Marker-assisted gamete selection for multiple disease resistance and grain yield in inter-gene pool and inter-racial populations of common bean

Abstract

Broadening the genetic base of existing breeding populations is crucial for increasing the variability and the chance of finding more promising genotypes. This study aimed at evaluating the agronomic performance and multiple disease resistance of F1.3 to F1.6 generations of 16 inter-racial small- and medium-seeded common bean populations selected in early generations using markers linked to genes for disease resistance. From 2013 to 2015, segregating F1.3 families from 16 populations were advanced to F1.5 following the gamete selection procedure at Kabete Field Station, University of Nairobi. The F1.6 lines were selected at Mwea Research Station of Kenya Agricultural and Livestock Research Organization (KALRO) for plant vigor, days to flowering and to physiological maturity, number of pods per plant, number of seeds per pod, 100-seed weight, field disease score and grain yield during the 2016 short rain season. Analysis of variance (ANOVA) and the least significant difference (LSD) test were performed to compare and separate means among different populations and lines within those populations. Pearson’s correlation coefficient was used to determine relationship between the grain yield and other agronomic traits. There were significant differences in grain yield among populations (P<0.05). Population KMA13-32 (KATB9 x Mex54 / G2333 // RWR719 / BRB191) with a mean yield of 2.84 t ha-1 out-yielded all other populations and commercial checks. Other high yielding populations were KMA13-31 (2.50 t ha-1) and KMA13-30 (2.25 kg ha-1). Grain yield was correlated with number of pods per plant (r=0.85***) and the seed yield per plant (r=0.97***) suggesting that these two traits can be used as an indirect selection criteria for grain yield. Inter-racial populations showed low to moderate disease infection levels in all the generations (1.0 to 5.0) while commercial checks were moderate to highly susceptible to most of the pathogens (3.1 to 9.0). After the F1.6 generation, 92 progeny rows from single plant selections belonging to five market classes were selected for further testing. The presence of transgressive genotypes combining high yield potential and multiple disease resistance in most of the populations confirmed the effectiveness of marker-assisted gamete selection and inter-racial crosses to improve seed yield of common beans.