GENOME MAPPING OF SOYBEAN CYST-NEMATODE RESISTANCE GENES IN PEKING, PI-90763, AND PI-88788 USING DNA MARKERS

Several sources of soybean cyst nematode (Heterodera glycines Ichinohe ; SCN) resistance have been identified in soybean [Glycine mar (L.) Me rrill]; yet, the genetic basis of this economically important trait re mains poorly characterized. This study was conducted to identify quant itative trait loci that control disease response in three commonly use d sources of SCN resistance. Using genetic markers, we analyzed three segregating soybean F-2 populations ['Evans' x 'Peking', Evans x Plant Introduction (PI) 90763, and Evans x PI88788] and compared the result s with those of a previous study involving PI 209332. For the Peking, PI 90763, and PI 209332 populations, races 1, 3, and 6 were used as SC N inoculum; for the PI88788 population, only races 3 and 6 were used. To uncover putative resistance loci, F-2 DNA marker genotypes at betwe en 63 and 99 loci in each population were contrasted with cyst indices averaged from 12 F-2:3 progeny individuals. Pour independent partial SCN resistance loci were uncovered at P < 0.0002 (probability per locu s). One of these loci, located at the top of linkage group 'G' near RF LP locus C006V, was significant at P < 0.0001 in all populations and r aces tested. Other significant loci included one near RFLP A378H at th e opposite end of linkage group 'G' from C006V, another on linkage gro up 'J' near marker B032V-1, and a fourth on linkage group 'N' near mar ker A280Hae-1. Comparisons between different SCN races indicated that some of the putative resistance loci behave in a race-specific manner. These results may serve as a resource for SCN researchers and soybean breeders by summarizing a wide range of genetic data on the soybean-S CN interaction.