Identification of biological variability of pyricularia oryzae and screening for variety resistance to rice blast disease in imbo plain region

In Burundi rice is a very important cereal crop used as a food of lux during the celebration of important social events. Unlikely, rice productivity is greatly reduced by the attack of rice blast disease caused by Pyricularia oryzae. Yield loss may go as high as 80% if conducive conditions are present. However, rice farmers are still using contributing factors to the disease development and fewer are known about the biological variability of blast disease. The present study was conducted in the Imbo plain, a natural region of Burundi with an overall objective to improve rice productivity by usage of rice blast disease resistant varieties. Assessment of blast disease severity in farmer’s rice fields was carried out using 0-9 scale and the use of contributing factors to the disease development was carried out using a direct interview method. Biological variability of the pathogen was done through the morphological and pathogenic characterization. Disease severity showed significant difference in different Imbo plain locations (P=0.000). Variety resistance in field conditions showed Gwizumwimbu and Kazosi as the highest susceptible varieties at the frequency of 11.1% and 9% respectively. However, no significance difference was observed (P>0.05). Morphological characterization led to 96 distinct isolates classified into four groups based on colony colours: white (45), grey (38), black (10) and brown (3); two groups based on the surface texture: cottony (69) and velvety (27) and two groups: irregular (69) and regular (27) based on the colony margins. Pathogenicity test using 29 isolates showed that variety Watt, Mugwiza and Vuninzara can be cultivated as resistant varieties (resistant at >60% to local isolates). Similarly, R-genes Piz-5 and Pi40 showed high resistance to P. oryzae isolates across Imbo plain. In conclusion, rice blast disease is distributed in all locations of Imbo plain region and isolates are diverse morphologically and pathogenically.

IRRI-Burundi’s plant phytopathology team mainly,