| Pear is a perennial crop,and its roots are easily infected by various pathogens,resulting in pear tree weakness and a decline in yield and quality,which has had a serious impact on Chinese rapid development of pear cultivation.In agriculture,the use of beneficial microorganisms for biological control of root diseases is becoming more important.Trichoderma spp.have been shown in studies to have a positive biocontrol effect.Pear root and rhizosphere soil samples were collected from the main pear-producing areas in China for this study.Tissue isolation and soil dilution were used to obtain Trichoderma strains.The species of Trichoderma in Chinese main pear producing areas were identified using molecular biological identification and morphological characteristics.The effects of Trichoderma hamatum and its culture filtrate on growth,conidial production,conidial germination rate,and pathogenicity of pathogens were studied,and the biocontrol potential of T.hamatum on the major pear tree diseases was evaluated.The results are as follows:1.Isolation and identification of Trichoderma strains in pear root and soil.From September 2021 to March 2022,a total of 31 pear root samples and 11 soil samples were collected from six provinces: Guizhou,Fujian,Shandong,Sichuan,Henan and Hubei.A total of 149 strains with colony morphological characteristics consistent with Trichoderma spp.were obtained by isolating from the samples and purifying.From 149 strains,45 representative strains were selected for molecular identification by multi-gene(ITS,RPB2 and TEF1)phylogenetic analysis in accordance with various sources and sample types.And observed their morphological characteristics.The results indicated that the 149 Trichoderma strains obtained in this study belonged to 10 recognized species.Trichoderma brevicompactum accounted for 21 of them,Trichoderma afroharzianum accounted for 6,Trichoderma hamatum accounted for 55,Trichoderma guizhouense accounted for 7,Trichoderma asperellum accounted for 4,Trichoderma spirale accounted for 5,Trichoderma virens accounted for 3,Trichoderma koningiopsis accounted for 11,Trichoderma atroviride accounted for 35 and Trichoderma yunnanense accounted for 2.The results showed that T.hamatum has the most strains,accounting for 36.9% of the obtained Trichoderma strains,and was distributed in the samples from four provinces.2.Evaluation of the biocontrol potential of T.hamatum.Eight pathogens of pear diseases including pear anthracnose disease,pear black spot disease,pear shoot canker disease,pear Valsa canker disease,pear stem canker disease,pear blight rot disease,pear white root disease and pear root rot disease were used as materials for the confrontation culture experiment with T.hamatum.The results showed that T.hamatum could significantly inhibit the growth of these eight pathogen colonies and could gradually cover the colonies and produce spores.Among them,FJG9-1,FJG9-2 and HBT3-7 had the best bacteriostatic effect on the eight pathogens.The effects of the culture filtrate of these three strains on the growth,conidial production,conidial germination rate,and pathogenicity of pathogens were further explored.The results showed that the three strains—FJG9-1,FJG9-2,and HBT3-7—could influence the growth rate of eight pathogens.Among them,the the growth rate of Phytophthora cactorum colony was most effectively inhibited by FJG9-1,with an inhibition rate of 89.7%.Three strains could significantly reduce the conidial production of Colletotrichum fructicola,Fusarium solani and Alternaria tenuissima,and FJG9-1 caused C.fructicola to be completely unable to produce conidia.Three strains could significantly reduce the conidial germination rate of C.fructicola,and FJG9-2 and HBT3-7 could reduce the conidial germination rate of F.solani.The disease prevention experiments with the culture filtrate of the above three strains on pear detached tissues and pear seedlings were carried out further.According to the results,the control effect of FJG9-1 on pear blight rot disease was 15.2%.FJG9-2 had control effects on pear anthracnose disease and pear dry rot disease of 36.7% and 52.4%,respectively.And HBT3-7 had control effects on pear shoot canker disease and pear Valsa canker disease of 27.8% and 20.2%.This study clarified the Trichoderma species found in the pear-producing regions of six Chinese provinces.It was found that the competitive ability of T.hamatum was stronger than that of pathogens.Its metabolites had inhibition activity and a biocontrol effect on the main pear tree diseases.The findings added to the diversity and geographical distribution of Trichoderma in China,as well as technical and material support for the use of Trichoderma in the treatment of pear diseases. |
