Virulence pattern of Pyricularia grisea isolates from farmers' fields on newly released upland rice cultivars

Abstract

The virulence pattern of the isolates of Pyricularia grisea from commercial fields of the upland rice (Oryza sativa) cultivars 'Primavera' and 'BRS Bonança' was analyzed. A hundred and seventy monoconidial isolates of the pathogen virulent to 'Primavera' and 139 to 'BRS Bonança' collected from eight fields, during two years (2001-2003) were tested, under greenhouse conditions, on six newly released rice cultivars. Differences in virulence pattern were observed in pathogenic populations of 'Primavera' and 'BRS Bonança'. Isolates with virulence to improved cultivars were common in samples from farmers' fields in the absence of aloinfection. The virulence frequency of P. grisea isolates collected from 'Primavera'' to cultivars 'BRS Vencedora', 'BRS Colosso', 'BRS Liderança', 'BRS Soberana', 'BRS Curinga' and 'BRS Talento', was high in descending order. On the other hand, in the fungus population of 'BRS BRS Bonança' virulence frequency was high in 'BRS Talento', followed by 'BRS Curinga', 'BRS Vencedora', 'BRS Liderança', 'BRS Colosso' and 'BRS Soberana'. While virulence to 'BRS Talento' was rare among isolates from 'Primavera', it was most frequent in isolates of 'BRS Bonança'. The six improved rice cultivars permitted to differentiating agriculturally important virulences in the pathogen population which can be utilized in selecting breeding lines for specific resistance, in rice blast improvement program.

Pathogenicity of rice blast isolates (Pyricularia oryzae) in irrigated lowland of Bangladesh

“…where they claimed that Pish, Pi9 and Pita-2 genes were quite ef- The gene-for-gene theory governs disease resistance, where an incompatible reaction occurs between host resistance genes and avirulent pathogen genes (Flor, 1971;Silue et al, 1992). Araújo et al (2005) reported significant variation in the proportion of blast races among different cultivars. The structure of a pathogen population can be significantly influenced by the host population (Chen et al, 1995).…”

“…Araújo et al. (2005) reported significant variation in the proportion of blast races among different cultivars. The structure of a pathogen population can be significantly influenced by the host population (Chen et al., 1995).…”

Use of local rice cultivars as additional differentials to identify pathotypes of Pyricularia oryzae

“…In a recent study for identifying pathotypes in upland rice, the Brazilian differentials showed greater differential ability than with the international differentials (Silva et al, 2007). The virulence pattern of isolates of P. grisea from commercial fields of widely grown upland rice cultivars Primavera and BRS Bonança was tested by Araújo et al (2005) on six newly released cultivars. These cultivars permitted to differentiate agriculturally important virulence in the pathogen population which can be utilized in selecting breeding lines for specific resistance in blast breeding program.…”