Phenotypic and genotypic screening for rust resistance in common bean germplasm in Uganda

Rust caused by Uromyces appendiculatus (Pers., Pers.) Unger is one of the major foliar diseases of common bean (Phaseolus vulgaris) in Uganda. The use of host resistance remains the best option in managing this disease. The objective of this study was to identify sources of broad-spectrum rust resistance in common bean germplasm including landraces, commercial and introduced genotypes using a combination of phenotypic and genotypic screening with simple sequence repeats (SSRs) markers located on chromosome Pv04. A total of 138 cultivars were field screened from 2014 and 2015 using alpha lattice design. The variance and correlation of disease incidence, area under the disease progression curve (AUDPC) and total grain yield were computed using GenStat. The polymorphism information content of the cultivars was determined, and the association of the markers and the disease resistance traits were analyzed using PowerMarker and TASSEL respectively. Resistance of each cultivar was compared to the presence and absence of amplified markers. There were highly significant differences (P < 0.001) among the cultivars for disease incidence, AUDPC and total grain yield and a strong correlation (P < 0.001) between disease incidence and AUDPC in both years. The SSR markers, BARC_PV_SSR04725, bean_ssr_0778 and bean_ssr_2892 were observed to be associated (P ≤0.05) with rust resistance. The two screening methods identified cultivars which included local cultivars, Nabufumbo, Kapchorwa white, and NABE as new sources of rust resistance. This study identified sources of rust resistance that would be useful in the bean breeding programmes in Uganda.
Uromyces appendiculatus, Phaseolus vulgaris, SSR markers, Broad spectrum rust resistance, AUDPC
Odogwu, Blessing A.; Nkalubo, Stanley T.; Mukankusi, Clare; Odong, Thomas; Awale, Halima E.; Rubaihayo, Patrick; Kelly, James D.. 2017. Phenotypic and genotypic screening for rust resistance in common bean germplasm in Uganda. Euphytica. 213: 49.