Pathogenicity of Pyricularia oryzae isolates obtained from cultivars grown in middle and high altitudes zones of Burundi

Abstract

Rice blast disease caused by the fungal pathogen called Pyricularia oryzae is an economically important disease distributed in rice-growing regions of the world. Understanding pathogenic variation among isolates paves a way towards the most effective ways to manage the disease. Thirteen isolates of P. oryzae from high and middle altitude rice ecosystems were inoculated into ten (10) cultivars most preferred by rice farmers in the middle and high-altitude areas of Burundi. The isolates were then evaluated for their ability to cause rice blast disease under screen house condition. A complete randomized design (CRD) with three replications was used. The tested cultivars were evaluated as susceptible(S) or resistant (R) to a particular P. oryzae isolate based on disease severity score determined through visual observation using a standard 0-9 scale developed by IRRI. Highly significant differences (p=0.000) between location were observed in rice blast disease incidence and severity. Significant differences (p=0.000) in blast incidence and severity were recorded between cultivars as well as isolate. Disease incidence and severity in the cultivars ranged from 11.11-33.33% and 3.70-69.14% respectively. Despite this variability in the isolate pathogenicity, three rice cultivars (Mugwiza, Rufutamadeni and V18) were less susceptible to the disease and hence can be regarded as having traits of resistance which can be used by rice farmers for managing rice blast disease in the two rice ecosystems of Burundi but also as parent materials for development of rice cultivars with resistance to rice blast.