Revision of Pyricularia oryzae and occurrence of new hosts for the pathogen in Iran

Pyricularia oryzae is the causal agent of rice blast disease, the most destructive, and an important disease of rice worldwide. To identify of host plants for P. oryzae in the north of Iran, and separation of this species from P. grisea, the infected tissues were sampled from rice, corn, sorghum, barley and wheat cultivation regions, tea, citrus orchards, and forest in southern of Caspian Sea from Astara in Guilan province to Gonbad-e Qabus in Golestan province during spring, summers and fall of 2012 and 2013. Out of 80 isolated pathogen, 50 and 30 isolates were identified as P. oryzae and P. grisea on the basis of morphological characteristics respectively. In order to investigation of phylogenetic relationships of studied isolates, ITS region of ribosomal DNA and MCM7 were amplified. Three major clades in cladogram of ITS and MCM7 were identified. Species of the P. oryzae and P. grisea put in clade one. Species that stand into this group have phylogenetic, morphology and host differences. Two other group associated with Magnaporthe sensu lato. Pathogenicity test of P. oryzae species were applied on corn (susceptible line B73), barnyard grass, foxtail, rice, eleusine and paspalum in greenhouse. The results showed that this species cause blast and leaf spot symptoms on corn, barnyard-grass, and foxtail. In this study, corn, banana, bermuda grass, paspalum and eleusine are reported as new hosts for the fungus in Iran.