Secondary hosts as potential inoculum source for rice blast pathogen in Argentina

Abstract

Rice Blast is the main disease of this crop in Argentina. It occurs sporadically at different rice growing areas, mainly in Santa Fe and Chaco provinces. However, when environmental conditions are favorable to disease development, Rice Blast can cause damages in other rice growing areas, such as Entre Ríos or Corrientes provinces. Inoculum survival and pathogen population specificity are important issues to understand Rice Blast epidemiology. Pyricularia grisea isolates from Phalaris canariensis, Stenotaphrum secundatum, Lolium perenneand Digitaria sanguinalis were collected in Entre Ríos fields in 2007. Greenhouse assays were performed. The isolates were artificially inoculated to rice genotypes, including differential lines with resistant genes Pi1, Pi2, Pita or Pi33; and commercial varieties as Cambá INTA-Proarroz, Puitá INTA-CL, or Supremo-13. Re-isolations of the pathogen from foliar symptoms were done. Any contamination was prevented. All isolates caused typical Rice Blast foliar symptoms in different rice genotypes. Differential line with Pi2showed symptoms with all the isolates evaluated. The other genotypes showed susceptible or no reactions, according to the isolate. Molecular characterization of original and re-isolated strains will be done. This work enhances the study of secondary hosts´ potential role in Rice Blast epidemiology in Argentina.