Efficacy And Mechanism Of Bio-control Fungi Strains Against Gray Mold Of Vegetables

In recent years,cultivation of vegetables under protected environment in China has become an important industry.However,cultivation of vegetables are subjected to attack by several pathogens during different stages of plant growth starting from seed sowing up to seedling to flowering stage because of conducive environment in green house.Gray mold caused by Botrytis cinerea Pers.Fr.is one of destructive pathogens of vegetables.Infection may occur in fruits,flowers,leaves,stem and seed.It has caused serious economic losses every year.Biological control is one of the best low-cost and ecologically sustainable methods for ranaging plant diseases.Some antagonists have biocontrol activity against B.cinerea.Among various biocontrol agents(BCAs)examined against B.cinerea,Trichoderma spp.have been widely studied for their biocontrol ability.Except for Trichoderma,we also evaluated the biocontrol potentials of two other antagonistic fungi,Penicillium spp.and filamentous basidiomycete.So the aim of the present study was to evaluate the biocontrol potentials and mechanisms of these antagonists(Penicillium spp.and filamentous basidiomycetes)against B.cinerea.Results achieved are summarized below.1.Out of 24 tested strains,12 strains namely Penicillium P416,P417,AV12,AV2,Trichoderma T121,T181,T581,T601,T1 and Basidiomycete DK3,DK4,DK6 were selected for their antagonistic activities against B.cinerea through dual culture screening tests.According to the results of leaves screening in vitro,we found that these three series of strains towards gray mold were antagonistic.The efficacy of Penicillium broth which contained spores to gray mold were higher than 66%,Trichoderma broth which contained spores were higher than 54%and the series of DK broth(without spores)were higher than 74%.2.Taxonomic identity was based on cultural characteristics,colony morphology and ITS sequence.Comparison with sequence in GenBank,P416,P417 and DK6 was identified as P.citrinum,P.griseofulvum and Irpex lacteus,respectively.3.When the plants of lettuce were co-inoculated with B.cinerea and effective antagonistic strains P416、P417、AV12 in the pots,respectively,lettuce leaves treated with broth cultures of Penicillium strains P416、P417、AV12 appeared healthier as compare to controls.Disease spots on lettuce leaves were also small.The biocontrol efficacy of DK6 was about 56%.In lettuce field experiments,it was found that biocontrol efficacy of P416,P417 and AV12 was 71.7%,69.7%and 33.7%,respectively.Biocontrol efficacy in case of DK6 was about 72.9%as compared to control.Meanwhile DK6 also promoted the germination and seedling growth of tomato.4.According to the study of machanisms of the fungal biocontrol agents above against B.cinerea,it was revealed that fermentation broths of P416 and P417 at different concentrations(1%,5%,10%)obviously inhibited the hyphal growth of B.cinerea.While both the fermentation broths of AV12 and DK6 slightly inhibited the hyphal growth.Treated with P416,P417,AV12 and DK6 both,respectively,the conidiophores of B.cinerea underwent abnormal development,and the mycelium and conidiophores of it were shriveled compared to untreated control.Moreover,fermentation broths of antagonistic strains could inhibit the spores germination and suppressed the germ tube elongation of B.cinerea.These results suggest that antagonistic strains(P416,P417 and DK6)have potentials to become promising BCAs,used as substitutes for chemical fungicides in B.cinerea control,which provides an easy method to protect vegetables and other agricultural commodities against pre-and post-harvest decay caused by B.cinerea.The study about these two types of strains fills the gaps in terms of prevention of gray mold.The present study is about antagonistic mechanisms of biocontrol strains against B.cinerea,which provides the premise and theoretical basis for B.cinerea biological control,and also provides an important reference for further exploration of these fungal biocontrol agents.