Plant Disease (2003) 87, 766-771

G. Godoy-Lutz, J.R. Steadman, B. Higgins and K. Powers (2003)
Genetic variation among isolates of the web blight pathogen of common bean based on PCR-RFLP of the ITS-rDNA region
Plant Disease 87 (7), 766-771
Abstract: Variability of 45 isolates of Rhizoctonia solani (teleomorph Thanatephorus cucumeris) causing web blight (WB) of common bean, Phaseolus vulgaris, was examined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the internal transcribed spacer regions (ITS1 and ITS2) and the 5.8S subunit (5.8S) of the nuclear ribosomal DNA repeat (ITS-5.8S-rDNA). Isolates were collected from diseased bean leaves from Argentina, Costa Rica, Cuba, Dominican Republic, Honduras, Panama, and Puerto Rico. These WB isolates belong to AG-1 and AG-2 based on anastomosis reaction. Isolates of AG-1 that cause WB were separated into three distinct groups of RFLP patterns from enzymatic digestion of a 740-bp PCR fragment. Microsclerotia-producing isolates (<1 mm) were differentiated from macrosclerotia-producing isolates (5 to 20 mm) based on PCR-RFLP patterns even though they are placed in the same AG1-1B subgroup by anastomosis reaction. WB isolates of AG-2 were separated into two distinct PCR-RFLP groups as previously reported. AG-1 macrosclerotial-producing isolates were the most virulent, whereas isolates of AG-2 were the least virulent. Genetic variability of the WB pathogen may have influenced the failure or success of management practices implemented in the past in Latin America.
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Database assignments for author(s): James R. Steadman

Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution
molecular biology - genes

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Rhizoctonia solani		Cuba
	Rhizoctonia solani		Dominican Republic
	Rhizoctonia solani		Honduras
	Rhizoctonia solani		Puerto Rico
	Rhizoctonia solani		Argentina
	Rhizoctonia solani	Beans (Phaseolus)	Costa Rica
	Rhizoctonia solani	Beans (Phaseolus)	Panama