Pathogenicity of Rhizoctonia solani, the causal agent of crown and root rot of cucurbits in Iran

Subject Areas : دو فصلنامه تحقیقات بیماریهای گیاهی

S.M. Mirmajlessi ¹ , Naser Safaie ² , H.A. Mostafavi ³ , S.B. Mahmoudi ⁴

1 - پژوهشگاه علوم و فنون هسته ای، پژوهشکده تحقیقات کشاورزی، پزشکی و صنعتی، کرج.
2 - گروه بیماری شناسی گیاهی، دانشکده کشاورزی، دانشگاه تربیت مدرس.
3 - پژوهشگاه علوم و فنون هسته ای، پژوهشکده تحقیقات کشاورزی، پزشکی و صنعتی، کرج.
4 - موسسه تحقیقات چغندر قند کشور.

Received: 2013-11-04 Accepted : 2013-11-04 Published : 2013-09-23

Keywords: Rhizoctonia solani, AG4, Crown and root rot, Cucurbits, Pathogenicity test,

Abstract :

The cucurbit damping off, root and crown rot caused by Rhizoctonia solani Kuhn are the most important diseases of these crops. In a survey of fields and greenhouses during 1384-1385 samples of cucumber, pumpkin, watermelon and melon, suspected of being infected by Rhizoctonia in Tehran, Mazandaran, Khouzestan and Isfahan provinces were collected and the fungus was isolated. In this study, 59 isolates of R. solani were recovered from soil, crown and roots of cucumber, pumpkin, watermelon and melon. Hyphae width ranged from 4.46 to 6.86 μm, and all of them were multinucleate. Anastomosis grouping showed that 81% of samples belonged to AG4 and the rest of isolates did not anastomose with either of the standards AG2 and AG7. The results of pathogenicity test showed that of the 59 recovered isolates, 97% were pathogenic, which in turn were classified in 10 separate categories based on their virulence. In this investigation two isolates of pumpkin and cucumber belonging to AG4 from Isfahan province appeared to be non pathogenic. This is considered to be the first report of AG4 on pumpkin in Iran.

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