Genetics of soybean agronomic traits: II. Interactions between yield quantitative trait loci in soybean

In order to breed efficiently, it is necessary to identify individual quant itative trait loci (QTLs) as well as interactions between these loci and to determine which QTLs produce phenotypes that are environment specific This can be done by linking QTLs to molecular markers, The objective of this re search was to carry out such an analysis for yield, one of the most complex agronomic traits. To do this, recombinant inbred lines of soybean [Glycine max (L,) Merrill] were characterized far molecular genetic markers and ana lyzed for yield in different environments. Interactions between QTLs were i dentified by subdividing the segregants into four sub-populations defined b y molecular alleles at pairs of unlinked loci. Differences in the mean yiel ds of these sub-populations defined interactions between QTLs. measurements of yield in genotyped, recombinant inbred populations derived from crosses of 'Minsoy' with 'Archer' (MA population) and `Noir 1' with Archer (NA pop ulation) hale identified a pair of interacting yield QTLs whose effect was independent of environment as well as a pair of loci whose interaction was environment specific Each example of epistasis, involved an allele specific interaction between the two QTLs, In the NA population, a pair of QTLs was identified in which Noir 1 alleles interact to specify a significant incre ase in yield that is not environment specific. These loci, located on linka ge groups (LG) U3 and U9, do not affect either height or maturity. In all e nvironments, the interaction between the QTLs was significant, In the MA po pulation, a pair of QTLs was identified in which the Minsoy alleles interac t to specify a significant increase in yield, However, this significant int eraction is environment specific One of the loci (on LG U14) is also associ ated with effects on height, seed weight, and maturity that are found in ot her environments, but these latter effects do not appear to involve any int eractions with other loci. The data from the MA population support the conc ept that interactions between QTLs also can result in location-specific eff ects on quantitative traits.