Selection of Shade Tolerant Bermudagrass Germplasms.

Bermudagrass (Cynodon spp.) is a highly recommended warm season grass for home lawns and golf courses in the USA transition zone as well as the southern USA because it has good drought, heat, and salt tolerance and is resistant to many pests. However, bermudagrass does not tolerate shade nearly as well as most grasses.  Worldwide bermudagrass collection has been amassed, and is in place for use at the Oklahoma State University turfgrass breeding program.  We believe similar or substantial genetic variation for shade tolerance in bermudagrass exists in the collection.  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.  This study consists of 45 bermudagrass selections and four standards, ‘Celebration’, ‘Patriot’, ‘TifGrand’, and ‘Tifton 10’.  Celebration, TifGrand, and Tifton 10 were chosen for their potential shade tolerance and Patriot was chosen for its likely poor shade tolerance.  Visual turf quality (TQ) and normalized difference vegetative index (NDVI) were assessed every two weeks in 2010 and 2011.   A significant decline in TQ was observed after adding additional 75% black woven shade cloth in 2010.  TQ decline increased from 7.5% in 2009 to 38.9% in 2010 and NDVI decline also increased from 5.2% to 23.9% in 2010.  Photosynthesis was measured from the 5 best selections and 5 worst selections of 2009 and four standards during spring, summer, and fall 2010 with a LI-6400 portable gas exchange system (LI-COR Inc., Lincoln, NE). The CO2 gas uptake was the fastest in the summer and the slowest in the spring for plants both in full sun and shade.