Study On The Inhibition Mechanism Of Chenopodium Album In Response To PA-2 Stress Of Aureobasidium Pullulans

The research,development and utilization of microbial-derived herbicides have always been the most difficult points in the research and development of biological pesticides.The cultivation conditions and herbicidal mechanisms of strains with herbicidal effects have been widely studied.In this experiment,a fungus isolated from the leaves of infected poplars in Ping'an County,Qinghai Province has a good control effect on several broad-leaved weeds.Through morphological analysis and ITS sequence detection,identified Aureobacidium pullulans.In order to improve the herbicidal effect of PA-2,we further studied the weed control mechanism of microorganisms on weeds.Using single factor to optimize the fermentation medium and optimal fermentation conditions of PA-2 strains,and to study the optimal composition of the culture medium components through Central Composite Design,to preliminary explore the growth inhibition of Chenopodium album by PA-2 strains It's metabolic action mechanism provides experimental basis for herbicides of microbial origin in the field of herbicide production and application.The results are as follows:1.Optimized the optimal medium for spore production of PA-2 strain,and determined that the most suitable components were: glucose 84.60 g,soybean powder 46.35 g,Na CI 2.59 g,Mg SO4 0.52 g,KCI 0.78 g,K2HPO4 6.5 g,(NH4)2SO4 0.52 g.The optimal fermentation conditions were: initial p H7.0,fermentation for 120 h,inoculation amount 8%,rotation speed 180 r/min,culture temperature 25 ?,and liquid volume 60 m L.2.The fermentation broth of PA-2 strain was extracted with an equal volume of n-butanol,and the crude extract of n-butanol phase was obtained by rotary evaporation,and its growth inhibition mechanism was investigated.The study found that the crude extract of 20mg/m L significantly increased the content of malondialdehyde,and the physiological indexes such as antioxidant enzyme activity,soluble sugar and soluble protein content all affected to varying degrees,of which the change in chlorophyll content was the most obvious;crude extraction The objects destroyed the ultrastructure of the mesophyll of the quinoa leaves,the chloroplasts swelled,and some of the chloroplasts appeared hollow and gradually disintegrated,seriously hindering the normal physiological photosynthesis of Chenopodium album.3.The fermented broth of Aureobasidium pullulans PA-2 was sprayed onto the leaves of Chenopodium album and sampled at different times for transcriptome sequencing.A total of 58,484,414 Unigenes were obtained by transcriptome sequencing,and the number of assembled genes was 69,404 with Q20 values above 97%.Through differential gene expression analysis,when the fermentation broth was sprayed to 5d,the differential gene expression was the most,and the up-regulated gene was twice that of the down-regulated gene.Analysis of KEGG metabolic pathways.PA-2 stress on Chenopodium album leaf resulted in biosynthetic pathways of secondary metabolites in leaves,plant hormone signal transduction,carotenoid biosynthesis,plant pathogen interactions and plant MAPK signaling pathway,starch and sucrose metabolism and other metabolic pathway stress responses,these pathways jointly participate in the regulation of the interaction mechanism between bacteria and plants.It was found that the highly expressed differential genes were also related to plant hormones such as anthocyanins,carotenoids and photosynthetic tentacle proteins,protein kinases,oxidoreductases,transferases and other metabolites.Screening 12 gene fragments related to chloroplast,involved metabolic pathways carotenoid biosynthesis(GO: 0016117),regulation of photosynthesis(GO: 0042548)and carbon fixation(GO: 0015977)and other metabolic pathways.This result indicates that when the fermentation broth destroys the weed chloroplasts,the genes related to chloroplasts and the metabolic pathways involved are obtained under stress.These differential genes may jointly participate in the interaction mechanism between weeds and PA-2,and play an important role in the regulation of weed defense against PA-2 fermentation broth infestation.