Plant Disease (2013) 97, 1626-1635

L.J. Patzek, L.J. du Toit, T.C. Paulitz and S.S. Jones (2013)
Stunting of onion in the Columbia Basin of Oregon and Washington caused by Rhizoctonia spp.
Plant Disease 97 (12), 1626-1635
Abstract: During 2009 and 2010, 45 isolates of Rhizoctonia spp. were recovered from onion bulb crops in the semiarid Columbia Basin of Oregon and Washington, in which patches of severely stunted onion plants developed following rotation with winter cereal cover crops. Characterization of isolates recovered from naturally infested soil and roots was performed by sequence analysis of the ribosomal DNA (rDNA) internal transcribed spacer region, with the majority of isolates (64%) identified as Rhizoctonia solani. In steam-pasteurized field soil, stunting of onion was caused by isolates of R. solani anastamosis groups (AGs) 2-1, 3, 4, and 8, as well as Waitea circinata var. circinata and binucleate Rhizoctonia AG E evaluated at 13 and 8 or 15 and 15°C day and night temperatures, respectively, typical of spring planting conditions in the Columbia Basin. Isolates of R. solani AG 5 as well as binucleate AG A and I were nonpathogenic. The most virulent isolates belonged to AG 8, although an AG 3 and an AG E isolate were also highly virulent. Isolates of AG 2-1 and 3 caused moderate levels of disease, while isolates of AG 4 and W. circinata var. circinata caused low levels of disease. Emergence was reduced by isolates of AG 2-1, 3, and E. When the various AGs were grown at temperatures of 5 to 30°C, the relative growth rate of the Rhizoctonia isolates was not positively correlated with virulence on onion within an AG.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Lindsey J. du Toit, Timothy C. Paulitz

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

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Rhizoctonia solani	Onion/garlic/leek (Allium)	U.S.A. (NW)
	Waitea circinata	Onion/garlic/leek (Allium)	U.S.A. (NW)
	Rhizoctonia AG-E	Onion/garlic/leek (Allium)	U.S.A. (NW)