Study On Growth Promotion And Resistance Enhancement Of Potato To Late Blight By Endophytic Fusarium Lateritium

Endophytes and plants have long-term mutually beneficial symbiosis and play an important role in biological processes such as plant growth and development,stress resistance and pest defense,and have the potential to be used as"plant vaccines",thus reducing the application of chemical fertilizers and pesticides.However,the interaction between endophytes and plants is not clear,which limits its popularization and application.Therefore,an in-depth study of the interaction between plants and endophytes will provide new ideas for crop field nutrition management and comprehensive prevention and control of diseases and insect pests.In this study,a strain of endophytic Fusarium lateritium was selected from the endophytic isolated and screened by Nothapodytes pittosporoides.The potato treated by the strain and its leaves in vitro were inoculated with Phytophthora infestans,and the disease index and physiological indexes were counted to explore the growth-promoting effect of the strain on potato and its control effect on late blight.The genetic transformation system of the strain was further constructed and the GFP fluorescence labeled strain was obtained.Based on this,the interaction process between fungi and plants was observed by staining and laser confocal microscope,the action site of the strain was identified,and the relative colonization of fungi in potato was detected by RT-qPCR.In addition,RT-qPCR was used to explore the expression patterns of fungi on potato growth and defense-related hormone genes,as well as the effects of fungi on root soil flora activity,and jointly reveal the physiological basis of fungi on potato growth promotion and disease control.The main results are as follows:1.F.lateritium significantly promoted the growth of potato,in which the plant height,total biomass,main root number and root biomass of the strain treatment group were 1.25,1.19,2.3 and 1.47 times higher than those of the control.2.F.lateritium increased the resistance of potatoes to late blight.Among them,the results of the biological test of potato late blight showed that the infection rate was 87.5%in the clear water treatment group and 37.5%in the F.lateritium treatment group.Leaf disease index analysis showed that the leaf disease spot and leaf damage area ratio of the strain treatment group were 2.24 cm² and 11.22%respectively,which were significantly lower than those of the control water treatment（4.14 cm² and 24.94%）.3.F.lateritium mediates the expression of plant hormone-related genes.Including auxin biosynthesis related genes（StYUC5）,jasmonic acid and salicylic acid pathway related genes（StPI-I,StPR1A）4.The vector pK₂-hyg-gpdA::gfp,was constructed to obtain GFP marker strain,and the genetic transformation conditions were optimized.5.Through propidium iodide（PI）staining,Trypan blue staining and RT-qPCR molecular quantification,it was shown that F.lateritium could colonize in potato roots,and the growth of fungi in the plant was relatively quantified.The mycelium growth of F.lateritium was found in the root epidermis and root cortex cells,and grew upward to the stem of the plant,which further clarified the action site of the strain.6.F.lateritium increased the activity of sulfate esterase in potato rhizosphere soil and increased the activity of potato rhizosphere soil.