Genotype x environment interaction and stability for isoflavone content in soybean
Isoflavones are naturally occurring compounds found in soybean [Glycine max (L.) Merr.]. Soybean isoflavone, as a quantitative trait, is subject to significant genotype x environment interaction, which makes breeding for this trait difficult. Thirty F4:7 soybean lines, derived from crosses of ‘RCAT Angora’ x CK-01 and ‘Heinong 35’ x RCAT Angora were classified within each population as high, intermediate, or low isoflavone. The lines, parents, and two maturity checks were grown in four locations in 2005 and six locations in 2006 across Ontario and Quebec, Canada. Isoflavone content of the mature seed was determined by near-infrared reflectance. The effects of genotype, environment, and the genotype x environment (G x E) interaction were significant. Consistently performing genotypes from the two populations were identified by several stability parameters. Genotype–genotype x environment (GGE) biplot demonstrated an ability to provide information on both the genotypes and the environments in which they were evaluated. The identification of genotypes with consistent placement in either the high- and low-isoflavone classes suggested that breeding for relative isoflavone content in soybean is possible, although breeding for absolute stability remains a challenge, given the large environmental influence on soybean isoflavone levels.