Selection of Potential Shade Tolerant Bermudagrass Germplasm.

Bermudagrass is highly recommended for home lawns as well as golf courses in the southern United States. However, bermudagrass does not tolerate shade nearly as well as most grasses. Bermudagrass is extremely variable (Taliaferro, 1995). Recently, researchers reported that a large genetic variability existed in a Chinese bermudagrass collection of more than 120 original accessions for adaptive, morphological, and fertility traits (Wu et al., 2006). Molecular markers and ploidy information further indicate substantial genotypic variation within the germplasm pool (Wu, 2004; Wu et al., 2004). A worldwide bermudagrass collection has been amassed, and is in place for use at the OSU turfgrass breeding program. The objectives of this study were to screen bermudagrass selections for their effectiveness in shaded environments and to determine turfgrass characteristics that may be useful for rapid screening of future selections for potential shade tolerance. 45 experimental units have been selected with four standards; Tifgrand, Tifton10, Celebration, and Patriot. The research was initiated in 2008. The turfgrass visual quality and normalized difference vegetative index (NDVI) were collected every two weeks during the growing season. In 2008, shade stress occurred on the shade site for 12% longer each day than on the sun site. This short duration of shade stress caused an average 4.9% decline in TQ and a 3.4% decline in NDVI in 2008. On May 7, 2009, a black woven shade cloth with 75% light reduction (10ft x 160ft) was installed on a hoop structure to provide longer and more uniform shade for the shade site. Consequently, the shade duration increased from 12% in 2008 to 52% in 2009. Also, it increased decline in TQ from 4.9% in 2008 to 12% in 2009 and a decline in NDVI of 3.4% in 2008 to 7.4% in 2009. The bermudagrass selections differed significantly (P=0.05) in TQ and in NDVI both in full sun and in shade in both 2008 and 2009. In 2010, an extra shade cloth with 75% light reduction will be added to provide extended shade in the morning and photosynthesis will be measured from the 5 best selections, 5 worst selections and four standards in May, July, and September with a LI-6400 portable gas exchange system (LI-COR Inc., Lincoln, NE). The experimental unit # 28 and #116 were selected to initiate the preliminary molecular selections in 2010.