IDENTIFYING ANASTOMOSIS GROUPS AND VIRULENCE OF THE ISOLATES OF R. SOLANI  ON POTATO.

S. Juber, K.

	IDENTIFYING ANASTOMOSIS GROUPS AND VIRULENCE OF THE ISOLATES OF R. SOLANI ON POTATO.
The Iraqi Journal of Agricultural Science
Article 1, Volume 43, Issue 3, 2013, Pages 74-86
Author
K. S. Juber
Abstract
The study includes a survey of potato stem canker in fields of Baghdad and Babylon province , identification of its pathogen and determination of anastamosis groups for the fungal isolates and control the disease by using some biological agents and chemical compounds induce resistance. Results of the field survey which was carried out in the potato fields of Baghdad and Babylon governorates showed the existence of the disease in percentage of disease incidence 24-40%. Results of laboratory isolation indicated that Rhizoctonia solani isolates had rapid growth with light to dark brown color and all of them formed sclerotia and most of them formed monilioid cells and their hyphae diameter ranged from 8-11 µm. The potato steam canker pathogen was identified as R. solani kühn and the identification was confirm by induce the sexual stage which was shown as Thanatephorous cucumeris (Frank) Donk. All tested isolates contained more than three nucleus in each cell. The detection for the pathogenic isolates of R. solani by using cabbage seeds showed that all the isolates were pathogenic and graduated in there pathogenicity in which 12 of it were highly pathogenic and completely prevented seed germination, while the percentage of seed germination in the treatments of the other isolates were ranged from 4-32%. Results of influence the pathogenic isolates on potato plants under green house condition indicated that all tasted isolates increased the percentage of the infected branches in which the disease incidence was 42.3-87.5% with disease severity of 15.8-53.3% comparing with the control treatment without pathogenic fungus which had zero disease incidence. Results of anastamosis groups identification for R. solani isolates indicated variation in their ability to infect the differential hosts through which it appears that the fungus isolates located within two anastamosis groups AG3 and AG4.

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