Submitted to: Journal of Agricultural Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/13/2007
Publication Date: 1/3/2008
Citation: Ortiz-Perez, E., Mian, R.M., Cooper, R.L., Mendiola, T., Tew, J., Horner, H.T., Hanlin, S.J., Palmer, R.G. 2008. Seed-Set Evaluation of Four Male-Sterile, Female-Fertile Soyban Lines Using Alfalfa Leaf-Cutter Bees and Honey Bees as Pollinators. Journal of Agricultural Science. 146:461-469. Interpretive Summary: Insects pollinate many horticultural, forestry, and field crops in addition to naturally occurring plants. One of the social insects, the honey bee, not only is an effective pollinator, but the hives are a source of honey. One of the solitary insects, the alfalfa leaf-cutter bee, is an important pollinator to produce alfalfa seed. To produce large quantitites of hybrid soybean seed, insect pollinators are necessary to transfer pollen from the male plants to the female plants. Fertilization occurs and hybrid seed is produced. Our objective was to compare the effectiveness of honey bees and alfalfa leaf-cutter bees on four male-sterile, female-fertile soybean lines at Ames, Iowa (2 years), and Wooster, Ohio (3 years). A common male parent was used at both locations. Honey bees and alfalfa leaf-cutter bees performed similarly at both locations. The rank order of the four lines in terms of the number of need per male-sterile line, was the same at both locations. Seed-set on the male-sterile, female-fertile plants was consistently higher in Wooster. Higher temperatures, relative humidity, and rainfall at Wooster may have favored pollinator activity. Costs of pollinators and personal preferences may be the factors to consider when selecting pollinators to produce hybrid soybean seed.
Technical Abstract: Male-sterile, female-fertile plants have been used to produce hybrid soybean seed. Manual cross-pollination using male-sterile plants to produce large quantities of hybrid seed is difficult and time-consuming, because of the low success rate in cross-pollination. Insect pllinators may be suitable vectors to transfer pollen, but the most suitable vector for pollen transfer from the male parent to the female parent has not been ifentified for soybean. The objective of this study was to evaluate seed-set four male-sterile, female-fertile soybean lines by using alfalfa leaf-cutter bees [Megachile rotundata (F.)] and honey bees [Apis mellifera (L.)] as pollinators. Seed-set was evaluated in summers 2003 and 2005 near Ames, IA, and in summer 2003, 2004, and 2005 near Wooster, OH. The results indicated significant differences for seed-set among male-sterile lines, suggesting perferential pollination. Male-sterile lines, ms1 (Urbana) and ms2 (Ames 2), had higher seed-set compared to ms6 (Ames 1), and ms6 (Corsoy 79). In Ames, ms1ms1 plants had the highest seed-set (72.12 seeds per male-sterile plant) in Wooster. Honey bees performed similarly to alfalfa leaf-cutter bees at both locations. Neither the effect of pollinator species nor the interaction effect of pollinator species x location was significant for any year. Costs and local conditions need to be addressed to support the choice of either pollinator species as a pollination vector to produce hybrid soybean seed.