Study Of Screeing Strains And Laboratory Efficacy Evaluation For G.Rosea UN₇-108

The gray mold caused by Botrytis cinerea is a worldwide disease. A variety of crops can be infected by the B. cinerea, such as the withering for flowers and stems as well as rot for seeds, especially serious to strawberries. G.rosea that can be acted as a biological controlling agent has been widely used. However, the G.rosea can not be implemented industrialization production due to its low spore quantity and poor bacteriostatic action.The G.rosea UN7-108was conducted single factor mutagenesis of ultraviolet, temperature, sodium nitrite and composite mutagenesis breeding of temperature-sodium nitrite to determine the best conditions for mutagenesis in this text. The experimental studies of biological characteristics and the bacteriostatic for the obtained bacterial strains are carried out to evaluate the mutant strain’s biocontrol property. Moreover, the indoor efficacy evaluation for the bacterial strains screened out is performed aiming at preparing for the field tests.The best mutagenesis time has been found in this research, which is expressed as follows:UV mutragenesis is120s, microwave irradiation is70s; sodium nitrite mutagenesis is15min; the compound mutagenesis of UV and sodium nitrite is that sodium nitrite for the first insulation15min, and then UV irradiated120s; the compound mutagenesis of microwave irradiation and sodium nitrite for the first insulation15min, and then microwave irradiated70s. According to the sporulation firstly and antibacterial activity secondly, the four mutant strains of UV-3, TR-3, NS-1and TN-1are obtained, and their spores’ production induced1.2times,1.3times,2.0times,1.5times and1.7times, respectively. The mutant’s genetic character with better bacteriostatic effect and biological character than the original strain is stable. In addition, strain UV-3that obtained through ultraviolet mutagenesis has the best charactor at all the strains. It can be found that UV-3has better antibacterial activity than original strain through indoor efficacy experiment on original strain and UV-3, when its’ spore concentration is1×107/ml. The germination inhibition rate, mycelial inhibition rate and prevention rate is81%,93%and96%, when the spore concentration is1×106/ml, the rates is58%,90%and93%, and there is no significant differences when the concentration is higer. In a conlusion, when the spore concentration is1×106/ml, mutant strain UV-3indoor efficacy is most ideal.