Location: Crop Germplasm ResearchTitle: Interspecific hybrids between pembagrass and St. Augustinegrass
|GENOVESI, A - Texas A&M Agrilife|
|JESSUP, R - Texas A&M University|
|ENGELKE, M - Texas A&M Agrilife|
|CHANDRA, A - Texas A&M Agrilife|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2017
Publication Date: 8/1/2017
Citation: Genovesi, A.D., Jessup, R.W., Burson, B.L., Engelke, M.C., Chandra, A. 2017. Interspecific hybrids between pembagrass and St. Augustinegrass. Crop Science. 57:2819-2827.
Interpretive Summary: St. Augustinegrass is an important turfgrass that is grown on the lawns of most homes in the southern United States, especially along the Gulf Coast. Even though it is a popular turfgrass, the grass is attacked by a number of disease and insect pests that reduce its attractiveness and desirability. Unfortunately, resistance to these pests has not been found in the grass. However, Pembagrass, a relative of St. Augustinegrass, has resistance to some of these pests, including gray leaf spot, southern chinch bug, and sting nematode. In this study, Pembagrass and St. Augustinegrass were crossed to transfer resistance to these pests from Pembagrass to St. Augustinegrass. However, when crosses are made between different species, hybrids are usually difficult to recover because of sterility problems and genetic differences. To increase chances of recovering hybrids, embryos in developing seed of the female parent were removed about one week after pollination and placed on an artificial growth media (source of food). These embryos grew into small plants and were planted into pots containing soil and later planted into the field. A total of 127 plants were recovered, but it was difficult to determine if they were actual hybrids based on their appearance because they resembled Pembagrass. Using molecular tools, we checked the genetic makeup (DNA) of the 127 plants and determined that all were hybrids. This is the first time hybrids have been produced between these two species and it provides a way to improve St Augustinegrass. This technique of growing developing embryos from crosses on an artificial food source should permit plant breeders to develop improved pest resistance varieties for the home owners in the southern United States and other warmer regions of the world.
Technical Abstract: St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] is a popular turfgrass in the southern United States and possesses the highest level of shade tolerance among warm-season turfgrasses. Its stoloniferous growth habit lends itself to vegetative propagation by turfgrass producers. Ploidy differences exist between popular diploid (2n=2x=18) cultivars such as 'Raleigh' and 'DelMar' and aneuploid (2n=4x=32) cultivars such as 'Floratam'. Polyploids have been documented as possessing genes for chinch bug resistance and drought tolerance, but they have been underutilized as a breeding resource due to sterility barriers resulting from ploidy differences. In previous work we described the use of embryo rescue as a tool that enabled the recovery of viable progeny from interploid (polyploid x diploid) crosses within St. Augustinegrass. Sterility barriers also exist and limit the use of close relative Pembagrass [Stenotaphrum dimidiatum (L.) Brongn.] as a genetic resource in crosses with St. Augustinegrass. Certain Pembagrass genotypes, however, have been documented as possessing genes for resistance to gray leaf spot, southern chinch bug and sting nematode, providing a further potentially valuable resource for St. Augustinegrass improvement. In this study we report: 1) the expanded use of embryo rescue technology to enable interspecific hybridization between Pembagrass and St. Augustinegrass, and 2) confirmation of 127 progeny as true hybrids between Pembagrass and St. Augustinegrass via utilization of parental-specific EST-SSR markers.