|ZHANG, TIEJUN - Washington State University|
|MILLER, DAVID - Dupont Pioneer Hi-Bred|
|BHAMIDIMARRI, SURESH - Dupont Pioneer Hi-Bred|
|JOHNSON, DAVID - Alforex|
|MONTEROS, MARIA - Samuel Roberts Noble Foundation, Inc|
|HO, JULIE - Forage Genetics International|
|REISEN, PETER - Forage Genetics International|
|Samac, Deborah - Debby|
Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2014
Publication Date: 12/23/2014
Citation: Zhang, T., Yu, L., Mccord, P.H., Miller, D., Bhamidimarri, S., Johnson, D., Monteros, M., Ho, J., Reisen, P., Samac, D.A. 2014. Identification of molecular markers associated with verticillium wilt resistance in alfalfa (Medicago sativa l.) using high-resolution melting. PLoS One. 1-18. https://doi.org/10.1371/journal.pone.0115953.
Interpretive Summary: USDA-ARS Prosser, the Samuel Roberts Noble Foundation, Forage Genetics International (FGI), Pioneer Hi-bred, and Alforex seeds agreed on a joint effort to identify publically available markers for selection for resistance to Verticillium wilt. Pioneer and Alforex generated and phenotyped biparental populations 188 and 164 individuals, respectively, using parents either resistant or susceptible to Verticillium wilt. Dr. Monteros supplied with lists of Noble-developed SNP markers located on the chromosomes identified in the first phase. We screened the parents and a subset of individuals from both Pioneer and Alforex populations with 156 SNP markers, using the high-resolution melting technique. Associations between marker genotypes and Verticillium wilt phenotype were analzed. Ten markers were significantly associated with Verticillium wilt resistance. The markers identified in this study could be used for improving resistance to Verticillium wilt in alfalfa.
Technical Abstract: Verticillium wilt (VW), caused by the soilborne fungus, Verticillium alfalfae, is one of the most serious diseases of alfalfa (Medicago sativa L.) worldwide. To identify loci associated with resistance to VW, an association study was conducted using autotetraploid alfalfa populations composed of 352 individuals. The samples were genotyped by high-resolution melting analysis of SNP markers. Polymorphic SNPs were identified based on the melting profiles and up to five clusters were obtained, representing the various allelic combinations in tetraploid alfalfa. Phenotyping was done by inoculation of the pathogen to replicated cloned plants of each individual and disease severity was scored using a standard scale (e.g. 1-5). Marker-trait association was analyzed by TASSEL using the general and mixed linear models. Ten markers were significantly associated with VW resistance and they were located on three chromosomal regions. Five significant markers on chromosome 8 contributed a total of 36% of the phenotypic variation explained and represent novel loci associated with VW resistance. Additional significant markers were identified on chromosomes 2 and 7, and they co-locate with the regions of VW resistance loci reported in M. truncatula. This study highlights the value of SNP genotyping to identify the disease resistance loci in tetraploid alfalfa. The markers identified in this study could be used for improving resistance to Verticillium wilt in alfalfa.