IDENTIFICATION OF PEANUT (ARACHIS-HYPOGAEA L) RAPD MARKERS DIAGNOSTICOF ROOT-KNOT NEMATODE (MELOIDOGYNE-ARENARIA (NEAL) CHITWOOD) RESISTANCE

DNA markers linked to a root-knot nematode resistance gene derived fro m wild peanut species have been identified. The wild diploid peanut ac cessions 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 acc essions and A. hypogaea cv. Florunner were crossed to generate the hyb rid 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 po pulation by bulked segregant analysis. Linkage was confirmed by screen ing 21 segregating BC4F2 and 63 BC5F2 single plants. Recombination bet ween marker RKN410 and resistance, and between marker RKN440 and resis tance, 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, i nherited from A. cardenasii or A. diogoi, and resistance was 9.0 +/- 3 .2% per generation. Markers RKN410 and RKN229 appeared to be linked ge netically and flank the same resistance gene. All markers were confirm ed by hybridization of cloned or gel-purified marker DNA to blots of P CR-amplified DNA. Pooled data on the segregation of BC5F2 plants was c onsistent with the presence of one resistance gene in the advanced bre eding lines. Different distributions of resistance in the BC5F2 progen y and TxAG-7 suggest the presence of additional resistance genes in Tx AG-7.