NEW RACES OF ANGULAR LEAF SPOT AND ANTHRACNOSE IN EASTERN AFRICA AND IDENTIFICATION OF SOURCES OF RESISTANCE

摘要

Angular leafspot (Pseudocercospora griseola) and anthracnose (Colletotrichum lindemuthianum) are among the most important biotic constraints to bean productivity in east, central, southern and West Africa, and worldwide (Teran et al, 2013). Other major bean diseases in eastern Africa include root rots (caused by Pythium and Fusarium spp.), bean common mosaic and common bacterial blight (Wortmann et al, 1998). Under favourable conditions, yield losses of 50 to 100 percent have been reported in susceptible cultivars. Breeding varieties with resistance to one or more these diseases is considered the most effective and sustainable strategy of reducing losses due to these diseases. Consequently, breeding for resistance to major diseases has been a majorgoal of bean improvement programs in eastern Africa for the last three decades (Kimani et al, 2005). Several resistant varieties have been developed and released for production in nearly all bean growing countries in East, Central, West and Southern Africa (Buruchara et al, 2011). However, several varieties have succumbed to diseases they were resistant to at the time of release. This has led to the hypothesis that new strains of these pathogens may have arisen. However, no systematic studies have beenconducted to provide supporting evidence. Knowledge of pathogen variability is essential for effective screening to identify useful sources of resistance and development of resistant varieties. The objectives of this study were to: i) Determine if thereis new pathogenic variation in major bean growing regions of Kenya, ii) Determine reaction of commercial varieties to recently collected isolates of five major diseases, and iii) Identify better sources of resistance for future breeding.