Screening And Activity Study Of A New Biocontrol Strain Against Botrytis

Currently the application of greenhouse becomes more widespread, the warm, moist and relatively closed environment becomes a breeding ground for the growth of Botrytis cinerea.Thus, the yield and quality of fruits and vegetables are restricted by mould. Gliocladium roseum can inhibit Botrytis and is known as a hyperparasitism biocontrol bacteria with high disinfection efficiency and high specificity. But wild strains can not be widely promoted because of its slow onset of action, poor production traits and low parasitic degree of sclerotia in soil.This article starts from Gliocladium roseum original strain. Gliocladium roseum is mutagenized by single factor such as sodium nitrite, UV and heat, compound mutations such as sodium nitrite-UV and heat-UV to obtain the optimum mutagenesis conditions. After comparing biological characteristics of the mutagenized strains, laboratory efficacy test are examined to evaluate their performances in biocontrol, therefore preparing for strawberry trials.The optimum mutagenesis conditions are determined by trials. UV mutagenesis: the distance under 40w UV light is 40cm, exposure time is 75 s; sodium nitrite mutagenesis:0.1mol/1 NaNO2 treated for 210s; heat mutagenesis:treated for 4min at 45 ℃; heat-UV compound mutagenesis:treated for 4min at 45 ℃ then by UV irradiation for 75s; sodium nitrite-UV mutagenesis:treated by 0.1mol/1 NaN02 for 210s, then by UV irradiation for 75s. Three mutant strains are created through the five methods, which have higher sporulation, improved antibacterial ability, vigorous growth and genetic stability. They are named UVL-2(UV mutagenesis for 55s), NAL-2(sodium nitrite for 90s), NUL-1 (sodium nitrite-UV compound mutations). The spore productions of the three mutant strains are respectively 3.21 times,3.73 times, 3.90 times the original strain. According to single point and multi-point confrontation results, sodium nitrite-UV compound mutation strain NUL-1 is found to inhibit Botrytis best, which is the most suitable for further laboratory efficacy experiments. As a superior strain screened, it is proved to have better antibacterial ability and control effect than the original strain and other mutant strains at the spore concentration of 106/ml. The pot experiment shows:NUL-1 can best inhibit Botrytis if sprayed 48h in advance, however, Oh the worst.