2007 Annual Report 1a.Objectives (from AD-416) Identify markers in a mapping population close to resistance gene to Columbia Root-knot Nematode derived from Solanum bulbocatanum. Physically locate position on BAC library. Clone gene(s) involved, and transform into potato to test for resistance conferring activity. 1b.Approach (from AD-416) A progeny derived from a cross between resistant and susceptible S. bulbocastanum parents will be screened for resistance. AFLP, SCAR and SSR markers will be assayed for linkage to resistance factors. Markers will be used to identify location on BAC contigs for chromsome XI, north arm. BACs will be sequence and resistance candidate genes identified, cloned and inserted into gene shuttle system. Gene action will be assessed for resistance properties in transgenic plants. Documents Reimbursable with UC Berkeley. Log 21373. Formerly 5354-21220-008-04R, 8/2003. 3.Progress Report This report serves to document research conducted under a reimbursable agreement between ARS and UC Berkeley. Additional details of research can be found in the report for the parent project 5354-21000-002-00D, "Potato Variety Improvement Through Gene Transfer and Virological Studies (National Program 301)." This grant is specifically to assist in the mapping and cloning of the RMC1(blb) gene from Solanum bulbocastanum for resistance to Columbia root-knot nematode resistance. We first tested a mapping population for markers closely linked resistance gene RMC1(blb). End sequences from bacterial artificial chromosome (BAC) library derived from Solanum demissium contained motifs of the N-gene from Nicotiana. These sequences mapped very close to the nematode resistance. The sequences were also useful in identifying BAC clones derived from a Solanum bulbocastanum parent that does not harbor the resistance, but rather the susceptible allele. Sequence of three BAC’s was obtained. Interestingly a number of N-like sequences were found. One complete N-gene sequence was found. Primers designed from this sequence were made and when amplification by PCR carried out certain amplicons segregated in complete agreement with resistance phenotype. These fragments have been cloned and have been sent for sequencing. We examined progeny of a breeding clone which also expresses tuber resistance. Upon recovering mostly parental phenotypes (i.e., root resistant/tuber resistant and root susceptible/tuber susceptible), and rarely a few recombinants (i.e., root resistant/tuber susceptible and root susceptible/tuber resistant) we concluded that the two types of resistance are controlled by separate genes that are closely linked. The tuber resistance is non-race and non-biovar specific. A clone with this combined phenotype is in its second year of testing in the Tri-State Trial System.