Iron and zinc grain concentrations diversity and agronomic performance of common bean germplasm collected from East Africa

Iron and zinc are essential micronutrients for normal human growth and development and are commonly deficient in diets of the most vulnerable. Common bean (Phaseolusvulgaris L.), one of the leading staple foods in East and Central Africa, is a valuable source of quality protein and micronutrients, specifically iron, zinc, and vitamins. Natural variation in micronutrient concentration exists among bean germplasm. Identification of varieties with high iron and zinc seed concentration (FESEED/ZNSEED) for promotion in food systems and utilisation in breeding programs is one strategy of addressing the problem of malnutrition in Africa. Three hundred and four lines sourced from theInternational Centre for Tropical Agriculture (CIAT) and its partners through the Pan Africa Bean Research Alliance (PABRA), were evaluated for agronomic traits, diseaseresponse, yield, FESEED, and ZNSEED. They were organized in four groups; PABRA fast track, Rwanda seeds of hope, HarvestPlus regional nutrition nursery and Uganda collection. Six checks were included; a universal high FESEED climbing bean (MIB465), low FESEED regional climbing bean (Decelaya), universal low FESEED bush bean (DOR500), regional high FESEED bush bean (RWR2154), and two yield checks (CAL96 and Vuninkingi for bush and climbing bean). The FESEED checks were selected based on their relative performance to other genotypes in several experiments by a community of bean breeders through the H+ program. Field trials were established at the National Agricultural Laboratories, Kawanda from 2011 to 2013. Days to maturity and flowering, vigor, yield, and reaction to diseases were evaluated. Micronutrient analysis was conducted using X-ray Fluorescence (XRF) and data confirmed using Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). Lines were significantly different (P≤0.05) in all the parameters assessed. FESEED and ZNSEED varied highly between seasons and among the entries ranging between 36-90 ppm and 24-47 ppm across the four nurseries. Twenty-six lines were selected as high iron beans (HIBs) based on XRF data; 12 of these were confirmed as HIB based on ICP data that is more accurate. Of these, two bush beans, Jesca (large purple speckled) and RW547 (medium grey) and two climbing beans, CAB2 (medium white seeded) and Ndimirakaguja (small cream) were the most superior in FESEED across seasons. With the exception of CAB2, these lines were relatively high yielding >2000 kgha-1. There was no significant correlation of FESEED or ZNSEED to yield. Nonetheless, FESEED and ZNSEED positively (0.59) correlated indicating that selection for superiority in one variable would result in a high value in the other.Key words: Common bean, Micronutrients, Anemia, Genetic variation, Yield, Disease

Variability in cooking time, iron and zinc content in common bean (Phaseolus Vulgaris L.) genotypes

Prolonged cooking time leads to structural changes at the grain cellular level, resulting in loss of nutrients such as iron (Fe) and zinc (Zn) which are among the main nutrients important in addressing micronutrient malnutrition. The aim of this study was to evaluate the diversity of cooking time, Fe and Zn content in a total of 152 common bean (Phaseolus vulgaris) genotypes from around Eastern Africa, in order to identify short cooking genotypes with high Fe and Zn content. Field trials were conducted at CIAT-Uganda research station over two seasons in 2016. Cooking time was estimated using an automated Mattson cooker at CIAT-Uganda while Fe and Zn content was determined using XRF analysis at Rwanda Agricultural Board (RAB) in Rubona. A wide variability was evident from the test genotypes both for cooking time and mineral concentration. Cooking time exhibited a continuous distribution ranging from 35-100 minutes for the first season and 43–122 minutes for the second season. Seventy-three percent of the test genotypes had Fe levels higher than the low Fe check, CAL 96 (55mg/kg) which is popularly known as ‘Nambale’ and a popular commercial variety in Uganda. A total of 15 genotypes (Amahunja, Awash melka, Bihogo, CAB 2, ECAPAN021, G858, Icaquimbaya, KK20, NABE12C, NABE4, NABE6, ROBA-1, RWR1873, RWV3006) were consistent in short cooking time for the two seasons and had a Fe content above the low Fe check (CAL96 – 55mg/kg). A high correlation (r = 0.71) was observed between Fe and Zn whereas a low correlation between cooking time and Fe (r = -0.04) and Zn (r = 0.04) was observed. Great variability was evident for both traits indicating possible improvement by breeding and thus the possibility of having short cooking common bean genotypes with high Fe and Zn content

Improvement of resistance to fusarium root rot through gene pyramiding in common bean

Fusarium root rot (FRR), caused by Fusarium solani f.sp. phaseoli , is one of the most serious root rot diseases of common bean ( Phaseolus vulgaris L.) throughout the world. Yield losses of up to 84% have been attributed to the disease. Development and deployment of resistant materials is the most feasible approach to managing the disease. The objective of this study was to estimate the number of pyramided Fusarium root rot resistance genes among the four resistant lines and determine their effectiveness in improving levels of resistance to Fusarium root rot in the susceptible bean cultivars. Crosses among four Fusarium root rot (Fusarium solani f.sp. phaseoli) resistant common bean (Phaseolus vulgaris) were developed. They involved six inbred lines, MLB-48-89A (M48), MLB-49-89A (M49), G2333 (G2) and G685 (G6), and two susceptible cultivars, K20 and Kanyebwa, The resistant lines were used to develop a double cross (DC) population. The DC F1 and each resistant parent were crossed to each of the two susceptible cultivars to form five-parent and single crosses, respectively. Developed populations were subjected to Fusarium solani f. sp. phasoeli isolate-3 under screenhouse conditions. There were segregation ratios of 15:1 (\u3c72 = 1.89, P = 0.17), 61:3 (\u3c72 = 0.18, P = 0.67) and 249:7 (\u3c72 = 1.74, P = 0.19) indicating that two, three and four genes independently condition resistance to F. solani in lines G2 x G6, M49 x M48 and (M49 x M48) x (G2 x G6). A good fit of only four genes in the double cross compared to two in the G2 x G6 , and three genes in the M49 x M48 cross suggests that at least one parent in the G2 x G6 cross have the same or closely linked genes as a parent in the M49 x M48 cross. The F1 means of the five-parent cross (FPC) involving either susceptible parent had lower disease scores, though not significantly (P > 0.05), than the single-crosses from that parent. The F2 of both FPC showed less disease than the single-cross (SC) means (P < 0.05) compared to the single-cross (SC) while the F2 of both FPC had a significant negative deviation (P < 0.05). The F2 frequency distributions also showed that the FPC in both Kanyebwa and K20 populations had higher proportions of resistant plants than any of the single crosses in the respective populations. The superior performance of the FPC over the SC demonstrates that combining resistance genes form different FRR resistance sources can provide a stable source of resistance than using single sources of resistance.Pourriture racinaire caus\ue9e par Fusarium solani f.sp. phaseoli est l\u2019une des plus dang\ue9reuses pourritures racinaires du haricot commun ( Phaseolus vulgaris L.) partout dans le monde. La maladie cause des pertes de rendement jusqu\u2019\ue0 84%. L\u2019objectif de cette \ue9tude \ue9tait d\u2019estimer le nombre de combinaisons de g\ue8nes de r\ue9sistance \ue0 la pourriture racinaire due au Fusarium parmi 4 lign\ue9es r\ue9sistantes et d\ue9terminer leur efficacit\ue9 dans l\u2019am\ue9lioration des niveaux de r\ue9sistance \ue0 la pourriture racinaire dans les vari\ue9t\ue9s sensibles. Les croisements ont \ue9t\ue9 d\ue9velopp\ue9s parmi les 4 vari\ue9t\ue9s de haricot commun r\ue9sistantes au Fusarium. Les croisements impliquaient six lign\ue9es, MLB48-89A, MLB-49-89A, G2333 et G685, et deux vari\ue9t\ue9s sensibles, K20 et Kanyebwa. Les lign\ue9es r\ue9sistantes \ue9taient utilis\ue9es pour d\ue9velopper une population \ue0 double croisement. Les individus de la g\ue9n\ue9ration F1 du double croisement et chaque parent r\ue9sistant \ue9taient crois\ue9s \ue0 chacun des deux cultivars sensibles pour former des croisements \ue0 cinq parents et simples, respectivement. Les populations d\ue9velopp\ue9es \ue9taient soumises \ue0 l\u2019isolat3 du Fusarium solani f.sp. phaseoli en serre. Les rapports de s\ue9gr\ue9gation \ue9taient de 15:1 (\u3c72 = 1.89, P = 0.17), 61:3 (\u3c72 = 0.18, P = 0.67) et 249:7 (\u3c72 = 1.74, P = 0.19), montrant que deux, trois et quatre g\ue8nes conditionnent ind\ue9pendamment la r\ue9sistance au F. solani dans les lign\ue9es G2 x G6, M49 x M48 et (M49 x M48) x (G2 x G6). Une bon adjustement de quatre g\ue8nes seulement dans le double croisement compar\ue9 \ue0 deux dans le croisement G2 x G6, et trois g\ue8nes dans le croisement M49 x M48 indique qu\u2019au moins un parent dans le croisement a les m\ueames g\ue8nes ou les g\ue8nes \ue9troitement li\ue9s pour un parent dans le croisement M49 x M48. Les moyennes des F1 issues des croisements \ue0 cinq parents impliquant le parent Kanyebwa et les populations de K20 avaient des d\ue9viations n\ue9gatives non significatives (P > 0.05) compar\ue9 au croisement simple. D\u2019autre part, les F2 des deux croisements \ue0 cinq parents avaient des d\ue9viations n\ue9gatives significatives (P < 0.05) issues des moyennes de croisements simples, ce qui indique une s\ue9v\ue9rit\ue9 des sympt\uf4mes de la pourriture racinaire plus faible dans les croisements \ue0 cinq parents que dans les simples croisements. La fr\ue9quence des distributions des F2 montrait aussi que les croisements \ue0 cinq parents \ue0 la fois dans les populations de Kanyebwa et celles de K20 avaient des proportions des plants r\ue9sistants plus \ue9lev\ue9es que toutes celles des croisements simples dans les populations respectives

Characterisation of Phaseolus coccineus interspecific germplasm accessions for disease resistance, grain market class and yield attributes

Sister species of the common bean ( Phaseolus vulgaris L.) are an attractive genetic resource to broaden the genetic base of this crop, especially for adaptation to extreme environments. The runner bean (Phaseolus coccineus) in particular, has been shown to contribute to disease resistance and tolerance to low soil fertility, and has been used to introduce these traits into the common bean. The objective of this study was to identify germplasm with agronomic traits suitable for cultivation from an interspecific population (Phaseolus coccineus G35346 x P. vulgaris; SER 16) of 186 bush lines. The lines, coded ALB and one yield check, CAL96, were field evaluated for three rain seasons; 2011a (March-June), 2011b (September-November) and 2012 (March-June) at the National Agricultural Research Laboratories (NARL)-Kawanda, Uganda. Artificial inoculum of bean common mosaic virus (BCMV) was applied to the field experiment in 2011a. The morphological (seed type and growth habit) and agronomic attributes (plant vigour, days to physiological maturity; DPM and days to 50% flowering; DF), reaction to occurring diseases and yield performance were monitored. The lines including root rot resistant and susceptible checks; MLB-49-89A, RWR 719 and CAL 96, were also subjected to inoculum of two major root rot pathogens; Fusarium solani f.sp. phaseoli (isolate FSP3) and Pythium ultimum (isolate MS61) under screen house conditions to select for root rot resistance. Results indicated significant differences (P<0.05) among the interspecific lines for the parameters measured. Days to flowering and to DPM ranged from 31-39 and 81-86, respectively. Field disease pressure was generally low, but in general, 50% of the lines had yield above the mean; while 8% maintained above average yield in all seasons. The superior lines included; ALB169 (mean yield 2,564 kg ha-1), ALB214 (mean yield 2,125 kg ha-1), ALB196 (mean yield 2,084 kg ha-1), ALB5 (2,062 kg ha-1), ALB152 (2,016 kg ha-1), and ALB179 (2011 kg ha-1), compared to the check CAL96 (1,607 kg ha-1). These lines, except ALB169 and ALB179, were resistant root rot. More lines expressed resistance to Fusarium than to Pythium root rot, with 21.5% showing resistance to both root rot isolates. Over 91% of the lines were small or medium seeded (< 35.0 g per 100 seeds), with red monochrome seed pattern; characteristics that are important for farmer acceptance.Les esp\ue8ces s\u153urs du haricot commun ( Phaseolus vulgaris L.) sont une ressource g\ue9n\ue9tique attractive pour accro\ueetre la base g\ue9n\ue9tique de la culture, sp\ue9cialement pour adaptation aux environnements extr\ueames. Le haricot rampant (Phaseolus coccineus) en particulier, contribue \ue0 la r\ue9sistance contre la maladie et \ue0 la tol\ue9rance \ue0 la faible fertilit\ue9 du sol de, et a \ue9t\ue9 utilis\ue9 pour introgresser ces traits dans le haricot commun. L\u2019objectif de cette \ue9tude \ue9tait d\u2019identifier le germplasm avec des traits agronomiques favorable \ue0 la culture d\u2019une population intersp\ue9cifique (Phaseolus coccineus G35346 x P. vulgaris; SER 16) d\u2019une s\ue9rie de 186 lign\ue9es. Les lign\ue9es le ALB cod\ue9 sur le rendement de contr\uf4le, CAL96, \ue9taient \ue9valu\ue9es pendants trois saisons pluvieuses 2011a (Mars-Juin), 2011b (Septembre-Novembre) et 2012 (Mars-Juin) aux laboratoires Nationaux des Recherches Agricoles (NARL)-Kawanda, Ouganda. L\u2019inoculation artificielle du virus mosa\uefque (BCMV) du haricot commun \ue9tait appliqu\ue9e aux exp\ue9rimentations du champ en 2011a. Les attributs morphologiques (type de graines et l\u2019habitude de croissance) et agronomiques (vigueur de plant, le nombre de jours de maturit\ue9 physiologique, DPM et le nombre de jours de 50% de floraison\ua0; DF)\ua0; la r\ue9action \ue0 l\u2019apparition de maladies et la performance de rendement \ue9taient suivis. Les lign\ue9es comportant des contr\uf4les r\ue9sistants et susceptibles \ue0 la pourriture des racines; MLB-49-89A, RWR 719 et CAL 96, \ue9taient aussi sujets \ue0 l\u2019inoculum de deux pathog\ue8nes majeurs causant la pourriture des racines\ua0; Fusarium solani f.sp. phaseoli (isolat FSP3) et Pythium ultimum (isolat MS61) sous les conditions de la serre afin de s\ue9lectionner pour la r\ue9sistance contre la pourriture des racines. Les r\ue9sultats ont indiqu\ue9 de diff\ue9rences significatives (P<0.05) entre les lign\ue9es intersp\ue9cifiques pour les param\ue8tres mesur\ue9s. Le nombre de jours de floraison et DPM ont vari\ue9 entre 31-39 et 81-86, respectivement. La pression des maladies du champ \ue9tait g\ue9n\ue9ralement faible, mais en g\ue9n\ue9ral, 50% des lign\ue9es ont eu un rendement au-dessus de la moyenne\ua0; alors que 8% ont maintenu leur rendement au-del\ue0 pendant toutes les saisons. Les lign\ue9es sup\ue9rieures comprenaient\ua0; ALB169 (rendement moyen 2 564 kg ha-1), ALB214 (rendement moyen 2 125 kg ha-1), ALB196 (rendement moyen 2 084 kg ha-1), ALB5 (2 062 kg ha-1), ALB152 (2 016 kg ha-1), et ALB179 (2011 kg ha-1), compar\ue9es aux contr\uf4les CAL96 (1 607 kg ha-1). Ces lign\ue9es, \ue0 l\u2019exception d\u2019ALB169 et ALB179, \ue9taient r\ue9sistantes \ue0 la pourriture de la racine. De nombreuses lign\ue9es ont exprim\ue9 leur r\ue9sistance \ue0 la pourriture de racines due au Fusarium qu\u2019au Pythium, avec 21.5% montrant leur r\ue9sistance aux deux isolats de pourriture de racines. En plus, 91% des lign\ue9es ont de petites ou moyennes graines (< 35.0 g par 100 graines), avec une monochrome rouge de motif germinal\ua0; des caract\ue9ristiques qui sont importantes pour l\u2019acceptation du producteur

Development, promotion and dissemination of improved Fusarium wilt resistant pigeon pea lines in drought prone areas of Uganda

Pigeon Pea (Cajanus cajan) remains a relatively untapped food legume crop in Uganda and in many parts of Africa mainly due to lack of promotion and availability of varieties that meet producer and consumers needs. The crop is a rich source of protein, fixes nitrogen in the soil and is tolerant to drought conditions. This makes it an ideal crop for the semi-arid areas of Africa. This project is using a participatory breeding approach to develop and promote consumer/market preferred pigeon pea varieties resistant to Fusarium wilt disease (Fusarium udum) and drought among farmers in northern Uganda. To do this, a collection of landraces and elite materials from Uganda, Malawi and ICRISAT is being screened for farmer desired qualities. Promising lines will be analyzed for performance under Fusarium wilt infection and drought, and thereafter selected lines will be entered into a breeding program. All research activities have been designed as part of two students' M.Sc. thesis research, involving a Ugandan and a Malawian studen

PREVALENCE OF ANGULAR LEAF SPOT DISEASE AND SOURCES OF RESISTANCE IN COMMON BEAN IN EASTERN DEMOCRATIC REPUBLIC OF CONGO

Angular leaf spot ( Pseudocercospora griseola Crous U, Brown) is one of the most important diseases hindering common bean ( Phaseolus vulgaris L.) production in the Great Lakes Region of Africa, including the Democratic Republic of Congo. The disease causes extreme yield losses, estimated at 384.2 tonnes per year, in Sub-Saharan Africa. Little is known about the distribution, severity and incidence of the disease and the effect of agronomic practices and environmental factors on the disease prevalence in the country to facilitate interventions. A field survey was conducted during two crop seasons, February to June and September to January, in two main beans growing zones of eastern DRC namely; sub-humid highland and sub-humid mid altitude at low latitudes, in South and North Kivu, respectively. Severity and incidence of angular leaf-spot and other occurring diseases were assessed on common bean plants in farmers\u2019 fields. Angular leaf spot in these fields had an average severity index (PSI) of 49.9%. PSI was significantly different (P<0.05) between districts and seasons. Using multiple regression analysis, independent variables: growth stage, cropping system, districts and altitude were shown to have significant influence on the observed PSI (P<0.05) with R2 = 96.2%. The highest severity (PSI=59.7%) was observed in Kabare district, and the lowest in Uvira district (PSI=39.5%). Screening of a set of 37 released common bean varieties in DRC using virulent Andean and Mesoamerican isolates identified four resistant bean varieties; ARA 4, COD MLV 059, MLV 224/94B, LSA 144 and Mexico 54. Some of these varieties possess useful traits, in addition to acceptable seed market class, and are hence recommended as suitable parents for ALS resistant variety development and promotion in ALS prone environments.La tache angulaire ( Pseudocercospora griseola Crous U, Brown) est l\u2019une des maladies les plus importantes qui entravent la production de haricot commun ( Phaseolus vulgaris L.) dans la r\ue9gion des Grands Lacs d\u2019Afrique, y compris la R\ue9publique D\ue9mocratique du Congo. La maladie provoque des pertes de rendement extr\ueames, estim\ue9es \ue0 384.2 tonnes par an en Afrique Sub-Saharienne. Ily a encore peu de connaissance sur la distribution, la gravit\ue9 et l\u2019incidence de la maladie et l\u2019effet des pratiques agronomiques et des facteurs environnement aux sur la pr\ue9valence de la maladie dans le pays pour faciliter les interventions. Une enqu\ueatesur le terrain a \ue9t\ue9men\ue9e pendant deux saisons de r\ue9colte, de F\ue9vrier \ue0 Juin et de Septembre \ue0 janvier, dans deux zones principals de culture de haricots de l\u2019est de la RDC, \ue0 savoir: Sous-humides de haute altitude et sous-humides \ue0 basse altitude, au Sud et au Nord-Kivu. La gravit\ue9 et l\u2019incidence de la tache angulaire des feuilles et d\u2019autres maladies ont \ue9t\ue9 \ue9valu\ue9es sur les plants de haricots dans les champs des agriculteurs. Ces champs \ue9taient infest\ue9s par la maladie, avec unindice de gravit\ue9 moyen (IPS) de 49.9%. PSI \ue9tait significativement diff\ue9rent (P <0.05) entre districts et saisons. En utilisant l\u2019analyse de r\ue9gression multiple, les variables ind\ue9pendantes: stade de croissance, syst\ue8me de culture, districts et altitude ont montr\ue9 une influence significative sur le PSI observ\ue9 (P <0.05) avec R2 = 96.2%. La s\ue9v\ue9rit\ue9 plus \ue9lev\ue9e (PSI = 59.7%) a \ue9t\ue9 observ\ue9e dans le district de Kabare et la plus faible dans le district d\u2019Uvira (PSI = 39,5%). La s\ue9lection d\u2019un lot de 37 vari\ue9t\ue9s de haricot distribu\ue9es en RDC utilisant des isolats virulents Andins et M\ue9soam\ue9ricains a permis d\u2019identifier quatre vari\ue9t\ue9s de haricots r\ue9sistants; ARA 4, COD MLV 059, MLV 224 / 94B, LSA 144 et Mexique 54. Certaines de ces vari\ue9t\ue9s pr\ue9sentent des traits utiles en plus de son acceptabilit\ue9 sur lemarch\ue9 des semences, et sont donc recommand\ue9s comme des parents appropri\ue9s pour le d\ue9veloppement et la promotion des vari\ue9t\ue9s r\ue9sistantes ALS

Effect of intermittent drought on phenotypic traits of F5 RIL Andean intra-gene cross population (BRB 191 X SEQ 1027) of common bean

Drought is a major constraint to common bean ( Phaseolus vulgaris L.) production in East Africa, where irrigation for the crop is very uncommon. The objective of this study was to identify drought tolerant lines and phenotypic traits underlying drought tolerance among 128 F5 recombinant inbred lines (RILs), derived from intra gene pool population, between drought tolerant BRB 191 (source of bc-3) and SEQ 1027. The population was evaluated with eight experimental checks that included BAT 477, CAL 96, DAB 441, DAB 494, and Diacol Calima, NABE 4, SCR 9 and SEQ 1003. A total of 20 phenological, morphological and physiological shoot traits were evaluated, under drought and non-stress conditions, in the field for 2 years (2014 and 2015) at Kawanda in Uganda. New sources of drought tolerance, and previously identified sources of drought tolerance in common bean (BAT 477, DAB 441 and DAB 494), were confirmed based on their superior geometric means and low drought susceptibility. Drought stress in the field significantly affected all measured traits, except harvest index and stem dry weight reduction (P<0.001). Drought significantly reduced yield, yield components and pod harvest index (P<0.01). However, chlorophyll content, canopy temperature, stem dry mass reduction, and 100 seed weight remained stable under season by genotype by water regime treatment interactions (S x G x T). The stability of these traits highlighted their usefulness in selecting for drought tolerance across different environments. Furthermore, pod partitioning index (PPI), harvest index (HI), chlorophyll content and stem dry weight reduction also remained stable under G x T effects. Significant correlations (P<0.001) were maintained between HI and PPI with seed yield under drought stress in field conditions, indicating that photosynthate remobilisation increases yield under drought stress conditions.La s\ue9cheresse est une contrainte major \ue0 la production du haricot commun ( Phaseolus vulgaris L.) en Afrique de l\u2019Est, o\uf9 l\u2019irrigation pour la culture est tr\ue8s rare. L\u2019objectif de cette \ue9tude a \ue9t\ue9 d\u2019identifier les lign\ue9es tol\ue9rantes \ue0 la s\ue9cheresse et les traits ph\ue9notypiques contr\uf4lant la tol\ue9rance \ue0 la s\ue9cheresse parmi les 128 F5 de lign\ue9es consanguines recombinantes, d\ue9riv\ue9es d\u2019une population intra-g\ue8ne de la r\ue9gion andine, entre la lign\ue9e tol\ue9rante \ue0 la s\ue9cheresse BRB191 (source du bc-3) et SEQ 1027. La population a \ue9t\ue9 \ue9valu\ue9e avec huit contr\uf4les exp\ue9rimentaux comprenant BAT 477, CAL 96, DAB 441, DAB 494, et Diacol calima, NABE 4, SCR 9 et SEQ 1003. Un total de 20 traits phr\ue9nologiques, morphologiques et physiologiques a \ue9t\ue9 \ue9valu\ue9, sous les conditions de stress hydrique, dans le champ pour 2 ans (2014 et 2015) \ue0 Kwanda en Uganda. De nouvelles sources de tol\ue9rance, et des sources de tol\ue9rance pr\ue9c\ue9demment identifi\ue9es dans le haricot commun (BAT 477, DAB 441 et DAB 494), ont \ue9t\ue9 confirm\ue9es sur la base des moyens de sup\ue9riorit\ue9 g\ue9om\ue9triques et de susceptibilit\ue9 de faible s\ue8cheresse. Le stress hydrique dans le champ a significativement affect\ue9 tous les traits mesur\ue9s, \ue0 l\u2019exception de l\u2019indice de r\ue9colte et la r\ue9duction du poids sec de la tige (P<0,001). La s\ue9cheresse a significativement r\ue9duit le rendement, les composantes du rendement et l\u2019indice de la r\ue9colte de la gousse (P<0.01). Toutefois, la temp\ue9rature de la canop\ue9e, la r\ue9duction du poids sec de la tige, et le poids de 100 graines sont rest\ue9s stables sous le traitement de l\u2019interaction entre la saison x g\ue9notype x r\ue9gime d\u2019eau de m\ueame que l\u2019interaction entre le g\ue9notype x le traitement (G X T) (P<0,001). La stabilit\ue9 de ces traits a montr\ue9 leur utilit\ue9 dans la s\ue9lection pour la tol\ue9rance \ue0 la s\ue9cheresse \ue0 travers les diff\ue9rents environnements. De plus, l\u2019indice du partitionnement de la gousse (PPI), l\u2019indice de r\ue9colte (HI), la teneur en chlorophylle et la r\ue9duction du poids sec de la tige sont rest\ue9s \ue9galement stables sous les effets de G x T. Des corr\ue9lations significatives (P<0,001) ont \ue9t\ue9 maintenues entre HI et PPI avec le rendement en graine sous le stress hydrique dans les conditions de champ, indiquant la viabilit\ue9 de la remobilisation de la photosynthate dans l\u2019augmentation du rendement potentiel sous les conditions de stress hydrique

Pathogenicity and virulence of Ugandan isolates of common bacterial blight disease pathogen ( Xanthomonas spp.)

Breeding for resistance is a major component in the integrated management of common bacterial disease of beans ( Phaseolus vulgaris L.). Use of less virulent strains or strains with attenuated virulence may lead to selection of resistant genotypes with intermediate response, when exposed to more virulent strains of the pathogen. The objective of this study to identify and characterise Ugandan isolates of common bacterial blight disease-causing pathogens for virulence. Bacteria were isolated from leaf samples collected from districts of Kabale, Masaka, Bukomansimbi, Mubende, Mbale, Bulambuli and Apac, all in Uganda, during the first season of 2016. The bacteria were tested for pathogenicity, as well as virulence on both breeding and local varieties. The study identified three most virulent isolates, namely MBL020, KAB-3 and BUL-14, all belonging to Xathomonas citri pv fuscans. These isolates are very similar to those previously identified from Uganda (NCPB 670 and NCCPB 1402) more than 50 years ago. The study further revealed that NAROBEAN1, NAROBEAN 2, NAROBEAN 4, VAX 3, VAX5 and NE 2- 14- 8 had better resistance compared to other tested genotypes.La s\ue9lection pour la r\ue9sistance est un \ue9l\ue9ment majeur de la gestion int\ue9gr\ue9e des maladies bact\ue9riennes courantes des haricots ( Phaseolus vulgaris L.). L\u2019utilisation de souches moins virulentes ou de souches \ue0 virulence att\ue9nu\ue9e peut conduire \ue0 la s\ue9lection de g\ue9notypes r\ue9sistants \ue0 r\ue9ponse interm\ue9diaire, lorsqu\u2019ils sont expos\ue9s \ue0 des souches plus virulentes du pathog\ue8ne. L\u2019objectif de cette \ue9tude etait d\u2019identifier et de caract\ue9riser les isolats ougandais de pathog\ue8nes causant la maladie bact\ue9rienne commune pour la virulence. Des bact\ue9ries ont \ue9t\ue9 isol\ue9es \ue0 partir d\u2019\ue9chantillons de feuilles pr\ue9lev\ue9s dans les districts de Kabale, Masaka, Bukomansimbi, Mubende, Mbale, Bulambuli et Apac, tous en Ouganda, au cours de la premi\ue8re saison de 2016. Les bact\ue9ries ont \ue9t\ue9 test\ue9es pour leur pathog\ue9nicit\ue9, ainsi que leur virulence \ue0 la fois pour la reproduction et vari\ue9t\ue9s locales. L\u2019\ue9tude a identifi\ue9 les trois isolats les plus virulents, \ue0 savoir MBL020, KAB-3 et BUL-14, tous appartenant \ue0 Xathomonas citri pv fuscans. Ces isolats sont tr\ue8s similaires \ue0 ceux pr\ue9c\ue9demment identifi\ue9s en Ouganda (NCPB 670 et NCCPB 1402), il y a plus de 50 ans. L\u2019\ue9tude a en outre r\ue9v\ue9l\ue9 que NAROBEAN1, NAROBEAN 2, NAROBEAN 4, VAX 3, VAX5 et NE 2- 14-8 avaient une meilleure r\ue9sistance par rapport aux autres g\ue9notypes test\ue9s