Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2006
Publication Date: 12/1/2006
Citation: Ortiz-Perez, E., Cianzio, S.R., Wiley, H., Horner, H.T., Davis, W.H., Palmer, R.G. 2006. Insect-mediated cross-pollination in soybean [Glycine max (L.) Merrill]:i. agronomic performance. Field Crops Research. 101:259-268. 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 give superior agronomic performance. Hybrids have been successful in cross-pollinated plants that have suitable sterility systems, e.g., maize. In most highly self-pollinated crops, commercial hybrids are not economical or agronomically superior to conventionally bred cultivars. However, the self-pollinated crop rice has been a commercial success. Soybean is a highly self-pollinated crop with the male and female reproductive organs within the same flower. Male-sterile, female-fertile lines are available in soybean. Our objective was to use insect-mediated cross-pollination to produce large quantities of hybrid soybean seed to test for agronomic performance, i.e. heterosis. Parents and single-cross hybrid seed from 9 combinations were tested for agronomic performance at three locations in 2003. Parents and three-way crosses (8 combinations) and backcrosses (8 combinations) were tested for agronomic performance at one location in 2004. Positive heterosis values for yield and seed protein content were observed for certain single-cross combinations. For three-way crosses, positive heterosis values were recorded only for seed protein content for certain combinations. For backcrosses, positive heterosis values were recorded for yield, seed oil, and seed protein contents. Our results indicate that yield heterosis greater than 10% with positive heterosis for oil and seed protein content is feasible in the same hybrid. These results give support towards the commercialization of soybean. Increased yields from hybrid soybean should benefit the farmer (profit), the seedsmen (profit), and ultimately the consumer through stable food costs with possible enhanced quality.
Technical Abstract: In soybean, manual cross-pollination to produce large quantities of F1 hybrid seed for yield trials is difficult and time-consuming. Conversely, insect-mediated cross-pollination has been shown to produce large quantities of hybrid seed in soybean and should facilitate the identification of heterotic patterns. The objective of the study was to compare F1 hybrid soybean yield and agronomic traits from single-crosses, three-way crosses, and backcrosses (BC1F1) produced by male-sterile lines and a selected group of male parents. In 2003, F1 seed of single-crosses and their parent lines were evaluated in replicated experiments at three locations. Also in 2003, three-way crosses, and BC1F1 seed were produced. In 2004, three-way crosses, BC1F1 crosses, and their parent lines were evaluated at one location. High-parent heterosis (HPH) in single-crosses for yield ranged from -65.70% to +16.17%; for protein content from -4.34 % to +3.53%, and for oil content from -13.22% to -0.84%. In three-way crosses, HPH for yield ranged from -25.21% to -4.50 %, for protein from -2.72% to +1.92%, and for oil from -5.87% to -1.20%. For BC1F1 crosses, HPH for yield ranged from -15.65% to + 41.97%, for protein from -2.57% to +1.69 %, and for oil from -2.47% to +2.22%. Our results indicated that yield heterosis greater than 10% is attainable and suggest that higher levels may be possible.