Identification of peanut (Arachis hypogaea L) RAPD markers diagnostic of root-knot nematode (Meloidogyne arenaria (Neal) Chitwood) resistance

DNA markers linked to a root-knot nematode resistance gene derived from wild peanut species have been identified. The wild diploid peanut accessions K9484 (Arachis batizocoi Krapov. & W. C. Gregory), GKP10017 (A. cardenasii Krapov & W. C. Gregory), and GKP10602 (A. diogoi Hoehne) possess genes for resistance to Meloidogyne arenaria. These three accessions and A. hypogaea cv. Florunner were crossed to generate the hybrid resistant breeding line TxAG-7. This line was used as donor parent to develop a BC4F2 population segregating for resistance. Three RAPD markers associated with nematode resistance were identified in this population by bulked segregant analysis. Linkage was confirmed by screening 21 segregating BC4F2 and 63 BC5F2 single plants. Recombination between marker RKN410 and resistance, and between marker RKN440 and resistance, was estimated to be 5.4 +/- 1.9% and 5.8 +/- 2.1%, respectively, on a per-generation basis. These two markers identified a resistance gene derived from either A. cardenasii or A. diogoi, and were closely linked to each other. Recombination between a third marker, RKN229, inherited from A. cardenasii or A. diogoi, and resistance was 9.0 +/- 3.2% per generation. Markers RKN410 and RKN229 appeared to be linked genetically and flank the same resistance gene. All markers were confirmed by hybridization of cloned or gel-purified marker DNA to blots of PCR-amplified DNA. Pooled data on the segregation of BC5F2 plants was consistent with the presence of one resistance gene in the advanced breeding lines. Different distributions of resistance in the BC5F2 progeny and TxAG-7 suggest the presence of additional resistance genes in TxAG-7.