Association Mapping of SSR Markers to Tomato Spotted Wilt Virus Resistance in Cultivated Peanuts

Abstract

Tomato Spotted Wilt Virus (TSWV), one of most serious diseases in peanut, is transmitted by thrips (Franklinieila occidentalis). The mechanism of TSWV resistance and relevant genes in peanut are still unknown. Breeding and selection of resistant genotypes is the optimal method to manage TSWV in peanut. In order to more efficiently breed resistant cultivars, marker assisted selection should be implemented in breeding program. Therefore, the objectives of this study are to screen the peanut U.S. peanut mini core collection to identify genotypes that are resistant to TSWV; to examine genetic diversity and population structure in the U.S. peanut mini core collection by SSR markers, and to conduct an association mapping of SSR markers to TSWV resistance in cultivated peanuts. One hundred eighteen genotypes of the U.S. peanut mini-core germplasm collection were used for screening for TSWV resistance by mechanical inoculation and ELISA assay. One hundred and thirty-three SSR markers were applied for genotyping the panel of 104 peanut genotypes. Four Two genotypes, PI356004, and PI493880, PI355271, and PI496401, were identified as resistant to TSWV based on the data from mechanical inoculation, ELISA, and field evaluation. Four subpopulations were classified by population structure analysis, and corresponded to botanical varieties to a certain extent. Association mapping analysis indicated that the five markers, pPGPseq5D5, GM1135, GM1991, TC23C08, and TC24C06, were consistently associated with visual symptoms by four models, Q model, PCA model, Q+K model, and PCA+K model. These identified markers accounts for 36.4% of the phenotypic variance for TSWV resistance. Moreover, pPGPseq5D5 and GM1991 were both associated with visual symptoms and ELISA resulting in a high R2. These highly resistant genotypes along with their associated markers could be used for the development of TSWV-resistant cultivars in a peanut breeding programs.