Population Structure and Association Analysis of the U.S. Peanut Mini-Core Collection By SSR Markers.

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 a breeding program. Therefore, the objectives of this study are to screen the 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 peanut.   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 genotypes. Four genotypes, PI356004, 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 types 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 accounted 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 development of TSWV-resistant cultivars in a peanut breeding program.