Molecular Mapping of QTL for Early Maturity in Peanut.

Early maturing peanut cultivars are a necessity in Virginia-Carolina and west Texas, regions that have short growing seasons with to cool night temperatures at season’s end.  However, breeding early cultivars is difficult because peanut maturity involves complex biochemical processes that are influenced by many genes and the environment.  Furthermore, current methods for maturity assessment are laborious and relatively subjective.  Molecular markers provide a powerful tool to improve the efficiency of breeding methods when using Marker Assisted Selection (MAS).  Among these markers, Simple Sequence Repeats (SSRs) are highly polymorphic even among the highly conserved elite US cultivated peanut genomes.  Establishment of associations between specific genomic regions and early maturing phenotypes, and subsequent implementation of MAS could provide an efficient and objective assessment method of maturity.  In the present study, two populations of recombinant inbred lines (RILs) were developed from the crosses of a high-oleic backcross derivative of Chico, a very early maturing Spanish-type cultivar, by PI 313949 and PI 365550, two Bolivian PIs with pronounced late maturity.  A total of 200 and 191 polymorphic markers for the Chico / PI 313949 and Chico / PI 365550 populations, respectively, were identified from a set of 426 SSR markers that had been previously found to be variable among other cultivated peanuts.  These markers were used to genotype the populations and to create two linkage maps.  Subsequently, genotypic and phenotypic data were analyzed, in order to identify QTL associated with early maturity.