| The use of chemical fertilizers and pesticides in agricultural production has caused negative effects of environmental and ecological pollution,quality of agricultural products and excessive pesticide residues.With the improvement of living standards,people are more and more highly praised for the green organic agricultural products.Now our country is also strongly advocating reduction quantity of the chemical fertilizers and pesticides to ensure the safety of agricultural products.A new measure with safety and effectiveness is urgently needed to replace the traditional chemical control.Biological control is using microorganism as a biological control agent to prevent and control plant disease,which has function of preventing disease and promoting growth of plant.In recent years,it has been paid more and more attention to its safety and efficiency.It has become an important measure to replace chemical control.Trichoderma spp.is a kind of widely used and effective fungal biocontrol agent.12 plant and soil samples were collected from vegetable fields,and 11 strains of Trichoderma were isolated and purified from these samples in this study.And strains M2 and MX with better antagonism against Fusarium oxysporum f.sp.momordicae(Fom)were screened.The control effect of Trichoderma strain M2 and MX on bitter gourd wilt was 79.27% and47.75%,respectively.By morphological identification and molecular identification based on ITS,tef1α and rpb2 genes,strain M2 was identified as Trichoderma virens and strain MX was identified as Trichoderma asperellum.Biological characteristics of two Trichoderma strains showed that they could grow and produce spores at 15-35℃.High or low temperature could inhibit the growth of the mycelium and sporulation.The optimum growth and sporulation temperature of two strains of Trichoderma were25-30℃.The optimum pH value of strain M2 is 6-7 for growth and sporulation;for strain MX is 5-6.the most suitable carbon source of strain M2 is glucose,fructose and lactose.The most suitable carbon source of the Trichoderma MX is glucose and sucrose;vitamin B6 can promote the mycelial growth and sporulation of strain M2 and MX,and the optimum nitrogen source of strain M2 is aspartate,beef extract and ammonium sulfate,for strain MX was ammonium sulfate,urea inhibited the mycelium growth andsporulation,and light conditions only had a great effect on the sporulation of two strains,Sustained light is the most favorable for sporulation.Strain M2 and MX had a broad antagonism against fungal pathogens.In the flat confrontation test with different pathogenic bacteria,two Trichoderma strains had the best inhibition effect on Valsa mali and Botrytis cinerea,and the inhibitory effect on Rhizoctonia solani,Botryosphaeria ribis,Alternaria alternata,Gloeosporium fructigenum,Corynespora cassiicola and Fusarium graminearum was not better than V.mali and B.cinerea,and the inhibition to Fusarium solani is poor.The colonization ability in plant tissues and soil of two strains in 49 days was detected by real time fluorescence quantitative PCR.The results showed that the colonization ability of two Trichoderma strains in root,stem and leaf tissues of bitter gourd was poor,but they could be colonized rapidly and steadily in the soil.The effects of three defensive enzymes(PPO,POD,PAL)activity and root activity in bitter gourd with two Trichoderma strains were measured in this study.The results showed that the application of Trichoderma could effectively improve the activity of defense enzymes in plants or postpone the decline trend,and thus reached the purpose of protecting the plant against pathogen.The inhibition to Fom of the non volatile secondary metabolites and the volatile secondary metabolites of two Trichoderma strains were tested in this study.The results showed that the non volatile secondary metabolites of two Trichoderma strains were strongly inhibited to Fom.The inhibitory effect of volatile secondary metabolites was not significant.Strain M2 and MX had promoted growth of plant of bitter gourd for production of new root and hair root development,enhancing fresh weight,dry weight,plant height and stem diameter etc.growth index.The ability of two Trichoderma strains to solubilizing phosphorus and potassium was quantitatively tested.The results showed that they have ability of phosphate solubilizing,which could promote the uptake of nutrients in soil by plants.The mechanism of two Trichoderma strains in preventing plant disease and promoting growth has been preliminarily explored.It can be seen that strains M2 and MX have good effect on disease prevention and have a certain growth promoting effect,which have great potential for application. |
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