Breeding runner bean for short‐day adaptation, grain yield, and disease resistance in eastern Africa

Abstract Runner bean ( Phaseolus coccineus  L.), also known as butter bean in Kenya, is a high value vegetable and grain crop traditionally grown in high altitudes (>1,800 m) of eastern Africa for domestic consumption and processing. However, it has not received attention from breeders. Consequently, farmers rely on low‐yielding landraces which are susceptible to diseases. Available long‐day vegetable type varieties are poorly adapted to tropical conditions. In 2005, a regional program was initiated at the University of Nairobi to develop tropically adapted short‐day varieties with better agronomic potential to meet both producer and consumer requirements. The objective of this study was to determine the agronomic potential of advanced grain‐type runner bean lines selected from populations derived from crosses between local landraces and long‐day European varieties. Fifty lines were selected from 139 F 6.8 lines based on their previous performance at Kabete Field Station and Ol Joro Orok in 2012 and 2013. The 50 lines were evaluated at both sites during the 2014 long rain season. The best 20 lines from both sites were further evaluated for agronomic characteristics, disease resistance, and yield. Results showed considerable variation for duration to flowering (40–55 days at three different sites), plant vigor, racemes per plant, reaction to diseases, and grain yield. The crop was extremely vigorous in Naivasha due to supplementary irrigation and fertilization regimes. The results indicated that new high‐yielding grain runner bean varieties with resistance to major diseases and tropical adaptation can contribute to improved productivity, food and nutritional security, and resilient livelihoods in the region, and regular supply of raw materials for the canning industry.