Pathogenicity within Bean Pythium Pathosystems of South western Uganda
V. Gichuru *
Faculty of Agriculture, Department of Crop Science, Makerere University, P.O.Box 7062, Kampala, Uganda, International Centre of Tropical Agriculture (CIAT-Kawanda), P.O.Box 6247, Kampala, Uganda and School of Pure and Applied Sciences, Department of Biological Sciences, Pwani University, P.O.Box 95-80108, Kilifi County, Kenya.
P. Okori
Faculty of Agriculture, Department of Crop Science, Makerere University, P.O.Box 7062, Kampala, Uganda.
R. Buruchara
International Centre of Tropical Agriculture (CIAT-Kawanda), P.O.Box 6247, Kampala, Uganda.
*Author to whom correspondence should be addressed.
Abstract
A pathosystem is a subsystem of an ecosystem and is characterized by the phenomenon of parasitism. The bean-Pythium pathosystem consists of the host (bean), the pathogen (Pythium) and their host-pathogen relation. Of interest is how the pathogen causes pathogenicity on other crops and beans. To investigate this, screen house experiments were set up to test the pathogenicity of Pythium species derived from non bean and bean host crops. Their pathogenicity was tested on maize, millet, sorghum, peas, susceptible bean variety (CAL 96) and resistant bean variety (RWR 719). The results indicated that distinct symptoms were observed in the roots and shoots of the crop species which are characteristic of Pythium infection. For instance peas had brownish watery stems and roots. Non bean host derived Pythium species were less virulent than bean pathogenic Pythium species. Sorghum and peas had the highest disease scores therefore were the most affected by Pythium. We concluded that there was cross pathogenicity among Pythium species. Also sorghum and peas were the crops contributing to the bean root rot epidemic since they succumb to Pythium infection.
Keywords: Pathosystem, Pythium, pathogencity, bean, sorghum, peas