Use of RFLP markers for identification of individuals homozygous for resistance to Meloidogyne arenaria in peanut

To increase the efficiency of breeding peanuts resistant to Meloidogyne are naria, we determined the utility of two RFLP loci linked to a single gene f or resistance in identifying individuals putatively homozygous for resistan ce. DNA was extracted from leaf samples collected from each of 548 individu als from three segregating BC7F2:4 breeding populations (TP293-3-3, TP296-4 and TP301-1-8). The DNA was then digested with Eco RI, and Southern blotte d to Hybond-N+ membranes. The membranes were probed with the RELP probe R24 30E, the autoradiographs scored for resistance genotype, then stripped and re-probed with the probe R2545E. Samples from which no data were obtained d ue to problems in extraction, digestion, or hybridization ranged from a low of 14.4% for TP301-1-8 probed with R2430E to a high of 38.9% for TP296-4-4 probed with R2545E. Locus R2430 identified 27.6, 65.1 and 29.5% of populat ions TP293-3-3, TP296-4-4 and TP301-1-8, respectively, as being homozygous for resistance. The second locus, R2545E, identified 24.5, 50 and 23.5%, re spectively, of these populations as homozygous for resistance. In glasshous e tests of nematode reproduction on progeny of individuals identified as ho mozygous for resistance based on RFLP patterns, all 15 individuals of each of the 11 single plant progeny lines tested were resistant. Conversely, all progeny from an individual identified as susceptible to M. arenaria based on RFLP patterns supported high levels of nematode reproduction.