A participatory rural appraisal was carried out in two major bean producing areas in Uganda. Diseases emerged as the most important constraint to production, with root rots clearly being the most important disease. Pythium is the major root rot pathogen but can occur in combination with Fusarium spp. or Rhizoctonia solani. Bean is grown in an intensive agricultural system together with sorghum, maize, sweet potatoes, Irish potatoes, bananas and peas. A study was carried out to determine the role of other crops in the disease problem. Pythium isolates significantly affected the level of disease on CAL 96, sorghum and peas, suggesting that these two latter crops could play a role in root rot. Therefore in developing management strategies for root rots, it would be advantageous to consider a systems' approach rather than a commodity approach. The effects of four root rot management options i.e. farmyard manure, green manure (Crotalaria), NPK fertilizer and a fungicide (Ridomil) previously known to have useful effects against bean root rots were evaluated on sorghum, maize, peas and beans. The amendments improved early season crop tolerance, crop survival, root rot severity and dry matter relative to the control. Ridomil apparently gave protection against Pythium species. Plant recovery was evident in plots amended with GM, FYM and NPK. The potential of biocontrol was explored. Isolates of P. ultimum and of Mortierella were screened against each other for their potential use as biocontrol agents. Mortierella markedly reduced disease severity when added as antagonist to the pathogenic Pythium.

Susceptible bean plants grown in soil infested with pathogenic Pythium species (KB4) without the biocontrol agent.		Susceptible bean plants grown in soil infested with pathogenic Pythium species (KB4) with a biocontrol agent (Mortierella spp.).

Finally, a backcrossing program to transfer resistance into popular market class types (backgrounds) was initiated in 2004. Twenty backcross populations were generated. Currently BC_s5F₃GLP2 x RWR 719 with 111 progenies have been given to partners in Kakamega (Kenya) and were also planted in Kawanda for seed multiplication. A molecular marker for a resistance gene was identified at CIAT headquarters.

Contact: Robin Buruchara