Evaluation Of A Screening Strategy For Biocontrol Of Banana Wilt By Plant Growth-Promoting Rhizophere And The Biocontrol Efficiency In Field Study

Banana wilt caused by Fusarium oxysporum f. sp. cubense is a soil-borne and vascular disease which occurred on most banana-producing countries in the world. It is one of the most destructive disease on banana industry, caused a very serious disservice. The pathogen of this disease can survive in soil for a long time. It also has many dissemination methods. So, it is difficult to control this disease. Traditional control methods such as breeding for disease resistance and chemical control, could not control this disease effectively. Therefore, biocontrol method becomes the hotspot of research.539bacteria strains were isolated from different microenvironment such as bulk soil, rhizosphere, surfaces of pseudostem, phyllosphere, endorhiza, interior of corm, interior of pseudostem, endosphere of infected and uninfected banana plants.69strains with antagonistic activity were screened out through in vitro test against Fusarium oxysporum f. sp. cubense race1and race4. Strains isolated from bulk soil showed strongest antagonistic activity. In the other hand, enzyme activities such as protease, chitinase, cellulase, siderophre and IAA of539strains were tested.According to the results of in vitro activities,177strains were screened out for assessment and cluster analysis using amplified ribosomal DNA restriction analysis and BOX-PCR fingerprint.20strains were selected for greenhouse study according to the results.Burkholderia sp.5BS21showed the strongest colonization ability in banana rhizosphere in colonization experiment, colonization reached4.45×10CFU/g fw60days after inoculation. Colonization in the rhizosphere of other strains were above103CFU/g fw. In greenhouse experiment, biocontrol efficiency of these antagonists was ranged from38.64%to84.09%, Enterobacter sp.3BJN7had the most significant efficiency. In addition, these strains can also promote plant growth, with a biomass increase of15.29-64.73%. Correlation analysis showed that there was a certain correlation between biocontrol efficiency in greenhouse and in vitro activity and colonization ability, the correlation coefficient was0.707.Eventually,5bacteria strains:Bacillus amyloliquefaciens2BS12, Burkholderia sp.5BS21, Serratia marcescens2BGN4, Stenotrophomonas sp.2BQN19, Enterobacter sp.3BJN7were screened out for field experiment. The biocontrol efficiency of these antagonists was ranged from29.58%to69.65%, Burkholderia sp.5BS21is the best one. There was also a certain correlation between biocontrol efficiency in field and in vitro activity and colonization ability, with the coefficient0.687.In addition, the efficiency of biopesticide Shudekang against banana wilt had also been evaluated in this paper. In greenhouse experiment, biopesticide Shudekang showed a significant biocontrol efficacy (76.19-86.67%) against Fusarium oxysporum f. sp. cubense race1and race4. It can also promote plant growth effectively, with6.42-24.32%biomass increase,4.97-14.85%height increase and3.05-14.29%in stem increase. In flowering period, the biocontrol efficiency was71.54%and57.15%by using biopesticide Shudekang in field experiment in Dongguan city and Zhuhai city, Guangdong Province, respectively. Disease severity of biopesticide Shudekang treatment was much lower than chemical control and water control.