Insect-mediated cross-pollination in male-sterile, female-fertile mutant soybean [Glycine max (L.) Merrill] lines

Abstract

<p>Currently, there is no economical way to produce large quantities of F1 hybrid soybean seed in the USA. One of the fundamental requirements for hybrid seed production is the availability of a stable male-sterile, female-fertile system. However, the more challenging barrier is the efficient transfer of pollen from the male parent to the female parent. This could potentially be achieved through pollinator insects. The objectives were to evaluate seed set among soybean lines segregating for male sterility, use phenotypic recurrent selection program to increase pollinator attraction of those male-sterile female-fertile identified as superior parental lines, and conduct agronomic tests for heterosis in the hybrids produced through insect-mediated cross-pollination. Differential seed set was observed among the evaluated lines, indicating that preferential pollination was present, which could suggest that selection among male-sterile, female-fertile lines can be made in order to obtain female parents suitable to produce hybrid soybean seed. Phenotypic recurrent selection in a favorable environment was successful in increasing the number of seed per male-sterile soybean plant. Mean seed-set per family as high as 304 seeds per male-sterile plant was observed after just two selection cycles. This suggested that very few genes with major effects may regulate the traits related to pollinator preference and out-crossing. A differential response was observed among the cross-combinations, suggesting variability for those traits among the parental lines. Evaluation of agronomic data revealed that positive heterosis was present in some of the crosses tested. Although heterosis is not a static attribute and is strongly affected by the environment, some promising parental combinations were found.</p>