Heterotic Patterns of Soybean Lines from 3-Way, 4-Way and 5-way Crosses, and Backcross Populations

Authors: PEREZ, PAOLA - ISU; CIANZIO, SILVIA - ISU; Palmer, Reid

Submitted to: Journal of Crop Production
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2009
Publication Date: 4/10/2009
Citation: Perez, P.T., Cianzio, S.R., Palmer, R.G. 2009. Heterotic Patterns of Soybean Lines from 3-Way, 4-Way and 5-way Crosses, and Backcross Populations. Journal of Crop Production. 23:95-118.

Interpretive Summary: Plant breeders continually try to improve plant cultivars, e.g., for yield potential, pest tolerance or resistance, seed and/or forage quality, etc. The use of hybrid plants, i.e., that are the result of crosses between two parents, generally exhibit superior agronomic performance. Hybrids that have been successful in cross-pollinated plants have desirable sterility systems, e.g., maize. In most highly self-pollinated crops, commercial hybrids are not economical or agronomically superior to conventionally-bred cultivars. An exception is the self-pollinated crop rice, which has been a commercial success worldwide. Soybean is a highly self-pollinated crop with the male and female reproductive organs within the same flower. Our objective was to use insect-mediated cross-pollination to produce large quantities of hybrid soybean seed to test agronomic performance, i.e., heterosis. Female parents were two male-sterile female-fertile lines with the ms3 and ms9 mutations. The male parents were six high yielding agronomic lines. The experiment was conducted at one location for two years. Populations consisted of F1, 3-way, 4-way, and 5-way crosses, and backcrosses (BC1, BC2, and BC3) derived lines. Positive heterosis values were observed for grain yield. Values depended upon specific female and male parent combinations, called specific combining ability. These results give support towards the commercialization of hybrid soybean. Increased seed yields from hybrid soybean should benefit the farmer (profit) and the seedsman (profit), and ultimately the consumer through stable food costs with possible enhanced quality.

Technical Abstract: Identifying heterotic patterns in self-pollinated crops such as soybean [Glycine max (L.) Merr.], requires, among other items, development of different populations types. Male-sterility systems combined with insect-mediated cross-pollination in soybean have been shown to produce large quantities of hybrid seed, which can be useful for studying heterotic patterns. This procedure was used to obtain large quantities of hybrid seed for replicated yield trials with the objective to evaluate seed yield and agronomic performance in hybrid soybean populations developed by single-crosses, three (3)-way, four (4)-way, and five (5)-way crosses, and backcrosses (BC1, BC2, and BC3) to estimate heterosis. Parental genotypes were male-sterile, female-fertile lines, selected for their excellent insect pollinator attraction, and a group of male parents selected for their agronomic performance. In 2005, hybrid seed of F1, 3-way and 4-way crosses, BC1, and BC2 populations of eight families were planted at one location in Iowa. In 2006, the 5-way crosses and BC3 populations were planted at one location in Iowa. All populations were evaluated in replicated field tests in Iowa. Yield mid-parent heterosis values (MPH) ranged from -35% to +17%, and high-parent heterosis (HPH) from -44% to + 13%. Backcross populations had higher heterosis estimates for yield than the other population types. Estimates of MPH and HPH obtained suggest that it is possible to identify heterotic patterns in soybean. However, the fact that negative heterosis values were also observed suggests that a large number of different parental combinations need to be evaluated to identify superior heterotic combinations. These evaluations will determine the feasibility of hybrid soybean production for commercial purposes.