Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/26/2005
Publication Date: 6/1/2006
Citation: Ortiz-Perez, E., Horner, H.T., Hanlin, S.J., Palmer, R.G. 2006. Evaluation of insect-mediated seed-set among male-sterile soybean lines segregating for the ms6 allele. Field Crops Research. 97:353-362 Interpretive Summary: Plants that are male-sterile, but female-fertile can be used as female parents in plant breeding programs. The seed produced on these female parents is called hybrid seed. Hybrid plants usually are superior agronomically to plants bred using other plant breeding methods. Soybean has the male and female reproductive structures within the same flower. Pollination and fertilization take place within each flower. Using the sterility system mentioned and the pollinating insect, alfalfa leaf cutter bee, 71 male-sterile, female-fertile soybean lines were evaluated for seed-set near Ames, Iowa in 2001, 2002, and 2003. The effect of environmental conditions on seed-set were most important. These conditions affected both the soybean plant, the insect pollinator, and the plant-pollinator interaction. Differences in seed-set among the 71 male-sterile lines indicates that selection for increased insect-mediated cross-pollination, i.e. increased seed set, should be possible in soybean. Plant breeders will benefit immediately from this information and can use it in certain plant breeding schemes, e.g., phenotypic recurrent selection.
Technical Abstract: Currently there is no economical way to produce large quantities of F1 hybrid soybean seed in the USA. One of the fundamental requirements 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. Our observations indicated that seed-set on male-sterile, female-fertile plants is a good indicator of insect attraction. The objective of this study was to evaluate seed-set among different male-sterile, female-fertile lines using a pollinator insect species. Thirty–four pairs of near-isogenic lines, their donor parent, and its two isogenic lines segregating for male-sterile (ms6) allele were used. Seed-set was evaluated in field-grown plants in 2001, 2002 and 2003 near Ames, IA. Although the observed seed-set was not commercially acceptable, our results indicated significant differences in seed-set among lines. This suggests that preferential attraction of pollinators occurred and selection among male-sterile, female-fertile lines could be used to obtain female parents suitable to produce larger amounts of hybrid soybean seed. In addition, the effect of flower color in seed-set was statistically significant. White-flowered lines produced more seed-set compared to purple-flowered lines. Lastly, the effect of environmental conditions on seed-set among male-sterile lines was of paramount importance to plant-pollinator interactions and needs to be assessed in order to establish an efficient hybrid soybean program.