Genome Wide Locus Interactions Underlie Crop Improvement In Soybeans

In soybean (Glycine max L. Merr.) combining resistance to diseases like sudden death syndrome and pests like the cyst nematode (SCN; Heterodera glycines I.) with high seed yield has been difficult. Molecular markers linked to quantitative trait loci (QTL) have not provided a complete solution. Sets of markers describing a collection of favorable alleles (linkats) may assist plant breeders seeking to combine both traits. The objective of this analysis was to identify linkats in genomic regions underlying seed yield and root resistance QTL. Used were groups of cultivars selected from a single recombinant inbred (RIL) population derived from ‘Essex’ by ‘Forrest’ (ExF) and Hartwig by Flyer (HxF). The yield was measured at four to eight locations.  SCN resistance was determined in greenhouse assays. SDS resistance was determined at 4 field locations. The mean seed yield was used to define 3 groups (each n=30), high, medium and low. SCN resistance formed 2 groups (SCN resistant (n=21) and SCN susceptible (n=69)). Microsatellite markers and SNP alleles were compared with seed yield and root SCN (Hetrodera glycines) resistance using mean analysis. The number, size and position of potential linkats were determined. Loci, genomic regions and linkats associated with seed yield were identified on linkage group (LG) K and with root resistance to SCN  on LG E, G, and D1b+W (chromosomes 15, 18 and 2). A repulsion phase linkat was found on LGD2 (chromosome 17). A method to identify and select for co-localized genomic regions will be presented.