Studies On The Resistance Induced By Chemicals Against Fungal Disease In Bluegrass And Its Resistant Mechanism

It is a new method to induce the resistance by some chemicals against turfgrass diseases.In this study, five chemical inducers, salicylic acid (SA) , oxalic acid, sodium sulfanilate, phenol and cycloheximide, were sprayed on Kentucky bluegrass (Poa prarensis L. ) , then the grasses were inoculated with Rhizoctonia solani and Pythium ultimum, which can result in brown patch and pythium blight on turfgrasses. The results were as follows:The effect of induced resistance to brown patch by SA was better than other four chemicals. The effective concentration of SA -induced resistance to brown patch was at a range of 0.01-O.lmM, and the average effect of induced resistance was over 50%. The optimum concentration is 0.05mM. Being treated with SA at 0.05mM, the average effects of induced resistance of the three cultivars, Award. Absolute and Marine, were 72.20%, 79.83%. 85.13%, respectively. The proper interval between SA treatment and inoculation was 3 days, and the resistance could be kept as long as 12-15 days. No inhibitory effect of SA at tested concentration on pathogen mycelial growth and their pathogenicities was observed, it proved that the reduction of the bluegrass diseases severity was due to the SA-induced resistance on bluegrass. Under continuously cutting condition, the SA-induced resistance decreased and the resistance duration was shorter than that was not cut.The mechanism of the induced resistance by SA was studied. The result showed that peroxidase(POD), polyphenoloxidase(PPO)and phenylanine ammonialyase (PAL) activities in bluegrass were all increased after being treated with SA or inoculated with pathogens, but SA-treated plants' enzyme activities was increased quickly and highly after inoculated compared with that was no treated.The raising rates of the three enzyme activities were coincided with the effects of SA-induced resistance of the three cultivars exactly.Two pathogenesis-related proteins . 3 -1, 3-glucanase and chitinase were also detected, the result showed that after inoculation , the two enzymes activities were increased, but there was no significant relation between the raising rate of the two enzyme activities and the effect of SA-induced resistance of the three cultivars .