Effect Of Cotton Biochar On Verticillium Dahliae And The Growth Of Cotton

Cotton is an important cash crop. Verticillium wilt of cotton, caused by Verticilliumdahliae Kleb., is serious soil-borne disease. Cotton stalk biochar was choosed as the material,we explore the effect of cotton biochar on the mycelial growth, microsclerotium germinationand toxin secretion of Verticillium dahlia Kleb and antagonistic actinomycetes. Experiment ingreenhouse or under pot conditions were conducted respectively to investigate the effect ofcotton biochar on the growth and resistance of cotton. The results and conclusions are listedbelow:1. The cotton biochar could slightly inhibit the mycelial growth and microsclerotiumgermination of V. dahlia, while could significantly reduce the toxicity of V. dahlia. Underliquid culture condition, the cotton biocha had promotion effect under solid culture conditionon the mycelial growth of V. dahlia. The cotton biochar inhibited the rate of themicrosclerotium germination. As treatment time went on, the inhibition effect disappeared.Adding the cotton biochar seriously reduced the toxicity of V. dahlia under liquid cultureconditions. In the mid-stage of liquid culturation, cotton seed germination rates were53.3%and33.3%after12days in the treatments of2.0g/L biochar and CK, respectively (P<0.05). Inthe prophase, middle and late stage, the seedling length in the treatment of0.5g/L biocharwere4.9,2.1and3.2times more than those in the CK treatment, respectively. Compared toCK, biochar enhanced the cotton seed germination, radicle length, plumule length andseedling length. Immersion test showed that the biochar reduced the harm of VD-toxin.TheVD-toxin with1g/L and2g/L biochar increased the root activity of cotton plant by43.0%and41.6%.The POD and PPO activity of cotton plant in treatment with1g/L biochar andVD-toxin reduced by25.2%and14.7%.2. The cotton biochar had no significant effect on the antagonism of actinomycetes.3. The biochar added into cotton cropping soil had an impact on soil microflora.The biochar changed the dominant microorganisms in the soil.Application with25g/kgand50g/kg biochar into soil increased B/F, B/A by186.0%,195.5%and44.9%,37.8%.Themixture of biochar and biocontrol agent significantly increased the quantity of the cottoncropping soil microorganism, especially in increasing the number and proportion of soilbacteria.and changed the number and proportion of the dominant microorganismsin in the soil. 100.0g/kg biochar with agent make the number and proportion of Streptomyces issignificantly higher than CK, while make the number of micromonospora reduction. Underunsterilized and sterilized conditions, the biochar increases the detectable amount ofbiocontrol agent. Bacillus cereus was all isolated in three different concentrations of biochartreatments, while in the control it was not detected.4. In the simulate conditions, the biochar added into cotton cropping soil had an impacton the growth of cotton seedling.①The root fresh weight, dry weight and length of cottonseedling in the treatment of50.0g/kg biochar were increased33.0%,3.7%and41.9%morethan those in the CK treatment. While100.0g/kg biochar significantly inhibit the growth ofthe cotton seedling, the total, upper ground and root fresh weight of cotton seedling in thetreatment of50.0g/kg biochar decreased by48.9%,49.7%and37.8%compared with the CK.The cotton seed germination rates were20.0%and90.0%after12days in the treatments of100.0g/kg biochar and CK, respectively (P<0.05).②Applicated with biocontrol agents, the25.0g/kg and50.0g/kg biochar had no significant effect on the emergence rate, biomass andbiological characteristics of cotton seedling, while the total, upper ground and root freshweight of the cotton seedlings in the treatments of100.0g/kg biochar significantly decreasedby42.0%,29.3%and36.2%.5. Under pot culture conditions, the biochar added into the soil had an impact on thegrowth, photosynthesis and the defense enzyme activity of cotton seedling.①The emergencerate of cotton seedling the number of ture leaves in the treatment of biochar increased by79.6%~111.1%and24.7%~27.7%compared with CK. Cultivated21weeks later, thetreatment of50.0g/kg and100.0g/kg biochar increased the total fresh weigh of cotton plantby33.0%and40.3%.And the treatment of25.0g/kg and100.0g/kg biochar increased the rootlfresh weigh and the fibrous number of cotton plant by33.0%and40.3%.②The biocharreduced the root and leaf defense enzyme activity and the root activity of cotton seedlingswere slightly lower than CK.③The net photosynthetic rate in treatment of100.0g/kg biochar increased by32.8%(P<0.05).The biochar treatments all reduced the intercellular CO2concentration ofleaves by19.2%~48.8%(P<0.05).