aerial tubers. The crop has
the highest value of the aggregate production compared to other crops in West Africa
(Elbehri 2013; Hollinger and Staatz 2015), with an apparent per capita consumption
that increased fastest in major producing countries of Ghana and Nigeria over the
period 1980–82 to 2007–09 (Hollinger and Staatz 2015). While some yam species
are important as food, others provide useful pharmaceutical products (Price et al.
2016; Tohda et al. 2017). Diosgenin and dioscorin are compounds isolated from yam
and used in the pharmaceutical industry (Obidiegwu et al. 2020). However, some
yam species are not edible due to poisonous substances (Dave et al. 2020; Joob and
Wiwanitkit 2014; Kyung-Sik and Taek Heo 2015; Yoon et al. 2019).
Yam is grown as an annual with a duration from planting to harvest ranging
from 8 to 12 months, depending on the agroecological conditions. Varieties in the
forest region typically have a longer crop duration due to the longer rainy season
than crops in the savanna. About 74.9 million tons of yam tubers are produced
annually in the world on about 8.9 million hectares of land with an average yield of
8.5 t/ha (FAOSTAT 2021). Africa contributes 97.8% to world production, and Benin,
Côte d’Ivoire, Ghana, Nigeria, and Togo account for 93.9% of world production
(FAOSTAT 2021). Nigeria alone produces 66.9% of global production. Yam is the
fourth most utilized root and tuber crop globally after potato (Solanum spp.), cassava
(Manihot esculenta), and sweetpotato (Ipomoea spp.), and it is the second in West Africa
after cassava (Lev and Shriver 1998).
1
Where yam is produced, it is a significant food source and cash crop, thus
combating malnutrition, food insecurity, and poverty (Obidiegwu et al. 2020). In
Nigeria and Ghana, 31.8% and 26.2% of the population depend on yam for food and
income security. Yam tubers have better nutritional attributes than other root crops
(Shajeela et al. 2011). The tubers are a good source of essential dietary supplements
such as protein and well balanced essential amino acids (Baah et al. 2009). Even
where yam is not a significant crop in some parts of Africa, it is considered a famine
food for small and marginal rural families and forest-dwelling communities during
periods of food scarcity (Ngo et al. 2015). In West Africa, yam is most preferred when
processed fresh. It is mainly consumed boiled in sauce or soup (using pieces directly
from the tuber or frozen chips from a supermarket), made into a dough by pounding
boiled tuber pieces or reconstituting from flour (as instant pounded yam or amala),
roasted, or fried.
Yam is often referred to as the “king of crops” in West Africa, and it is essential
in the socio-cultural life of the population. It is used in ceremonies related to fertility
and marriages, cultural rites of passage, thanksgiving, petitions, and annual festivals
held to celebrate its harvest (Obidiegwu and Akpabio 2017; Nweke 2016). Poor seed
and ware yam storage systems cause seasonality in the price and quality of available
yams. Surplus during peak production season leads to price ‘crashes’, affecting
farmers, while scarcity at other times causes a lack of affordability by consumers
and undernutrition. Cropping of yam, especially seed, throughout the year therefore
contributes immensely to the regional requirement for food and income.
2. Trends and Systems of Yam Production
A 70 percent increase in global food production is required to feed an additional
2.3 billion people by 2050 (FAOSTAT 2021), while food production from developing
countries should almost double. Yam production in West Africa increased from
8.3 million tonnes in 1961 to 74.2 million tonnes in 2019. Figure 1 shows a decline
in the average world yield to a present average of 8.5 t/ha, although yam has a
potential of 40 to 50 t/ha (Adewumi et al. 2022; FAOSTAT 2021). The increase
in production is due to an expansion of the area cultivated (Frossard et al. 2017).
However, low productivity in most production systems results from poor quality
of soils and inputs, accompanied by little or no application of improved agronomic
practices (limited weeding, low planting density, persistent virus infections, no pest
and disease management). Although there are improved and released varieties in
major producing countries such as Nigeria and Ghana, local landraces still dominate
farmers’ varieties mainly due to challenges associated with large-scale multiplication
2
of seed to meet demand. Smallholder farmers who constitute the most producers
mainly cultivate yam in the richest soils available to them. As fertility reduces, they
use the land for other crops while yam cultivation is moved to more fertile soils.
However, with an increase in population and pressure on agricultural land, the
availability of fertile land is reducing. Therefore, marginal soils and non-traditional
yam lands are put under cultivation to obtain the same yields or less.
 
 
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((FFAOSTAT 202211).) .
Trraaddiittiionalllly,, ffarrmers use whole tuberrss orr llaarrggee sseetttss ((sslilciceedd ppoortritoionns sofo ftutubebresr)s )
ofo2f 0200t oto5 5000g go orrm moorreea assp pllaannttiing materials (seeds)) and ppllaanntt inin mmoouunndds spprerpeparaerded 
usuisninggt otoppsosoili.l.M Moosstt yyaam ffaarrmers grow tthe crop wiitthouutt iinnppuutsts ssuucchh aas sfefertritliilziezre roro r
unudnderetratkakeec rcoroppm maannaaggeemeenntt prraaccttiicceess tto cconttrroll peessttss aanndd ddisiseeaassees s(M(Migignnouounan aete atla. l.
2021051)5.).I tIti sisf rfreeqquueennttllyy iinntteerrccrrooppppeedd,, bbuutt ssoollee ccrrooppss aarree aalslsoo ccoommmmonon ini nWWesets At Afrficriac. a.
AAt ht ahravrvesets,t,f afarmrmeerrsss soorrtt ssmaallll-- ttoo meeddiiuum--ssiizzeedd ttuubbeerrss ((220000 gg toto 11 kkgg) )fofor rrereuuses easa s
seseededs,s,w whhilielel alargrgee-s-sizizeedd ttuubbeerrss ((>>11 kkgg)) aarree uusseedd aass ffoooodd.. TThheeyy aarree sstotoreredd aanndd eaetaetnen 
pipeiceecmemeaelalo orrs osoldldi ninm maarrkkeettss wwhheenn ccaasshh iiss nneeeeddeedd.. TThhee sseeeedd--ssizizeedd tutubbeersr saarer estsotorerded 
totob rberaekakd odromrmanacnycyb ebfeofroerep plalnantitninggin int htheen nexetxct rcorpopppininggs esaesaosonn, o, or rt htheyeya raerep plalnantetdedi n
neinw nlyewprlyep parreepdafireedld fsiewldhse rwehthereey twheilyl bweildl obrem daonrtmuanntitl uthnetisl ttahret  osftatrhte orfa itnhye sreaainsoy n
thsreeaesoton ftohurerem too nfotuhrs mlaotenrt.hs later. 
  
3
3 
 
3. Opportunities for Increased Income, Employment, and Food Supply in Seed 
Yam Production 
Seed3. Otupbpoerrtsu nairtiee sefxopr Ienncsreivasee, dsIonmcoemteim, Eemsp laocycmoeunnt,tianngd Ffooord 6S3u%pp loyfi ntoSetaedl variable 
productYiaomn Pcroosdtus,c taionnd are bulky and expensive to transport (Manyong 2000; Agbaje 
et al. 2005). SAeesd ptluabnetrisngar emeaxtpeerniasilv, et,hseo ymaemtim teusbaecrc ohuanst ian gmfeoarg6e3r% mouf lttoitpallivcaartiiaobnle ratio of 
1:3 to 1:p5r ocdoumctpioanrceodst st,oa nsodmare bcuelrkeyaalsn d(1e:x3p0e0n)s.i vTehteo tlroawns pmorut l(tMipalniycoantigo2n0 0r0a;tAe gibsa aje critical 
constraient ta lt.o2 0i0n5c).rAeasspilnagnt iynag m apterroiadl,uthcteioyanm atnudbe pr hroasdaumcteiavgietrym, rueltsiupllitciantigo ninra tthioeo fscarcity 
and hig1h:3 ctoo1s:t5 ocof mqpuaarleidtyto sseoemde ycearmea ls(A(1i:g30h0e).wTih eetlo awl.m 2u0l1ti7p)l.i cTathioen craotnesiseqaucreinticcael is that 
improvceodn,s trrealienat stoedin cyreaamsin vgayraimetpierso daurceti ornaraenldyp frooduuncdti vwityi,thre sfualrtimngeirns,t haensdca rtchitey use of 
and high cost of quality seed yam (Aighewi et al. 2017). The consequence is that
farmer-ismavpreodv esde,erde liesa stehde ynaomrmva.r Aietbieosuatr ea rtahrierlyd foofu nhdarwvietshtefadrm yearms,  atnudbethrse aursee oref served 
for seedfa rfmore rt-shaev endesxete dcrisotph.e Tnohrums., Afbroumt  aat hWirdeosft hAarfvreicstaend yparmodtubcetrisoanr eorfe s7er0v.8ed million 
tonnes, fiotr ise eesdtifmorattheedn tehxat tc roovpe. rT 2h3u.s6, mfroimllioanW teosnt nAefrsi,c asnompreo douf cwtiohnicohf 7w0o.8umldil lhioanve been 
used ast foononeds,, iits irseessetirmvaetedd ftohra tpolvaenrt2in3.g6  mthileli onnetxotn cnreos,ps o(mFiegoufrweh 2ic)h. Cwoonultdinhuavoeubse reencycling 
of plantuinsegd masaftoeordi,ails orefsteernv erdedfourcpelasn qtiunagltihtye  nbeyx taccrcoupm(Fiugluartein2)g.  Cpoensttisn uaonuds rdeicsyecalisnegs. After 
of planting material often reduces quality by accumulating pests and diseases. After
plantingpl,a snotimnge, sfoamrme fearrsm cearsnc satnilslt irllerseesrevrvee uupp ttoo aat hthiridrdof othf ethquea qnutitaynotfitsyee odfp sleanetde dplanted 
to replatocer epthlaocseeth tohseatth wat owuoludld eventutualalyllnyo tnsoptr osupt rdouue tt odpuooer tqou aplitoyo(rA iqguheawliit1y9 9(8A),ighewi 
1998), fufurrtther  deepplelteintignagp ao tpenotieanl ftoiaodl faonoddin acnomd einsocuormcee.  source. 
  
Figure 2.F Yigaumre t2u. bYearms otuf bueprs toof u1 pktgo, 1wkhgi,cwh hairceh garoeogdo ofodrf olorclaolc afol foodo danandd eexxppoorrtt,, are used as 
seed andu csuetd ianstose medinanisdecttust oinft 3o0m tion i5s0et tgs foofr3 0mtuol5t0ipglifcoartmiounl.t iSpoliucartcieo:n P. Sicoturrces:  Pbiyct uauretshors. 
by authors.
The traditional methods to produce seed yam include cutting ware-sized tubers 
The traditional methods to produce seed yam include cutting ware-sized tubers
into seeidn tsoizseee,d hsairzve,ehstairnvges ttihneg stahme sea mcreocpro tpwtiwceic e(th(thee fifirrsstt hhaarrvveesstti sisu usesdedfo frofro ofodod and 
the secoand tfhoers esceoendd)f, osrosreteidn)g, s osreteindg seizeed stiuzebeturbse, ras,nadn duussiningg onllyyt htehhee hadeapdor tpionrstions of 
tubers (oAf tiugbheersw(iA iegth eawl.i e2t0a1l5. )2.0 1T5h).eTshee soepotpiotinons smullttiipplylyy aymamve rvyesrloyw slylowwitlhy nwo ith no 
guarantgeuea roafn steeeeodf qseueadlqituya.l iTtyh. iTsh sisitsuitautaitoionn ffoorrmmeeddt hthe eb absaissfiosr ftohre tYhaem YImampr oIvmempernotvement 
for Incfoomr Inec oamneda ndFFoooodd SSeceucruitryitiny Wienst AWfriecsat( YIAIFfSrWicAa ) i(nYitIiaItFivSeWofAth)e Iinnteitrinaattiivonea l of the 
International Institute of Tropical Agriculture (IITA). The focus was on developing 
4
methods to improve the quality of seed yam and rapidly multiply the seed to meet 
the needs of farmers for increased productivity. Any technology to rapidly multiply 
the crop is an opportunity to develop seed yam production-related businesses as a 
source of income, especially for youths and women. The development of hitherto 
non-existent seed yam enterprises will fill the gap in the supply of quality seed yam 
and create job opportunities. 
  
4 
Institute of Tropical Agriculture (IITA). The focus was on developing methods to
improve the quality of seed yam and rapidly multiply the seed to meet the needs of
farmers for increased productivity. Any technology to rapidly multiply the crop is
an opportunity to develop seed yam production-related businesses as a source of
income, especially for youths and women. The development of hitherto non-existent
seed yam enterprises will fill the gap in the supply of quality seed yam and create
job opportunities.
4. The Key Elements of the YIIFSWA Project
YIIFSWA is a ten-year project, implemented from 2011 to 2021 with grants
provided by the Bill and Melinda Gates Foundation (BMGF) to the International
Institute of Tropical Agriculture (IITA) in two phases of five years each. The project’s
focus was to improve the productivity of yam through enhancing its seed systems.
4.1. Summary of Achievement of the First Phase of the YIIFSWA Project
The first five years of the YIIFSWA project (September 2011 to December 2016)
facilitated activities to increase yam productivity (yield and net output) by 40% for
200,000 smallholder farmers in Ghana and Nigeria. Another goal was to generate
international research goods that will double the income of 3 million yam producers
in a 10-year horizon. During this first phase, YIIFSWA initiated the development of
formal yam seed production systems, leading to the first set of certified seed yams
for sale to ware yam producers in May 2016. This significant step in developing the
yam seed market was critical to sustaining commercial production and marketing
of high-quality seed yam. Diagnostics tools for virus detection and technologies for
elimination of virus infected sources from seed production, high-ratio propagation
technologies (HRPTs) such as the Temporary Immersion Bioreactor System (TIBS)
and aeroponics, and seed yam quality management protocols as well as quality
standards for seed yam certification were developed.
Over 65,000 farmers were trained to improve their seed production techniques
using the adaptive yam minisett technique (YIIFSWA 2017), which is similar to what
is used in the traditional seed production system (Aighewi et al. 2014). Yam-growing
households in Ghana and Nigeria were characterized through a baseline survey
(Mignouna et al. 2014a, 2014b). Economic assessments showed gains from the
various technologies emanating from YIIFSWA and their relative profitability
(Mignouna et al. 2020). Thousands of training materials (flyers, books, videos, and
posters) were produced and disseminated to stakeholders to improve their capacities
in seed and ware yam production, handling, and marketing (YIIFSWA 2017).
5
4.2. Summary of Achievements of the Second Phase of the YIIFSWA Project (YIIFSWA-II)
A primary goal of the YIIFSWA II project was to significantly increase yam
productivity by at least 30% by delivering clean, quality seed yam of improved
varieties to at least 320,000 smallholder farmers for long-term benefits in Nigeria and
Ghana. This initiative aimed to improve the yield gains of the rural and urban poor,
with more gender-equitable income for participants in the yam value chain. The
project achieved its vision of demand creation, improving production systems and
enhancing the enabling environment for improved varieties through four objectives:
i. Increase productivity and income by empowering smallholder ware yam
producers with the seed of improved varieties. Three improved and released
varieties of D. rotundata (TDr 89/02665 named Asiedu and TDr 95/19177 named
Kpamyo) and one of D. alata, (TDa 98/01176 named Swaswa) were introduced
to farmers in demonstration plots to show the potential of improved varieties.
Their mean productivity was higher than that of the local farmers’ preferred
varieties amounting to 38% productivity increase.
The project developed functional and sustainable seed systems by strengthening
national agricultural research institutions to produce high-quality breeder seed yam
of improved varieties using the TIBS. In 2020, the Ghana Crops Research Institute
(CRI), with the assistance of the YIIFSWA-II project, produced 350% of its target of
21,840. The Savannah Agricultural Research Institute (SARI) in northern Ghana,
with the support of the project, established its first TC Laboratory since inception
and produced 399% of its yearly target of 8736 breeder seed plantlets using TIBS.
The National Root Crops Research Institute (NRCRI- Umudike) of Nigeria produced
104% above its target of 21,840 breeder seeds in 2020. The breeder seeds produced
by NRCRI were partially distributed to two private seed companies (Nwabudo
Agro Seeds and Inputs Ltd. and Strategic Seeds Nigeria Ltd.) and to the Federal
Ministry of Agriculture and Rural Development. In total, 221,735 breeder seeds were
produced by IITA and NARIs within the year 2020 exceeding the target production
of 71,872 by 309%.
ii. YIIFSWA developed, demonstrated, and trained private seed companies on
foundation seed production models using best management practices in
aeroponic and hydroponic systems. These activities were aimed to deliver
high-quality seeds of improved varieties to farmers at the right time and prices
to encourage adoption through commercial seed entrepreneurs. One of the
primary outcomes of the project was to establish a functional, scalable, and
sustainable foundation and commercial seed systems that are driven by the
6
private sector. The project accomplished this by identifying and developing the
capacities of nine private seed companies in Ghana (3) and Nigeria (6). These
seed companies together with some of the NARIs produced about 3.6 million
foundation tubers of 25 g each in 2020.
iii. Raise the awareness of policy makers of the economic impact of the yam
sector through advocacy and information dissemination strategies, including
developing and implementing investment targets to popularize YIIFSWA’s
improved seed yam technologies for increased production, adoption, and
scaling. This was to influence key stakeholders and decision-makers to raise the
profile of yam in relevant fora and debates in Nigeria, Ghana, and beyond. This
caused the Federal Government of Nigeria to include yam in its list of priority
crops. In addition, new investments were engaged in the yam development
sector, especially in seed yam for Ghana and Nigeria totaling USD 1,959,159
(USD 1,509,968 and USD 449,191 in Nigeria and Ghana, respectively).
iv. Empower women to participate profitably in the commercial yam seed value
chain. Customarily, women’s participation in the yam value chain is limited
due to some socio-cultural settings. The project was deliberate in ensuring that
women were part of the seed yam value chain. Randomly selected yam farmers
in Nigeria have been growing yam for a mean period of 17.5 and 26.57 years
for female and male, respectively, while in Ghana, female experience was
18.37 years and males 19.34 years. Only 35.93% of females and 52.68% males
had heard of a yam project in the last seven years. It was observed that 19.57%
of females and 31.83% of males had heard about the YIIFSWA project, while
only 14.57% of females and 20.37% of males had benefited from the programme.
The same trend was also observed in Ghana. Out of the total number of
farmers trained on the adaptive minisett technique of seed yam production
during the first phase of the project, 39.6% were women. During the second
phase, female-owned private seed companies were targeted for partnership
and capacity building. Hence, there was one each in Nigeria and Ghana out of
the total of nine for both countries.
The implementation of YIIFSWA II ensured that all the advances made in
establishing the yam seed system by YIIFSWA were fully transferred to and
operationalized by National Agricultural Research Institutes (NARIs) and private
seed companies. Additionally, enhanced on-farm agronomic packages were
accessible and utilized by seed and ware yam farmers to increase productivity and
income generation. Beneficiaries of the project include seed and ware yam producers
and their family members, processors, marketers, transporters, and consumers.
7
5. Novel Yam High Ratio Propagation Systems: Outcomes and Prospects in
Adaptation to Climate Change and Nutrition Security
The YIIFSWA project developed and standardized a tissue-culture-based heat
therapy combined with a meristem culture procedure to generate virus-free yam
planting material. This procedure had a 73% success rate in eliminating the yam
mosaic virus (YMV), the most frequently contaminating virus in yams in West
Africa (Balogun et al. 2017a). This procedure established YMV-free stocks of 25 yam
genotypes consisting of improved varieties and landraces, which were used as stocks
for rapid bulking of clean planting material using the TIBS, an advanced high-ratio
in vitro propagation technology also standardized by YIIFSWA.
Plantlets from TIBS are of better quality than those from conventional
tissue culture (CTC). TIBS plantlets are more vigorous and resilient to post-flask
acclimatization. Due to more efficient process control, large batches are handled
more easily for scale-up propagation with lower risks of mix-ups. The propagation
ratio in TIBS was five to six per plantlet every eight to ten weeks compared to three
to four every 12 to 16 weeks in CTC (Balogun et al. 2017b). Up to 300 single-node
vine cuttings were obtained per plant that was derived from TIBS plantlet and grown
aeroponically (Maroya et al. 2014c, 2017), while the drip system hydroponics further
saves on electricity needs in the production system (Balogun et al. 2020, 2021). About
100 single-node vine cuttings can be made per TIBS plantlet using hydroponics after
eight weeks of growth, with 95% rooting success followed by field planting. After
five months of hydroponic growth, the seed tubers ranged from 5 g to 220 g per plant.
Aeroponics yam propagation started under the YIIFSWA project in 2013 at
IITA-Ibadan, Nigeria (Maroya et al. 2014a, 2014c). Atomizing nozzles ensure the
most effective nutrient delivery in this system by turning the nutrient solution into
a mist, which is absorbed through the cell walls of the plant’s roots by osmosis.
Genotypes of both D. rotundata and D. alata were successfully propagated with
aeroponics using both pre-rooted and freshly cut two-node vine cuttings. Three
types of planting materials are generated from the aeroponics production system:
mini-tubers which range from 0.2 g to 110 g depending on the genotype, harvest
age, and the composition of the nutrient solution, the aerial bulbils from both water
yam and white yam varieties, and single-node cuttings from vines (Maroya et al.
2014b). All the propagules had a propagation rate of over 90%. Yam vine cuttings
were previously known to grow slowly, but those from aeroponic plants produced
new leaves 14 to 21 days after planting. The single-node vine cuttings from aeroponic
plants produce an average of 200 to 300 cuttings per plant in four to six months. A
manual was produced to help private seed companies to establish their aeroponics
8
systems with step-by-step instructions for building and managing the system for
foundation seed production (Maroya et al. 2017). In 2017, the YIIFSWA-II project
funded each of five selected seed companies with USD 30,000, half of the cost to build
a screen-house and an aeroponics system. The project produced and distributed
virus-indexed plantlets for multiplication to seed companies. Relevant stakeholders
were trained, including postgraduate degree students, to apply various propagation
techniques through participatory research. After training, new technical information
on the high ratio propagation of yam was constantly provided, accompanied by
backstopping partners and other stakeholders.
The capacities of the seed regulatory agencies of Nigeria, the National
Agricultural Seed Council (NASC); and of Ghana, the Plant Protection and
Regulatory Services Directorate (PPRSD); were also enhanced. As coordinators
in the management of seed quality in their respective countries, they were trained
and provided with equipment to ensure that high-quality seeds of authentic varieties
were produced and sold.
6. Improved Yam Seed Systems as Key to Building Resilience in Production to
Enhance and Sustain Food Security
A functional yam seed system is essential to build resilience in the ware yam
production systems. As the most critical and expensive input of yam production,
the seed should be healthy to generate healthy plants in the field and reduce yam’s
current high postharvest losses estimated at 30%. Seed health influences the shelf life
of harvested ware tubers or postharvest storage quality since pests and diseases are
easily transferred from the field into storage and over different seasons through the
seed. Therefore, a yam seed system must have protocols to ensure the production
of seed tubers at a high rate of multiplication. Rapid propagation of pest- and
disease-free seeds and a network of commercial seed producers within a formal
seed system are crucial for disseminating improved varieties for sustained and
increased productivity. Extension services were used to educate farmers on plant
health management in the field to recognize pest and disease symptoms and carry
out positive selection practices to sustain good yields.
Technologies for breeder seed production were transferred to the following
NARIs, the National Center for Genetic Resources and Biotechnology (NACGRAB)
and the National Root Crops Research Institute (NRCRI) in Nigeria, and the Crops
Research Institute (CRI) and Savanna Agricultural Research Institute (SARI) in Ghana.
These institutions were provided with equipment and supplies for backup electricity,
TIBS, post-flask handling and documentation, and initial clean stock of planting
9
 
Technologies for breeder seed production were transferred to the following 
NARIs, the National Center for Genetic Resources and Biotechnology (NACGRAB) 
and the National Root Crops Research Institute (NRCRI) in Nigeria, and the Crops 
Research Institute (CRI) and Savanna Agricultural Research Institute (SARI) in 
Ghana. These institutions were provided with equipment and supplies for backup 
mealteecrtiraiclsit.yT, hTeIBNSA, pRoIsst-nfolawskp hroanvdidliencgl eaannd bdroeecudmerepnltaantitoinn,g amnda tienriitailasl tcoleparni vsatotecks eoefd 
copmlapnatinnige smfoartefroiualnsd. aTthioen NseAeRdIsp rnoodwu cptiroonv.ide clean breeder planting materials to 
privTahtee sienendo cvoamtiopnans idese vfoerl ofopuenddbaytioYnI IsFeSeWd pArotoduimctiporno. ve yam seed systems have
addedThvea liunenotvoatthioensy admevcerlooppedby buy sYinIIgFSvWinAes tfoo rimpproropvaeg aytaimon .seBede fosyrestenmows ,hyavaem 
viandeds ewde vrealmuea itnol tyhceo ynasmid cerroedp basy tuhseinagp pvainreastu fosrf oprrompaanguaftaiocntu. rBienfgorpeh nootows,y ynatmha vteins efos r
stworeargee minatiunblye rcso. nInsitdheernedew ass etehde parpopdaurcattiuosn sfoyrs temmasn,ulefaacfltuesrsinngo dpahloctuotstyinngthsaatrees ufsoerd 
storage in tubers. In the new seed production systems, leafless nodal cuttings are 
in TIBS, while those with leaves are planted in various hydroponic systems or rooted
used in TIBS, while those with leaves are planted in various hydroponic systems or 
anrdoopteladn atendd ipnlathnteefide ilnd t(hFei gfuierled 3()F.igTuhree n3o).d Tahl ec untotidnagls cwutittihngles awf ictahn leaalsf ocabne apllsaon bteed 
diprelacntltyedin dtihreecfitleyl dinfo rthsee efdieylda mfopr rsoedeudc tyioanm. Mpreotdhuocdtsioonf. pMroedthuocdinsg omf ipnritoudbuecrisngo f
lemssinthitaunbe1r0s go,f wlehssic hthapne r1fo0 rgm, wexhcieclhle pnetlryfoirnms eeexdceyllaenmtlyp riond suecetdio yna(mA ipgrhoedwuicteiot na l.
20(2A1i)g,hheawvei aelts oalb. ee2n02d1e),v ehlaovpee da.lsIfo wbiedeenly daedvoeplotepdedb.y Isfe ewdidcoemly paadnoiepst,etdh ebrey wsoeeudld 
becolmespsapnrieess,s uthreereo nwouuslidn gbey laemss pturebsesrusrefo ornf uoosidnga ynadms etuebde.rsS fixors feoeodd caonmd pseaendi.e Ssixin 
Nsigeeedri acoamnpdatnhireese inin NGighearniaa aanrde  uthsrieneg itnh Ge hinannoa vaartei ounsisndge tvheel oinpneodvaatniodnssc daleevdelboypethde 
YIaInFdS WscAalepdr objye ctthfeo Yr IsIeFeSdWpAro pdruocjetciot nfo. r seed production. 
 
FFiigguurree 33.. TTyyppeess ooff yyaamm pplalannttiinngg mmaatteerriiaallss ((aa)).. IInn vviittrroo ssiinnggllee nnooddee ccuuttttiinnggss ffoorr 
mmuullttiipplliiccaattioionn ini ntemtepmorpaoryr aimrymiemrsmione rbsiioorneacbtioorr seyasctetomrs;s (ybs)t Eexm vsi;tro(b n)odEaxl cvuitttriongns owditahl 
leaf for multiplication in various hydroponics systems, soil, and composite media; (c). 
cMutitniintugbserws iftrhomle eaxf vfiotrro msinuglltei pnloidcae tpiolanntisn fovr avrinioeu asndh tyudbreor pploannitcinsgs mysatteermiasl ,psroodilu,catinodn 
cionm thpeo fsieiltde omr escdrieae;n(hco)u. sMe. Sinoiutrucbe:e Prsictfurorems beyx avutihtroorss. ingle node plants for vine and
tuber planting material production in the field or screenhouse. Source: Pictures by
authors.
9 
10
The HRPTs developed by YIIFSWA are contributing to the efficient production
of end-user preferred improved varieties. According to previous studies by CIRAD
and partners, flour from dried chips made from the late maturing, multiple tubering
(5–10 tubers per plant) varieties of D. cayenensis and D. rotundata with relatively high
dry matter content (around 40%) and tolerance to poor soil conditions were most
demanded for preparation of amala, a popular food in Nigeria and Benin. This link
between food demand and preferred variety confirms that seed systems need to
choose their promoted varieties based on market demand. However, the delivery
rate of improved varieties is slow due to the low propagation ratio in traditional yam
cultivation, where cropping is seasonal, with a single annual production cycle that is
significantly limited by season (Orkwor and Asadu 1998). Weather elements are also
crucial for yam production ranging from water, light, nutrients, and temperature.
Yam requires 20 ◦C to 30 ◦C for optimum growth. However, according to the IITA’s
Geospatial laboratory, in 2015, temperatures lower than 20 ◦C were recorded only
in January and December, a period that is typically outside the crop growth period,
while at least 7 out of the 12 months in 2005, 2010, 2015 and 2017 recorded higher
than 30 ◦C (Personal communication) with associated rising air temperature and
carbon dioxide levels. The impact of climate change on the yam yield, including
its vulnerability to climate-change-related soil conditions, has been discussed by
Srivastava et al. (2012).
Just as drought causes significant losses, floods also cause significant yield
losses (Balogun and Gueye 2013). These climate-related scenarios force farmers to
vacate flood- or drought-prone farmlands or risk immense losses due to inadequate
photosynthetic rates, tuber bulking, and premature senescence. While there
have been significant breakthroughs in the real-time availability of geographical
information systems, its utilization in timing yam production is yet to be entirely
scaled and adopted at the level of producers and processors. The scarcity of clean
planting materials (Aighewi et al. 2015, 2021), dormancy of the tuber for about
four months, and uncontrolled sprouting after dormancy break limits the control of
the cropping calendar by farmers and reduces profits (Craufurd et al. 2001). This
established need for resilient, climate-smart mitigation strategies is also addressed
by the gains from the YIIFSWA project, especially in terms of yam cropping cycles.
Seed production can be carried out in controlled environments during the offseason,
and ware yam production timed to maximize the available rainy period.
Table 1 shows the timing of seed yam production based on the traditional
system relative to the HRPTs. Two cropping cycles are possible per year, from May to
December and October to August. Previously, 14 t/ha at 40,000 stands for seed yam
11
production was recorded. If the same land is used, up to 30 t/ha will be produced
per cycle when vine cuttings are used, giving 60 t/Ha per year. With continuous
availability of seed yam from the HRPTs, ware yam can be produced throughout
the year, combining the traditional cycle of October to July with the HRPT cycle of
May to December. This scheme is more amenable to delayed rains if supplemental
irrigation is provided. Significantly more land can also be used for yam production
due to 500-fold more seed yam, which culminates in more food availability.
Table 1. Seed yam production based on novel high ratio propagation technologies.
Before Current Revolution (Now) Prerequisite
Stock One tuber One tuber
6 gives 6
Cut portions mother 6 gives 6 mother plants
plants
October to
August January to May/June July to December
6 mother
Year 1 6 mother ure plantlets in laboratory
plants plants × 30 180 Tissue Cult
nodes cleaned CTC Lab
Production
6 cut of 3240
180 × 3 = 540 × 3 = 1620 × 2 = breeder TIBS Lab,
Year 2 portions per 1620 3240
mother plant 540 plantlets plants in AS, HS, Air
= 36 in 11 TIBS plantlets in seedlings in
32 TIBS Vivipak Aeroponics Cooling
and
Hydroponics
6 cut
portions Production of 3240 × 100 =
Year 3 from 36 324,000 single node vine Field planting of breeder vine Supp
mother seedlings from AS/HS plants seedlings for foundation seed,
plants = 216 in nurseries 324,000 seed tuber production irrigation
6 cut
portions Field planting of foundation
Year 4 from 216 Dormancy of foundation seed seed tubers certified seed Supp
mother tubers production using AYMT irrigation
plants = 1296 (324,000 × 2 = 648,000)
AS = aeroponic system; HS = hydroponic system. Source: Maroya et al. (2022).
van Etten et al. (2017) has established that the access farmers have to quality
seed and the functionality of seed systems in relation to production, distribution,
innovation, and regulation determines the efficacy in contributing to sustainable
agrobiodiversity and food systems. Available evidence has shown that the YIIFSWA
II project has impacted all four aspects. However, it is necessary to incorporate good
practices for efficient soil and water management as well as good agronomic and
agroecological practices that mitigate and enhance the adaptation to climate change
in future projects.
12
An additional benefit of the novel high-ratio propagation system is the
mitigation against hidden hunger. Nutrients can be dosed to yam grown
in aeroponics and hydroponics systems. High-quality planting materials of
improved varieties are disseminated as reported by a study conducted by YIIFSWA
(unpublished) to determine the nutrient components that limit the propagation
ratio and quality of plantlets in the TIBS. Using white and water yam varieties,
Kpamyo and Swaswa, respectively, the nitrogen (N), potassium (K), and phosphorus
(P) concentrations in culture medium were determined every two weeks for ten
weeks and in plantlets at transplanting. After eight weeks of culture, the pH and
refractometer values for medium acidity and sugar concentration were determined in
the varieties. In Swaswa, N, P, and K in the medium reduced by 83.8, 96.2, and 28.7%,
while it was 63.3, 61.2, and 23.1% in Kpamyo over the ten-week period. Reduction
in K concentration at two weeks was limited to Swaswa. In Kpamyo, adding P at
two weeks and N at six weeks would be beneficial. Thus, it is necessary to consider
diet requirements from seed production to determine optimum fertigation regimes.
This will ensure that plants absorb the available nutrients in sufficient quantities
for storage in tubers, which can also be fortified with additional micronutrients if
processed into other products after harvest.
7. Outcomes and Impact on Reducing Hunger by Raising Food Security
Food security is commonly defined as the access by all people to sufficient food
for active and healthy life (World Bank 1986). Three critical dimensions implicit in
this definition are (i) the availability of sufficient quantity and appropriate quality of
food supplied through own production or otherwise; (ii) access by all households
and individuals to enough and adequate resources to acquire such food; and (iii) the
utilization of this food through an adequate diet, water, sanitation, and health care
(Timmer 2012). In the developing world, household food security is largely linked to
food availability from household production. Gifts and transfers from friends and
relatives also play essential roles. Food purchased are also common but limited due
to a lack of liquidity.
7.1. Changes Perceived in Household Food Consumption Status of Yam Growing Areas of
Nigeria and Ghana
Food deficit was the main periodic shock experienced by most households across
the yam-growing areas of Nigeria and Ghana. This type of vulnerability results from
qualitative analysis considering the respondents’ perception about the number of
households affected by food shortages and the frequency of food shortages during a
13
season. To assess the farm household’s food consumption during surveys organized
by the YIIFSWA project, memory recall on different food shortage scenarios in the
past 12 months was employed.
Following the baseline survey, an end-line survey was performed within the
same major yam-producing zones in Nigeria and Ghana using the same multistage,
random sampling design, drawing on 1400 households based on the same sampling
frame (Mignouna et al. 2016). The respondents were asked whether their households
ha d sufficient food during the previous year. Figure 4 shows how households
peorccceaisvioednatlh feoiordf oshoodrtsaegceu drietycresatasteuds b. yT 2h7is%p peoricnetps tfiroonmw aabsouotb 6s2e%rv teod 3t5o%b, ewdhiiflfee trheen t
behtowueseenhothldest twhoatr roeupnodrtseodf hsauvrivnegy as. fAoofdte rsuthrpelpusro ijneccrte’sasfierds tbpyh 2a6s%e, fcrhoamn gaebsoiunt s8h%o ctok s
fa3c4e%d  b(yFihgouures e4h)o. ldAslmpuorsst uninog dthifefeirrelinvceel ihwoaosd osbtrsaetrevgeyd wbeertwe neeonti cheodubsyehcoolmdsp athriantg 
threeiprobratesdel innoe fsoiotuda sthioonrttaogeth beuet nndo lsiunrep. lus and food shortage throughout the year. 
 
 
FFiiggure 4. Channggeess inin hhoouusesheohlodl dfofoodo dcocnosunmsupmtiopnt iostnatsutsa tiun sai n12a-m1o2n-mtho pnetrhiopde rfoior dyafomr 
ygarmowginrgo whoinugsehhooludss eihn oNldigseirnia Nanigd eGrihaanaan.d SoGuhrcaen: a(M. Sigonuorucnea:  (eMt ailg. n20o1u4naa, 2e0t1a4bl., 22001174aa,, 
22001147bb,).2 017a, 2017b).
IPnoNsitiigveer ciah,anfrgoems inth feoobda csoelnisnuemtoptieonnd stlaintues,  whoeures erehpooldrtsedr,e apnodrt tehdesae prerdobuacbtiloyn 
resulted from increased productivity due to interventions of the YIIFSWA project. 
in food shortages throughout the year from about 5% to 1%. In comparison,
They are good indicators of food security improvement in the region, likely due to 
reYpIoIFrtSsWoAn ’os ccinatseirovneanltfioonosd. sThhoirst atgraenssdlaetcerse aisnetod far ocmon3t2ri%buttoioanb oouf t t2h6e% p(rFoijgeuctr ein4 ).
Hroeudsuechinogld vsutlhnaetrarbeipliotyrt etod fnooodf oiondsecsuhroirtyta agme,obnugt rnuoraslu hropuluseshionlcdrse ainse tdhef rsoumrvaeybeodu t
44a%reatso. 54% during the two periods. Households reported that food surplus was
almost unchanged during the same periods. In Ghana, the remarkable observations
7.2. Project Impact on Food Security 
Total household expenditure includ14ed expenditures on non-food items and 
consumables. Under food expenditure, all the food items consumed by the 
household during a year were collected. Food consumption included food that the 
household purchased, produced, and received from other sources. The total 
expenditure on food, obtained by aggregating expenditure on all food items, was 
used to estimate the project’s impact on food security. The total expenditure for each 
food group was calculated by aggregating the expenditure of all food and non-food 
items falling within a group. The results of the propensity score matching (PSM) 
presented in Table 2 show that the Average Treatment Effect on the Treated (ATT) 
of YIIFSWA project on food security (per capita expenditure on food) of beneficiaries 
in Nigeria and Ghana were about USD 55 and USD 94 for the Radius Matching 
13 
from baseline to the end line are that the proportion of households that reported
occasional food shortage decreased by 27% points from about 62% to 35%, while
the households that reported having a food surplus increased by 26% from about
8% to 34% (Figure 4). Almost no difference was observed between households that
reported no food shortage but no surplus and food shortage throughout the year.
Positive changes in food consumption status were reported, and these probably
resulted from increased productivity due to interventions of the YIIFSWA project.
They are good indicators of food security improvement in the region, likely due to
YIIFSWA’s interventions. This translates into a contribution of the project in reducing
vulnerability to food insecurity among rural households in the surveyed areas.
7.2. Project Impact on Food Security
Total household expenditure included expenditures on non-food items and
consumables. Under food expenditure, all the food items consumed by the household
during a year were collected. Food consumption included food that the household
purchased, produced, and received from other sources. The total expenditure on
food, obtained by aggregating expenditure on all food items, was used to estimate
the project’s impact on food security. The total expenditure for each food group was
calculated by aggregating the expenditure of all food and non-food items falling
within a group. The results of the propensity score matching (PSM) presented in
Table 2 show that the Average Treatment Effect on the Treated (ATT) of YIIFSWA
project on food security (per capita expenditure on food) of beneficiaries in Nigeria
and Ghana were about USD 55 and USD 94 for the Radius Matching technique. These
results imply that the beneficiaries that profited directly or indirectly from the project
are more food secure than the non-beneficiary farmers.
In summary, this study sought to find out the average treatment effect on the
treated, which gives the average effect of the project on food security. The results
showed a positive impact on food security, implying that the increase in productivity
generated by the project interventions led to increased household food security and
poverty reduction in the region.
15
Table 2. Impact of YIIFSWA on food security.
SWA
Country Parameter YIIFSWA YIIF
Beneficiaries Non-Beneficiaries Difference S.E.
Nearest Neighbor Matching
Unmatched 348.90 291.10 57.80 17.57
Nigeria ATT 350.52 295.54 54.98 19.46
ATU 290.50 325.00 34.50 .
ATE 38.16 .
Unmatched 715.32 630.36 84.96 179.19
ATT 718.09 623.95 94.14 175.80
Ghana
ATU 635.62 721.47 85.85 .
ATE 89.41 .
ATT: Average Treatment Effect on the Treated; ATU: Average Treatment on Untreated; ATE:
Average Treatment Effect. USD 1 = GHS 1.85 = NGN 157. Source: (Mignouna et al. 2014a,
2014b, 2017a, 2017b).
8. Conclusions
The YIIFSWA initiative has focused on efficient seed yam propagation and
production, significantly impacting the yam value chain. The project has developed
high-ratio propagation technologies and seed-health management innovations to
improve the seed quality and increase productivity by supplying yam farmers with
healthy seeds. The new methods emphasize using vines and minitubers of less than
10 g to produce seed tubers and free large quantities of tubers for food. Stakeholders’
capacities were enhanced through training on improved seed production methods
and equipment to build resilience and sustainability, and increase seed production
for income, nutrition, and food security.
9. Recommendations
The gains from the innovations contributed by the YIIFSWA project are visible.
However, greater emphasis is required for scaling innovations, especially in certified
seed production, for higher impact. Further research efforts are necessary to identify
cheaper alternatives in the novel seed yam propagation technologies that will increase
the profit margins in seed yam businesses. Studies are also required to identify the
most appropriate agronomic practices and control of yam tuber dormancy to allow
integration into cropping cycles in the face of production intensification and the
changing climate.
16
Author Contributions: Conceptualization, B.A.; writing—original draft preparation, B.A.,
R.A.; writing—review and editing, B.A., N.M., R.A., D.M., M.B., P.L.K.; project administration,
N.M., R.A.; funding acquisition, IITA: R.A., N.M., P.L.K., M.B., D.M. and B.A. All authors have
read and agreed to the published version of the manuscript.
Funding: This research was funded by the Bill and Melinda Gates Foundation, bearing
Investment Number OPP1159088. Grant to the International Institute of Tropical Agriculture,
Ibadan, Nigeria, November 2016 to 31 December 2021. IITA receives funding for research on
yams from the CGIAR Research Program on Roots, Tubers, and Bananas (CRP-RTB) between
2011–2021 and the ongoing CGIAR Seed Equal Initiative, both supported by CGIAR Trust
Fund donors.
Conflicts of Interest: The authors declare no conflict of interest. The funders had no role in
the design of the study; in the collection, analyses, or interpretation of data; in the writing of
the manuscript, or in the decision to publish the results.
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