MORPHOLOGICAL AND AGRONOMIC TRAITS VARIATIONS FOR MUNGBEAN VARIETY SELECTION AND IMPROVEMENT IN UGANDA

Mungbean ( Vigna radiata L. Wilczek), is a pulse species that is widely cultivated in sub-tropical and tropical regions of the world. Unfortunately, the yield of mungbean in Uganda is very low mainly due to inherent genotype failures and losses due to pests and diseases. To achieve a gain in yield through breeding requires collection, characterisation, and evaluation of germplasm, as the first step in identifying genotypes with the desired characteristics. The objective of this study was to describe the nature and extent of genotypic variation among mungbean collections for a range of traits of potential agronomic and adaptive interests in Uganda. A total of 35 mungbean accessions acquired mainly from the World Vegetable Centre (AVRDC) in Taiwan, two local ricebean ( Vigna umbellata (Thunb.) Ohwi and Ohashi) and one local blackgram genotype ( Vigna mungo ) were evaluated for several diverse traits for two cropping seasons at two different locations in Uganda. Genotype by environment interaction (GEI) was significant (P < 0.001) for all the traits, indicating inconsistent performance by some genotypes across two locations and two seasons. However, AMMI bi-plot identified stable genotypes for grain yield, while GGE bi-plot identified the best genotypes in a hypothetical environment. The magnitudes of estimated broad sense heritability (H) for the traits used were generally high. However, single link dendogram and Principal Component Analysis (PCA) revealed narrow diversity in the mungbean collection. The positive relationship between seed size and yield in this sub-set of mungbean germplasm can be used in a breeding programme for a potential gain in selecting large seeded and high yielding genotypes.Le haricot mungo ( Vigna radiata L. Wilczek), est une esp\ue8ce de plante qui est largement cultiv\ue9e en r\ue9gions tropicales et subtropicales. Le rendement actuel du haricot mungo en Ouganda est comparativement bas par suite d\u2019\ue9checs li\ue9s au g\ue9notype et pertes dues aux maladies et pestes. Afin de r\ue9aliser un gain de rendement \ue0 travers l\u2019am\ue9lioration, il s\u2019av\ue8re n\ue9cessaire de faire la collection, la caract\ue9risation, et l\u2019\ue9valuation du germplasme, comme premi\ue8re \ue9tape dans l\u2019identification des g\ue9notypes avec des caract\ue9ristiques d\ue9sir\ue9es. La variation parmi 38 accessions de haricot mungo obtenues du World V\ue9g\ue9tale Centre (AVRDC), une vari\ue9t\ue9 locale de haricot riz ( Vigna umbellata (Thunb.) Ohwi et d\u2019 Ohashi) et un g\ue9notype de blackgram ( Vigna mungo ) local, \ue9tait \ue9valu\ue9e pour plusieurs traits directs pendant deux saisons culturales dans des lieux diff\ue9rents en Ouganda. Une variation substantielle \ue9tait observ\ue9e dans diff\ue9rent traits de potentiel agronomique et performance adaptive. L\u2019interaction g\ue9notype par environnement (GEI) \ue9tait significatif (P < 0.001) pour tous les traits, indiquant une performance inconsistante de quelques g\ue9notypes \ue0 travers deux milieux et deux saisons. Par ailleurs, un AMMI bi-plot a identifi\ue9 des g\ue9notypes stables en termes de rendement en grain, alors que le GGE bi-plot a identifi\ue9 les meilleurs g\ue9notypes dans un environnement hypoth\ue9tique. Les niveaux de l\u2019h\ue9ritabilit\ue9 estim\ue9e (H) pour les traits utilisees \ue9taient g\ue9n\ue9ralement \ue9lev\ue9s. Par ailleurs, le lien simple du dendogramme et l\u2019analyse par composantes Principales (PCA) ont r\ue9v\ue9l\ue9 une petite diversit\ue9 dans la collection du haricot mungo. Une corr\ue9lation positive entre la taille du grain et le rendement dans ce sous groupe du germoplasme du haricot mungo peut \ueatre utilis\ue9e dans le programme d\u2019am\ue9lioration pour un gain potentiel dans la s\ue9lection des g\ue9notypes \ue0 grains larges et rendement \ue9lev\ue9s

Application of pollen germination media on stigmas during pollination increases seed set in east African highland cooking bananas (Musa spp.)

Open Access Journal; Published online: 27 May 2021Seed set in East African Highland Cooking bananas (EAHBs) is extremely low and therefore hampers breeding. Pollen–pistil interaction is a key contributing factor. We assessed the effect of pollen germination media (PGM) on seed set in EAHBs. Five EAHB cultivars were pollinated with pollen from the wild banana ‘Calcutta 4’. Glucose-based PGM sprayed on freshly emerged stigmas significantly increased seed set per 100 fruits per bunch. Increases were 73.5% in ‘Enzirabahima’, 39.9% in ‘Mshale’, and 302.4% in ‘Nshonowa’. However, PGM did not increase seed set in the female sterile ‘Mlelembo’ and ‘Nakitembe’. As larger bunches were more fertile, good field management practices are also recommended to get more seed to improve breeding efficiency

Seed set patterns in east African highland cooking bananas show asymmetric distribution in bunches and fruits

Open Access Journal; Published online: 14 Apr 2021Low female fertility in bananas is the biggest hurdle for banana breeding. The aim of this study was to determine seed set patterns in East African Highland Cooking bananas (EAHBs) to inform future decisions on a more targeted approach of increasing seed set and subsequently banana-breeding efficiency. Matooke (AAA) and Mchare (AA) bananas are genetically distinct but belong to the same genetic complex, referred to as EAHBs. Seed set patterns in “Enzirabahima” (AAA), “Mshale” (AA), and “Nshonowa” (AA), all with residual fertility, were examined after hand pollination with a highly male fertile wild banana “Calcutta 4” (AA). Seed set in “Enzirabahima” is predominant in distal hands. Mchare cultivars have a slightly more even distribution of seeds in their hands compared to “Enzirabahima”. There is a gradual increase in seed set from proximal to distal hands with a slight drop in the last hand. This pattern is more definite in “Enzirabahima” and “Mshale”, while “Nshonowa” has a somewhat inconsistent pattern. There is also a drop in seed set per 100 fruits per hand from small to larger bunches. However, larger bunches have a higher pollination success compared to smaller bunches. They therefore set more seed on 100 fruits per hand and per bunch basis, if bunches without seed are accounted for. Pollination success rate increases from smaller to larger bunches of EAHBs. Seed set is biased toward the distal third part of fruits of examined EAHBs, as well as tetraploid Matooke hybrid “401K-1” (AAAA), and improved diploid “Zebrina” GF (AA) that were used for comparison. In comparison, in the highly female fertile “Calcutta 4”, seed set is along the entire length of the fruit. Seed set bias in the distal hands and distal end of fruits suggests a systematic mechanism rather than a random occurrence. It is expected that this information will provide a foundation for increased crossbreeding efficiency in bananas

Seed set patterns in east African highland cooking bananas are dependent on weather before, during and after pollination

Open Access Journal; Published online: 29 Jun 2021Seed set in banana is influenced by weather, yet the key weather attributes and the critical period of influence are unknown. We therefore investigated the influence of weather during floral development for a better perspective of seed set increase. Three East African highland cooking bananas (EAHBs) were pollinated with pollen fertile wild banana ‘Calcutta 4′. At full maturity, bunches were harvested, ripened, and seeds extracted from fruit pulp. Pearson’s correlation analysis was then conducted between seed set per 100 fruits per bunch and weather attributes at 15-day intervals from 105 days before pollination (DBP) to 120 days after pollination (DAP). Seed set was positively correlated with average temperature (P < 0.05–P < 0.001, r = 0.196–0.487) and negatively correlated with relative humidity (RH) (P < 0.05–P < 0.001, r = −0.158–−0.438) between 75 DBP and the time of pollination. After pollination, average temperature was negatively correlated with seed set in ‘Mshale’ and ‘Nshonowa’ from 45 to 120 DAP (P < 0.05–P < 0.001, r = −0.213–−0.340). Correlation coefficients were highest at 15 DBP for ‘Mshale’ and ‘Nshonowa’, whereas for ‘Enzirabahima’, the highest were at the time of pollination. Maximum temperature as revealed by principal component analysis at the time of pollination should be the main focus for seed set increase

Use of timelapse photography to determine flower opening time and pattern in banana (Musa spp.) for efficient hand pollination

Open Access Journal; Published online: 30 Sep 2021Sterility and low seed set in bananas is the main challenge to their conventional genetic improvement. The first step to seed set in a banana breeding program depends on pollination at the right time to ensure effective fertilization. This study aimed at determining bract opening time (BOT) to enhance efficient pollination and seed set in bananas. A Nikon D810 digital camera was set-up to take pictures of growing banana inflorescences at five-minute intervals and time-lapse movies were developed at a speed of 30 frames per second to allow real-time monitoring of BOT. Genotypes studied included wild banana (1), Mchare (2), Matooke (4), Matooke hybrid (1), and plantain (1). Events of bract opening initiated by bract lift for female flowers (P < 0.01) started at 16:32 h and at 18:54 h for male flowers. Start of bract rolling was at 18:51 h among female flowers (P < 0.001) and 20:48 h for male flowers. Bracts ended rolling at 02:33 h and 01:16 h for female and flowers respectively (P < 0.05). Total time of bract opening (from lift to end of rolling) for female flowers was significantly longer than that of male flowers (P < 0.001). On average, the number of bracts subtending female flowers opening increased from one on the first day, to between one and four on the fourth day. The number regressed to one bract on day eight before start of opening of bracts subtending male flowers. There was a longer opening interval between bracts subtending female and male flowers constituting spatial and temporal separation. Bract rolling increased from partial to complete rolling from proximal to the distal end of the inflorescence among female flower. On the other hand, bracts subtending male flowers completely rolled. Differences in BOT of genotypes with the same reference time of assessment may be partly responsible for variable fertility. Hand pollination time between 07:00 and 10:00 h is slightly late thus an early feasible time should be tried

Studies for improving pollination and fertilization efficiency in East African Highland Matooke and Mchare Bananas (Musa spp.)

IITA supervisor: Dr. Swennen, R.Matooke and Mchare are two distinct subgroups of East African bananas (EABs) (Musa spp.) that are endemic to the Great Lakes region of East Africa. In this region, they are pivotal in for food and income security of more than 70 million people. However, productivity of these EABs is significantly constrained by pests and diseases that reduce the yield and directly affecting the livelihoods of banana farming communities in the region. While cultural methods of disease and pest control are widely applied, approaches that are tailored via genetic improvement are preferred because of their long-term sustainability. Conventional genetic improvement of bananas through hybridization is slow due to the complexity of factors that lead to sterility. Most of the popular banana cultivars are sterile and hardly produce seed after artificial and natural pollination. For example, in an earlier study, only 37 out of 78 Matooke cultivars were reported to set seed after artificial pollination. On the other hand, Mchare breeding only started recently in Uganda and Tanzania and their female fertility potential has not been characterized. Therefore, the main objective of this study was to contribute towards the development of effective techniques for overcoming sterility in Matooke and Mchare bananas. Specifically, the study objectives were to; (a) characterize flower opening time and behavior in selected subgroups of bananas, (b) increase in vitro and in vivo pollen germination as well as increase ovule fertilisation rates in East African Highland cooking bananas, (c) ascertain seed set patterns in East African Highland cooking bananas in relation to the bunch, fruit, and weather, (d) develop pollination techniques that increase seed set in East African Highland cooking bananas The general study approach was to reassess the factors reported to affect seed set in banana before coming up with pollination techniques for overcoming sterility. To characterize flower opening, a Nikon camera was set up to take pictures at 5-minute intervals through the flowering period. Timelapse movies were developed and played and the exact time of bract opening was recorded. To improve pollen germination and ovule fertilization, varying levels of glucose, fructose, sucrose, glucose plus fructose, and glucose plus fructose plus sucrose based pollen germination media were compared. Glucose at 30 g/L gave the highest pollen germination and was compared with diluted banana nectar. The effect of 30 g/L glucose pollen germination media on stigma receptivity was tested. To determine seed set patterns, pollinations were made on EABs using wild banana ‘Calcutta 4’ between January 2016 and January 2019. Seed set per hand was recorded as well as fruits per hand and total hands per bunch. Weather attributes were also correlated with seed set before, during, and after pollination. Principal component analysis (PCA) was used to tease out the most influential weather attribute. Development of in vivo pollination techniques involved stigma receptivity enhancement, pollinating about a day before natural flowering opening, and evening pollination. Wild fertile banana ‘Calcutta 4’ was used as the pollen source. There are differences in start of female flower opening for selected banana sub-groups (P < 0.01) with a range of 14:54 – 20:19 h and an average of 16:32 h. On the other hand, male flowers start opening later between 16:53 – 1:03 h with an average of 18:54 h. This implies that the adopted pollination time of 7:00 – 10:00 h is too late. For pollen germination, glucose at 30 g/l performed better than sucrose and diluted banana nectar (P < 0.001). When applied to stigmas, it enhanced receptivity as more pollen germinated in a shorter time. Pollen germination media also increased ovule fertilization rates. Observed seed set in hands is not equal to expected seed set in different bunch size categories (P < 0.05, 0.01, 0.001). Enhancing stigma receptivity did not change the observed seed set pattern thus, stigma receptivity is not responsible for this pattern as earlier reported. Weather is significantly associated with seed set before, during, and after pollination in EABs. Temperature was most influential with a high temperature required before and during pollination while a low temperature was required after pollination. Among new pollination techniques, the use of glucose based pollen germination media significantly increased (P < 0.05) seed set in EABs with residual fertility but not in sterile cultivars. Pollinating in the evening did not increase seed set as female and male flowers did not open in synchrony. On the other hand, forcing flowers open and pollinating about a day before natural opening did not also increase seed set likely because of immature stigma tissues. The general objective of the study was partially achieved as seed set increase was observed in the new pollination techniques of enhancing stigma receptivity. The achieved increases are still a small fraction of potential seed set which can be as high as 30,000 seeds per 100 fruits. Data from this research has laid a firm foundation for further research especially in overcoming sterility, further increase in seed set and embryo germination rates