The Action Mode Of LH-2010A Against Phytophthora Capsici And Its Action Mechanism

LH-2010A(N-（3-chloro-5-（trifluoromethyl）pyridine-2-methyl-2,3,5,6-four fluorine-4-methoxy benzamide） is a novel pesticide product with independent intellectual property right in China, and it is a new kind of high efficient and broad-spectrum fungicide. In this paper, the effect of LH-2010A against Phytophthora capsici’s biological characteristics were investigated, including the mycelial growth, zoospores release and mycelial yield of P. capsici.; and also studied the action mechanism of LH-2010A on P.capsici., it consists of the morphology and ultrastructure of mycelia, energy metabolism, respiratory metabolism and respiration metabolic pathway, membrane permeability, soluble protein content,DNA content and the control effect of LH-2010A against P.capsici..The main findings are as follows:（1） LH-2010A has strong inhibition on mycelial growth and mycelial yield of P. capsici., with EC₅₀ values of 7.14 μg/mL, 5.12 μg/mL, respectively. But it also showed the weak inhibition on zoospores release with EC₅₀ value of 16.34 μg/mL.（2） Observed under an optical microscope, the treatments have excessive branching and become shorter, with the emergence of the phenomenon of distortion; Scanning electron microscopy revealed hyphae branch without LH-2010A has normal growth and uniform thickness, but the hyphae treated with LH-2010A has been the emergence of the phenomenon of aggregation of mycelium. Observed under TEM, the result showed the mycelium cultivated under normal conditions exhibit a clear, orderly distribution of plasma membrane, vacuole and liposomes and other cytological ultrastructure. However, the mycelium treated with LH-2010A showed the development of a thicker and multilayer cell wall, and the increaseing of liposome, and the cells appeared deformed.（3） Bioassay result showed that LH-2010A has strong inhibition on mycelial growth, and the inhibition was positive correlation with concentration. But the inhibition of LH-2010A on mycelial growth was reduced by the addition of different concentrations of ATP（1 or 5 μg/mL）, which suggested that the action mechanism of LH-2010A was connected with impairment of the energy generation system.（4） Mycelial respiration rate test was studied to evaluate the inhibition on metabolic approaches of embden-meyerhof-parnas（EMP）, tricarboxylic acid cycle（TCA）, hexose monophosphate（HMP） and the bypass oxidation pathway by measuring the oxygen consumption of LH-2010A combining with four representative inhibitors to metabolic approaches. LH-2010A has the least superpose rate with palonic acid, the result indicated that LH-2010A could inhibit the approach of TCA significantly.（5） The relatively leakage was determined to evaluate the cell membrane permeability of P. capsici. treated with LH-2010A.The research showed the conductivity of mycelia cell suspension increased in the presence of LH-2010A, which indicated that LH-2010A had effect on cell membrane permeability, and this effect was positively correlated with concentration. We conclude LH-2010A damaged the membrane of P.capsici., leading to intracellular electrolyte leakage, and resulting in an increase in membrane permeability.（6） The result showed P. capsici.mycelium soluble protein content reduced because of the presence of LH-2010A, and this inhibition was related to concentration. This discovery indicated LH-2010A may inhibit the mycelium synthesis of soluble protein. DNA content also decreased when treated with LH-2010A, but under 5% significant level the difference was not notable, indicating that LH-2010A may have no effect on synthesis of P. capsici. mycelium.（7）Houseplants experimental data indicated LH-2010A has better control effect against P. capsici. Leonian, and its protective effect is better than therapeutic effect. After treated with LH-2010A, the content of SA, the activity of PAL and POD in pepper leaves has a certain degree of increase, this result determined that LH-2010A can cause pepper acquired resistance.