Isolation Of Bio-control Bacteria Against Fusarium Wilt And Their Colonization In Banana Rhizosphere Soil

Fusarium wilt caused by Fusarium oxysporum f.sp.cubense(Foc)has become one of the most devastating fungal diseases of bananas.However,Plant Growth-Promoting Rhizobacteriac(PGPR)are becoming a research focus,and show great potential in improving crop habitats and resistance to plant diseases.In order to explore some PGPR that can be applied to control the banana wilt disease,we first isolated 71 strains of antagonism that inhibited the growth of Foc by co-culture on plate.Among them,27 strains were isolated from the banana rhizosphere,and 44 strains were isolated from the rhizosphere soil of Chinese chive(Allium Tuberosum Rottler).Secondly,base on the 16s sequence and the effects of antagonism against Foc,three strains were selected to a further study.The three strains were M8(Bacillus amyloliquefaciens)from banana rhizosphere soil,and C5 {Bacillus subtilis)together with C14(Pseudomonas fluorescens)from Chinese chive rhizosphere soil.After inoculation of the three strains to banana plant for 15 days,we found that the three strains could not only have a significant promotion effect on banana growth,but also have an obviously increased resistance to Foc.The results were as follows:(1)when inoculated with strain M8,C5 and C14,the plant growth and pseudostem girth of banana plants and chlorophyll content in banana leaves were significantly increased compared to control(CK);(2)when inoculated with M8 and C5 strains,pathogen-related enzyme activities of the banana plants,such as banana alanine ammonia lyase(PAL),polyphenol oxidase(PPO)and peroxidase(POD),were significantly enhanced;(3)the expression of disease resistance related genes,MaPR-2,MaPPO,MaMBL and MaPOD,in bananas were signifeicantly induced by the treatments of strain M8,C5,and C14;(4)The Fusarium wilt disease index were declined distinctly in the C5 treatment(disease index was 21.8%)compared to the control(disease index was 43.4%).The incidence for M8 and C14 treatment was 24.5%and 30.1%,respectivily.(5)The number of M8,C5,and C14 in banana rhizosphere soil increased significantly compared to the control soil without bananas plant.Finally,in order to explore the colonization of the three strain in the plant rhizosphere induced by banana allelopathies.Banana root exudates and residue degradants were collected to treat the three stains.The results showed that root exudates and residue degradants can significantly promote the growth of M8,C5 and C14.Some representative phenolic acids of bananas root exudates were added to the growth mediums to study the effect of the phenolic acids on the three stains.Results showed that(1)Malic acid,ferulic acid,and strawberry acid significantly promoted the growth of M8,while the effect of salicylic acid and p-hydroxybenzoic acid were not obvious;(2)Malic acid significantly promoted the growth of C5,while salicylic acid,ferulic acid,strawberry acid and p-hydroxybenzoic acid had no effect on the growth of C5.(3)Malic acid,salicylic acid,strawberry acid and p-hydroxybenzoic acid significantly promoted the growth of C14,but the effect of ferulic were not obvious.The results of this study can provide practical reference for the prevention and control of banana blight,and can provide reference for the development of new biological pesticides.