Effects Of 8 Biocontrol Agents On The Main Diseases And Fruit Quality Of Litchi

Litchi chinensis Sonn.belongs to Sapindaceae,Lychee genus,which is a valuable fruit in the south subtropical region of China and one of the four best fruits in the south of China.Peronophythora litchii Chen ex Ko et al.mainly causes blight of litchi and has become the most damaging disease on litchi.Litchi anthracnose is caused by Colletotrichum gloeosporioides Penz.,which seriously endangers the production safety of litchi.Although chemical control can effectively control the disease development,but will lead to pesticide residues,pathogens generate drug resistance and other issues.And P.litchii belongs to oomycetes which is diploid biology and far away from the fungus on genetic evolution.This results the broad-spectrum fungicides which are used in the prevention and treatment of fungal diseases,have poor control effect on P.litchii.Therefore,seeking more ways to prevent diseases is the trend of the times in the litchi production,biological control has also been more and more attention.Based on the production reality and ecological balance,this study selected 8 kinds of biocontrol agents(Five kinds of Bacillus subtilis,one kind of Trichoderma and two kinds of Shin chemerin).Firstly,eight kinds of biocontrol agents were tested for their antibacterial activity in the laboratory to determine whether it can effectively inhibit the growth of P.litchii.and C.gloeosporioides.After being effective,they were field-tested with 3 concentration gradients for each drug on two lychee varieties of Baitangying and Feizixiao.Taking the harvested fruits to the laboratory to determine the average weight and the average solids content,then observed the incidence of different treatments in the most appropriate conditions.Explored the simple antibacterial mechanism of the three biocontrol agents with potentia.The main results are summarized as following:1.The antibacterial experiments showed that the 8 biocontrol agents all had significant antibacterial effects on P.litchii.and C.gloeosporioides.2.The results of field experiments showed that the average solids content,averageweight and pericarp color of litchi fruits treated with Lvqun were significantly higher than those of the control group,especially at the concentration of 6 g/L.The average solids content,average weight and pericarp color of litchi fruits treated with Ningdun were significantly higher than those of the control group,especially the dilution of 125 times.Duokang does not affect the average solids content and average weight of fruit,but it will seriously affect the skin color,makes the fruit late maturing.3.Under the most suitable condition for storage,due to the different disease resistance of different varieties of litchi,the incidence of Baitangyi is faster average of 3-5 days than Feizixiao,indicating that Feizixiao more resistant than Baitangying.Analyzed the data of Baitangying's disease index after stored 6 days and Feizixiao's fruit disease index after stored 9 days showed that the Duokang,Ningdun and Lvkangwei all can significantly reduce litchi fruit disease index in the same time.And Duokang is the best one,especially when it was diluted 150 times,can reduce fruit disease index about 40% lower.4.Combined with the field test results,simply explored the antibacterial mechanism of three potential biocontrol agents that Lvqun,Ningdun and Lvkangwei.The results showed that the three kinds of biocontrol agents all can inhibit the growth of both pathogens when they are incubated against P.litchii.and C.gloeosporioides.on the flat.But the inhibition is reversible.And the three biocontrol agents all can inhibit sporocysts germination of P.litchii.Lvqun will make sporocysts and mycelium of P.litchii.become deformity,but C.gloeosporioides.is not affected.In the late of cultivation,Lvkangwei doesn't work on P.litchii.and Ningdun doesn't work on C.gloeosporioides.The VOCs produced by Ningdun and Lvkangwei don't have significant effect on P.litchii.and C.gloeosporioides.The secondary metabolites produced by Ningdun had a significant inhibition on P.litchii.and had no significant inhibition on C.gloeosporioides.;the secondary metabolites produced by Lvkangwei showed no significant inhibition on P.litchii.and C.gloeosporioides.;Lvqun had a significant inhibition both on P.litchii.and C.gloeosporioides.