Screening Of Bacillus Producing Indole Acetic Acid And Study On Their Impact Of Plant Growth Promotion

Indole acetic acid(IAA)is an important plant hormone that stimulates plant growth,Which widely distributed in plants.IAA has been proved to be beneficial to the germination and seedling growth,as well as the roots elongation.IAA plays an important role in plant growth regulation.15 strains,with highly production of IAA,was isolated and screened from acidic soil of South C hina,by hydrothermal heating and nutrient agar plate incubation.Further identification was consducted by physiological characteristics and 16 S r DNA sequences.Three high efficient strains,named Y2,Y3,Y4 stood out and were further applied to pot experiments to ensure their growth promotion of cabbage and maize.The main results were as follows:(1)15 strains were preliminary isolated from five different plant rhizosphere soil based on their ability of producing IAA.The production of IAA of the strains were up to 11.6-30.17?g·m L-1.Considering the stability of subculture,strain Y2,Y3,Y4 were selected for further study,IAA production of the chosen strains were 28.44?g·m L-1,30.17 ?g·m L-1,26.66?g·m L-1 respectively after cultivating for 24 hours.(2)The selected strains were proved to produce siderophores,ammonia proteases,and phosphorus solution and other growth-promoting traits.The water-soluble hosphorus content of strain Y2,Y3,Y4 were 209.1 mg·L-1,253.6 mg·L-1,98.7mg·L-1 after culturing in calcium phosphate liquid medium for 7 days.Moreover,the strains can survival in Nutrient agar with 9%-13% Na C l added.Strain Y3 presented positive in tests of starch hydrolysis,citrate utilization,methyl red.(3)The strains Y2,Y4 were identified as Bacillus megaterium,Y3 was identified as Bacillus aryabhattai based on its 16 S r DNA gene sequence.The ability of plant growth-promoting of the strais were checked through plate germination tests.(4)The results of maize germination test showed the germination rates were increase(5)by 4.76%,8.91%,8.69% via inoculatingstrains compared to CK.Meanwhile,strains handled increased the shoot length by 36.93%-118.3%.The effect of the strain on the germination of maize seeds was significant.(6)The cabbage pot experiment result show that significant growth promotion of the plants were achieved after inoculated with strains agent.Compared with plant CK,the plant height increased 7.01% to 19.82% respectively.The fresh and dry weight increased 15.79% to 153.23% separately.The treatment of strain could also significantly increase the accumulation of N,P and K in cabbage plants.(7)The application of strains in maize pot experiments was consistent with cabbage,and the strains were beneficial for the growth of maize during different periods.The Pot experiments showed the maize biomass such as plant height,steam diameter,leaf number increased of 23.13% to 26.13%,25.77% to 29.37%,15.54% to 16.31% correspondingly compared to CK treatment.The accumulation of N,P,K in maize plants revealed that the strains could promote the absorption of mineral elements.When strain Y3 inoculated,the concentration of total nitrogen,phosphorus a nd potassium in maize plants were increased by 68.41%,34.43%,15.66%.The strains could effectively promote the growth and improve the quality of maize.This study has isolated and identified three strains of bacillus Y2,Y3,Y4 from rhizophere soil,and confirmed their effect on the growth of cabbage and maize via pot experiment.Hence,these strains will have great potential in the biofertilizer industry.