Bipolaris species associated with rice plant: pathogenicity and genetic diversity of Bipolaris oryzae using rep-PCR in Mazandaran province of Iran

Ninety one monoconidial Bipolaris isolates were obtained from lesions on different parts of rice in different locations of Mazandaran province during the summer of ۲۰۰۹. Bipolaris species were identified using morphological features such as color and shape of colony and color and size of conidia and conidiophores. The isolates were separated into two species; ۸۵ (۹۳.۴%) isolates belonged to Bipolaris oryzae and the remaining ۶ (۶.۶%) isolates to Bipolaris cynodontis. Therefore B. oryzae is regarded as the major cause of rice brown spot disease in Mazandaran province. In order to analyze genetic diversity among B. oryzae isolates, ۷۱ isolates were subjected to fingerprinting analysis by rep-PCR using BOX and REP primers. In cluster analysis, ۱۵ clonal lineages and ۵۴ haplotypes were identified. The largest clonal lineage contained with ۳۶ haplotypes was the most common lineage. These results also indicate a relatively high level of genetic diversity among B. oryzae isolates. Also, pathogenicity test of a few B. oryzae isolates (۱۲ isolates) was conducted under greenhouse condition and showed that those isolates were pathogenic to rice seedlings of cv. Tarom. All isolates produced some leaf spots ۲۴ h after inoculation.