Identification of sources of resistance to common bacterial blight in common bean in Ethiopia

Abstract

Common bacterial blight (CBB) caused by Xanthomonas axonopodis pv. phaseoli and X. axonopodis pv. phaseoli var. fuscans is one of the major biotic constraints limiting common bean (Phaseolus vulgaris L.) production and productivity in Ethiopia. The objective of this study was to identify new sources of CBB resistance from a diverse panel of genotypes to develop CBB‐resistant common bean varieties. One hundred and ten diverse accessions were evaluated for CBB resistance at three hotspot sites (Melkassa, Arsi Negelle and Mieso) for two seasons (2017 and 2018) in Ethiopia. Data on mean disease severity on leaf (SL) and mean disease severity on pod (SP), the area under disease progress curve (AUDPC), number of pods per plant (PP), number of seeds per pod (SPP) and grain yield (GY) were collected. Data were subjected to standard analysis of variance and principal component analysis. The genotype × site interaction (G × E) had significant (p < .05) effect on all assessed traits. This indicated the presence of marked variation among tested genotypes in CBB resistance across the testing sites. Genotypes including SEC21, SEC23, SMC21, VAX6, SEC12, SEC25, SMC22, VAX5, SEC20, SEC22, SEC24, SEC26, SMC16 SMC24, VAX6, SEC25, SEC21, SEC23 and SMC21 exhibited lower values of SL, SP and AUDPC which are useful genetic resources for future CBB resistance breeding programmes. Nasir provided a grain yield of 3.45 ton/ha followed by VAX1 (2.86 ton/ha) and Hawassa Dume (2.83 ton/ha). Further, CBB‐resistant and high yielding genotypes had the higher PPP and SPP making them ideal candidates for common bean breeding in Ethiopia or similar agro‐ecologies emphasizing CBB resistance and enhanced agronomic traits.

Evaluation of common bean (Phaseolus vulgaris) genotypes for resistance to common bacterial blight and angular leaf spot diseases, and agronomic performances

“…Hence, it could be evidence to get sources of disease resistance from elite lines, landraces and released varieties, probably also from gene pools could be used in the common bean breeding system. In this regard, studies by Tumsa et al (2020) tested 110 bean genotypes and found that 32 of the genotypes had superior CBB resistance reaction and agronomic performances which confirm for the present finding. Similarly, Adila et al (2021) reported that common bean genotypes performed variably to CBB infections, grain yield and yield components under field conditions.…”

“…Variable reactions among the genotypes showed the possibility of obtaining genes for resistance and confirmed the presence of genes for resistance having varying genetic potentials to adjust under different environments ( Rezene and Mekonin, 2019 ; Tumsa et al., 2020 ; Adila et al., 2021 ). Beebe et al.…”

“…This might explain that disease pressure had negative effects on the crop developmental stages. In common bean genotypes evaluation studied by Lemessa and Tesfaye (2005) , angular leaf spot severity negatively correlated with yield parameters and, similarly, Tumsa et al. (2020) and Adila et al.…”

“…Disease severity was used to identify disease resistance reactions and indicated the existence of potential sources of resistance against CBB and ALS diseases in the evaluated common bean genotypes in the two years. Previous studies also reported the presence of marked genetic variation Variable reactions among the genotypes showed the possibility of obtaining genes for resistance and confirmed the presence of genes for resistance having varying genetic potentials to adjust under different environments (Rezene and Mekonin, 2019;Tumsa et al, 2020;Adila et al, 2021). Beebe et al (2010) indicated a wider window for variation in phenology and disease resistance ability could be due to enormous variation in the gene pools and races of genotypes.…”

“…However, crop rotation could be a challenge because of the shortage of cropping land and use of chemicals for spray and seed treatment is often expensive and not readily available to or affordable by smallholder farmers. Therefore, use of genetic resistance is the best strategy, economical and environmentally resilient method of disease management approach in common bean production ( Tumsa et al., 2020 ; Adila et al., 2021 ). High levels of host resistance could minimize yield losses, reduce use of chemicals, facilitate integrated disease management scheme and increase distribution of pathogen-free seeds (Singh and Schwartz, 2010).…”