| Since the first description of the peanut root-knot nematode, Meloidogyne arenaria, in 1889, yield losses due to this pathogen have been increasingly recognized. The discovery of wild Arachis species resistant to root-knot nematodes has provided a source of resistance. The identification of the nematode-resistant, interspecific hybrid TxAG-6, which is cross-compatible with cultivated peanut, has enabled resistance genes from wild species to be introgressed through a backcross breeding program into cultivated peanut.; In order to increase the efficiency of selecting individuals with a homozygous resistant genotype, the utility of marker-assisted selection was determined. RFLP loci R2430E and R2545E, linked to one side of the resistance locus, were used to identify the genotype of 548 individuals from three segregating BC7F2:4 breeding populations (TP293-3-3, TP296-4-4, and TP301-1-8). RFLP analysis resulted in identifying individual plants that were homozygous for resistance with less time and resources than by conventional screening for the resistance phenotype in greenhouse tests.; RFLP loci putatively flanking the resistance locus were identified to increase the confidence of genotype identification. Individuals that segregated for resistance were used in linkage analysis of 6 RFLP loci. S1018E and R2430E were identified as flanking the resistance locus with linkage distances of 1.8 cM and 1.2 cM, respectively. The F2 generations from the cross between A. hypogaea x TxAG-6 and three BC3F 1 individuals were evaluated for resistance based on nematode reproduction under greenhouse conditions. The ratio of the resistant and susceptible individuals for all populations fit the expected ratio for resistance being governed by one dominant gene and one recessive gene. These results suggest TxAG-6 and the BC3F1 individuals possess a second, recessive, gene for resistance to M. arenaria, in addition to the dominant gene identified previously. (Abstract shortened by UMI.)... |
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