Study On The Mechanism Of Tyrosinase-resistant Bacillus Subtilis P9 Strain Improving Drought Resistance Of Peanu

Peanut is an important cash crop in China,but drought has seriously affected the growth and production of peanut.Plant growth-promoting rhizobacteria（PGPR）can promote plant growth and enhance resistance to adversity.A strain of Tsukamurella tyrosinosolvens P9 with multiple growth-promoting characteristics was isolated in the laboratory,which could promote the growth of peanut.In this study,to elucidate the mechanism of drought resistance of peanut by P9 strain,the effects of the growth-promoting characteristics of P9 strain under simulated drought stress;after inoculation of P9 strain,the effects on the growth,physiological characteristics and gene expression of peanuts under drought stress and re-watering seedlings,the effects on the growth and development of peanuts at maturity stage and pod quality after drought,and the effects on the microbial diversity under different stages after stress were analyzed.The main research results are as follows:Drought stress can reduce the ability of Tsukamurella tyrosinosolvens P9 to secrete IAA,siderophore and ACC deaminase,but the strain still has certain growth-promoting properties even under the stress of 30%concentration of PEG6000,indicating that it has stronger stress resistance and growth-promoting properties.The effects of P9 inoculation on the growth and physiological characteristics of peanut seedlings under drought stress showed that the strain could significantly promote the growth of peanut under drought stress.The water content and chlorophyll content of peanut leaves,the activities of CAT and SOD（except for 6 days of stress）of peanut leaves in inoculation+stress group were significantly increased,and the length,width and opening of stomata were significantly increased.The content of malondialdehyde and H₂O₂decreased significantly.NBT staining showed that P9 reduced the accumulation of O^2-under stress.After re-watering for 7 days,the inoculated plants recovered faster and grew better.Leaf transcriptome analysis showed that inoculation of strain P9 could improve peanut growth and enhance drought resistance by activating the expression of genes related to carbon fixation,pentose and glucuronic acid interconversion,peroxisome,sesquiterpene and triterpene biosynthesis in photosynthetic organisms under drought stress.After re-watering,inoculation of P9strain could enhance the expression of genes related to photosynthesis--antenna protein,porphyrin and chlorophyll metabolism,carbon fixation in photosynthetic organisms,peroxisome,circadian rhythm--plant,sesquiterpene and triterpene biosynthetic pathways in re-watering peanut,and promote the rapid recovery of growth after drought.The growth and development indexes and pod quality of peanuts were measured after the conventional culture was continued to mature stage.The results showed that the growth of peanuts subjected to stress at seedling stage were inhibited when they developed to mature stage,and P9 inoculation could improve the growth and root development of peanuts at mature stage after drought.Increased leaf water content,chlorophyll content,proline content,SOD activity,CAT activity and POD activity,decreased malondialdehyde and H₂O₂content,in which all alleviated the effects of stress on subsequent plant growth and development.At the same time,soil physical and chemical properties were improved to improve the yield index and pod quality of peanut.The results showed that inoculation with P9 could increase the abundance of Proteobacteria in the rhizosphere soil under drought stress,re-watering and maturation stages,and decrease the abundance of Acidobacteria in the three stages.But the effects on the abundance of actinomycetes varied.The results showed that inoculation with P9could increase the abundance of Basidiomycetes and decrease the abundance of Ascomycota and Mortierella in peanuts under drought stress.It also increased the abundance of Ascomycetes and decreased the abundance of Basidiomycetes and Sporoides in re-watering peanut.At the mature stage,the bacteria could increase the abundance of Ascomycetes and basidiomycetes,and decrease the abundance of Mortierella.The results indicated that P9 inoculation could change the rhizosphere microbial community structure and promote plant growth under different treatments and developmental stages.