| Plant endophytic bacteria are a kind of microbial resources with extremely high biological value.In order to obtain bacterial strains with antibacterial and growth-promoting properties,this study isolated and purified peanut endophytic bacteria from different varieties of peanut seeds,and studied its antibacterial,growth-promoting,exercise and other activities,through pot experiment to verify its antibacterial and growth-promoting ability.According to morphology,physiology and biochemistry,16S rDNA sequence alignment,the dominant strains were identified.1.Collect 22 kinds of peanut varieties from different sources to separate peanut endophytic bacteria.Through surface disinfection and tissue block separation methods,a total of 52 peanut endophytic bacteria were isolated from peanut seeds,among which,they were isolated from wet peanuts 28 strains of endophytic bacteria,24 strains of endophytic bacteria were isolated from dried peanuts,including 6 strains of cocci and 46 strains of bacilli,among which 42 strains produced spores.2.Test the antibacterial ability and exercise ability of the 52 strains of peanut endophytic bacteria.The main pathogens of peanuts,Aspergillus flavus,Fusarium oxysporum,and Sclerotium rolfsii were used as targets.The plate confrontation method was used to investigate the antibacterial ability of peanut endophytic bacteria.The results showed that there were 31 endophytic antagonistic strains with antibacterial effects on the three pathogens.Among them,the strains with the best inhibitory effect on Aspergillus flavus are PHH3-3G and YH9326-1G,and the width of the inhibition band is 13.33±0.58 mm;the strain with the best inhibitory effect on Fusarium oxysporum is HY9120-4S,WH8-1S,YZ9847-2S,the widths of the inhibition zone are 17.00±0.00 mm,17.00±1.00 mm,17.33±0.58 mm;the strain with the best inhibitory effect on Sclerotium rolfsii is PH58-3G,and the width of the inhibition zone is 15.33±0.58 mm.The results of the colony exercise test showed that there were 32 peanut endophytic bacteria with exercise ability,among which there were 11 strains with a moving diameter of 85 mm or more,namely HY25-3G,JH13-1G,PH28-1G,PH28-2G,PH58-2G,PHH3-3G,PHH3-5G,HY9120-4S,PH28-1S,WH8-1S,HY16-2S.3.Inspect the growth-promoting performance of peanut endophytic bacteria through the ability of solubilizing phosphorus,producing IAA,and producing siderophores.The ability of endophytic bacteria to dissolve inorganic phosphorus was evaluated by the phosphate circle method.There are 9 peanut endophytic bacteria with phosphate solubilizing ability,namely: PH28-1G,BS-1G,HY60-2S,HY967-1S,HY1607-1S,W1561-1S,W1561-2S,KN71-2S,PH28-3S,the R values are 2.19±0.07,1.62±0.19,1.28±0.07,2.53±0.39,1.23±0.08,1.21±0.06,1.70±0.12 1.60±0.36,1.18±0.02,among which the strains with strong phosphorus solubilizing ability are PH28-1G and HY967-1S.The Salkowski colorimetric method was used to investigate the performance of peanut endophytic bacteria producing IAA.There were 7 peanut endophytic bacteria capable of producing IAA.The yield of IAA was 6.14-99.52?g/m L,and the yield of 5 strains was higher than 50 ?g/m L.They are HY60-2S,HY9120-2S,YZ9847-1S,YHH1-2S,PH28-2S.Among them,strains PH28-2S and YZ9847-1S have the highest IAA yields,reaching 99.52±0.51 ?g/m L and 99.35±0.22?g/m L,respectively,belongs to IAA high-yielding strain.The CAS plate method and MKB liquid culture method were used to investigate the siderophore-producing performance of peanut endophytic bacteria.There were 46 endophytic bacteria with siderophore-producing ability.The siderophore activity unit was 4.13%-68.52%,there are 6 strains with activity units higher than 50%,namely HY50-2S,PH58-3G,PHH3-3G,PHH3-4G,PHH3-5G,and PHH5-4G.Among them,the strain with the highest siderophore production is PH58-3G.The siderophore activity unit is 68.52%,which is a siderophore-producing bacteria with high chelating ability.4.Comprehensive bacteriostatic and growth-promoting properties,6 strains of endophytic bacteria with good performance in all aspects were screened out for pot experiment to verify their antibacterial and growth-promoting properties.Among them,PHH3-3G has the best performance.Its parameters for agronomic traits such as plant height,root length,total fresh weight,plant fresh weight,root fresh weight,total dry weight,plant dry weight,and root dry weight are 24.10± 3.88 cm,15.45±1.15 cm,5.72±0.18 g,4.24±0.17 g,1.52±0.28 g,1.54±0.13 g,0.91±0.03 g,0.61±0.11 g;The agronomic parameters of the control treatment were: 20.15±2.41 cm,13.75±1.71 cm,4.29±0.69 g,3.31±0.34 g,1.26±0.06 g,1.46±0.07 g,0.77±0.06 g,0.51±0.01 g;The direct extraction method was used to determine the chlorophyll content of peanut leaves.The data showed that the chlorophyll content of leaves treated with strain PHH3-3G was 3.88±0.20 mg/g,and the control was 2.44±0.16 mg/g;The root vigor of peanut plants was determined by TTC method.The root reduction intensity of peanuts treated with PHH3-3G was 0.076±0.005 mg TTF/(g·h),and the control was0.024±0.018 mg TTF/(g·h).Based on the above data,the plant height,total fresh weight,plant fresh weight,chlorophyll content and root vigor of the plants treated with strain PHH3-3G were significantly higher than the control level(P<0.05).The potted control effect showed that the disease index of the peanut plants treated with PHH3-3G was 21.6±1.61,which was significantly lower than 49.06±1.90(P<0.05)of the disease control,there is no significant difference compared with carbendazim(18.71±1.28),which is the control drug.The control effect of the inoculated strain PHH3-3G against peanut sclerotiae reached 55.96%,only lower than the control effect of carbendazim(61.87%).Strain PHH3-3G aseptic fermentation broth inhibited the growth of peanut sclerotium hyphae by 52.14%,and inhibited sclerotia germination by 40.59%,which were significantly different from the control(P<0.01).In summary,the peanut endophytic bacteria PHH3-3G has good growth-promoting and antibacterial properties on peanut plants.Comprehensive morphological identification,physiological and biochemical identification,16S rDNA sequence comparison,strain PHH3-3G was identified as Bacillus velezensis. |
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