Effects of the Dt 2 and S Alleles on Agronomic Traits of F 1 Hybrid Soybean

Agronomic evaluation of F 1 hybrid soybean [ Glycine max (L) Merr.] will be useful for germplasm evaluation, recurrent selection, and estimating heterosis. We anticipated that vegetative heterosis, commonly observed in soybean, could increase early lodging and pod abortion, reducing grain yield. Under these circumstances, observed hybrid grain yield would not reflect the true potential of the hybrid as expressed in later generations. The Dt 2 (semideterminate stem type) and S (short internode stem type) alleles have been shown to reduce excessive vegetative growth and lodging in narrow‐row production of inbred soybean. Our objectives were (i) to determine the per se effects and effects on heterosis, for agronomic traits, of the semideterminate ( Dt 2 _) and short ( S _) stem types in hybrid soybean, (ii) to assess their potential in facilitating germplasm evaluation and recurrent selection, and (iii) to determine if either stem type would be agronomically desirable in commercial hybrid soybean production. Near‐isogenic inbred lines and hybrid (F 1 ) lines were evaluated replicated three‐row plots. The Dt 2 and S alleles affected agronomic traits of hybrids and inbreds similarly. The Dt 2 and S alleles hastened maturity, decreased plant height and lodging, and increased harvest index per se values. The Dt 2 allele decreased seed weight and protein content. Both the per se and heterosis data suggest that the Dt 2 and S alleles would not be consistently beneficial to germplasm evaluation or recurrent selection. The per se data suggest that the S allele might be useful for both inbred and commercial hybrid soybean.