Location: Corn Insects and Crop Genetics Research2011 Annual Report
1a. Objectives (from AD-416)
Objective 1: Identify and utilize fertility/sterility mutants in a phenotypic recurrent selection program for insect-mediated cross-pollination to increase hybrid seed production. Objective 2: Identify phenotypes/genotypes that can be characterized and molecularly mapped that contribute to insect-pollinator attraction and reward.
1b. Approach (from AD-416)
Soybean accessions in the USDA germplasm collection will be crossed with known cytoplasmic restorer lines to identify cytoplasmic male sterile cytoplasms. Sterility mutants (nuclear) obtained via gene tagging from the w4-mutable system will be characterized genetically. Both the cytoplasmic and nuclear sterility mutants will be used in a phenotypic recurrent selection system, with insect-mediated cross-pollination, to increase hybrid seed production. The plant factors that contribute to the increased attraction/reward of the insect pollinators will be identified, characterized, and molecularly mapped.
3. Progress Report
Progress was made on all objectives and their sub-objectives. More germplasm was used in cross-pollinations. Progress was made on cytoplasmic male sterility (a type of plant sterility that will greatly enhance hybrid breeding in soybean) in the USDA-ARS soybean germplasm. Unfortunately, in certain genetic backgrounds and environments, male sterility is not complete. This is a common occurrence in cytoplasmic male-sterile systems. In 2011, the search for maintainer and restorer soybean germplasm was initiated to preserve our supposed cytoplasmic male-sterile germplasm. Additional fertility/sterility mutants were molecularly mapped. Plant structure (floral display and floral design) and chemical traits associated with soybean insect-pollinator attraction and reward were identified and characterized. We used the proboscis extension response (PER) technique to train honeybees to differentiate among soybean genotypes selected on the basis of out-crossed seed-set. Soybean accessions in the USDA germplasm collection were crossed with known cytoplasmic restorer lines to identify cytoplasmic male sterile germplasm. Sterility mutants will be characterized genetically. Cytoplasmic (or extra-nuclear) and nuclear sterility mutants will be used in a plant breeding system using generational selections that will take advantage of insect-mediated cross-pollination, to increase hybrid seed production.
1. Identification of soybean germplasm with supposed cytoplasmic male-sterility (CMS). Additional germplasm was screened in an attempt to identify CMS because all restorers did not give complete restoration. Identification of soybean germplasm with cytoplasmic male-sterility will be useful to produce commercial hybrid soybean seed, enhancing soybean performance for producers. ARS researchers in Ames, Iowa, molecularly mapped all male-sterile, female-sterile mutants in the ARS germplasm collection. The location (clusters on certain chromosomes) of these sterility mutants expands our knowledge about the chromosomal distribution of sterility mutants. The discovery and characterization of CMS and nuclear male sterility provides the genetic material to determine heterosis, higher seed use yield. If successful, this is one step closer to commercial hybrid soybean. There was a very high positive correlation between bee response (PER) and high and low seed-set lines.
Yang, N., Moon, J., Lee, Y., Lee, S., Kim, H., Hwang, C., Back, K., Palmer, R.G., Jeong, S. 2010. Genetic and sequence analysis of genes controlling natural variation of seed-coat and flower colors in soybean. Journal of Heredity. 101(6):757-768.