Germplasm of common beans from the Mesoamerican gene pool races: Durango, Jalisco, Mesoamerica and Guatemala have highest genetic variation for the crop's improvement. The objective was to assign 50 common bean germplasm in Uganda into its gene pool races based on analyses of population structure. Secondly, to estimate heritability and effects of genotype × environment (GXE) interaction on common bean agronomic and yield traits in space and time. Sample genomic DNA was amplified in 2011 with 22 Simple sequence repeat markers (SSRs) and alleles separated using capillary electrophoresis. Field evaluations were conducted in 2010 and 2011 at NaCRRI and 2015 at CIAT – Kawanda. Multivariate analyses of SSRs data identified four subgroups within the germplasm: K4.1–K4.4, with corresponding Wrights fixation indices (FST) as 0.1829 for K4.1, 0.1585 for K4.4, 0.1579 for K4.2 and least for K4.3 at 0.0678. Gene pool race admixtures in the population (14%) were notable and attributed to gene flow. Four superior parents currently used in improving resistance to major diseases grouped as; Jalisco for MLB49-89A; Mesoamerica for MCM5001 and G2333; Durango for MEXICO 54. Heritability values for yield traits estimated using phenotypic data from above fixed parents, was above 0.81. Season and location had significant effect (P < 0.05) on numbers of: flower buds per inflorescence, pod formation and weight of 100 seeds. The findings will improve understanding of co-evolutionary relationships between bean hosts and pathogens for better disease management and will broaden the germplasm base for improving other tropical production constraints.

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Iron and zinc are essential micronutrients for normal human growth and development and are commonly deficient in diets of the most vulnerable. Common bean (Phaseolus vulgaris 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 the International Centre for Tropical Agriculture (CIAT) and its partners through the Pan Africa Bean Research Alliance (PABRA), were evaluated for agronomic traits, disease response, 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.

Root rots cause severe yield losses of up to >70% in common bean (Phaseolus vulgaris L.) in most parts of the world, with devastating effects on the major commercial bean cultivars in East and Central Africa. Increased intensity of droughts and rains, and higher temperatures influence the occurrence and distribution of root rots, resulting in increased epidemics. The causal pathogens tend to occur in a complex, and since most cultivars do not have broad resistance, adverse effects continue to occur. The objective of this study was to evaluate the levels of dual resistance of new breeding lines (BL) developed for root rot resistance, as well as Andean (ADP) genotypes, for resistance to Fusarium (FRR) and Pythium root rots (PRR). Altogether, 316 new BL developed for root rot resistance and 295 ADP bean genotypes were evaluated at Kawanda in Uganda. There were significant differences (P<0.05) among genotypes for both root rots and yield. Thirty and 1.9 percent of the BL and ADP genotypes expressed resistance to both root rots. In addition, more than 80% of ADP genotypes showed susceptibility to both root rots. Yield was generally poor with means of 458 kg ha-1 for ADP, and ranging from 949 to 1075 kg ha-1 for the BL groups. Nonetheless, the 0.3 and 2.4% of the ADP and BL that yielded >2000 kg ha-1 expressed high yield potential, considering that majority of the genotypes yielded below 1000 kg ha-1.