|POUDYAL, DIPAK SHARMA - Washington State University|
|DU TOIT, LINDSEY - Washington State University|
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/2015
Publication Date: 4/1/2015
Citation: Poudyal, D., Paulitz, T.C., Du Toit, L.J. 2015. Evaluation of Onion Genotypes for Resistance to Stunting Caused by Rhizoctonia solani AG 8. HortScience. 50:551-554.
Interpretive Summary: Stunting of onions caused by Rhizoctonia solani AG 8 is a major problem in irrigated onions in the Columbia Basin. This causes large patches of stunted onions, with reduced yields and bulb size. One possible method of managing this diseases is to identify resistance. We tested 35 genotypes and cultivars in inoculated experiments in the greenhouse. Plant height was a good measure of the disease. However, we did not find any resistance, but some varieties such as Stirling were more susceptible than other varieties. SN 483 and SN 559 from Numhems Seeds showed the least damage.
Technical Abstract: A total of 35 onion genotypes was evaluated for resistance to onion stunting caused by Rhizoctonia solani anastomosis group 8 (AG-8) under temperature-controlled greenhouse conditions (15 ± 1oC) in 2013. Each onion genotype was planted in a cone-tainer with and without inoculation with R. solani AG 8 inoculum (1% w/w) with five replications, maintained for 45 days and experiment was repeated twice. Percentage reduction in plant height of onion genotypes did not differ significantly in either trial. Reduction in plant height ranged from 24% (Lasalle) to 62% (R14882) in Experiment 1 and 22% (PX07713218) to 53% (Montblanc) in Experiment 2. Percentage reduction in root length and total biomass did not differ significantly in Experiment 1 but differed among onion genotypes in Experiment 2. The range of reduction in root length was 9% (R14889) to 76% (Sterling) in Experiment 1 and 14% (SN325) to 74% (Sterling) in Experiment 2. Reduction in total biomass ranged from 18% (Elbrus) to 69% (Sterling) in Experiment 1 and 29% (SN232) to 79% (Sterling) in Experiment 2. Plant height, root length, and total biomass of 11 of the inoculated genotypes (R14883, R14885, R14886, R14887, PX07713218, Lasalle, SN307, SN368, SN435, SN483, and SN559) in Experiment 1 and five genotypes (R14882, R14888, R14889, PX07713218, and SN272) in Experiment 2 did not differ significantly from the control genotypes, respectively. However, the percentage reduction in plant height among these genotypes was =22, indicating susceptibility of all genotypes to R. solani AG 8.