The Effect of GA2ox Gene Transformation on Creeping Bentgrass Shade Tolerance.

Turfgrasses are full sun plants which require a minimum of four to six hours of sun per day. Turf grown in shade exhibits increased stem elongation and becomes weakened. Dwarfism might improve turfgrass quality and reduce management cost. The purpose of this study was to examine the effect of GA2-oxidase gene overexpression on creeping bentgrass (Agrostis stolonifera L.) growth and development under restricted light conditions. Greenhouse studies were performed at The Ohio State University, Columbus OH from 10 Jul to 3 Aug 2007 and 5 May to 5 October 2008. Two glyphosate-tolerant controls: Ar237 and Ar261 containing the CP4 EPSPS gene, two lines, Ax6548 and Ax6549, transformed with CP4 EPSPS and the runner bean GA2- oxidase gene, and two conventional creeping bentgrass cultivars, ‘LS44’ and ‘Crenshaw’ were evaluated. In 2007 turf was subjected to full sun, plant canopy shade, and neutral shade where light reduction and R: FR was 90% and .28, and 85% and 1.29 for canopy shade and neutral shade, respectively. In 2008 study has been modified with respect to light treatments. Turf plants were assigned to full sun, photoselective green polyethylene film (R:FR 0.7), and black shade cloth (R:FR 1.28, light reduction 60%). Turf was evaluated for visual quality (density and color), growth rate, canopy-level chlorophyll content, and total nonstructural carbohydrates levels. The levels of GA1 and GA4 were assessed in 2008. In 2007 both shade treatments caused a significant decrease in turf overall quality, regardless the examined line. Total chlorophyll concentrations were greatest in full sun and varied significantly between all light environments and particular creeping bentgrass plants. In general experimental line x6548 and LS44 cultivar exhibited the highest and x6549 the lowest levels of total chlorophyll. Overall both GA2-oxidase experimental lines exhibited the lowest and LS44 the greatest vertical growth rate.