| Tomato bacterial wilt, a devastating soil-borne disease caused by Ralstonia solanacearum(R.s), is one of the most important diseases during tomato growth, especially in continuous cropping conditions and caused hard hit of tomato yield in China. How to control of R.solanacearum is a world wide research program. The traditionally farming control methods have rarely provide long-term control to tomato bacterial wilt while application of resistant cultivars and chemicals are not effective enough for control this disease, and also chemical application could causes environmental problems. Biological control of soil-born disease is an efficient and environmentally friendly way and is receiving more and more attention recently.In this study, an efficient antagonism bacterial strain, named N5, was isolated from soil samples in Yingtan, Jiangxi, China. The bio-organic fertilizer made of organic fertilizer (pig manure compost and amino acid fertilizer) and antagonism strain N5was prepared and its ability to control tomato bacterial wilt was evaluated. The main results obtained are listed as follows:Several antagonistic strains were obtained against R.solanacearum, the best antagonistic strain N5from these isolates was screened. According to biochemical and physiological characteristics, morphological characters, and16S rRNA gene sequence analysis, the strain N5was primarily identified as Bacillus methylotrophicus.Strain N5also inhibited some other plant fungi pathogens, such as Verticillium dahliae Kleb, Sclerotinia sclerotiorum (Lib.) de Bary, Fusarium oxysporum f.sp. cubense, Fusarium oxysporum f.sp. melonis, Fusarium oxysporum f.sp. cucumerinum and Rhizoctonia solani. The antibacterial substances in the fermentation broth of strain N5were resistant to trypsin and alkali, but sensitive to ultraviolet radiations. Cells suspension(108 cfu·mL-1)of strain N5could promote the germination rate of tomato seeds with6.8%higher than control.The effect of the specific bio-organic fertilizer made of B. methylotrophicus N5for tomato growth-promoting was evaluated in pot experiments. Six treatments were designed as following:(l)CC (CK+CK), chemicals used in both of nursery soil and transplanting soil;(2)CB (CK+BIO), chemicals used in nursery soil, organic fertilizer used in transplanting soil;(3)00(OF+OF), organic fertilizer used in both of nursery soil and transplanting soil;(4)0B (OF+BIO), organic fertilizer used in nursery soil, bio-organic fertilizer used in transplanting soil;(5)BC (BIO+CK), bio-organic fertilizer used in nursery soil, chemicals used in transplanting soil;(6)BB (BIO+BIO)Bio-organic fertilizer used in both of nursery soil and transplanting soil. The results indicated that bio-organic fertilizer containing strain N5could promote the tomato growth. The fresh-weight of tomato plants increased by2.27and1.14times respectively and tomato root activity increased by2.21and1.76times respectively in BB treatment than that in CC and00treatments. The ability of strain N5to produce siderophores and IAA was probably the growth-promoting mechanisms of the specific bio-organic fertilizer made of B. methylotrophicusN5.The capability of the specific bio-organic fertilizer (N5) to control the bacterial wilt of tomato was evaluated in pot experiment designed as above and chemical fertilizer and normal organic fertilizer (without N5) were used for comparison. Results revealed that specific bio-organic fertilizer (N5) could effective inhibit the growth of pathogenic R. solanacearum and reduce the disease incidence. The suppressive rate against tomato bacterial wilt was up to69%compared with the chemical fertilizer. The pot experiment results also showed that application of bio-organic fertilizers could increase the numbers of bacteria and actinomycetes and reduce fungal populations in rhizosphere soil. PCR-DGGE results showed that bio-organic fertilizers could increase the diversities of bacteria and actinomycetes and reduce fungal diversity.Proteins in culture broth of strain N5was precipitated with ammonium sulphate. The antibacterial effect was observed in precipitated substances with30-50%of ammonium sulphate. Nine lipopeptides synthesize related genes, which encoded four kinds of lipopeptides were found from strain N5by PCR. Lipopeptides from strain N5culture were extracted and analyzed with HPLC-MS, indicated that strain N5could produce iturin A, fengycin and surfactin, and fengycin was the main antibacterial substances. The optimizing medium for strain N5was Landy medium. The optimal culture conditions for strain N5were initial pH7.0,1%of inoculums, culture temperature32℃, rotating speed of incubator170r·min-1for60hours. |
PDF Full Text Request