Heterosis As Evidence Of Yield Alleles From Wild Soybean.

To guarantee future global food security and sustainable crop production, there is strong need for broadening the relatively narrow genetic base of the soybean (Glycine max [L. Merr.]) germplasm and looking for new resources to develop soybean cultivars.  Wild soybean (Glycine soja [Sieb. and Zucc.]) may be an excellent source of new agronomic alleles for this purpose.  Heterosis for yield is proposed as a signal for detecting yield alleles in wild soybean.  The objectives of this study were to 1) examine heterosis in F₂ bulks derived from the cross of parental cultivar N7103 and 19 breeding lines, which were developed from a cross between G. max cultivar N7103 and G. soja accession PI 366122, 2) assess whether heterosis could detect the presence of yield alleles derived from wild soybean, and 3) ascertain the possibility of predicting heterosis using genetic markers and agronomic traits.  The individual F₂ bulked seed were yield tested in replicated bordered row plots at four locations in 2012.  Two cross combinations showed significant (P ≤ 0.05) percent midparent heterosis for yield (+9% and +10%).  One cross showed significant heterosis over a theoretical maximum that could be expected based on dominance effects coming from only the G. max parent.  Thus, these results suggest that yield alleles reside in wild soybean.  The percent of G. soja alleles present in each breeding line, based on 558 single nucleotide polymorphic markers, positively and significantly (P ≤ 0.05) associated (r = 0.60) with midparent heterosis.  Genetic distance may be used as a guide for plant breeders when incorporating diverse germplasm into breeding programs and help predict future agronomic performance.