Genotypic Performance of Short-Day Runner Bean (Phaseolus coccineus L.) Lines Combining High Grain Yield and Disease Resistance

Runner bean (Phaseolus coccineus L.) offers a great potential as a grain legume in Africa. However, its productivity is low because no improved short-day varieties are available. The aim of this study was to evaluate advanced short-day runner bean lines for high grain yield, resistance to diseases and suitable for cultivation under tropical conditions. F6.8 recombinant inbred lines developed from crosses between local landraces and high yielding imported variety (White Emergo) were evaluated in 2013 and 2014 in a randomized complete block design with three replicates at Kabete (1860 m.a.s.l.) and Ol Joro-Orok (2300 m.a.s.l.) in Kenya. Four local runner bean landraces were used as checks. Analysis of variance showed that there were significant differences for days to flowering, response to diseases and grain yield among the evaluated lines. Improved lines flowered within 49 to 52 days in 2013 and 34 to 58 days in 2014.The improved lines flowered earlier at Kabete than Ol Joro-Orok and showed a higher degree of resistance (scores 1-3) to the major diseases rust, bean common mosaic virus (BCMV) and powdery mildew. The mean grain yield at Kabete was 4,426 kg ha-1 compared to 6,523 kg ha-1 at Ol Joro-Orok giving an average yield advantage of up to 67% compared with local short-day landraces. The results indicated that new high yielding short-day runner bean varieties with resistance to major diseases and tropical adaptation can be obtained from these lines.