Promoting Effect Of Metabolites Of Alternaria Alternata SDTF0011 On Tobacco

Tobacco,whose quality and yield have great influence on national economy,is one of the most important economic crops in the world.At present,the quality and yield of tobacco differ greatly in different regions of China.One of the main methods to improve tobacco production is the use of chemical pesticides,which not only causes residual risk,environmental pollution,may also break the ecological balance.Therefore,it is necessary to seek a kind of highly effective,non-toxic and environmentally friendly biological insecticides to improve the quality and yield of aobacco and reduce the dosage of chemical pesticides.Among them,the unique biocontrol potential of Alternaria alternata has been increasingly accepted.In this study,SDTF0011,a fungus with strong biological activity on plant germination,was isolated from the soil,and its species status was determined by SEM observation,physiological and biochemical tests and molecular biological identification.At the same time the greenhouse experiment measured the effect of fermentation liquid of the fungi on tobacco growth,defense enzyme activity,MDA and chlorophyll contents.The metabolites of SDTF0011 were analyzed by high performance liquid chromatography(HPLC)and liquid chromatography-mass spectrometry(LC-MS).The indoor germination test of the tobacco plant used metabolite explored the action mechanism of the fungal metabolite on the tobacco growth-promoting effect,and provided a theoretical basis and application basis for the application of the bio-pesticide on tobacco.The specific experimental results are as follows:1.A phylogenetic tree was established after the mycelia of the fungus SDTF0011 observed by SEM,physiological and biochemical tests and ITS gene sequence analysis,and finally the fungus was identified as Alternaria tenuissima.2.In the greenhouse pot experiment,the metabolite fermentation broth of Alternaria tenuissima SDTF0011 strain can significantly promote the growth of tobacco plants,and the fermentation broth is diluted 50 times to spray the plants,which has the best growth promoting effect on tobacco.And its plant height,stem diameter and the highest number of effective leaves were 1.23,1.27,1.39 times of the control group,and induced the increase of defense enzyme activity,MDA content and chlorophyll content in tobacco leaves,which effectively promoted the growth and development of tobacco plants and improved its ability to resist the harsh environment of the outside world.3.In this experiment,high performance liquid chromatography(HPLC)was primarily used to analyze the metabolites of Alternaria tenuissima SDTF0011 strain to determine the target substance,and then its structural components were analyzed by ultra-high performance liquid chromatography-mass spectrometry(UPLC-MS)to determine its as a cyclic structure compound.The indoor germination test of tobacco plants showed that the promoting effect on tobacco seed germination was the best,when the concentration of metabolites was 0.25 mg/L.4.Field experiments in Tai ’an and Weifang showed that the metabolites of Alternaria tenuissima SDTF0011 strain of very fine chain spore had a significant effect on promoting the growth of tobacco.When the fermentation broth was diluted 50 times and the average amount of effective components per hectare was 696.96 mg,the effect on promoting the growth of field tobacco was the best,and the yield of tobacco could be increased by 35.62%.