Breeding climbing beans resistant to angular leaf spot, pythium root rots and fusarium wilt

 A. Musoni, R. Buruchara & P. Kimani

Beans (Phaseolus vulgaris L.) are an important source of dietary protein in east and central Africa.  In Rwanda, beans supply 65% of dietary protein. New, improved and high yielding climbing bean varieties selected using farmer participatory approaches and released in early 1990’s had by 1995 been adopted by 47% of households. Productivity of beans at farm level increased by 250%, particularly in high potential zones of northern Rwanda.  The most widely adopted cultivar (by 80% of farmers) was Umubano (G2333) because of its superior agronomic, culinary, market qualities, yield potential (4 to 4.5 ton ha^-1,) and resistance to anthracnose. However, due to its high susceptibility following an outbreak of Fusarium wilt in late 90’s, many farmers abandoned growing Umubano. Similarly, susceptibility of traditional and new climbing bean varieties to angular leaf spot and Pythium root rot diseases meant that the high yielding potential of the climbing beans in the Great Lakes Region of central Africa could not be fully realized. Previous evaluations had shown that Vuninkingi (G685) and Flora were resistant to F. oxysporum, SCAM 80 CM/15 and RWR 719 resistant to Pythium root rots, and MEX 54 to angular leaf spot. The objective of this research was to improve and to develop well adapted high yielding climbing bean varieties combining resistance to the three diseases in preferred seed types. Consequently, multi-parent crosses were made in several combinations using Umubano, Ngwinurare and Vuninkingi as popular and adapted parents and MEX 54, Vuninkingi and SCAM 80 CM/15 as sources of disease resistance. F₂ progenies were screened for resistance based on natural infestation in disease hot spots.  This will be followed by artificial inoculation of selected materials in a screenhouse. Recombinants for resistance to angular leaf spot, fusarium wilt, Pythium root rots and anthracnose will be selected. Studies on the nature of inheritance of resistance to Fusarium wilt are also in progress.