MOLECULAR MARKERS FOR RESISTANCE TO HETERODERA-GLYCINES IN ADVANCED SOYBEAN GERMPLASM

Germplasm line J87-233 is resistant to soybean cyst nematode (SCN) rac es 1, 2, 3, 5 and moderately resistant to race 14 with resistance deri ved from 3 primitive sources, 'Peking', PI 88788 and PI 90763. F-2:3 p rogeny of J87-233 and SCN-susceptible 'Hutcheson' cross were evaluated for response to SCN races 1: 2, 3, 5 and 14. Linkage groups (LG) A, B , F, G, J, M, N, S were tested with 215 genomic clones and 45 decamers for parental genotypes. QTL for race 1 and QTL for race 3 were detect ed on LG A2, the region of BLT65V and SCAR 548/563(1100/1025,975). The cluster analysis of 12 soybean cultivars and 38 plant introductions c onfirmed association of SCAR(1100/1025,975) with resistance to races 1 and 3, and suggested possible DNA rearrangements that might give rise to new resistance specificities in the region. The highly significant association of K69T marker with SCN race 1 resistance in conjunction with its location, 18.5 cM from the reported QTL, exemplifies the impo rtance of the QTL locus on LG G and suggests expansion of the Linkage map in the LG G-terminal region. Detected interaction between loci on LG A2 and LG G, and also with loci on LG F and LG M, may play a signif icant role in the genotype-specific response to SCN. Identification of two major regions on LG A2 and LG G for SCN resistance shows their ap plicability to advanced germplasm, however, transmission of molecular marker alleles indicates that applied markers are not yet reliable in revealing all possible recombination events in breeding for SCN resist ance.