Study On The Growth-promoting Effect Of Trichoderma On Muskmelon And The Control Effect Of Vine Blight

Didymella bryoniae is a common disease of cucurbitaceae,which was been found everywhere,especially under the condition of the facility agriculture environment,being more serious and seleading to the obvious reduction of melon yield,and huge yield loss,which has become one of the main bottlenecks in the production of melon under the facility agriculture environment.Producers mainly use chemicals agents to inhibit the occurrence of Didymella bryoniae in melon cultivation.However,the use of a large number of chemical agents not only increased the resistance of pathogens,but also led to excessive residues of chemical agents in melon fruits and soil pollution.As an important bioagent,Trichoderma has attracted extensive attention of researchers and growers,and it has been found that Trichoderma can effectively inhibit the hypha growthof pathogens and the occurrence of fungal diseases.However,there were few reports about the effect of Trichoderma on Didymella bryoniae and its application in protected melon production.In this study,different strains of Trichoderma and the pathogen of Didymella bryoniae were obtained and used as experimental materials to investigate the inhibition of Trichoderma on the pathogen of Didymella bryoniae and the control effect in field.The results were as follows:1.The results showed that 19 strains of Trichoderma could significantly inhibit the growth of the pathogen of Didymella bryoniae by the use of flat panel confrontation test method,and the inhibition rate was from 72.20%to 86.64%,in which the inhibition rate of Trichoderma harzianum DQ002 on Didymella bryoniae was the highest?up to 86.64%?,followed by Trichoderma echinosporum DQ001?up to 85.42%?,Trichoderma longibrachiatum DQ004?up to85.03%?and Trichoderma viridis DQ003?up to 84.51%?,and space competition and heavy parasitic effect of Trichoderma on the pathogen were the most important ways.According to the above results,the bacteriostatic tests of the volatile substances and liquid metabolites of four Trichoderma strains were carried out.It was found that the inhibition rate of the volatile substances of four Trichoderma strains to the pathogen of Didymella bryoniae was from 3.95%to 10.17%,and the inhibition rate of the liquid metabolites to Didymella bryoniae was from8.04%to 20.98%,in which the inhibition rate of Trichoderma harzianum DQ002 was highest.2.Based on the above results,the promotion effect of Trichoderma harzianum DQ002 on melon seedlings was conduced under the inoculations of the pathogen of Didymella bryoniae Compared with CK?water treatment?,the growth of melon seedlings was inhibited by inoculating 1.0�10⁵ cfu/mL of Didymella bryoniae pathogenalone.However,under the condition of inoculating pathogen of Didymella bryoniae,the inoculation of Trichoderma harzianum DQ002 could significantly alleviate the inhibition of pathogen on the growth of melon seedlings,in which the treatment of the inoculation of Trichoderma harzianum DQ002 by followed the inoculation of Didymella bryoniae pathogen?T4?could notably promote the growth of melon seedlings under the pathogen stress,and the effect of promoting growth of T4 treatment on melon seedlings was better than that of T3 treatment?inoculation of Didymella bryoniae pathogen by followed the inocution of Trichoderma?.3.Compared with the single inoculation of the pathogen?T1 treatment?,the inoculation of Trichoderma harzianum DQ002 regulated the PPO,POD,SOD and?-1 3-glucanase activity in the roots,stems and leaves of melon seedlings,weakening the injury of H₂O₂ and superoxide ion?O^-₂?accumulation on the plant,and promoting the synthesis and accumulation of lignin in all parts of the plant by activating PAL and cellulase activity,which enhanced the resistance of the melon plant to the pathogen of Didymella bryoniae,and then promoted the growth of melon seedlings under the stress of Didymella bryoniae.4.The inoculation experiment of Trichoderma harzianum DQ002 and pathogen in greenhouse was carried out in order to verify the control effect of Trichoderma harzae on melon vine blight in field.The incidence rate of melon seedlings inoculated with the pathogen of Didymella bryoniae alone was 55%.Nevertheless,the incidence rate of Didymella bryoniae on melon seedlings in the treatment of inoculation of Trichoderma harzianum DQ002 in root?A1?and the treatment of spraying of Trichoderma harzianum DQ002 on shoot?A2?were 21.67%and30%respectively,under the inoculation of Didymella bryoniae pathogen.While the incidence rate of Didymella bryoniae on melon seedlings of CK2?Hymexazol W.P treatment?was up to38.33%.Therefore,the use of Trichoderma harzianum DQ002 had significantcontrol effect,being remarkably higher control effect than that of chemical fungicides,and the control effect of Trichoderma harzianum DQ002 by the inoculation in roots?A1?was better than that of the sprying on shoot under the inoculation condition of Didymella bryoniae in leaves?A2?.5.The inoculation experiment in greenhouse showed that inoculation of the pathogen restricted the absorption and accumulation of melon seedlings on nitrogen?N?,phosphorus?P?and potassium?K?,while the use of the chemical agent?Hymexazol W.P?could weaken the absorption suppression of melon seedlings on N,P and K;Under the condition of inoculation of the pathogen of Didymella bryoniae,the inoculation of Trichoderma harzianum DQ002significantly promoted the the absorption and accumulation of melon seedlings on nitrogen?N?,phosphorus?P?and potassium?K?.Compared with the treatment of inoculation of Didymella bryoniae pathogen?CK1?,the content of N,P in root,stem and leaf of melon seedlings treated with the watering of Trichoderma harzianum DQ002 were increased by 7.64%,14.10%and9.07%respectively,while the content of N,P in root,stem and leaf of melon seedlings treated with the sprying of Trichoderma harzianum DQ002 in shoot were ennhanced by 3.21%,8.1%and 4.26% respectively.