Biological Characteristics Of Two Strains Of Trichoderma Spp.Isolated From Rice Rhizosphere And Their Biocontrol Potential Research

Rice Sheath Blight is an important fungal disease in rice production,which seriously influences field and quality of rice.Trichodermaare a kind of popular biocontrol fungi,existing in rhizosphere soil everywhere,and they are often used as biocontrol agents.In this study,by means of culture confrontation test between 64 strains of fungi isolated from rice rhizosphere soil and Rhizoctonia solani WH-1,two strains of fungi(3S1-13 and 4S2-46)were screened to act as biocontrol agents because their antagonistic band width is more than 15 mm,which were determined to belong to Trichoderma harzianum by morphological characteristics and analysis of ITS sequence.Biological characteristics of two Trichoderma strains 3S1-13 and 4S2-46 were explored.Two Trichoderma strains didn't produce conidia on PDA culture,but this ability was recovered on PDA included 1% yeast;different kinds of carbon and nitrogen sources can be used for growth and conidia production;nutrient-deficient experiment shows carbon,nitrogen and phosphorus sources are essential for normal physiology.The growth rate of hyphal of two strains of Trichoderrma at 28? was fastest and quantity of conidia was largest;and the growth rate was fastest at pH6.Two strains of Trichoderma had the biocontrol potential on rice sheath blight.The hyphae of Trichoderma spp.can recognize the mycelium of R.solani,and then produce a ring structure for parasitism;Trichoderma spore suspension(108/ml)had obvious lesion extension inhibition effect no matter that prior to and post inoculation;the inhibitory activity of the fermentation broth of 7 d at the temperature of 28? in culture of sucrose ammonium sulfate mediumwas both more than 90%;the fermentation broth could effectively inhibit the formation of sclerotia,resulting in the decrease on the quantity and dry weight;the fermentation activity was disappeared under the treatment of high temperature more than 60? and protease K.Two strains of Trichoderma 3S1-13 and 4S2-46 had the growth-promoting effect on rice.The fermentation of strain 3S1-13 and 4S2-46 can improve germination rate of soil seed by 24.77% and 25.91%,respectively;the fermentation broth of two Trichoderma strains could effectively promote the growth of rice seedling by 29.27% and 33.13%,and root length 16.86% and 17.60%,and fresh weight 47.18% and 48.77%,respectively.The results above indicated that spore suspension and filtrates of two Trichoderma strains had the potential of control of rice sheath blight,and besides,filtrate had the potential of growth-promotion of rice.