Identification of Rare Recombinants Leads to Tightly Linked Markers for Nematode Resistance in Peanut.

Strong host resistance to root-knot nematode (RKN; Meloidogyne arenaria) introgressed from a wild diploid species to cultivated peanut was previously shown to be located on a large chromosomal region of linkage group A09. Little to no recombination in mapping populations has hindered fine mapping of the resistance genes. In order to further delineate the introgressed region, additional polymorphic markers were added to the linkage group A09 using a recombinant inbred line population developed from Gregory x Tifguard in which Gregory is the susceptible parent and Tifguard is the resistant parent harboring the alien introgression. Map distance within the introgressed region based on this population increased to 8 cM compared with zero recombination in an earlier generation. Lines with rare recombination within this introgressed region were phenotyped and it was demonstrated that one portion of the introgressed region confers moderate resistance while a smaller, distal portion confers strong resistance to RKN. Molecular markers associated with the introgressed region conferring strong resistance can be deployed in peanut breeding programs to improve selection for RKN resistance. [ABSTRACT FROM AUTHOR]