Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/2/2005
Publication Date: 11/14/2005
Citation: Renganayaki, K., Jessup, R.W., Burson, B.L., Hussey, M.A., Read, J.C. 2005. Identification of male-specific AFLP markers in dioecious Texas bluegrass. Crop Science. 45:2529-2539. Interpretive Summary: Texas bluegrass is a cool-season grass that is native to the southern Great Plains of the United States. Its popularity and importance as a forage and turf grass have increased over the past several years. This grass has an unusual flowering behavior in that it produces flowers that are either female or male. These flowers are on different plants, and some plants have only female flowers while others produce only male flowers. So there are female plants and male plants. This is called dioecy. Because of this, the only way Texas bluegrass will produce seed is by cross-pollinating female and male plants. Many economically important cereal crops, such as wheat, oats, rice, etc., are self-pollinated and it is very difficult to produce hybrids. When hybrids are produced in these crops, grain production is greatly increased because of hybrid vigor. If dioecy could be transferred to these cereal crops, it would be very easy to produce hybrids and grain yield would be greatly increased. This could potentially go a long way toward increasing grain production and eliminating starvation in many of the areas of the world that are subject to famine. Texas bluegrass will not cross with any of these cereals because they are not closely related. Thus, molecular approaches will have to be used to transfer dioecy from Texas bluegrass to one of these cereal crops. The first step in doing this is to determine where the gene(s) that control dioecy in Texas bluegrass are located. In this study, we were able to develop a genetic map of Texas bluegrass and identify some molecular markers that are close to the dioecy gene(s) and this is the first step toward obtaining these genes. This genetic map also will be useful in the breeding and improvement of other forage and turf grasses.
Technical Abstract: Dioecy is a breeding system that promotes cross-pollination in plants. The transfer of this trait into economically important self-pollinated cereal crops would revolutionize the production of hybrids in these species and provide a means for increasing yields because of heterosis. In the Poaceae, molecular markers have not been linked to this important trait; however, Texas bluegrass (Poa arachnifera Torr.) is a polymorphic dioecious species that provides an opportunity to genetically map the dioecy locus. In this study, AFLP-based linkage maps were constructed for both the maternal and paternal plants used to develop a mapping population of Texas bluegrass. The maternal map contained 126 SDRFs, 31 linkage groups, 1744 cM, and an average marker spacing of 13.8 cM. The paternal map contained 210 SDRFs, 46 linkage groups, 2699 cM, and an average marker spacing of 12.9 cM. Approximately 76 to 81% of the Texas bluegrass genome was covered. Two AFLP markers (txbg7 and txbg154) mapped equidistantly (9.5 cM) on opposite sides of the dioecy locus (Pdiol) on the paternal map. These markers provide a preliminary tool for study sex determination and a framework for further characterization of the genomic region conferring dioecy in Texas bluegrass.