New Anastomosis Group G (AG-G) of binucleate Rhizoctonia sp., the causal agent of root rot disease on miniature roses in Iran

Abstract

<em>Rhizoctonia</em>-like fungi were isolated from the infected roots of miniature rose (<em>Rosa</em> <em>hybrida </em>cv. Linda) plant with chlorosis and necrosis symptoms, grown in commercial glasshouse in Rafsanjan, Iran, during the autumn of 2011. All of the isolates were identified as binucleate <em>Rhizoctonia</em> sp. on the basis of hyphal characteristics and nuclei number. They were tested for detection of the anastomosis group, optimum growth temperature, rDNA-ITS region traits and pathogenicity on miniature rose <em>in vivo</em> and <em>in vitro</em>. The analysis of hyphal reaction anastomosis was carried out with the tester isolates of binucleate <em>Rhizoctonia</em> AG-A, AG-Ba, AG-G as well as multinucleate <em>Rhizoctonia</em> AG2-2IIB and AG4-HGI already detected on miniature rose. The optimum temperature for growth of binucleate <em>Rhizoctonia</em> sp. was 35^°C. In <em>in vivo</em> test, the symptoms of root rot were observed 35 days after inoculation and mortality happened two weeks later. According to molecular and anastomosis test groups, our results showed that all the isolates have the maximum similarity to AG-G. This is the first report of anastomosis group G (AG-G) of binucleate <em>Rhizoctonia </em>sp., thecausal agent of root rot disease on miniature roses in Iran.