Towards Identification of SSR Markers Linked To Tswv Resistance In Peanut (Arachis hypogaea L.).

Spotted wilt caused by tomato spotted wilt virus (TSWV) is one of the major diseases affecting peanut (Arachis hypogaea L.) production in the Southeastern USA. Occurrence, severity, and symptoms of spotted wilt disease are highly variable from season to season making it difficult to efficiently evaluate breeding populations for resistant line selection. Molecular markers linked to spotted wilt resistance could overcome this problem and allow selection of resistant lines regardless of seasonal conditions. The objective of this study is to identify the simple sequence repeat (SSR) markers linked to TSWV resistance in peanut through 1) evaluating the TSWV reaction of the F₂ and F_2:3 populations; 2) screening polymorphic SSR markers between the two parental lines of the F₂ population, and mapping the TSWV resistance loci using SSR genotyping of the F₂ population. 

A total of 199 F₂ progeny derived from the cross between Florida-EP^TM'113', a TSWV resistant variety and Georgia Valencia, a highly susceptible cultivar were evaluated by ELISA (enzyme-linked immunosorbent assay) for the presence of TSWV. The F_2:3 population were further phenotyped using a visual 1 to 10 scaling method on both canopy and seed coat and ELISA Immunostrip. The ELISA and Immunostrip results confirmed that most of the symptomatic plants were infected by TSWV with some exceptions, which didn’t display visual symptoms but exhibited positive ELISA reactions. This result indicates that ELISA and Immunostrip may be a better method for phenotyping TSWV infection in peanut. For genotyping, a total of 2000 SSR markers with high polymorphic information content or mapped on peanut linkage groups were screened against the two parental lines of the F₂ segregating population. Totally, 186 polymorphic SSR markers were screened, which will be used to map the TSWV resistance conferred by Florida-EP^TM'113' and to identify the flanking markers linked to spotted wilt resistance.