Utilization of differential line and vegetative compatibility group methods for the characterization of isolates of Magnaporthe oryzae from Africa

Rice blast, caused by Magnaporthe oryzae, is a disease that can cause severe losses in rice yields. Recent studies showed that demand for rice is increasing faster than the increase in production in Africa, and there is a need to mitigate production challenges such as rice blast. Breeding for resistance to rice blast in Africa requires knowledge of M. oryzae diversity and the history of resistance in the pathosystem. A core collection isolates of M. oryzae (n=100) from nine African countries (Benin, Burkina Faso, Ghana, Kenya, Mali, Nigeria, Tanzania, Togo, and Uganda) were assessed for vegetative compatibility groups (VCG) and for disease reactions based on an International Rice Research Institute set of differential lines and African interspecific cultivars. Preliminary analysis showed that VCGs were unique for each country, but the virulence phenotypes of isolates were not associated with the country of origin. Avirulence was observed in a range 25%-75% of the subset (n=49) of the isolates that were pathotyped using the 31 differential lines. The Pi9 resistance gene was most effective against the core set of isolates, conferring resistance against 75% of the isolates, followed by unknown resistances in two African interspecific cultivars, which conferred resistance against 56% of the isolates. Findings of this study will facilitate resistance breeding efforts to enhance effective control of rice blast in Africa