Common bean (Phaseolus vulgaris L.) is an important legume crop worldwide. The International Centre for Tropical Agriculture (CIAT) and its national partners in Africa aim to overcome production constraints of common bean and address the food, nutrition needs and market demands through development of multitrait bean varieties. Breeding is guided by principles of market‐driven approaches to develop client‐demanded varieties. Germplasm accessions from especially two sister species, P. coccineus and P. acutifolius, have been utilized as sources of resistance to major production constraints and interspecific lines deployed. Elucidation of plant mechanisms governing pest and disease resistance, abiotic stress tolerance and grain nutritional quality guides the selection methods used by the breeders. Molecular markers are used to select for resistance to key diseases and insect pests. Efforts have been made to utilize modern genomic tools to increase scale, efficiency, accuracy and speed of breeding. Through gender‐responsive participatory variety selection, market‐demanded varieties have been released in several African countries. These new bean varieties are a key component of sustainable food systems in the tropics.
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.
This article explores the informal seed business, focusing on the yellow bean in Tanzania. The yellow bean is a major bean type traded, yet little is known about the seed supply that fuels it. The survey research in 2019 encompassed larger grain traders, informal seed traders, and retailers, covered major production, distribution and sale hubs, and was complemented by GIS mapping of seed and grain flows and DNA fingerprinting of yellow bean samples. Results showed that traders buy and sell grain and informal seed: it is not one business or the other, but both. Informal seed is an important moneymaker, representing between 15 and 40% of trader business in non-sowing and sowing periods, respectively. In the year monitored, 100% of the yellow bean seed was drawn from the informal sector, amounting to $US 4.35 million just among those sampled. Nevertheless, the informal and formal sectors are clearly linked, as over 60% of the beans sampled derived from modern varieties. Informal traders prove key for: sustaining the grain business, serving the core of the seed business, and moving varieties at scale. More explicit efforts are needed to link the informal sector to formal research and development partners in order to achieve even broader impacts.
Common bean (Phaseolus vulgaris L.) is important in African diets for protein, iron (Fe), and zinc (Zn), but traditional cultivars have long cooking time (CKT), which increases the time, energy, and health costs of cooking. Genomic selection was used to predict genomic estimated breeding values (GEBV) for grain yield (GY), CKT, Fe, and Zn in an African bean panel of 358 genotypes in a two‐stage analysis. In Stage 1, best linear unbiased estimates (BLUE) for each trait were obtained from 898 genotypes across 33 field trials in East Africa. In Stage 2, BLUE in a training population of 141 genotypes were used in a multivariate genomic analysis with genome‐wide single nucleotide polymorphism data from the African bean panel. Moderate to high genomic heritability was found for GY (0.45 ± 0.10), CKT (0.50 ± 0.15), Fe (0.57 ± 0.12), and Zn (0.61 ± 0.13). There were significant favorable genetic correlations between Fe and Zn (0.91 ± 0.06), GY and Fe (0.66 ± 0.17), GY and Zn (0.44 ± 0.19), CKT and Fe (−0.57 ± 0.21), and CKT and Zn (−0.67 ± 0.20). Optimal contributions selection (OCS), based on economic index of weighted GEBV for each trait, was used to design crossing within four market groups relevant to East Africa. Progeny were predicted by OCS to increase in mean GY by 12.4%, decrease in mean CKT by 9.3%, and increase in mean Fe and Zn content by 6.9 and 4.6%, respectively, with low achieved coancestry of 0.032. Genomic selection with OCS will accelerate breeding of high‐yielding, biofortified, and rapid cooking African common bean cultivars.
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.
Dry bean (Phaseolus vulgaris L.) is a globally important leguminous food crop. Yields can be reduced by high incidence of soilborne oomycetes that cause seedling disease. Breeders have attempted to develop Pythium root rot-resistant bean varieties; however, relationships between dry bean and most soilborne oomycete species remain uncharacterized. Oomycete species (n = 28), including Pythium spp. and Phytopythium spp., were tested in a growth chamber seedling assay at 20°C and an in vitro seed assay at 20°C and 26°C to evaluate their pathogenicity and virulence on ‘Red Hawk’ dark red kidney bean and ‘Zorro’ black bean. Root size or disease severity was significantly impacted by 14 oomycete species, though results varied by bean variety, temperature, and assay. Of these 14 pathogenic oomycete species, 11 species exhibited significant differences in DSI due to temperature on at least one bean variety. Pythium aphanidermatum, P. myriotylum, P. ultimum, P. ultimum var. sporangiiferium, and P. ultimum var. ultimum were the most virulent species in both assays, causing seed rot and pre-emergence damping-off of dry bean. Oomycete species were clustered into three groups based on symptom development: seed rot pathogens, root rot pathogens, or nonpathogens. Intraspecific variability in virulence was observed for eight of the 14 pathogenic oomycete species. Improved understanding of Pythium and Phytopythium interactions with dry bean may enable breeders and pathologists to more effectively evaluate strategies for oomycete seedling disease management.
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.
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