Jasmonic and salicylic acid effects on bacterial etiolation and decline disease of creeping bentgrass

Creeping bentgrass (Agrostis stolonifera), an important turfgrass on golf course putting greens can become plagued by bacterial etiolation disease caused by Acidovorax avenae subsp. avenae (Aaa). There are no known pesticides that have been shown to be effective in managing this disease. This series of hydroponic growth chamber studies investigated whether pre-treating plants with SA or JA could be effective in reducing disease symptoms of Aaa in creeping bentgrass 'Penn-A4' (Aaa sensitive) and 'Tyee' (more tolerant). The treatments included foliar application of 10 μmol/L SA, 20 μmol/L SA, 0.5 mM JA in 0.02% ethanol and 2 mM JA in 0.02% ethanol prior to exposure to heat stress (35 °C) and optimal temperature (23 °C) with or without Aaa inoculation. Physiological measurements included turf quality (TQ), leaf and root electrolyte leakage, chlorophyll content (CHL), photochemical efficiency and root viability. No significant differences were detected in either cultivar due to chemical or heat treatment alone, which indicates chemical treatments had specific effects on plant responses to bacteria and were not confounded by plant heat stress symptoms. SA application reduced Aaa disease symptoms of both cultivars under both optimal and high temperature treatments. At both 23 °C and 35 °C, the severity of disease in plants treated with SA was less than in control plants based on all measurements in our experiment. Creeping bentgrass 'Tyee' treated with JA showed significantly higher TQ than control plants at 35 °C. 'Penn-A4' treated with JA only showed significantly higher CHL than control at 23 °C. SA and JA treatments could be viable methods to induce creeping bentgrass tolerance of bacterial pathogens; however, field testing of these methods is needed.