Marker-assisted selection of Columbia root-knot nematode resistance introgressed from Solanum bulbocastanum

The Columbia root-knot nematode (Meloidogyne chitwoodi Golden et al.) is a serious pest that reduces tuber quality of potato (Solanum tuberosum L.) in the U.S. Northwest and other parts of the world. A gene, [R.sub.Mc1(blb), derived from the Mexican wild species Solarium bulbocastanum Dunal, encodes resistance to this pest. An F1 mapping population with >250 individuals generated from an intraspecific cross between resistant and susceptible clones of S. bulbocastanum, SB22 and PT29, respectively, was used for marker screening and genetic linkage analysis. One amplified fragment length polymorphism marker and five sequence tagged site (STS) markers cosegregated with [R.sub.Mc1(blb). The five STS markers were developed from bacterial artificial chromosome (BAC) end sequences of BAC clones that were derived from another wild species, S. demissum Lindl, and contained homologs of resistance gene N against tobacco mosaic virus. These markers were tested on families that were part of the introgression of [R.sub.mc1(blb)] into advanced breeding lines in [BC.sub.5]. The utility of an efficient alternative to greenhouse and field phenotypic screening was demonstrated, The results of this study confirm that molecular markers closely linked to [RM.sub.Mc1(blb)] will assist in a selection program, reducing expense and time involved in root-knot nematode screening.