Induction of plant defense response by salicylic acid in perennial ryegrass turf against gray leaf spot caused by Magnaporthe oryzae
A. RAHMAN (1), W. Uddin (1). (1) Pennsylvania State University, State College, PA, U.S.A.
A study was conducted to determine the salicylic acid (SA)-mediated defense response against gray leaf spot disease in perennial ryegrass turf. High performance liquid chromatography analysis of perennial ryegrass (cultivar Legacy II) leaf extracts showed that the basal level of endogenous salicylic acid is significantly low (41.12 ± 5.4 ng/g fresh weight) compared to the high amount reported in rice (5000-30,000 ng/g fresh weight). Following the inoculation of perennial ryegrass plants with <i>Magnaporthe oryzae</i>, the concentration of endogenous SA in perennial ryegrass increased over fivefold (>230 ng/g fw) within 72 hours. Exogenous application of 1.5 mM SA to perennial ryegrass reduced gray leaf spot incidence and severity by 31 and 35%, respectively. Similarly, 5 mM BTH (benzo(1,2,3) thiadiazole-7-carbothioic acid S-methyl ester), a chemical analogue of SA, also reduced gray leaf spot incidence by 50% and disease severity by 70%. This study indicates that SA-mediated defense response plays a role in protecting perennial ryegrass against gray leaf spot disease. The levels of expression of different pathogenesis-related (PR) genes associated with SA mediated suppression of gray leaf spot disease in perennial ryegrass will be further discussed.
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