Genetic progress achieved in bean breeding in Uganda

Several cultivars of common bean (Phaseolus vulgaris L.) have been released in Uganda over a period of five decades, but the genetic gain to selection in respect of yield and agronomic characteristics has not been determined. This study was conducted to estimate the gain in selection over the 1960 - 2016 period, of common bean breeding in Uganda. Twenty nine bush and eleven climbing type cultivars were evaluated for yield and yield components, in three locations, during 2017B and 2018A cropping seasons. The study was carried out at the National Crop Resources Research Institute (NaCCRI), Nakabango Research Institute in central and Kwachwekano Zonal Agriculture Research Institute in southwestern Uganda. The design used was a randomised complete blocks with three replicates for the climbing types; and a 3x10 Alpha lattice design with three replicates for bush types. Significant differences (P<0.001) were recorded among cultivars for most traits in both bush and climbers, except seed number per pod (NSP). The range of genetic gain in grain yield was between 1,505 to 2,418 kg ha-1 for bush type cultivars, and 1,641 to 2,687 kg ha-1 for the climbing types. Yield has increased by16.3 and 26.3 kg ha-1 per year for bush and climbers, respectively; with a relative gain of 1.27%/year for bush types and 1.54%/year for the climbing types. Biomass yield and harvest index explained most of the variation in grain yield and number of pods per plant in climbing types. Among climbing types, biomass yield was significantly and positively correlated with grain yield per plant and grain yield per ha (P<0.05, and r= 0.87) and with grain yield per ha (P<0.01 r = 0.98) for bush types, biomass yield was significantly and positively correlated with grain yield per plant (P<0.05, and r= 0.59) and with grain yield per ha (P<0.01 r = 0.80) and harvest index (P<0.5 r = 0.80)

DEVELOPMENT OF INTERMITTENT DROUGHT STRESS TOLERANT COMMON BEAN GENOTYPES IN UGANDA

Common bean ( Phaseolus vulgaris L.) varieties that are high yielding and drought-tolerant are crucial in coping with the effects of drought, that is prevalent among small scale producers living in Uganda. The objective of this study was to assess the level of drought tolerance in bean genotypes to be used for the initial development of drought-tolerant genotypes in Uganda. Three local genotypes and five exotic drought-tolerant lines were phenotyped under well-watered and drought-stress conditions. Drought tolerant genotypes were selected basing on high value for the geometric mean for seed yield and low drought susceptibility indices. The exotic lines, SEN 98, SCR48 and SEN 99, emerged superior in these attributes, and in pod partitioning index (PPI) and pod harvest index (PHI). Thus, these genotypes could be useful sources of genes for drought tolerance in the bean breeding programme in Uganda. The local genotype, NABE 15 was similar to the three promising materials for PPI and PHI. Pods per plant and seed weight were the yield components most affected by drought, with reductions of 82 and 78 %, respectively, for SEN 98.Les vari\ue9t\ue9s \ue0 haut rendement du haricot commun ( Phaseolus vulgaris L.) qui sont tol\ue9rant \ue0 la s\ue9cheresse sont tr\ue8s importantes pour faire face aux effets n\ue9fastes de la s\ue9cheresse, auxquels sont confront\ue9s les petits producteurs en Ouganda. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer le niveau de tol\ue9rance des \ue9cotypes de haricot commun pouvant \ueatre utilis\ue9es pour un d\ue9but de cr\ue9ation de vari\ue9t\ue9s tol\ue9rante \ue0 la s\ue9cheresse en Ouganda. Trois \ue9cotypes locaux et cinq venus d\u2019ailleurs ont \ue9t\ue9 \ue9valu\ue9s sous diff\ue9rentes conditions de disponibilit\ue9 en eau\ua0; bien arros\ue9 et non arros\ue9. Des \ue9cotypes tol\ue9rants \ue0 la s\ue9cheresse ont \ue9t\ue9 s\ue9lectionn\ue9s sur la base de leur rendement en grains en consid\ue9rant leur moyenne g\ue9om\ue9trique et de leur faible indice de susceptibilit\ue9 \ue0 la s\ue9cheresse. Les \ue9cotypes venus d\u2019ailleurs\ua0tels que SEN 98, SCR48 et SEN 99 sont les meilleurs de cette s\ue9lection, ils pr\ue9sentent \ue9galement les indices de partionnement (PPI) et de r\ue9colte (PHI) les plus \ue9lev\ue9s. Ainsi, ces \ue9cotypes pourraient \ueatre utilis\ue9s comme sources g\ue9n\ue9tiques de tol\ue9rance \ue0 la s\ue9cheresse dans les programmes d\u2019am\ue9lioration v\ue9g\ue9tale en Ouganda. Pour ce qui concerne les PPI et PHI, l\u2019\ue9cotype local NABE 15 avait les m\ueames performances que les trois \ue9cotypes performants venus d\u2019ailleurs, Mais le nombre de graine par gousse et le poids des graines sont tr\ue8s affect\ue9s par la s\ue9cheresse, avec une baisse de 82 et de 78% respectivement par rapport \ue0 l\u2019\ue9cotype SEN 98

Evaluating genetic association between fusarium and pythium root rots resistances in the bean genotype RWR 719

Resistance to Fusarium root rot ( Fusarium solani f.s.p phaseoli ) has been reported in common bean ( Phaseolus vulgaris L.) sources and is usually associated with Pythium root rot resistance. Pythium root rot ( Pythium ultimum var ultimum ) resistance is controlled by a single dominant gene, marked by a SCAR marker PYAA19800 . It remains unclear whether the inheritance to resistance of these two bean root rots is genetically independent. We evaluated the association of Fusarium root rot resistance with the Pythium root rots resistance gene and/or the molecular marker PYAA19800 in genotype RWR 719. Two populations; F2 and F2:3 lines, generated from RWR 719 (resistant) 7 K132 (susceptible) were respectively screened with Fusarium solani and Pythium ultimum isolates, and root damages were scored based on the CIAT 1 \u2013 9 scale. Additionally, the F2:3 lines were screened with PYAA19800. The F2 segregation ratio deviated from a single gene model for reaction to Fusarium solani. The F2:3 lines fit the model for a single dominant gene that confers resistance to Pythium ultimum. Fusarium solani and Pythium ultimum resistances were inherited independently. There was lack of association between PYAA19800 and Fusarium solani resistance, but the PYAA19800 was strongly associated with Pythium ultimum resistance. This contradicts the assertion of linkage of the two resistances that was deduced based on the joint occurrence of both resistances in the available donor genotypes.La r\ue9sistance \ue0 la porriture racinaire par suite du Fusarium solani f.s.p Phaseoli a \ue9t\ue9 signal\ue9e dans les sources du haricot commun ( Phaseolus vulgaris L.) et commun\ue9ment associ\ue9e \ue0 la r\ue9sistance de la pourriture racinaire due au Pythium . La r\ue9sistance \ue0 la pourriture racinaire due au pithium ( Pythium ultimum var ultimum ) est control\ue9e par un unique g\ue8ne dominant marqu\ue9 par un marquer SCAR PYAA19800. Il demeure incertain si l\u2019h\ue9ritage de la r\ue9sistance \ue0 ces deux types de pourriture racinaire du haricot est g\ue9n\ue9tiquement ind\ue9pendant. Nous avons \ue9valu\ue9 l\u2019association des g\ue8nes de r\ue9sistance \ue0 la pourriture racinaire due au Fusarium solani et au Pythium ultimum et/ou le marqueur mol\ue9culaire PYAA19800 dans le g\ue9notype RWR 719. Deux populations, F2 et F2:3 issues du croisement entre 719 (r\ue9sistant) 7 K132 (sensible) ont \ue9t\ue9 respectivement test\ue9es avec des isolats de Fusarium solani et Pythium ultimum, et les d\ue9g\ue2ts \ue9taient mesur\ue9s sur base de l\u2019\ue9chelle de cotation de 1 \ue0 9 du CIAT. Additionnellement, F2:3 \ue9taient test\ue9es avec PYAA19800. Le rapport de s\ue9gr\ue9gation de F2 a d\ue9vi\ue9 du mod\ue8le unique pour la r\ue9action au Fusarium solani. Les lign\ue9es F2:3 se sont adapt\ue9es au mod\ue8le de l\u2019unique g\ue8ne dominant qui conf\ue8re la r\ue9sistance au Pythium ultimum. Les r\ue9sistances au Fusarium solani et au Pythium ultimum \ue9taient ind\ue9pendamment h\ue9rit\ue9es. Il n\u2019y avait aucune association entre PYAA 19800 et la r\ue9sistance au Fusarium solani, mais le PYAA19800 \ue9tait un g\ue8ne unique dominant avec r\ue9sistance au Pythium ultimum. Ceci contr\ue9dit l\u2019assertion du lien de ces deux r\ue9sistances d\ue9duit sur base de l\u2019occurrence combin\ue9e de toutes les deux resistances dans les g\ue9notypes donneurs disponibles

SUSCEPTIBILITY TO BRUCHIDS AMONG COMMON BEANS IN UGANDA

The bean bruchids, Acanthoscelides obtectus Say and Zabrotes subfasciatus Boheman (Coleoptera: Bruchidae), are cosmopolitan pests of stored dry common beans ( Phaseolus vulgaris L. ), causing damage through reduction of grain quality and seed germination. Biological resistance to these bruchids was definitively established in non-cultivated bean accessions, and has been introgressed into a range of drybean market classes. However, existing resistance to bruchids in Uganda\u2019s common bean germplasm has not been systematically studied. In this study, 45 bean genotypes from the National Bean-Breeding Programme (25 genotypes) and agroecologically diverse bean growing areas in Uganda (20 genotypes), were evaluated for postharvest bruchid resistance. None of the evaluated bean genotypes expressed resistance to either bruchid species, with all the 45 bean genotypes supporting bruchid development, reproduction and feeding. All genotypes were severely damaged by bruchids feeding, resulting in significant (P<0.05) reduction of seed germination. Reduction in seed germination was related to the number of emergence holes and seed size; small bean seeds damaged by up to 2 bruchid emergence holes had a 7.1% reduction in germination, while large bean seeds with a similar number of emergence holes showed a 25% reduction in germination. Whereas this study further confirms bruchids as important storage pests of beans causing direct loss through consumption of the seed and indirect loss through viability deterioration, the resistance to bruchids in the evaluated range of Uganda\u2019s dry bean germplasm is inadequate for direct exploitation in a breeding programme.Les bruches du haricot, Acanthoscelides obtectus Say et Zabrotes subfasciatus Boheman (Coleoptera: Bruchidae), sont des ravageurs cosmopolites des haricots secs stock\ue9s ( Phaseolus vulgaris L. ), provoquant des dommages en r\ue9duisant la qualit\ue9 des grains et le pouvoir germinatif des semences. La r\ue9sistance biologique \ue0 ces bruches a \ue9t\ue9 d\ue9finitivement \ue9tablie dans des lign\ue9es non cultiv\ue9es de haricots et a \ue9t\ue9 introgress\ue9e dans une gamme vari\ue9e de haricots commercialis\ue9s. Cependant, la r\ue9sistance actuelle aux bruches dans le mat\ue9riel g\ue9n\ue9tique des haricots commun\ue9ment r\ue9pandus en Ouganda n\u2019a pas \ue9t\ue9 syst\ue9matiquement \ue9tudi\ue9e. Dans la pr\ue9sente \ue9tude, 45 g\ue9notypes de haricots provenant du Programme national d\u2019am\ue9lioration du haricot (25 g\ue9notypes) et de diverses zones agro-\ue9cologiques de culture de haricots en Ouganda (20 g\ue9notypes), ont \ue9t\ue9 \ue9valu\ue9s pour leur r\ue9sistance post-r\ue9colte aux bruches. Aucun des g\ue9notypes \ue9valu\ue9s n\u2019a exprim\ue9 de la r\ue9sistance aux deux esp\ue8ces de bruches, et tous les 45 g\ue9notypes ont favoris\ue9 le d\ue9veloppement des bruches, leur reproduction et leur alimentation. Tous les g\ue9notypes ont \ue9t\ue9 gravement endommag\ue9s du fait de l\u2019alimentation des bruches, ce qui a entra\ueen\ue9 une r\ue9duction significative (P <0,05) de la germination des graines. La r\ue9duction du pouvoir germinatif \ue9tait li\ue9e au nombre de trous caus\ue9s sur les graines et \ue0 la taille des graines; les petites graines de haricot endommag\ue9es avec jusqu\u2019\ue0 2 trous ont montr\ue9 une r\ue9duction de 7,1% de leur pouvoir germinatif, tandis que les grandes graines de haricots endommag\ue9es avec le m\ueame nombre de trous ont connu une r\ue9duction de 25% de pouvoir germinatif. Bien que cette \ue9tude confirme davantage que les bruches sont d\u2019importants ravageurs en phase de stockage des haricots causant des pertes \ue0 la fois directe par la consommation de la graine et indirecte par la d\ue9t\ue9rioration de la viabilit\ue9 des semences, la r\ue9sistance aux bruches dans la gamme \ue9tudi\ue9e du mat\ue9riel g\ue9n\ue9tique de haricots secs de l\u2019Ouganda est insuffisante pour une exploitation directe dans un programme d\u2019am\ue9lioration vari\ue9tale

Identification of common bean genotypes with dual leaf and pod resistance to common bacterial blight disease in Uganda

Common Bacterial Blight (CBB), caused by Xanthomonas axonopodis pv. phaseoli (Xap) and Xanthomonas axonopodis pv. phaseoli var. fuscans (Xapf), is a serious disease that affects common bean production worldwide. In Uganda, it is the most severe and widely occurring bacterial disease, causing significant yield losses in common bean. Although various sources of resistance have been developed around the world, none of the varieties grown in Uganda is known to be resistant. The objective of this study was to identify lines with combined leaf and pod resistance for introgression into locally adapted but susceptible Ugandan genotypes. A total of 132 common bean accessions was evaluated in a screenhouse and under field conditions, in an 11x12 alpha lattice design. Genotypes were inoculated with a local isolate in a screenhouse; while the plants were left to undergo natural infestation in field. Results indicated significant differences (P<0.001) in genotypic reactions against the CBB disease, with a range of disease scores of 2.2 - 7.8 on leaves and 2.6 - 7.1 on pods (1-9 CIAT disease scale), suggesting high genetic variability among the tested germplasm. Relatively low correlation (r = 0.39) was observed between leaf and pod reactions, suggesting differential expression of CBB resistance in these two plant organs. Overall, four genotypes, NE2-14-8, NE17-14-29, NE14-09-78 and VAX3, consistently showed resistance in both screenhouse and field evaluations, leaf and pod inoculations and at all sampling stages. These genotypes were, therefore, identified for transferring CBB resistance into Ugandan susceptible market class bean varieties.Le fl\ue9trissement bact\ue9rien commun (CBB) caus\ue9 par Xanthomonas campestris pv. phaseoli (Xcp) et Xanthomonas spp. var. fuscans (Xcpf) est une s\ue9rieuse maladie qui affecte, de fa\ue7on globale, la production du haricot commun. En Ouganda, elle est, de loin, la maladie bact\ue9rienne la plus s\ue9v\ue8re et vastement r\ue9pandue causant de pertes significatives au rendement du haricot commun. Malgr\ue9 que de nombreuses sources de r\ue9sistance aient \ue9t\ue9 d\ue9velopp\ue9es dans le monde, aucune des vari\ue9t\ue9s cultiv\ue9es en Ouganda n\u2019est connue \ueatre r\ue9sistante. L\u2019objectif de cette \ue9tude \ue9tait d\u2019identifier des lignes \ue0 r\ue9sistance combin\ue9e des feuilles et gousses pour son introgression dans les vari\ue9t\ue9s locales adapt\ue9es mais susceptibles. Au total, 132 accessions de haricot commun \ue9taient \ue9valu\ue9es sous serre et dans le champ dans un dispositif experimental alpha-lattice 11x12. Les g\ue9notypes \ue9taient inocul\ue9s sous serre par un isolat local pendant que l\u2019infestation \ue9tait naturelle dans le champ. Les r\ue9sultats montrent de diff\ue9rences hautement significatives dans la r\ue9action des g\ue9notypes face \ue0 la maladie CBB avec des scores variant de 2,2 \ue0 7,8 sur les feuilles et de 2.6 \ue0 7.1 sur les gousses (l\u2019\ue9chelle 1-9 de CIAT) indiquant une forte variabilt\ue9 g\ue9n\ue9tique au sein du germoplasm test\ue9. Une corr\ue9lation relativement faible (r = 0.39) \ue9tait observ\ue9e entre la r\ue9action des feuilles et celle des gousses sugg\ue9rant une expression diff\ue9rentielle de la r\ue9sistance \ue0 la maladie CBB dans ces deux organes de la plante. De fa\ue7on g\ue9n\ue9rale, quatre g\ue9notypes NE2-14-8, NE17-14-29, NE14-09-78 and VAX3 ont \ue9t\ue9, de fa\ue7on constante, r\ue9sistants aux \ue9valuations sous serre et dans le champ, aux inoculations des feuilles et des gousses et durant toute la p\ue9riode de mesure. Ces g\ue9notypes \ue9taient donc identifi\ue9s pour le transfert de la r\ue9sistance dans les vari\ue9t\ue9s locales susceptibles d\u2019Ouganda

Herança da resistência em feijoeiro à murcha causada por Curtobacterium flaccumfaciens pv. flaccumfaciens

O objetivo deste trabalho foi determinar a herança da resistência à murcha de Curtobacterium em feijoeiro. Foram realizados dois experimentos: no primeiro, cinco genótipos de feijoeiro, com diferentes reações de resistência à murcha de Curtobacterium, foram cruzados em arranjo dialélico; e no segundo, dois cruzamentos entre genótipos resistentes e suscetíveis - IAC Carioca Aruã x SCS Guará e IAC Carioca Pyatã x Pérola - foram realizados para dar origem às gerações P1, P2, F1, F2, RC1 e RC2. Em ambos os experimentos, a resistência do feijoeiro à murcha bacteriana foi avaliada por meio da inoculação do isolado Cff 2634. A análise dialélica mostrou que, embora efeitos aditivos e não aditivos estejam envolvidos, houve maior participação de genes com efeito aditivo no controle genético da resistência à murcha bacteriana, o que mostra a possibilidade de se obter sucesso com a seleção. A herança da resistência à murcha de Curtobacterium é complexa, com mais de três genes envolvidos, e herdabilidade no sentido restrito de 29%, para o cruzamento 'IAC Carioca Aruã' x 'SCS Guará', e de 44%, para o cruzamento 'IAC Carioca Pyatã' x 'Pérola'

Estimation of Banana Yield Based on Bunch Phenology

Cooking bananas (Musa cvs.) are the most important food crop in Uganda and considerable research attention is now focused on yield declines experienced in long-term banana production areas. Measurement of banana bunch weight using field scales is rapid and reliable, but not always possible during field monitoring because it requires that either farmers, possess and, reliably use scales or that researchers are present during the short interval between bunch harvest and marketing or consumption of bananas. Furthermore, occasional theft of banana bunches from field experiments pose serious sources of experimental error owing to the large mass of individual bunches and relatively few banana plants per experimental plot. The phenology of 317 banana bunches of Musa cv. Mbwaziirume obtained from a three year-old field experiment at the Mukono District Farm Institute was used to construct two estimates of individual bunch volume. Crude cylindrical volume (CCV) is based on the distance between the upper and lower most hands (length) and the maximum bunch girth (circumference). Aggregate finger volume (AFV) is based on the mean length and maximum circumference of three banana fingers x mean number of fingers per hand x number of hands per bunch. Both volume estimates were expressed as litre bunch-1 and compared to individual banana bunch mass (kg bunch-1) using linear regression procedures. Banana bunch mass varied from 0.9 to 15.9 kg and bunch volumes between 0.5 to 45.9 l. Both volume estimates yielded significant relationships with mass as a dependant variable where bunch (kg) = 0.56 + 0.33 CCV (r = 0.85) and bunch (kg) = 0.66 + 0.49 AFV (r = 0.94). These relationships were established across a range of management practices including retention of crop residues and addition of 10 t ha-1 yr-1 napier grass (Pennisetum atropurpureum) or cattle manure. Bunch mass varied from 4.11 to 8.28 kg in relation to management and these changes were reflected in the slope values of CCV but not AFV, suggesting that AFV provides a more robust estimate, however, CCV is more easily obtained from non-destructive field measurements.Les bananes constituent une culture vivri\ue8re en Uganda et une recherche consid\ue9rable met l\u2019acc\ue8s sur la r\ue9duction de rendements experiment\ue9e depuis longtemps dans les r\ue9gions de production. La mesure du poids du r\ue9gime de banane utilisant des balances de champs est rapide et sure, mais pas toujours possible durant le suivi des champs parce qu\u2019il requiert que, soit le fermier poss\ue8de une balance sure ou soit que les chercheurs soient pr\ue9sents entre la petite p\ue9riode de recolte du regime et la commercialisation \ue0 la consommation de la banane. Plus encore des voles occas\ueeonnels des regimes de banane en champs d\u2019\ue9xperimentation constitute des sources d\u2019\ue9rreurs \ue9xperimentales en raison de la grande masse de r\ue9gime individuel et relativement peut de plantes de bananes par parcelle. La phenologie de 317 r\ue9gimes de bananes de Musa cv. Mbwazirume obtainus du champs d\u2019essas \ue2g\ue9 de 3 ans \ue0 l\u2019Institut de Ferme au district de Mukono \ue9t\ue9 utilis\ue9e pour construire deux estimations du volume de regime individuel. Le volume cylindrique brut (CCV = VCB) est bas\ue9 sur la distance entre la sup\ue9rieure et la plus basse extr\ue8me main (longeur) et la circonfer\ue9nce maximale du r\ue9gime. Le volume du doigt aggr\ue9g\ue9 (AFV) est bas\ue9 sur la moyenne de la longeur et la circonf\ue9rence maximale de 3 doigts de banane x la moyenne du nombre de doigts par main x nombre de mains par r\ue9gime. Les deux volumes ont \ue9t\ue9 exprim\ue9s en litre/r\ue9gime et compar\ue9s \ue0 la masse de r\ue9gime individuel (kg/r\ue9gime) utilisant de proc\ue9dures de la regression lin\ue9aire. La masse du r\ue9gime de banane a vari\ue9 de 0.9 \ue0 15.9 kg et le volume de r\ue9gime entre 0.5 \ue0 45.91. Les deux estimations ont produit de relations significatives avec la masse comme variable dependante o\uf9 le r\ue9gime (kg) = 0.56 + 0.33 CCV (r = 0.85)et le r\ue9gime (kg) = 0.66 + 0.49 AFV (r = 0.94). Ces relations ont \ue9t\ue9 \ue9tablies \ue0 travers une s\ue9rie de pratiques de gestion incluant \ub1 la retention des r\ue9sidus de plantes et \ub1 l\u2019addition de 10 t ha-1(Pennisetum atropurpureum) ou le fumier de vache. La masse du r\ue9gime a vari\ue9 de 4.11 \ue0 8.28 kg en relation avec la gestion et ces changements ont \ue9t\ue9 reflect\ue9s dans les valeurs de pente de CCV et non pas pour AFV, indiquant que AFV produit une estimation plus robuste, alors que CCV est facilement obtainu dans la mesure non destructive en champs