Golf Course Management

JUL 2014

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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07.14 GOLF COURSE MANAGEMENT 89 CUTTING EDGE Teresa Carson Endophyte-mediated biotic resistance in turfgrass Turfgrass-fungal endophyte mutualism is of broad signifcance in turf. Festuca and Lolium species are known to harbor Epic loë fungi in their aboveground tissues. The en - dophyte infection is asymptomatic and typi- cally confers benefts to its plant host, which in turn makes nutrients accessible to the en - dophyte. An intriguing aspect of this mutual- ism is manifested in the endophyte-mediated disease resistance unique to the F. rubra (red fescue)–E. festucae interaction. Field studies have shown that dollar spot disease caused by Sclerotinia omoeocarpa is effectively hindered in endophyte-infected F. rubra. Another study reported that endophyte-infected F. rubra is toxic to chinch bugs. In order to understand the mechanisms driving these advantages, we analyzed clonally propagated endophyte-free and E. festucae-infected F. rubra for differen - tial plant gene expression. Analysis of the E. festucae data revealed that the most abundant E. festucae transcript constituted >10% of its transcriptome. Strikingly, the second-most abundant endophyte gene encodes a small secreted antifungal protein. Current studies are aimed at determining if the endophyte antifungal protein may be involved in the ob - served endophyte-mediated dollar spot resis- tance. Endophyte genes that may confer biotic resistance to Epic loë-infected plants were also discovered. We have recently demonstrated one such gene to be insecticidal against black cutworms. — Karen V. Ambrose and Faith C. Be- langer, Ph.D. (belanger@aesop.rutgers.edu), Rut- gers University GABA mitigates drought stress damage in perennial ryegrass Perennial ryegrass is an important for- age and turfgrass species that is sensitive to drought stress. The objective of this study was to investigate whether gamma aminobutyric acid (GABA) may play a role in promoting drought tolerance in grass species. GABA was exogenously applied as foliar spray at the rate of 50 millimoles/liter or 70 millimoles/liter to CSI perennial ryegrass under well-watered or drought-stressed conditions in a controlled- environment growth chamber. The effect of GABA on the growth physiology, drought stress response, antioxidant activity and lipid peroxidation of perennial ryegrass exposed to drought stress was measured. GABA-treated ryegrass exposed to drought stress had higher relative water content (RWC), turf quality and peroxidase activity and lower wilt rating, can - opy temperature, electrolyte leakage and lipid peroxidation compared to untreated plants. GABA application had no signifcant effect on the activity of superoxide dismutase and cata - lase under well watered and drought condi- tions. GABA application at 50 millimoles/liter was found to be more effective in alleviating drought stress damage in ryegrass. The results from this study suggest that GABA mitigated drought stress damage in perennial ryegrass by maintaining higher RWC and membrane sta - bility. — Sanal Kumar Krishnan, Kevin Laskowski, Vijaya Shukla and Emily B. Merewitz, Ph.D., Michi - gan State University, East Lansing, Mich. Teresa Carson (tcarson@gcsaa.org) is GCM 's science editor. Photo by E. Merewitz Leaf sheath epidermal peel of big bluegrass infected with Epichloë stained with Rose Bengal. Fungal hyphae growing in between the plant cells are indicated by arrows. Photo by F. Balengar 080-089_July14_TechwellCuttingEdge copy.indd 89 6/17/14 2:32 PM

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