The use of multiplexed simple sequence repeat (SSR) markers for analysis of genetic diversity in African rice genotypes

Rice is an emerging food and cash crop in Eastern Africa. Thousands of germplasm accessions have been introduced from major rice breeding centers, such as the International Rice Research Institute (IRRI), and Africa Rice but the genetic variability among the introduced rice germplasm is unknown. Knowledge on genetic diversity would be useful in designing measures for comprehensive breeding and conservation. To address this knowledge gap, 10 highly polymorphic rice simple sequence repeat (SSR) markers were used to characterize 99 rice genotypes to determine their diversity and place them in their different population groups. The SSR markers were multiplexed in 3 panels to increase their throughput. An average of 15.9 alleles was detected, ranging from 6 alleles detected by marker RM7 to 30 by marker RM333. The UPGMA dendogram based on Nei’s genetic distance cluster analysis, revealed 5 genetic groups among the genotypes tested. Analysis of molecular variance indicated that 97% of the diversity observed was explained by differences in the genotypes themselves, and only 3% was due to the sources from which the genotypes were obtained. This study sets the stage for further diversity analysis of all the available germplasm lines using SSR markers to ensure effective utilization and conservation of the germplasm.Keywords: Genetic diversity, simple sequences repeat (SSR) markers, multiplexing, rice genotypes, structure. Abbreviation: IRRI, International Rice Research Institute; SSR, simple sequence repeat; NaCRRI, national crops resources research institute; RAPD, random amplified polymorphic DNA; AFLP, amplified fragment length polymorphisms; RFLP, restriction fragment length polymorphisms; SNP, single nucleotide polymorphisms; BAC, bacterial artificial chromosome; PAC, P1-derived artificial chromosome; PCR, polymerase chain reaction; Ho, heterozygosity; He, heterozygosity

A comparative study of the physicochemical properties of starches from root, tuber and cereal crops

Some properties of starches from cassava, potato and sweet potato were compared with cereal starches from maize, wheat, millet and sorghum. The aim was to determine the properties of tuber and root crop starches and compare them with cereal starches in addition to unravelling the potential of commonly grown sorghum and millet climate resilient crops as cheap and sustainable sources of starch. Significant variations were observed for amylose content and solution properties of starches, where blue values for amylose ranged from 0.355 in potato to 0.476 in cassava, but were averagely low in cereal starches. Amylose leaching increased with temperature with the highest value (0.432) in cassava at 80°C compared with cereal starches (average 0.361). Starch amylosis increased with time of hydrolysis and was highest (>16%) for millet and sorghum and least for potato (<8.5% average). Average swelling power at 80°C was high for cassava (8.58 g/g) and potato (8.44 g/g) compared with sweet potato (6.88 g/g) and low among cereal starches (5.17 g/g). Similarly, starch solubility was low in potato (0.77 g/g) and sweet potato (0.577 g/g) compared with cassava (1.23 g/g). The paste clarity was also high for cassava (48.32%) and potato (42.16%) and least for sweet potato derived starches (23.22%) and all the cereal starches (14.97%). These properties demonstrate the untapped potential of cassava and tuber based starches for use in food and non-food applications previously dominated by cereal starches.Key words: Tuber starch, root crop starches, cereal starches, amylose, amylosis

Farmers perceptions on dual-purpose sorghum and its potential in Zambia

Food feed crops play a cardinal role in mixed crop-livestock production systems yet views of farmers on their usage are limited. Farmers perceptions in predominant sorghum growing areas of Zambia were solicited on socio-economic factors affecting sorghum production, awareness and willingness to adopt dual-purpose sorghum cultivars for food and feed. Preferred traits of a model dual-purpose cultivar were identified. The aim of the study was to generate information that would support the genetic improvement of dual-purpose sorghum. Questionnaires were used to generate this information. Results showed that less than 50% of sorghum growing SSFs had limited knowledge on the use of sorghum to produce feed silage; however, there was full awareness among the LSFs. Among other traits, farmers ideal variety should combine high grain yield potential (100 %) with high biomass (100 % of LSFs and 80 % of SSFs) and high stem sugar content (100 % of LSF and 70 % of SSFs). All the SSFs and 20 % of the LSFs indicated that adequate production could be hampered by low grain yield, poor access to improved seed and unavailability of farmers- preferred cultivars. DOI: http://dx.doi.org/10.3329/ijarit.v4i2.22654 Int. J. Agril. Res. Innov. & Tech. 4 (2): 76-81, December, 201

Amylose content and grain appearance traits in rice genotypes

Amylose content (AC) and grain appearance traits of rice ( Oryza sativa L.) represent a major problem of rice marketing in many rice producing areas in the world. In Uganda, cooking, eating and appearance qualities remain undefined in the rice breeding programme. The objective this study was to determine amylose content of rice genotypes, and its relationship with grain appearance traits; and mode of its inheritance in selected rice genotypes. Forty genotypes were planted in two seasons (2015B and 2016A), in alpha lattice design at National Crop Resource Research Institute in Uganda. Seven parents, involving 3 low and 4 intermediate amylose content genotypes selected in 2015B season,were crossed in a half diallel,and the F1 were advanced to F2 generation, which together with parents were planted in the field. Amylose content (AC), kernel width (KW) and kernel length (K/L) to width ratio were affected by both genetic effects and genotype by season (G x S) interactions; while kernel length was mainly affected by genetic factors. Genotypes were grouped into low, intermediate and high amylose content categories depending on the environment where the genotypes were grown. Three genotypes (Namche 1, P62H17 and 1190) had no significant responsesin amylose content in different growing seasons, suggesting that these genotypes were stable. Amylose content correlated weakly and negatively with physical appearance quality traits of the grain; implying that improvement in amylose content would not affect grain size and shape.There were significant differences (P<0.001) among parents for general combining ability (GCA) and among crosses for specific combining ability (SCA) (P<0.5) for amylose content; indicating that both additive and non-additive gene actions were responsible for the inheritance of AC. However, the variance component of GCA was larger than for the SCA, implying that the inheritance of amylose content was more conditioned by the additive gene effect.La teneur en amylose (TA) et les caract\ue9ristiques d\u2019aspect du grain du riz ( Oryza sativa L.) repr\ue9sentent un probl\ue8me majeur de commercialisation du riz dans de nombreuses r\ue9gions productrices de riz dans le monde. En Ouganda, les qualit\ue9s de cuisson, d\u2019alimentation et d\u2019apparence restent ind\ue9finies dans le programme d\u2019am\ue9lioration du riz. L\u2019objectif de cette \ue9tude \ue9tait de d\ue9terminer la teneur en amylose des g\ue9notypes de riz et sa relation avec les caract\ue9ristiques d\u2019apparence du grain; et son mode de transmission dans des g\ue9notypes de riz s\ue9lectionn\ue9s. Quarante g\ue9notypes ont \ue9t\ue9 plant\ue9s au cours de deux saisons (2015B et 2016A), dans la conception de lattice alpha \ue0 National Crop Resource Research Institute en Ouganda. Sept parents, impliquant 3 g\ue9notypes \ue0 faible teneur en amylose et 4 g\ue9notypes s\ue9lectionn\ue9s lors de la saison 2015B, ont \ue9t\ue9 crois\ue9s sur un demi-diall\ue8le et les F1 ont \ue9t\ue9 avanc\ue9s \ue0 la g\ue9n\ue9ration F2, qui a \ue9t\ue9 plant\ue9e avec les parents sur le terrain. La teneur en amylose (TA), la largeur du noyau (LN) et le rapport longueur / longueur du noyau (K / L) sur la largeur \ue9taient affect\ue9s \ue0 la fois par les effets g\ue9n\ue9tiques et par les interactions g\ue9notype par saison (G x S); tandis que la longueur du noyau \ue9tait principalement affect\ue9e par des facteurs g\ue9n\ue9tiques. Les g\ue9notypes ont \ue9t\ue9 regroup\ue9s en cat\ue9gories de teneur faible, interm\ue9diaire et \ue9lev\ue9e en amylose, en fonction de l\u2019environnement o\uf9 les g\ue9notypes ont \ue9t\ue9 cultiv\ue9s. Trois g\ue9notypes (Namche 1, P62H17 et 1190) n\u2019ont pas eu de r\ue9ponses significatives concernant la teneur en amylose au cours de diff\ue9rentes saisons de croissance, ce qui sugg\ue8re que ces g\ue9notypes \ue9taient stables. La teneur en amylose \ue9tait en corr\ue9lation faible et n\ue9gative avec les caract\ue9ristiques de qualit\ue9 de l\u2019apparence physique du grain; ce qui implique que l\u2019am\ue9lioration de la teneur en amylose n\u2019affecterait pas la taille et la forme des grains. Il y avait des diff\ue9rences significatives (p <0,001) entre les parents pour la capacit\ue9 de combinaison g\ue9n\ue9rale (CCG) et entre les croisements pour la capacit\ue9 de combinaison sp\ue9cifique (CCS) (p <0,5) pour la teneur en amylose; indiquant que les actions g\ue9niques additives et non additives \ue9taient responsables de la transmission du TA. Cependant, la composante de variance de la CCG \ue9tait plus importante que celle de la CCS, ce qui implique que la transmission du contenu en amylose \ue9tait davantage conditionn\ue9e par l\u2019effet du g\ue8ne additif

Inheritance of resistance traits to African stem borer in grain sorghum

The African stem borer ( Busseola fusca [Fuller]) is an important insect pest of cereals, mainly maize, sorghum and millets. The pest causes up to 80% reduction in grain yield, depending on the pest population in the field, cultivar and the management practices employed. This reduction in yield translates into food insecurity, especially in semi-arid lands (ASALs) where sorghum is cultivated by small holder farmers. This study investigated the inheritance of resistance traits to the African stem borers in grain sorghum in Kenya. The experimental material consisted of seventeen sorghum lines with varying levels of resistance to the African stem borer. The mating design employed was North Calorina Design 2, where 15 sorghum lines were used as females on two males. The crosses were evaluated in two seasons at University of Embu farm in 2011/2012 short and long seasons replicated twice. Artificial infestation with African stem borer neonates was done 30 days after planting using a camel brush. Data collected included stem borer damage and agro-morphological traits. Genetic analyses were performed using a line x tester method using Genstat statistical software. It was found that both additive and non-additive gene effects were important in conditioning resistance traits to the African stem borer. This implies that expression of high leaf glossiness, plant vigour and bloom waxiness in F1 hybrids is conditioned by additive genes and these traits can be used as morphological markers to select for resistance to the borer in sorghum. ICSB 464 x ICSB 473 was the best combiner for stem borer resistance and grain yield. Parents ICSA 464, ICSB 464 and ICSB 474, were among the good combiners for resistance to the stem borer. These parents can be utilised in developing superior sorghum hybrids resistant to the insect pest.Le foreur africain de tiges ( Busseola fusca [Fuller]) est un insecte ravageur important pour les c\ue9r\ue9ales, principalement le ma\uefs, le sorgho et le mil. L\u2019 insecte r\ue9duit jusqu\u2019\ue0 80% le rendement en grains, en fonction de la population d\u2019 insecte dans le champ, du cultivar et des pratiques de gestion employ\ue9es. Cette r\ue9duction de rendement cause une ins\ue9curit\ue9 alimentaire, en particulier dans les zones semi-arides (ASAL) o\uf9 le sorgho est cultiv\ue9 par de petits agriculteurs. Cette \ue9tude a examin\ue9 la transmission des caract\ue8res de r\ue9sistance aux foreurs africain de tiges chez le sorgho \ue0 grains au Kenya. Le mat\ue9riel exp\ue9rimental consistait en dix-sept lign\ue9es de sorgho pr\ue9sentant diff\ue9rents niveaux de r\ue9sistance au foreur africain de tiges. Le plan d\u2019accouplement utilis\ue9 \ue9tait le North Calorina Design 2, o\uf9 15 lign\ue9es de sorgho \ue9taient utilis\ue9es en tant que femelles sur deux m\ue2les. Les croisements ont \ue9t\ue9 \ue9valu\ue9s au cours de deux saisons \ue0 la ferme de l\u2019Universit\ue9 d\u2019Embu en 2011/2012 des saisons courtes et longues ont \ue9t\ue9 r\ue9pliqu\ue9es deux fois. L\u2019infestation artificielle de nouveau-n\ue9s avec des t\ue9tranyques a \ue9t\ue9 r\ue9alis\ue9e 30 jours apr\ue8s la plantation \ue0 l\u2019aide d\u2019une brosse \ue0 chameaux. Les donn\ue9es collect\ue9es comprenaient les dommages caus\ue9s par les foreurs de tiges et les caract\ue9ristiques agro-morphologiques. Les analyses g\ue9n\ue9tiques ont \ue9t\ue9 effectu\ue9es \ue0 l\u2019aide d\u2019une m\ue9thode de test de ligne x utilisant le logiciel statistique Genstat. Il a \ue9t\ue9 constat\ue9 que les effets g\ue9n\ue9tiques additifs et non additifs \ue9taient importants pour conditionner les caract\ue8res de r\ue9sistance au foreur de tiges. Cela implique que l\u2019expression de g\ue8nes additifs conditionne l\u2019expression d\u2019une brillance \ue9lev\ue9e des feuilles, de la vigueur des plantes et du fart de la floraison chez les hybrides F1. Ces caract\ue8res peuvent \ueatre utilis\ue9s comme marqueurs morphologiques pour s\ue9lectionner la r\ue9sistance au foreur du sorgho. ICSB 464 x ICSB 473 \ue9tait le meilleur combineur pour la r\ue9sistance des foreurs de tiges et le rendement en grains. Les parents ICSA 464, ICSB 464 et ICSB 474 figuraient parmi les bons combinateurs pour la r\ue9sistance au foreur. Ces parents peuvent \ueatre utilis\ue9s pour d\ue9velopper des hybrides de sorgho sup\ue9rieurs r\ue9sistants \ue0 l\u2019insecte ravageur

Influence of spectral properties on cassava leaf development and metabolism

Cassava’s importance as a food security crop in Sub Saharan Africa will be enhanced by its special traits such as tolerance to drought and high yields under hydrothermal stress. Some of the special traits which include the light reflective and absorptive properties of the leaves that depend on the surface characteristics of the leaves, are variety dependent and may influence the plants’ reaction to light; hence, its photosynthetic capacity. We investigated the differences in the leaf spectral properties in different cassava varieties and related them to leaf biochemical properties using 20 cassava varieties established in a randomized complete block design in Kasese, western Uganda. Time dependent changes in leaf spectral characteristics were studied using Digimizer software and related to changes in sugar and pigment properties. Changes in the amount of reflected light were observed for the three main wavelengths used by plants (blue, green and red) with the blue being the most preferred. Total soluble free sugars exhibited a diurnal pattern from lower values (0.07 mg/g) after the dark period to higher values (0.313 mg/g) as the day progressed and was different from those of translocatable sugars such as sucrose. Chlorophyll a exhibited a curved pattern in all varieties increasing with increase in light intensity from 09:00 h (0.18 ug/g), peaking at 15:00 h (0.22 ug/g) and dropping down in concentration by 18:00 h (0.16 ug/g). Significant differences were observed in cassava varieties for the concentration of chlorophylls and carotenes. The results were obtained at a time of optimal growth conditions (four months after planting) and were used to classify these varieties into three broad groups showing that studies on spectral properties of leaves can still give a lot of insights in selection for stress tolerance under less optimal stress. The significant changes observed in the phenotype especially the foliar portion of the plant with the stay green and early recovering mechanisms of tolerance identified also tarried well with observed spectral differences. The results show that studies on plant spectral properties can be important in making inferences on the plants physiological and growth status.Keywords: Spectral properties, tolerance mechanisms, physiology, reflectance

INHERITANCE OF RESISTANCE TO SESAME GALL MIDGE IN UGANDA

Sesame gall midge, caused by Asphondylia sesami Felt, is an important constraint to sesame ( Sesamum indicum L. ) production in Uganda. Few genotypes have been reported on sesame gall midge, especially hairy genotypes. However, for genetic improvement, there is need to understand the mode of resistance to sesame gall midge in these genotypes. Thirty sesame genotypes were screened for gall midge resistance, under field conditions at Ngetta Zonal Agricultural Research development Institute (ZARDI) in northern Uganda. The spreader row technique was used in order to increase insect pressure on the tested genotypes. The half diallel method 2, model 1 was used to cross 5x5 parents. The result showed that non-additive gene action was important in the inheritance of resistance to sesame gall midge. Cross analysis showed that the GCA x site and SCA x site interactions were significant (P< 0.05), indicating that the additive and non-additive gene actions simultaneously controlled the inheritance for the resistance. The estimate of heritability in narrow sense genetic coefficient of determination (analogue heritable proportion) showed that the resistance was not highly heritable. Estimates of GCA and SCA effects suggest that the parent, Local158, was the best combiner for resistance to gall midge; while the parent AjimoA1-5 was the poorest combiner for the trait. Crosses Local158 x 7029-1-2 and Sesim1 x AjimoA1-5 were the best for the resistance to sesame gall midge. The estimates of genetic effects for resistance to sesame gall midge, showed predominance of additive and additive x additive type of epistasis in the inheritance of the resistance, though dominance also had a role in the cross Sesim1 x 7020-1-2.La c\ue9cidomyie du sesame, caus\ue9e par Asphondylia sesami Felt, est une contrainte majeure \ue0 la production du s\ue9same ( Sesamum indicum L. ) en Ouganda. Tr\ue8s peu de g\ue9notypes r\ue9sistants \ue0 la c\ue9cidomyie de s\ue9same ont \ue9t\ue9 enregistr\ue9s, en particulier les g\ue9notypes \ue0 pubescence. Cependant, pour une am\ue9lioration g\ue9n\ue9tique, il est n\ue9cessaire de comprendre le mode de r\ue9sistance en jeu. Trente g\ue9notypes de s\ue9same ont \ue9t\ue9 \ue9valu\ue9s en plein champ pour la r\ue9sistance \ue0 la c\ue9cidomyie de s\ue9same, \ue0 Ngetta, Institut Zonal de Recherche D\ue9veloppement en Agriculture (ZARDI) au nord de l\u2019Ouganda. La technique d\u2019\ue9pandage en ligne a \ue9t\ue9 utilis\ue9e dans le but d\u2019accroitre la pression d\u2019insecte sur les g\ue9notypes test\ue9s. La m\ue9thode2, mod\ue8le 1 de croisements diall\ue8le sans r\ue9ciproques a \ue9t\ue9 utilis\ue9e sur 5x5 parents. Le r\ue9sultat montre que l\u2019action non additive des g\ue8nes est tr\ue8s importante dans l\u2019h\ue9r\ue9dit\ue9 de la c\ue9cidomyie de s\ue9same. L\u2019analyse des croisements a montr\ue9 que l\u2019habilet\ue9 combinatoire g\ue9n\ue9rale (GCA) et l\u2019habilet\ue9 combinatoire sp\ue9ciale (SCA) montrent varient de fa\ue7on significative d\u2019un site \ue0 un autre (P< 0.05), ceci indique que l\u2019effet additif et non additif des g\ue8nes contr\uf4lent l\u2019h\ue9r\ue9dit\ue9 de la r\ue9sistance \ue0 la c\ue9cidomyie de s\ue9same de fa\ue7on simultan\ue9e. L\u2019\ue9valuation de l\u2019h\ue9ritabilit\ue9 au sens strict a montr\ue9 que le caract\ue8re r\ue9sistant n\u2019est hautement h\ue9ritable. L\u2019estimation des effets de GCA et SCA sugg\ue8re que le parent Local158, \ue9tait le meilleur combineur pour la r\ue9sistance \ue0 la c\ue9cidomyie de s\ue9same, tandis que le parent AjimoA1-5 \ue9tait le pire combineur. Les croisements Local158 x 7029-1-2 et Sesim1 x AjimoA1-5 \ue9taient les meilleurs pour la r\ue9sistance \ue0 la galle de s\ue9same. Les estimations des effets g\ue9n\ue9tiques pour la r\ue9sistance \ue0 la c\ue9cidomyie de s\ue9same a montr\ue9 la pr\ue9dominance d\u2019\ue9pistasis de type additive et additive x additive dans l\u2019h\ue9r\ue9dit\ue9 de la r\ue9sistance \ue0 la galle de s\ue9same, bien que la dominance aussi joue un r\uf4le dans le croisement Sesim1 x 7020-1-2

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)

GENETIC DIVERSITY AMONG SORGHUM LANDRACES OF SOUTHWESTERN HIGHLANDS OF UGANDA

Sorghum ( Sorghum bicolor L. Moench) is an economic and staple crop in sub-Saharan Africa. The genetic diversity in its germplasm is an invaluable aid for its crop improvement. The objective of this study was to assess the existing genetic diversity among sorghum landraces in the southwestern highlands of Uganda. A total of 47 sorghum landraces, collected from southwestern highlands of Uganda, were characterised using 12 qualitative and 13 quantitative traits. The study was conducted at Kachwekano Research Farm in Kabale District, at an altitude of 2,223 m above sea level, during growing season of December 2014 to August 2015. Panicle shape and compactness were the most varied qualitative traits. Grain yield (1.23 to 11.31 t ha-1) and plant height (144.7 to 351.6 cm) were among quantitative traits that showed high variability. Days to 50% flowering (115 to 130 days) showed the least variability. Results of UPGMA cluster analysis generated a dendrogram with three clusters. Panicle weight, leaf width, stem girth, exertion length, peduncle length, panicle shape and compactness, glume colour and threshability were major traits responsible for the observed clustering (P<0.001). Principal Component Analysis revealed the largest variation contributors.Le sorgho ( Sorghum bicolor L. Moench) est une culture vivri\ue8re de grande consommation en Afrique au sud du Sahara. La diversit\ue9 g\ue9n\ue9tique au sein de son germplasm est d\u2019une valeur incalculable pour la production de semences am\ue9lior\ue9es. L\u2019objectif de la pr\ue9sente \ue9tude \ue9tait d\u2019\ue9valuer la diversit\ue9 existante au sein des cultivars des plateaux du Sud-ouest d\u2019Ouganda. Au total, 47 accessions de sorgho, collect\ue9es des plateaux du Sud-ouest d\u2019Ouganda, ont \ue9t\ue9 caract\ue9ris\ue9es en se servant de 12 traits quantitatifs et de 13 traits qualitatifs. L\u2019\ue9tude s\u2019est d\ue9roul\ue9e \ue0 la ferme de recherche de Kachwekano dans le district de Kabal\ue9, zone situ\ue9e \ue0 2223m d\u2019altitude, pendant la saison culturales de Decembre 2014 \ue0 Ao\ufbt 2015. La forme des panicules, et leur densit\ue9 \ue9taient les traits qualitatifs les plus diversifi\ue9s. Le rendement en grains (1,23 \ue0 11,31 t ha-1) et la hauteur des plants (144,7 \ue0 351,6 cm) \ue9taient les traits quantitatifs ayant pr\ue9sent\ue9 une grande variabilit\ue9. Le d\ue9lai de 50% de floraison (115 \ue0 130 jours) \ue9tait le trait le moins variable. La classification num\ue9rique a g\ue9n\ue9r\ue9 un dendrogramme avec trois groupes. Le poids des panicules, la largeur des feuilles, la circonf\ue9rence de la tige, la longeur des insertions, la longueur des p\ue9doncules, la forme des panicules et leur densit\ue9, la couleur de la glume et la facilit\ue9 au d\ue9corticage \ue9taient les traits majeurs ayant contribu\ue9 \ue0 la r\ue9partition en groupes (P<0.001). L\u2019analyse en composantes principales a r\ue9v\ue9l\ue9 les contributeurs \ue0 la plus grande variabilit\ue9

Effectiveness of pyramided genes in conferring resistance to anthracnose disease in common bean populations

Anthracnose disease (Colletotrichum lindemuthianum (Sacc. et. Magn) Lams. Scrib.) is one of the most devastating diseases that constrain common bean production in Uganda. A cascading pedigree pyramiding scheme was used to develop common bean populations to evaluate the effectiveness of pyramided and single resistance genes (Co-42, Co-43, Co-5, and Co-9) on disease development. Detached leaf trifoliates of F4:6 genotypes were screened with four C. lindemuthianum races (352, 713,767 and 2047). Disease severity data were subjected to ANOVA. Races, genotypes and Race x Genotype interaction were significant. Genes Co-42 and Co-5 conferred resistance to the four races and the gene pyramids Co-42+Co-5+Co-9 and Co-42+Co-5 had the lowest severity scores. Gene Co-43 conferred resistance to race 352 and weak resistance to race 713; whereas gene Co-9 conferred resistance to race 352. Co-43+Co-9 gene pyramid showed resistance only to race 352. The Co-42 and Co-5 genes conferred resistance to all the four races 352, 713, 767 and 2047. The single gene Co-42 was not significantly different from the pyramids Co-42+Co-5+Co-9 and Co-42+Co-5 (P<0.01). Similarly, the Co-5gene was not significantly different from Co-42+Co-5, Co-42+Co-9 and Co-5+Co-9 pyramids. The Co-9gene showed antagonism in all pyramids. These results indicate that pyramiding of resistance genes would be effective for disease management in Uganda, but pyramids with Co-9 gene would be less effective