1 of 13Food and Energy Security, 2024; 13:e70010 https://doi.org/10.1002/fes3.70010 Food and Energy Security ORIGINAL ARTICLE OPEN ACCESS A Functional Analysis of Inflorescence Architecture in Musa L. (Musaceae) David W. Turner1 | D. Jane Gibbs2 | Walter Ocimati3 | Guy Blomme4 1Institute of Agriculture, The University of Western Australia, Perth, Western Australia, Australia | 2Consultant, Perth, Western Australia, Australia | 3Bioversity International, Kampala, Uganda | 4Bioversity International, Addis Ababa, Ethiopia Correspondence: David W. Turner (david.turner@uwa.edu.au) Received: 20 June 2024 | Revised: 20 September 2024 | Accepted: 27 September 2024 Funding: This work was supported by the Directorate General for Development, Belgium through the Consortium for Improving Agriculture- based Livelihoods in Central Africa (CIALCA). We thank the CGIAR initiative on Transforming Agrifood Systems in West and Central Africa (TAFS- WCA) for covering the staff time of the Bioversity authors. We acknowledge the financial contribution of the CGIAR Research Programme on Roots, Tubers and Bananas and the CGIAR funding donors. Funding bodies were not involved in any part of the execution of this research. D.W.T. and D.J.G. did not receive funding from any agencies. Keywords: banana | cincinni | cushion meristem | inflorescence meristem | Musa | peduncle | plantain ABSTRACT Inflorescence architecture underpins sexual reproduction in wild Musa species and productivity in edible banana cultivars. In a functional analysis, we identified the apical inflorescence and lateral ‘cushion’ meristems and the change in flower type as the three primary components that generate inflorescence architecture. Five genotypes of two clone sets of edible plantains (Musa AAB) were grown for four generations along an elevation gradient (1100–2200 m, 16°C–24°C) straddling the equator in the humid highlands of East Africa. The data consisted of reproductive peduncle length at harvest (Pr), fruit per hand (Fh) and hands per bunch (Hb). The activity of the apical inflorescence meristem drives peduncle length and gen- erates lateral ‘cushion’ meristems which determine Fh. However, Hb is determined by a change in flower type—from fruit forming to non- fruit forming. Site temperature affected Hb more than Fh, while the development of the genet (rhizome) changed the allocation of resources between Hb and Fh, independently of the effect of site temperature. Clone sets differed in their response to genet development. Cooler temperatures reduced the number of fruit- forming flowers in an inflorescence and changed the balance away from female towards male flowers. In banana breeding schemes, manipulating inflores- cence components independently raises options for producing genotypes better suited to markets, environments and cultural practices. 1 | Introduction 1.1 | Inflorescence Architecture Inflorescences of Musa L. (Musaceae), whether of the wild spe- cies or edible cultivars, are spectacular because of their charac- teristic form, large size and variety of colours. The fruit of edible cultivars contributes to our diet and is important in smallholder agriculture and in commerce. Morphologically, the inflorescence is a thyrse. The main axis, or peduncle, is a raceme with the inflorescence meristem at its apex. It supports lateral branches or nodes that originate from the activity of the inflorescence meristem. Each lateral node is called a ‘hand’ and is itself an inflorescence: a scorpi- oid cyme or cincinnus (Fahn 1953; Kirchoff 2017). The cincinni arise from a lateral ‘cushion’ meristem subtended by a bract. The basal section of the reproductive peduncle contains fruit- forming flowers that are female, or in some wild species, may be This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2024 The Author(s). Food and Energy Security published by John Wiley & Sons Ltd. https://doi.org/10.1002/fes3.70010 https://doi.org/10.1002/fes3.70010 mailto: https://orcid.org/0000-0002-0117-2926 mailto:david.turner@uwa.edu.au http://creativecommons.org/licenses/by/4.0/ http://crossmark.crossref.org/dialog/?doi=10.1002%2Ffes3.70010&domain=pdf&date_stamp=2024-10-16 2 of 13 Food and Energy Security, 2024 hermaphrodite (perfect). The distal section has cincinni of non- fruit- forming flowers that are either neuter or male (Fahn 1953; Simmonds 1966; Argent 1976). The change in flower type from female to neuter or male sets the limit of the fruit- forming flowers and defines the ‘bunch’ of commerce. Following the ABC model of flower develop- ment, changes in flower type involve a change in gene expres- sion in the androecium and gynoecium of developing flowers, including the whorls of male flowers in the Musaceae (Bartlett and Specht 2010). Dodsworth (2017), Irish (2017) and Bowman and Moyroud (2024) present recent reviews of the ABC model. The changes in flower type in Musa are significant as the ova- ries of neuter and male flowers are greatly reduced and do not contain ovules, compared with female flowers (Fahn  1953). Male flowers are short- lived and usually abscise, leaving a ‘clean’ male peduncle where they occur. The inflorescence meristem at the apex of the peduncle terminates when it forms a final cincinnus, or flower, of neuter or male flowers (White 1928; Simmonds 1954; Adheka and De Langhe 2018; Adheka et al. 2018). Conveniently, the endpoint of activities of the three primary components of inflorescence architecture can be measured at fruit maturity. The length of the peduncle (Pr), with its female and male sections, the number of flowers in individual nodes of the female peduncle (fruit per hand, Fh) and the number of nodes of fruit- bearing flowers on the peduncle (hands per bunch, Hb) can be easily measured. Termination of the peduncle may occur either well before flowering immediately after female flowers have formed, or at an intermediate stage to coincide with flowering, or well after flowering, after hundreds of nodes of male flowers have formed (White  1928; De Langhe  1961). Resulting differences in the length of the male peduncle, which occurs among the wild Musa species (Argent 1976) as well as cultivated genotypes (De Langhe 1961), contributes to changes in the sex ratio within an inflorescence. The product of Fh and Hb within the female peduncle deter- mines the total fruit- forming flowers per bunch, Fb. The number and arrangement of female flowers in the wild- seeded bananas describe the spread of receptive flowers in space and time. In the edible bananas, where the parthenocarpic development of fruit is the focus, the number and arrangement of female flowers is important in productivity and marketing. 1.2 | Genotypes, Genes and Development of the Genet Clone sets of plantains (Musa AAB) differ in their inflores- cence architecture (De Langhe  1961; Tezenas du Montcel, De Langhe, and Swennen  1983; Swennen, Vuylsteke, and Ortiz  1995). For example, the French and False Horn clone sets differ in the number of fruit per bunch (Fb) and in the length of the male peduncle. The differences in Fb are caused more by differences in fruit per hand (Fh), than in hand num- ber (Hb). These differences make them suitable for examining changes in inflorescence architecture across environments. At the molecular level, in the East African Highland bananas (AAA), Nyine et  al.  (2019) established associations between Hb and loci on chromosome 9 and Fb at two loci on chromo- some 10, reinforcing the genetic component of inflorescence architecture. They did not include the number of fruit per hand (Fh) as a separate trait despite it being a component of Fb. Molecular studies indicate an association between a trait and genetic loci, but other studies are needed to show how these associations may be expressed differently across en- vironments or during genet development. The genet is the branched rhizome supporting ratoon crops. Nyine et al. (2017) pointed out the need to understand variation in the expression of traits in different environments to increase the accuracy of models used in genomic selection. The first generation of a banana plant has few resources im- mediately available from the parent mat or genet (Turner et al. 2020). Rather, lateral buds (suckers) grow from the newly established plant, forming the next generation and the new genet. In a functioning genet, the rhizome of a previous gener- ation provides reserves for subsequent generations (Walmsley and Twyford  1968; Robinson and Nel  1985; Daniells and O'Farrell  1987) and influences gene expression in the in- florescence. In ratoon crops, the genet usually contributes more fruit- forming flowers than are present in the plant crop (Simmonds 1966). By comparing data from the plant crop (C1) with those of ratoon crops (C2–C4), the contribution of the genet to the architecture of the inflorescence can be evalu- ated, especially where environments are relatively stable within and between years. 1.3 | Inflorescence Architecture and Environment Over the last 130 years, studies of the inflorescence of Musa have described its features and interpreted these in devel- opmental and botanical terms (Baker  1893; White  1928; Fahn 1953; Alexandrowicz 1955; Ram, Ram, and Steward 1962; Ganry 1977; Kirchoff 2017). Other studies have linked bunch formation to a single environment (Summerville  1944; Ganry  1977; Robinson and Nel  1985) but to our knowledge, the relationships between the functional components of in- florescence architecture across different environments have not been explored. The magnitude of Hb, Fh and peduncle lengths are expected to be affected differently by environ- mental and plant resources because of their different origins. Together, they produce inflorescence architectures that are quantitatively different between environments, crop cycles and clone sets. Our hypothesis was that the independent components Hb, Fh and peduncle length will respond differently to environment and genet development in different genotypes. Previous publications, arising from the experiment reported here, examined the yield, agronomic (Sikyolo et al. 2013) and developmental aspects (Turner et  al.  2016) of the plant crop cycle. Sivirihauma et  al.  (2016) examined the yield and agro- nomic performance of the ratoon crop cycles while Turner et al. (2020) examined vegetative reproduction across all cycles. Here, we evaluate our hypothesis about how the environment and genet development functionally change inflorescence ar- chitecture in Musa. 20483694, 2024, 5, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/fes3.70010 by R eadcube (L abtiva Inc.), W iley O nline L ibrary on [16/10/2024]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 3 of 13 2 | Materials and Methods 2.1 | Data and Its Analysis We sought to establish relationships between the functional components of inflorescence architecture and site character- istics, particularly mean annual temperature. At the equator, temperature is seasonally stable at each site but varies from one location to another associated with their different eleva- tions. Edaphic factors differed between sites, particularly soil P and, to a lesser extent, K concentrations (Sikyolo et al. 2013). Consequently, data were modified to account for these differ- ences. We used ANOVAs to determine the significance of the ef- fect of sites, cultivars and crop cycles on measured variables and regressions to determine the association between site tempera- ture and each modified variable. At Ndihira, the highest site, cool temperatures affected fruit development and counts were based only on those fruit that met commercial requirements. Counts of Fb and Hb made at harvest did not reflect these values at flowering and so adjustments were made to arrive at a set of calculated values of Fh and Hb at flowering for Ndihira. The experimental plots were rain- fed and soil water supply may be important as well as site temperature. Unfortunately, there were uncertainties in the calculation of rainfall and evaporation was measured at only one site (Sikyolo et al. 2013). Soil texture may be a proxy for soil water holding capacity and rooting depth but including it in the regression analyses only accounted for a small amount of variation between sites in addition to that accounted for by site temperature. Therefore, we accepted site temperature as the dominant environmental factor affecting the variables of interest. In addition, measurements of site tempera- ture were compared with calculated temperature using the adi- abatic lapse rate, with good agreement. 2.2 | Sites, Cultivars and Clone Sets The field experiment in North Kivu Province, Democratic Republic of Congo, straddled the equator and began in 2008 (Sikyolo et al. 2013). The sites were at Mavivi, elevation 1066 m, mean annual temperature 23.5°C; Maboya, (1412 m, 21.4°C); Butembo (1815 m, 18.8°C) and Ndihira (2172 m, 16.1°C). Mavivi is the most northerly site at Lat. 0.569° N and Ndihira is the most southerly site at Lat. −0.250° S (Figure 1) (Sikyolo et al. 2013). Means of daily maximum and minimum temperature differed by about 12°C across all sites but within each site mean monthly temperatures were reasonably constant throughout the year with month- to- month variation being only 1.4°C. The five plantain cultivars of medium height (Musa AAB Plantain subgroup) represented two Plantain clone sets, French and False Horn (Sikyolo et al. 2013; Sivirihauma et al. 2016). Each cultivar grows commonly in North Kivu but not across the range of elevations included here (Sikyolo et al. 2013). The morphological features of the inflorescence used to classify clone sets (Tezenas du Montcel, De Langhe, and Swennen 1983; Swennen, Vuylsteke, and Ortiz  1995) varied across sites and so we reassessed the accepted clonal grouping of the culti- vars. Here, we grouped ‘Kotina’ and ‘Vuhembe’ with the False Horn clone set and ‘Musilongo’, ‘Nguma’ and ‘Vuhindi’ with the French clone set. This differed from the arrangement used by Sikyolo et al.  (2013); Sivirihauma et al.  (2016) and Turner et  al.  (2016, 2020) who placed ‘Musilongo’ in the False Horn clone set and ‘Vuhembe’ in the French clone set. The clone sets differ in their inflorescence architecture. Genotypes in the French clone set usually have more Fb (Fb = 70–130 cf. 23–70) and longer male peduncles, than those of the False Horn clone set; however, Hb is similar in both (5–11) (Tezenas du Montcel, De Langhe, and Swennen  1983). Thus, French genotypes have more fruit per hand than those of False Horn. The shorter male peduncle of the False Horn genotypes arises from early termination of the inflorescence meristem. Early cultivators may have selected for this difference, but it is also seen in the wild Musa, for example, in Musa monticola found at elevations of 1200–1700 m in Sabah (Argent 2000) and in Musa acuminata ssp. banksii which contributed to the A ge- nome of the edible AAB plantains. A common feature of plantain culture is a decline in yield (kg/ha/year) from one generation to the next that may be at- tributed to low soil fertility, pest and disease status and de- layed sucker production. The onset of decline can be rapid happening in two cycles but no decline is observed when plan- tains are cultivated in home gardens (Braide and Wilson 1980; Salau, Opara- Nadi, and Swennen 1992). This experiment fell between these two extremes because soil fertility was suffi- cient to minimise the effects from the decline in addition to the separation of the plots from nearby banana fields, reducing the transfer of pests and disease. Some decline was observed but not uniformly across sites or cultivars. Its contribution to missing data was small compared with damage from storms and wind and, at lower elevations, delayed suckering and wee- vil borer (Cosmopolites sordidus). The decline appeared in cycles 3 and 4 at Maboya and more so at Mavivi (Sivirihauma et al. 2016). At the end of the experiment, there were 4 missing genets at Mavivi to 2 at Ndihira. Missing data reduced the error degrees of freedom in the ANOVAs but, with 15 single- genet replications, not sufficiently to limit the precision of the statistical analyses. FIGURE 1 | The location of the four sites in North Kivu, DRC, in relation to latitude (South/North) and longitude (East). The legend shows the respective elevations (m) and annual mean temperature (°C) of the sites. One degree of longitude at the equator (0° latitude, x- axis) is equivalent to 111 km. -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 29.0 29.2 29.4 29.6 29.8 30.0 La tit ud e, d eg re es S ou th /N or th Longitude, degrees East Mavivi, 1070 m, 23.5C Maboya, 1410 m, 21.4C Butembo, 1820 m, 18.8C Ndihira, 2170 m, 16.1C 20483694, 2024, 5, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/fes3.70010 by R eadcube (L abtiva Inc.), W iley O nline L ibrary on [16/10/2024]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 4 of 13 Food and Energy Security, 2024 2.3 | The ‘Modified’ Data Set and a Calculated Data Set for Ndihira We took account of the soil concentrations of P and K (Sikyolo et  al.  2013) and ‘modified’ Fh, Hb, Fb and Pr as described in Turner et al. (2020) and Blomme et al. (2020). The calculated in- dices provided the proportional effect of nutrient supply assum- ing adequate supply is 1.0. The supply indices for P for each site were: Mavivi 0.68, Maboya 0.71, Butembo 0.78 and Ndihira 0.93 and for K: Mavivi 0.91, Maboya 0.90, Butembo 1.00 and Ndihira 0.94. Less soil P was available at lower than at higher elevations, but K supply was close to ‘adequate’ at most sites. K supply was less likely to constrain growth than P supply. As Fb = Fh × Hb (Equation 1), the values of Hb and Fh were modified by dividing the measured values by SQRT (P or K) of the respective nutrient supply indices, as appropriate and Fb calculated. Reproductive peduncle length was modified in the same way. At Ndihira, the highest and coolest site, each bunch had fruit but only those of commercial size at maturity were counted in the main experiment (C1–C4). This excluded deformed fruit arising from female flowers which did not develop under the cool conditions, but were present at flowering (Sivirihauma et al. 2016). This procedure excluded Ndihira for determining the association between site temperature and parameters Fb, Hb and Fh. We required the total number of fruits formed per bunch at Ndihira, whether they had grown or not. Counts of total fruit and hand numbers on bunches in ratoon crop cy- cles (C > 4) at Butembo and Ndihira were used to calculate the Ndhi ratio (= value at Ndihira/value at Butembo) for each pa- rameter (Table 1). The measured values of Fh, Hb or Fb from Butembo, multiplied by the relevant Ndhi ratio (Table 1), gave the calculated data for Ndihira for each cultivar. The Ndhi ratios for ‘Musilongo’ are lower than for other cultivars be- cause the bunches at Ndihira were much smaller than those at Butembo. ‘Measured’ data collected in the main experiment at fruit ma- turity were the length of the female and male sections of the peduncle (C2–C4) and for the female peduncle, the total num- ber of fruit per bunch, Fb and number of hands per bunch, Hb (C1–C4). We calculated Fh, (Equation 1) the length of the reproductive peduncle and the proportion of it that supported fruit (Pf ). The number of fruit on an inflorescence of Musa, Fb, is 2.4 | The Exponential Reciprocal Function and the Curvature Coefficient Regression analyses of the modified data of clone sets (individual cultivars were used in the ANOVAs) established the relationships between site temperature and inflorescence variables Fh, Hb, Fb, Pr and Pf. The exponential reciprocal function provided the best fit for the data based on F ratio, probability and r and it fitted all pa- rameters of the inflorescence. The function has the following form: where Y is the parameter or variable, T is site temperature, A is a theoretical asymptote or maximum value of Y and C is a cur- vature coefficient, which is negative. The asymptote A has little biological meaning in the current context because of the lim- ited range of site temperatures (16.1°C–23.5°C). The coefficient Tb, could be interpreted as a base temperature where Y = 0.0. However, we chose to vary it to estimate the maximum F ratio in the regression ANOVA. We used the correlation coefficient, r, to assess the strength of the relationship between a variable and site temperature and C to assess its shape in a quantitative way. For 0.0 < r < 0.70 the association was weak; moderate when 0.70 < r < 0.90 and strong when r > 0.90. An increasingly negative value of C visually indi- cated a greater displacement of the function from the asymptote, A and a change in the shape of the relationship between the vari- able and site temperature. The values of C were allocated to three categories based on their magnitude. For −0.01 < C < −0.10 the parameter was stable over most of the temperature range, while for −0.10 < C < −1.0 the parameter changed over the tempera- ture range of interest with the change becoming greater as C became increasingly negative (C < −1.0). 2.5 | The Effect of the Genet To examine the effect of the genet on the three parameters of the inflorescence in each clone set we compared Fh, Hb and Fb for C1 (cycle 1, genet absent) with those of C2–C4 (genet present) in a graphical form. In this case, the values for C1 at Ndihira were calculated from the values at Butembo using the Ndhi ratio de- rived from ratoon crop cycles (Table 1). 2.6 | Statistical Analyses The experiment at each site was a randomised block design with 15 single- genet replications (Sikyolo et al. 2013). For measured data ANOVAs were calculated using R (R Core Team 2019) and treatment means were compared using LSD at p = 0.05. The LINEST function in Excel (v 2203) fitted the regressions of the exponential reciprocal equation using a natural log transform of the data (Equation 3): (1)Fb = Hb × Fh (2)Y = A ⋅ exp( − C ∕(T − Tb)) (3)ln(Y ) = ln(A) − C ∕(T − Tb) TABLE 1 | The Ndhi ratios of Fh, Hb and Fb for the five cultivars of the main experiment used to calculate the Ndihira data set. Data were from cultivars present after the main experiment (Cycle > 4) and were adjusted for soil P and K concentrations. Cultivar Ndhi ratio Fh Hb Fb ‘Kotina’ 0.97 0.60 0.58 ‘Vuhembe’ 0.87 0.71 0.62 ‘Musilongo’ 0.49 0.35 0.17 ‘Nguma’ 0.85 0.70 0.60 ‘Vuhindi’ 0.81 0.66 0.53 20483694, 2024, 5, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/fes3.70010 by R eadcube (L abtiva Inc.), W iley O nline L ibrary on [16/10/2024]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 5 of 13 Differences between values of −C for clone sets were evaluated with t- tests at p = 0.05. The impact of modifying the data was evaluated by comparing variation within the data set before and after modification. For the SQRT(PK) modification, parameter values were divided by the soil supply index, which was less than 1.0 and so the variation within the whole data set increased. Examining the F ratio for sites indicated how the ANOVA had partitioned variation between and within sites (Mead, Curnow, and Hasted 1993). 3 | Results 3.1 | The Effect of Site and Cultivar on Measured Data of Hb, Fh, Fb, Pr and Pf Increasing elevation decreased Hb, especially at Ndihira (Table 2A). Across the other three sites, with increasing eleva- tion, Hb fell significantly (p = 0.05) by about 30% in the two False Horn cultivars but not as much (15%) in two of the three French cultivars. The exception was the French cultivar ‘Nguma’ which had more hands at Butembo (8%) than at the lowest elevation at Mavivi (Table 2A, p = 0.05). False Horn cultivars had fewer Fh (11–17) than the French cultivars (17–24). Across sites, measured Fh was relatively sta- ble but severely reduced in all cultivars at Ndihira (p = 0.05). The False Horn cultivar ‘Kotina’ was an exception because it had 30% less Fh at Mavivi, the lowest site, than at Butembo (Table 2A). The effect of sites on the number of Fb in different cultivars re- flected changes in Fh and Hb, the components of Fb. Usually, Fb declined from Mavivi up to Butembo but these changes, while significant (p = 0.05), differed in magnitude according to cul- tivar. The Fb of ‘Vuhembe’ fell by 24% but ‘Nguma’ had more Fb at Butembo than at Mavivi, an increase of 9%. In ‘Kotina’, opposing changes of Hb and Fh with increasing elevation stabi- lised Fb from Mavivi up to Butembo. ‘Musilongo’ and ‘Vuhindi’ had about 8% less Fb at Butembo than at Mavivi (Table 2A). At Maboya, Fb in all cultivars was less than at Mavivi or Butembo. Across sites and cultivars at fruit maturity, the reproductive pe- duncle length varied two- fold from about 80–160 cm (Table 2B). In False Horn cultivars, the inflorescence meristems had ter- minated by fruit harvest but in the French cultivars were still growing. Differences in Pr between cultivars were greater at lower than at higher elevations and the two False Horn cultivars had a Pr 15–60 cm shorter than those of the three French culti- vars (p = 0.05). The exception was ‘Vuhembe’ which had a much longer reproductive peduncle than expected at Ndihira. From Mavivi to Butembo, the False Horn cultivars had a high Pf (66%–74%) compared with the French cultivars (52%–60%) (Table 2B). At Ndihira, the Pf of all cultivars in both clone sets was reduced to 17%–26%, only one third of the values reached at sites of lower elevation. At Maboya, for each cultivar, the fe- male proportion of the peduncle, Pf, was like those at Mavivi and Butembo, even though the absolute values of Hb, Fh, Fb and Pr differed greatly between sites. 3.2 | Changes to the Data Caused by Modification As expected, modifying the measured data increased the site means for Hb, Fh and Fb, but to different degrees, depending on the magnitude of the PK supply index at each site (Table 3). At Mavivi and Maboya, modification increased the means of Hb and Fh by about 27%. At Butembo the increase was 14%, about half of this. The calculated data for Ndihira increased Hb by 35% more than the measured value and Fh almost five- fold more. These increases in Hb and Fh flowed through to the Fb data where the increase was 61% at Mavivi and eight- fold for the calculated Ndihira data (Table 3). 3.3 | Fitting the Exponential Reciprocal Function to the Modified Data Exponential reciprocal functions where site temperature was fitted to the data for each architectural parameter were signifi- cant at p = 0.001, except for Fh of the False Horn clone set which was not significant (Table 4). Depending on the variable and the clone set r ranged from 0.08 to 0.94. In both clone sets, Hb was more strongly associated with site temperature, T, (r > 0.70) than Fh (r < 0.51) but Pf had the strongest association (r > 0.90). In the French clone set, Pr had a moderately strong association with T (Table 4). In the False Horn clone set, Fh had weak associations with T, as did Pr (Table 4). In this data set, Hb rather than Fh, drove the curved association between Fb and T in both clone sets. Indeed, Fh was much more stable than Hb over the range of T included here. In the False Horn clone set, Pr was stable across the temperature range of interest, with C = −0.016. In contrast, the French cultivars had a moderate response to T, with C = −0.581. In the modified data, where the Ndihira values were calculated, warming temperatures increased Hb two- fold (Figure  2A). At the coolest temperature, the French and False Horn clone sets had similar Hb, while at higher temperatures the French clone set had more Hb than the False Horn clone set. The False Horn clone set showed an almost linear reduction in Hb as the tem- perature fell, but the Hb of the French clone set was more stable at warmer temperatures (Figure 2A). Across the three warmer sites, Fh of the French clone set was about 50% more than the False Horn and both clone sets showed a stable relationship with T (Figure 2B). At the coolest site, the Fh of the False Horn clone set was little affected but was reduced in the French clone set. Fb reflected the changes of its two com- ponents, Fh and Hb. As site temperature rose, Fb increased in the two clone sets over the range (Figure 2C). The French clone set had a longer reproductive peduncle, Pr, than the False Horn clone set (Figure  3A). In the False Horn clone set, the shorter Pr was stable across the temperature range, but cooler temperatures shortened Pr in the French clone set such that at the coolest temperature Pr was similar in length in both clone sets (Figure 3A). 20483694, 2024, 5, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/fes3.70010 by R eadcube (L abtiva Inc.), W iley O nline L ibrary on [16/10/2024]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 6 of 13 Food and Energy Security, 2024 The False Horn clone set had a higher proportion of female re- productive peduncle than in the French clone set (Figure 3B), reflecting in part the differences in total Pr length (Figure 3A). Low temperatures severely reduced the female proportion to a fifth in both clone sets. 3.4 | Effect of the Genet on Hb, Fh and Fb The presence of the genet in the ratoons reduced Hb but increased Fh, compared with the plant crop where the genet was absent (Figure  4A,B). Cultivars of the False Horn clone set showed a TABLE 2 | Measured values of A. Hb, Fh, Fb and B. Pr and Pf of five cultivars of plantains (AAB) from two clone sets grown over four sites of differing elevations in North Kivu, Democratic Republic of Congo. The data are from three ratoon crop cycles (C2–C4). For each mean, n = 45. A Parameters of the female peduncle Parameter Hands/bunch, Hb Clone set False Horn French Site/cultivar ‘Kotina’ ‘Vuhembe’ ‘Musilongo’ ‘Nguma’ ‘Vuhindi’ Mavivi, 1066 m 5.29 4.67 5.57 5.42 5.63 Maboya, 1412 m 3.69 3.73 3.91 4.73 4.67 Butembo, 1815 m 3.60 3.49 4.73 5.86 4.73 Ndihira, 2172 m 2.12 2.04 2.36 2.07 1.94 LSD, p = 0.05 0.23 Parameter Fruit per hand, Fh Mavivi 11.8 14.4 20.2 24.1 21.8 Maboya 14.6 13.9 21.9 20.9 17.2 Butembo 17.4 14.6 21.6 24.2 24.4 Ndihira 2.6 3.3 2.4 2.9 3.5 LSD, p = 0.05 0.2 Parameter Fruit per bunch, Fb Mavivi 58.8 65.7 110.8 127.4 120.2 Maboya 52.9 50.4 83.1 97.1 79.0 Butembo 59.8 49.5 100.3 139.2 113.3 Ndihira 5.0 6.0 5.0 5.5 5.9 LSD, p = 0.05 1.3 B Dimensions of the reproductive peduncle Parameter Length of reproductive peduncle, Pr, cm Cultivar ‘Kotina’ ‘Vuhembe’ ‘Musilongo’ ‘Nguma’ ‘Vuhindi’ Mavivi 128 95 143 148 142 Maboya 78 80 121 141 111 Butembo 109 95 137 159 132 Ndihira 107 130 105 100 107 LSD, p = 0.05 3 Parameter Female proportion of reproductive peduncle, Pf, % Mavivi 74 74 57 66 60 Maboya 73 69 52 61 56 Butembo 70 66 58 59 57 Ndihira 22 17 26 26 18 LSD, p = 0.05 1 20483694, 2024, 5, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/fes3.70010 by R eadcube (L abtiva Inc.), W iley O nline L ibrary on [16/10/2024]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 7 of 13 greater reduction in Hb than did those of the French clone set. The reduction in Hb from C1 to ratoon crops occurred at all sites and in a comparable manner, especially for the False Horn cultivars. For False Horn cultivars at Mavivi, the changes in Hb and Fh compensated one another giving a similar Fb from plant crop to the ratoon crops as the genets developed. However, as elevation increased, the bunches of ratoon crops had fewer Fb than the plant crops and this was particularly noticeable at Ndihira, the highest and coolest site (Figure 4A). For the French cultivars, the changes in Hb and Fh were such that at all sites the Fb of ratoon bunches was greater than those of plant crops (Figure 4B). So, even though there was a reduction in Hb, the increase in Fh more than compensated, thus increasing Fb. 4 | Discussion Site temperature and the presence of the genet affected the three independent components of inflorescence architecture in both clone sets of edible Musa (AAB) in this experiment, broadly sup- porting the hypothesis. In both clone sets, Fb decreased at cooler temperatures, but lower temperatures affected Hb more than Fh. Thus, the activity of the lateral cushion meristem in producing fruit- forming flow- ers within a node is less affected by changes in site temperature than the change in gene expression producing the switch from fruit forming to non- fruit- forming flowers. For the genet, across all site temperatures, Hb was lower in the ratoons than in the plant crop, while Fh increased. These effects happened at all sites and so are independent of temperature, indi- cating a change in the allocation of reserves with genet develop- ment. This was an unexpected result as usually Hb and Fh benefit from the extra resources available in the genet. The clone sets dif- fered in the magnitude of the changes in Hb and Fh, but not in their general direction. In the French clone set, the genet boosted Fb because the increase in Fh more than compensated for the re- duced Hb. In the False Horn clone set, the increase in Fh was not sufficient to compensate for the reduced Hb. We suggest that the source of the reserves allocated to the lateral cushion meristems to determine Fh, differs from that used to hasten the onset of changes in gene expression in nodes of fruit- forming flowers that determine Hb. The reserves present in the genet may be allocated to increase Fh production in ratoon crop cycles, while those usu- ally allocated to Hb were reduced, possibly because of allocation to developing sib- suckers in this experiment (Turner et al. 2020). 4.1 | Fruit per Bunch, Fb, per Hand, Fh and Hands per Bunch, Hb Increasing Fb can contribute to increased seed production in individual inflorescences of wild Musa spp. and to increased TABLE 3 | The effect of (i) modifying Hb, Fh and Fb for P and K concentrations in soil, SQRT(PK) and (ii) calculating the Ndihira data using the Ndhi ratio procedure on site means of parameters of inflorescence architecture. Data are for ratoon crops C2–C4 averaged over all cultivars. ‘Measured’ is the original data. Site Mavivi Maboya Butembo Ndihira LSD Site temperature, °C 23.5 21.4 18.8 16.1 p = 0.05 Data/parameter Hands/bunch, Hb Measured 5.31 4.15 4.48 2.11 0.10 SQRT(PK) 6.75 5.19 5.07 2.25 0.12 SQRT(PK), Ndhi calc 6.75 5.19 5.07 2.86 0.12 Parameter Fruit/hand, Fh Measured 18.3 17.6 18.9 2.8 0.6 SQRT(PK) 23.3 22.0 23.1 3.0 0.7 SQRT(PK), Ndhi calc 23.3 22.0 23.1 17.6 0.8 Parameter Fruit/bunch, Fb Measured 97 73 92 6 2 PK 156 113 118 6 3 PK, Ndhi calc 156 113 118 52 3 Parameter Total peduncle length, Pr, cm Measured French 144 125 143 104 4 Measured False Horn 112 79 102 118 4 SQRT(PK) French 183 156 162 111 3 SQRT(PK) False Horn 142 99 115 127 3 20483694, 2024, 5, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/fes3.70010 by R eadcube (L abtiva Inc.), W iley O nline L ibrary on [16/10/2024]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 8 of 13 Food and Energy Security, 2024 bunch weight in the edible bananas. In the data reported here, Fb was affected by site temperature, clone set and the genet. There was a clear difference between clone sets (Figure 2C) in absolute terms, but for both clone sets the increase in Fb with warming site temperatures was of a similar proportion, about 100% across the range (Figure 2C). This would suggest a simi- lar response of each clone set to temperature, at least in relative terms. We found that the responses of Fh and Hb to site tempera- ture differed and so while at the level of Fb, the response of the two clone sets was similar, they arrived at that ‘similarity’ by different pathways. Morphologically, each node on the peduncle consists of a bract subtending the lateral ‘cushion’ meristem from which the flowers arise and fruit are attached. The number of flowers and subsequently Fh is determined during the early develop- ment of the hand, with a single cincinnus taking up to seven plastochrons to form (Fahn 1953). The flower initials that arise within the cushion meristem first appear about three nodes distant from the apical inflorescence meristem (White  1928; Fahn  1953; Ram, Ram, and Steward  1962; Moncur  1988; Kirchoff 2017). At this point, the peduncle has already begun to expand radially. The cushion meristem, subtended by the bract, is arc- shaped on the expanding peduncle and its final length can physically limit Fh. In the developing inflorescence, the basal width of the bract provides the outer limit of the cushion meristem as the radial growth of the base of the bract is completed before the growth of the cushion meristem it subtends (Fahn 1953). The cushion may not develop to the full extent of the bract base (Kirchoff 2017) and the number of flower initials that form then depends on the length of the cushion and the space occupied by each flower meristem. Flower meristems appear within the cushion, usually in a se- quence best described as a cincinnus (Fahn 1953; Kirchoff 2017). If temperature affects the rate at which flower meristems are produced, but not the size of the bract base then, because the latter limits the length of the cushion meristem, it is unlikely that an association between site temperature and Fh will be es- tablished. Consistent with this interpretation, the association between site temperature and Fh was weak in the data illus- trated in Figure 2B except for lower Fh in the French clone set at Ndihira, the coolest site. Fh varies from hand to hand within an inflorescence (Alexandrowicz  1955; De Langhe  1961; Swennen and Vuylsteke 1987) but associated data for the width of the base of the subtending bract are not available. Measurements of pedun- cle size and bract basal width would be informative in identify- ing the factor(s) reducing Fh in the cultivars of the French clone set at Ndihira. Hb is a function of the rate of lateral node production by the inflorescence meristem and an irreversible change from fruit forming to non- fruit- forming flower types along the develop- mental sequence of the peduncle. In Musa, there are several flower types: fruit- forming hermaphrodite and female flowers and non- fruit- forming transitional, neuter and male flowers. TABLE 4 | Coefficients of the exponential reciprocal functions in Figure 2A–C (Equation 3), fitted to data for five parameters each of False Horn and French clone sets. Within a parameter, A coefficients followed by the same uppercase letter are not significantly different at p = 0.001 (t- test). Tb is the coefficient that maximises the F ratio. Within a parameter, C coefficients followed by the same uppercase letter are not significantly different at p = 0.001 (t- test). Clone set A Tb, °C Curvature coefficient, C r p Hands per bunch, Hb French 6.98 A 15.1 −0.81 A 0.75 *** False Horn 20.1 B 5.0 −22.78 B 0.87 *** Fruit per hand, Fh French 26.2 A 15.9 −0.074 B 0.51 *** False Horn 16.8 B 15.9 −0.010 C 0.08 0.097 Fruit per bunch, Fb French 190 A 15.2 −1.09 B 0.74 *** False Horn 179 B 10.5 −8.21 C 0.83 *** Length of reproductive peduncle, Pr, cm French 183 B 15.0 −0.581 B 0.73 *** False Horn 115 C 15.9 −0.016 C 0.16 0.001 Proportion of peduncle with female flowers, Pf French 60.8 A 15.9 −0.201 B 0.92 *** False Horn 75.5 B 15.9 −0.290 C 0.94 *** ***Probability for the regression is < 0.001. 20483694, 2024, 5, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/fes3.70010 by R eadcube (L abtiva Inc.), W iley O nline L ibrary on [16/10/2024]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 9 of 13 Not all species or cultivars have all types, but all species and cul- tivars have the change from fruit forming to non- fruit- forming flowers. The change in flower type separates the basal section with its fruit- forming hands from the non- fruit- forming distal section of the inflorescence (White 1928). If Hb is determined by a permanent switch in gene expression within the whorls (W3 and W4) of developing flowers, then accumulated reserves may function as an independent fac- tor affecting the timing of this change. This interpretation is consistent with the observation that the number of flowers per hand does not normally change with the change in flower type, from one hand to another, during inflorescence development (Alexandrowicz 1955; Swennen and Vuylsteke 1987). Compared with Fh, Hb was quite sensitive to site temperature (Figure  2A). While Hb was greatest at the warmest site and least at the coolest site for both clone sets, there was a differ- ence between clone sets in response to temperature. Cultivars of the False Horn clone set showed an almost linear decline in Hb as temperature fell, whereas with the French clone set the decline in Hb with decreasing temperature was slight at first, then becoming increasingly greater as temperature fell. The rate at which the hands of female flowers are produced at the inflorescence meristem and the time from inflorescence ini- tiation to when the switch in gene expression occurs in whorls 3 and 4 of developing flowers, are the two processes that deter- mine Hb. The temperature of the meristem strongly affects the rate of node production with slower rates at cooler temperatures (Savvides et al. 2016). The change in flower type is sensitive to the quantity of reserves accumulated before the inflorescence was initiated (Turner and Gibbs 2018). Thus, the reserves affect FIGURE 2 | The association between site temperature and (A) Hb, (B) Fh and (C) Fb for False Horn and French clone sets of plantain. Curves are the exponential reciprocal function fitted to the modified data with the calculated data for Ndihira for cycles C2–C4 (False Horn n = 360, French n = 540). Points are site means (False Horn n = 90, French n = 135). Solid lines indicate the French clone set and broken lines the False Horn clone set. The C coefficient appears after the legend for each curve. For each parameter, all values of C are significantly different at p = 0.01. 0 1 2 3 4 5 6 7 8 15 17 19 21 23 25 Ha nd s/ bu nc h Site temperature, °C A. Hands/bunch False Horn, -22.8 False Horn means French, -0.82 French means 0 5 10 15 20 25 30 15 17 19 21 23 25 Fr ui t/ ha nd Site temperature, °C B. Fruit/hand False Horn, -0.010 False Horn means French, -0.074 French means 0 50 100 150 200 250 15 17 19 21 23 25 Fr ui t/ bu nc h Site temperature,°C C. Fruit/bunch False Horn, -8.21 False Horn means French, -1.099 French means FIGURE 3 | The association between site temperature and (A) Reproductive peduncle length, Pr, cm, (B) Proportion of peduncle that is female, Pf, %, for False Horn and French clone sets. Curves are the exponential reciprocal function fitted to bulked data for cycles C2– C4 (False Horn n = 360, French n = 540). Points are site means (False Horn n = 90, French n = 135). Solid lines indicate the French clone set and broken lines the False Horn clone set. The C coefficient appears after the legend for each curve. For each parameter, all values of C are significantly different at p = 0.01. 0 20 40 60 80 100 120 140 160 180 200 15 17 19 21 23 25 Re pr od uc tiv e pe du nc le le ng th ,c m Site temperature, deg C A. Peduncle length False Horn, 0.02 False Horn means French, -0.58 French means 0 10 20 30 40 50 60 70 80 15 17 19 21 23 25 Pr op or tio n of pe du nc le th at is fe m al e, % Site temperature, deg C B. Proportion of peduncle that is female False Horn, -0.29 False Horn means French, -0.20 French means 20483694, 2024, 5, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/fes3.70010 by R eadcube (L abtiva Inc.), W iley O nline L ibrary on [16/10/2024]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 10 of 13 Food and Energy Security, 2024 Hb indirectly through their accumulation before the inflores- cence formed and their subsequent effect on gene expression in the flowers when they begin to develop. 4.2 | Plant Reserves and Inflorescence Architecture As the plant moved from the plant (C1) to ratoon crop cycles (C2– C4), the genet developed with reserves present in the rhizome and stems of earlier generations becoming available for use by the current generation. These reserves complement the carbohy- drates available from the functional leaves of the current genera- tion with the expectation that the inflorescences of ratoons would be larger (more Hb and Fh) than those of the plant crop. This fea- ture is usually observed (Robinson and Nel 1990). However, the magnitude of the change may differ according to the genomic group and whether Fh and/or Hb is affected (Table 5). From the data of Turner and Hunt (1984), Fh increased pro- portionately much more than Hb as the genet developed. Cultivars of the AAA genomic group (mostly Cavendish gen- otypes) changed the most, increasing by 60% (Table 5). These data are consistent with the reserves accumulated by previous generations, which now form part of the genet, being used to support the development of the inflorescence of the current generation. The development of the genet in the French and False Horn clone sets decreased Hb at all four sites (Figure 4) in contrast to what may be expected based on the observations of Turner and Hunt (1984) across a range of genotypes (Table 5). On the other FIGURE 4 | The changes in Hb, Fh and Fb from plant crop (C1, base of arrows, genet absent) to ratoon crop cycles (C2, C3 and C4, tip of arrows, genet present) for (A) False Horn cultivars and (B) French cultivars. Data were ‘modified’ and the calculated Ndihira data were used for C1. Each symbol type represents a different site (see legend). Open symbols and dotted arrows show changes for Hb and Fb, solid symbols and arrows show changes for Hb and Fh. The arrows show the direction and amount of change from C1 to C2, C3 and C4. Each arrow is the linear trend line and starts at C1 and ends at C2, C3 and C4. The y- axes in A and B have different ranges and in A, for each point, n = 30 and for B, n = 45. 0 10 20 30 40 50 60 70 80 90 100 110 120 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 Fr ui tp er ha nd (F h, so lid )o rf ru it pe rb un ch (F b, op en ) Hands per bunch, Hb A. FALSE HORN Mavivi Fh Maboya Fh Butembo Fh Ndihira Fh Mavivi Fb Maboya Fb Butembo Fb Ndihira Fb 0 50 100 150 200 250 0 10 20 30 40 50 60 70 80 90 100 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 Fr ui tp er bu nc h, Fb Fr ui tp er ha nd ,F h Hands per bunch, Hb B. FRENCH Mavivi Fh Maboya Fh Butembo Fh Ndihira Fh Mavivi Fb Maboya Fb Butembo Fb Ndihira Fb 20483694, 2024, 5, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/fes3.70010 by R eadcube (L abtiva Inc.), W iley O nline L ibrary on [16/10/2024]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 11 of 13 hand, Fh increased from plant to ratoon crops at all sites except for the False Horn clone set at Ndihira, the coolest site. Turner and Gibbs (2018) used the data of Turner and Hunt (1987) from a plant crop to argue the case for Hb being affected by carbo- hydrate reserves accumulated by the plant before the inflorescence was formed. Removal of all leaves, or half of each leaf, during the mid- vegetative growth phase reduced Hb, formed in the following floral phase, by 40%–50%. Defoliation in the floral phase, when hands are forming, did not change Hb (Figure  5). A lesser pro- portional effect (20%–30%) of defoliation was recorded for Fh, but there was a phase shift as well. In contrast to Hb, Fh was reduced when plants were defoliated in their floral phase beginning −13 to −8 leaves before flowering, but not in the mid- vegetative phase (Figure 5). In the presence of the genet, defoliation had a lower proportional impact on Fh and Hb, with reductions of 7%–8%. However, Hb was reduced only when plants were defoliated in the mid- vegetative phase, not the floral phase, indicating Hb de- pends on reserves accumulated before the inflorescence is formed. With the genet present, defoliation in either the vegetative or floral phases reduced Fh, although the effect was small. Reserves influ- ence Fh more than current photosynthates when the genet is pres- ent, compared with its absence. If these relationships hold for the two Musa AAB clone sets grown in North Kivu, then a reduction of Hb in the ratoon crop cycles would imply that reserves accumulated before the inflo- rescence was present were not sufficient to delay the change in flower type and maintain or increase Hb. The reserves had either not been accumulated or had already been used for an- other purpose. The reduced Hb in the ratoon crop cycles (Figure 4) may have been caused by the allocation of resources to the development of sib- suckers rather than Hb. The reason for the difference in the behaviour of Hb between plant crop and ratoons in this experiment and that of Turner and Hunt (1984) may lie in the different agronomic strategies used for desuckering (prun- ing). Turner and Hunt (1984) used the single sucker follower system with surplus suckers removed three times per year, equivalent to 4–5 times per life cycle, meaning that suckers were removed when they were small. On the other hand, in the experiment conducted by Sikyolo et al. (2013), the suckers remained on the parent plant until flowering, when all were counted and removed except the one retained for the next gen- eration. This delay in desuckering meant that many suckers were more developed before their removal. Suckers remaining attached to the parent plant benefit considerably in terms of growth (Eckstein and Robinson 1999) and are likely to capture more resources, reducing the capacity of the ratoon sucker se- lected for the next generation to accumulate reserves in the mid- vegetative phase. Genet development had a very different effect on Fh compared with Hb. It increased Fb considerably. We attribute this to more reserves being allocated to the expanding tissues behind the in- florescence meristem allowing extended cushion meristems to develop across all site temperatures and in all ratoon crop cycles. The reserves accumulated before floral initiation that affect Hb, do not affect Fh and so the reserves that contribute to increased Fh in ratoon crops must have another source. This may be in the genet, which is absent from the plant crop. Hb and Fh, both of which contribute to inflorescence architecture in Musa are independent components affected differently by envi- ronmental and internal plant factors. These different mechanisms would allow changes in Hb and Fh in wild species that may affect success in pollination by visiting birds and animals. In cultivation, they offer options for managing the balance between Hb and Fh either genetically or by management practices. 4.3 | Peduncle Total Length, Pr and the Proportion That Was Female, Pf The timing of termination of the inflorescence meristem dif- fers between the two clone sets. The mature male peduncles of cultivars of the False Horn clone set contain about 50 nodes (De Langhe  1961), while those of the French clone set con- tain about 100. Since the plastochron of node production in the floral phase is about 5 times faster than the phyllochron (Turner 1981) and about 10–11 leaves emerge from a shoot in the floral phase, which ends at flowering, then in the False Horn clone set all nodes on the male peduncle present at fruit TABLE 5 | The proportional (%) change in Fh and Hb from the plant crop (no genet) to the second ratoon (genet present) for 24 Musa cultivars in the AAA, AAB + ABB, genomic groups grown in the subtropics of North- eastern New South Wales. Data from Turner and Hunt (1984). Genome (n) Increase in fruit/hand, Fh, % Increase in hands/bunch, Hb, % AAA (17) 60 15 AAB + ABB (7) 23 16 FIGURE 5 | The effect of defoliation at various stages before flowering of the plant crop (no genet) on the Fh and Hb of inflorescences that subsequently emerged, expressed as a proportion of the control (no defoliation). The inflorescence usually begins to form −11 leaves before flowering (range −8 to −14). Each point is for a single inflorescence. Data from Turner and Hunt (1987). y = 0.0105x2 + 0.3223x + 3.0609 R² = 0.6457 y = 0.0095x2 + 0.2445x + 2.2632 R² = 0.3364 0.00 0.20 0.40 0.60 0.80 1.00 1.20 -25 -20 -15 -10 -5 0 Hb ,F h pr op or tio n of co nt ro l Leaves between defoliation and flowering Hb Fh Poly. (Hb) Poly. (Fh) 20483694, 2024, 5, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/fes3.70010 by R eadcube (L abtiva Inc.), W iley O nline L ibrary on [16/10/2024]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 12 of 13 Food and Energy Security, 2024 maturity are already present at flowering. In this clone set, the inflorescence meristem will have terminated and the growth of the male peduncle after flowering, will be entirely due to elongation of the internodes. For the French clone set, termination of the inflorescence mer- istem occurs after fruit maturity, which is from 4 to 8 months after flowering, depending on the site (Sikyolo et  al.  2013). These differences between clone sets in the onset of inflores- cence meristem termination are important for interpreting the different responses of Pr to site temperature (Figure 3A). A reduction in Pr was expected as site temperature decreased because of the effect of temperature on the rate of node pro- duction, but the similarity of Pr across sites in the False Horn clone set suggests the negligible effect of site temperature in this clone set on either node number or the internode length. The slightly longer reproductive peduncle at Ndihira, the cool- est site (Figure 3A), is consistent with measurements of Sikyolo et  al.  (2013) and with a later termination of the inflorescence meristem. This is more likely than an increase in internode length which for female peduncles of the False Horn clone set was 12 cm at Ndihira, compared with 20 cm at the warmer sites. In the French clone set, the length of the reproductive peduncle and its reduction as site temperature fell cannot be attributed to the termination of the inflorescence meristem as it is still func- tional at fruit maturity. Rather, it indicated the effect of site tem- perature on the elongation of internodes of the male peduncle. The female proportion of the reproductive peduncle, Pf, was gov- erned by Hb and the internode length within the female pedun- cle. At Ndihira, internode length was 11–12 cm and the same for each clone set, compared with 16 cm at the three warmer sites for French and 20 cm for False Horn. Lower Hb and reduced in- ternode length both contributed to a reduced length of female peduncle at Ndihira and a substantial reduction in Pf, compared with the three warmer sites. For a single inflorescence of a wild species of Musa, Pf is a proxy for the balance between reproductive effort allocated to seed and pollen production. The data for the two clone sets examined here suggest a proportional shift from the production of female flowers at warm sites towards a high proportion of peduncle that supports male flowers at cooler sites. Variation of inflorescence parameters within a season is com- monly observed, especially away from the equator (Turner 1981). This is usually attributed to month- to- month differences in temperature and rainfall. In this experiment, site temperature within a year varied by only 1.4°C (Sikyolo et al. 2013). If the re- lationships recorded here are applicable more broadly, then one may expect Hb to be reduced more than Fh depending on how the developmental sequence of the bunch coincided with sea- sons of warmer or cooler weather. In this way, seasonal changes in temperature may contribute to seasonal differences in Fb. In terms of the number of female flowers per generation, the high number of suckers produced by plantains at high elevations (Sikyolo et al. 2013; Sivirihauma et al. 2016; Turner et al. 2020) more than compensated for the reduced Pf of individual inflorescences, the 5- fold increase in sucker numbers from Mavivi to Ndihira more than balancing the reduction in Fb. However, this compensation assumes all suckers develop sufficiently to flower and sib suckers within a generation do not reduce Fb, both of which are unlikely (Swennen et al. 1984). Nonetheless, the pro- duction of more suckers at high elevations could be a strategy of the plant to increase female flowers for pollination per generation but spread across more individuals within that generation. Author Contributions D.W.T., D.J.G., W.O. and G.B. conceived the ideas, designed the meth- odology and analysed the data. D.W.T. and D.J.G. wrote the first draft of the paper. All authors contributed to the final draft of the paper and have read and agreed to the published version. Acknowledgements We thank colleagues Prof. W. Armstrong and Dr. J. Armstrong for their comments on an earlier draft. We thank Charles Sivirihauma for data collection in the experimental fields and for providing information about nematode and weevil infestations across sites. We thank the reviewers for their helpful comments. Open access publishing facilitated by The University of Western Australia, as part of the Wiley - The University of Western Australia agreement via the Council of Australian University Librarians. Conflicts of Interest The authors declare no conflicts of interest. Data Availability Statement The data that support this study will be shared on request. References Adheka, J. G., and E. De Langhe. 2018. “Characterisation and Classification of the Musa AAB Plantain Subgroup in The Congo Basin.” Scripta Botanica Belgica 54: 1–104. Adheka, J. G., D. B. Dhed'a, D. 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Zellforschung und Mikroskopische Anatomie 7: 673–733. 20483694, 2024, 5, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/fes3.70010 by R eadcube (L abtiva Inc.), W iley O nline L ibrary on [16/10/2024]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense A Functional Analysis of Inflorescence Architecture in Musa L. (Musaceae) ABSTRACT 1   |   Introduction 1.1   |   Inflorescence Architecture 1.2   |   Genotypes, Genes and Development of the Genet 1.3   |   Inflorescence Architecture and Environment 2   |   Materials and Methods 2.1   |   Data and Its Analysis 2.2   |   Sites, Cultivars and Clone Sets 2.3   |   The ‘Modified’ Data Set and a Calculated Data Set for Ndihira 2.4   |   The Exponential Reciprocal Function and the Curvature Coefficient 2.5   |   The Effect of the Genet 2.6   |   Statistical Analyses 3   |   Results 3.1   |   The Effect of Site and Cultivar on Measured Data of Hb, Fh, Fb, Pr and Pf 3.2   |   Changes to the Data Caused by Modification 3.3   |   Fitting the Exponential Reciprocal Function to the Modified Data 3.4   |   Effect of the Genet on Hb, Fh and Fb 4   |   Discussion 4.1   |   Fruit per Bunch, Fb, per Hand, Fh and Hands per Bunch, Hb 4.2   |   Plant Reserves and Inflorescence Architecture 4.3   |   Peduncle Total Length, Pr and the Proportion That Was Female, Pf Author Contributions Acknowledgements Conflicts of Interest Data Availability Statement References