Effects of six metabolites on rice resistance to blast fungus， Magnaporthe oryzae

【Objective】Analyzing the effect of primary metabolites during interaction of rice and Magnaporthe oryzae on rice blast morphogenesis and defense response，to provide basic data for the formulation of green control measures for rice blast in production.【Method】The six primary metabolites with a certain concentration（dopamine hydrochloride， L-glutamine，tyramine，α-pinene，L-tryptophan，galactinol）were used to treat the rice blast strains to observe the effects of metabolites on colony growth，strain morphology（sporulation，hypha germination and appressorium formation）of M.oryzae. On this basis，the same concentrations of metabolite standards were used to treat 36 h- and 48 h- infected rice to investigate symptom of rice blast disease，analyze defense gene expression，and detect reactive oxygen species（ROS） content and peroxidase（POD）activity.【Result】Except for L-glutamine and L-tryptophan，which had a significant effect on the growth of the rice blast fungus colony on the ninth day of growth（P<0.05，the same below），the other four metabolites had no significant effect on the growth of the rice blast fungus colony（P>0.05）. Six kinds of primary metabolites of rice had inhibitory effect on sporulation of M.oryzae，among which tyramine and α-pinene had the most obvious inhibitory effect. Dopamine hydrochloride significantly inhibited the spore germination of M.oryzae，while the other five metabolites had no obvious effect on the spore germination ofM.oryzae.Six kinds of primary metabolites of rice could significantly promote the growth of germ tube ofM.oryzae. Dopamine hydrochloride and L-tryptophan promoted appressorium formation，while L-glutamine and tyramine inhibited appressorium formation. Six kinds of primary metabolites in rice reduced the symptoms and disease index of rice blast at 36 and 48 h after inoculation with M.oryzae，among which dopamine hydrochloride，tyramine and galactitol had the best control effect on rice blast. The control effect of the six kinds of primary metabolites on rice blast at 48 h was higher than that at 36 h. Further studies found that dopamine hydrochloride and galactitol inhibited the expression of jasmonic acid（JA）signaling genes OsCOI1a，OsCOI1b and OsMYC2 in rice at 36 and 48 h of rice blast fungus infection，but the JA repressor gene OsJAZ9 was up-regulated and induced ROS-related genes OsRbohB，OsRbohA and the disease-related genes OsPR10a，OsPR5 were up-regulated. Among them，the expression levels of ROS-related genes and disease course-related genes in rice induced by the two metabolites at 48 h of M.oryzae infection were higher than those in infected rice at 36 h after M.oryzae. Both metabolites inhibited JA signaling genes. Dopamine hydrochloride induced obvious increase in POD activity and a certain degree of increase in ROS content in rice at 36 and 48 h of M.oryzae infection.【Conclusion】Metabolites can improve rice blast resistance of susceptible rice variety through affecting the morphological development of rice blast fungus，inducing the expression of defense-related genes and increasing POD activity in susceptible rice. Therefore，the six metabolites have potential applications in the green control of rice blast disease.