| Tea plants are susceptible to a variety of fungal diseases during growth,and among these,blister blight disease(BB)caused by Exobasidium vexans Massee is one of the most serious fungal diseases.This disease is widely distributed,harmful,and difficult to control,which has seriously hindered the development of China’s tea industry.At present,there is a lack of biological agents for preventing and controlling this disease.Therefore,this study was conducted to investigate the field efficacy of the plant-derived fungicide Isobavachalcone(IBC)as a test agent and its effect on the main biochemical components of tea leaves when used as a single agent and its mixture with aminoglycosides against BB disease.The physiological and biochemical basis of its induction of tea tree resistance to BB disease was initially investigated.The dynamic changes of fungal community diversity of susceptible leaves without susceptible stage and the effect of agent treatment on fungal community diversity of susceptible leaves were investigated,to provide new ways and important references for the green integrated control of the disease.1.The results of the field efficacy test of IBC against BB disease showed that the efficacy of two consecutive foliar sprays of IBC 300,600,1200,and 1600 times at an interval of six days at the early stage of BB disease incidence was 57.80,60.61,37.46 and 20.06%,respectively.Its 600 x solution had the highest efficacy and significantly reduced the incidence and disease index of BB disease.Its 600 times solution mixed with 500 times solution of amino-oligosaccharide showed a significant improvement in prevention effectiveness,which could reach 68.57%.Meanwhile,compared with the control group,the mixture could significantly increase the total content of free amino acids in tea leaves.2.The results of basic physiological and biochemical studies showed that exogenous spraying of a 600-fold solution of IBC significantly increased the activities of PPO,POD,?-1,3-glucanase,and chitinase in disease-susceptible fresh leaves compared with the control.It also up-regulated the expression of PPO,PAL,JARI,MYC2,NPRI,CSA034045,CSA028450,CSA010816,and CSA023709 genes.Its 600-fold solution mixed with a 500-fold solution of amino-oligosaccharide further enhanced the effects on defense enzyme activities and resistance gene expression,significantly increasing the activities of PPO,CAT,PAL,POD,SOD,?-1,3-glucanase and chitinase.The expressions of PP0,CAT,ANR,JARI,MYC2,NPRI,PRI,CSA012876,CSA034045,CSA028450,CSA023709,NUue108377,F3 H,C4H and TLP genes were also up-regulated.3.The dynamics of fungal community diversity in susceptible leaves at different susceptible stages of BB disease.The test results showed that the dominant fungal phylum in all samples was Ascomycota,followed by Basidiomycota,and the dominant fungal genus was Cladosporium,followed by Colletotrichum.The relative abundance of Ascomycota increased with the increase in disease severity,while the relative abundance of Basidiomycota showed a decreasing trend.the relative abundance of Cladosporium and Colletotrichum increased with the increase in disease severity.The relative abundance of Exobasidium,the causative agent of BB disease,was higher in the disease site than in the healthy site,and the relative abundance of the fungus in the disease site tended to increase and then decrease.Alpha index analysis showed that the diversity and abundance of the fungal community in the healthy part were higher than in the disease site.With the increase in disease severity,the diversity and abundance of the fungal community in the diseased area tended to increase and then decrease.4.Effect of IBC on the fungal community diversity of BB disease susceptible leaves.The results of the test showed that the IBC 600 x treatment significantly reduced the fungal community diversity on the third day after application.Fungal community composition analysis showed that both treatment groups significantly increased the relative abundance of Ascomycota phylum and decreased the relative abundance of Basidiomycota phylum compared to the untreated group.Moreover,both treatment groups significantly decreased the relative abundance of genera such as Colletotrichum and Exobasidium,and increased the relative abundance of Cladosporium. |
