Screening Of Biocontrol Bacteria And Determination Of Resistance Of Peanut Varieties To Peanut Wilt

The bacterial wilt is the important disease affecting peanut production in China,the disease occurred more seriously in South China.Peanut bacterial wilt usually occurred in about 1/10 of the total area of peanut planting area,causing great losses.At present,biological control of peanut bacterial wilt is becoming a research focus for scientists going in for plant protection.Screening of biocontrol bacteria against Ralstonia solanacearum and test of peanut resistance to peanut bacterial wilt were conducted in this study,the results were shown as following:1.Screening of antagonistic bacteria: in this study,more than 300 bacterial strains were isolated from the crop rhizosphere soil.7 antagonistic bacterial strains were obtained by dual-culture method,3 antagonistic bacterial strains A27,Ab and A38 produced great inhibition zone,their diameters were 9.5 mm、10.5mm and 15 mm,respectively.2.Identification of antagonistic strains:(1)Identification of antagonistic strain A27.The strain A27 was identified based on analysis of A27 16 S r RNA gene and physiological and biochemical characteristics test.The result showed that,the near full-length sequence of 16 S r RNA gene was amplified from strain A27 with primers 27 F and 1492 R,obtaining a PCR product of 1386 bp.A BLAST search in Gen Bank revealed the highest similarity(100%)to sequences of Pseudomonas aeruginosa.Then,according to difference of strain A27 and the related bacteria in physiological and biochemical characteristics refering to Bergey’s Manual of Systematic Bacteriology(Second Edition),19 physiological and biochemical characteristics were selected to test,the results indicated that,similarity of physiological and biochemical characteristics between strains A27 and P.aeruginosa was 89.47%.Therefore,a strain A27 was preliminarily identified as P.aeruginosa.(2)Identification of antagonistic strain A38.The strain A38 was identified based on analysis of A38 16 S r RNA gene and physiological and biochemical characteristics test.The result showed that,the near full-length sequence of 16 S r RNA gene was amplified from strain A38 with primers 27 F and 1492 R,obtaining a PCR product of 1435 bp.A BLAST search in Gen Bank revealed the highest similarity(99%)to sequences of Pseudomonas aeruginosa.Then,according to difference of strain A38 and the related bacteria inphysiological and biochemical characteristics refering to Bergey’s Manual of Systematic Bacteriology(Second Edition),19 physiological and biochemical characteristics were selected to test,the results indicated that,similarity of physiological and biochemical characteristics between strains A38 and P.aeruginosa was 78.95%.Therefore,a strain A38 was preliminarily identified as a P.aeruginosa.(3)Identification of antagonistic strain Ab.The strain Ab was identified based on analysis of Ab 16 S r RNA gene and physiological and biochemical characteristics test.The result showed that,the near full-length sequence of 16 S r RNA gene was amplified from strain Ab with primers 27 F and 1492 R,obtaining a PCR product of 1401 bp.A BLAST search in Gen Bank revealed the highest similarity(99%)to sequences of Bacillus velezensis,Bacillus subtilis,Bacillus polyfementicus,Bacillus amyloliquefaciens and Bacillus siamensis.Then,according to difference of strain Ab and the related bacteria in physiological and biochemical characteristics refering to Bergey’s Manual of Systematic Bacteriology(Second Edition),21 physiological and biochemical characteristics were selected to test,the results indicated that,similarity of physiological and bioche mical characteristics between strains Ab and B.siamensis was 95.24%.Therefore,a strain Ab was preliminarily identified as a B.siamensis.3.Efficacies of antagonistic strains to peanut bacterial wilt: in potted peanut experiment,antagonistic strains A27,Ab and A38 were respectively spread to peanut plants inoculated with Ralstonia solanacearum 2 days ago,the results showed that the control effect of three strains were12.16%、25.66%和 52.71%,respectively.The control effect of antagonistic strain A38 was significantly higher than that of antagonistic strain Ab and A27.4.Identification of resistance of peanut varieties to bacterial wilt: Through artificial inoculation,resistance of 80 kinds of peanut varieties to bacterial wilt was tested,the results indicated that,1 peanut varieties(Q506)was highly resistant,taking up 1.25% of all peanut varieties tested,34 peanut varieties were moderately resistant,taking up 42.5% of all peanut varieties tested;Among them,the incidence of Peanut varieties S48 was 11.25%,which was close to the high resistance and the resistance was significantly higher than that of other cultivars;30 varieties being moderately susceptible,taking up 37.5%,17 varieties being highly susceptible varieties,taking up 21.25%.