Screening Of Plant Growth-promoting Rhizobacteria And Its Application In Strawberry

Fragaria ananassa Duchesne has been introduced from abroad.In recent years,it has achieved rapid development in Chinabecause of its good taste,rich in nutrients,coupled with short cultivation cycle,fruitful results and high economic benefits for the northern region,especially in Shandong.However,strawberries are vulnerable to a variety of diseases such as leaf spot,powdery mildew,and other diseases,which restrict their development.Plant growth-promoting rhizobacteria(PGPR)on the one hand can secrete and produce some hormones(such as auxin)that promote plant growth to directly promote plant growth,on the other hand,it can inhibit the growth of pathogenic bacteria by producing antibacterial substances.,thereby slowing the adverse effects of plant diseases on plant growth.Using PGPR strains to promote the growth of strawberry plants and inhibit the threat of disease,promote strawberry plant growth and increase the economic benefits of strawberries.This study identified strawberry and gerbera rhizosphere strains with protease-producing ability,phosphate-reducing ability,IAA-producing ability,potassium-releasing ability,iron-producing carrier capacity,and ability to antagonize pathogenic bacteria.The optimization of the culture medium was further applied to the pot experiment of strawberry plants to verify its growth promoting effect and provide basis for the development and application of strawberry microbial fertilizer.The main research results are as follows.A total of 56 strains of protease-producing bacteria,6 strains of phosphorus-resolving bacteria,10 strains of IAA-producing bacteria,17 strains of potassium-releasing ability,and 39 strains of iron-producing bacteria were screened from the rhizosphere of strawberry and gerbera.Four strains with good effect were screened by functional screening and identified by colony morphology observation,physiological and biochemical experiments,and 16 S rDNA sequence analysis to identify K1 as Bacillus siamensis and KFH3 as Bacillus velezensis and FJ06-10 are Pseudomonas corrugata and CT1-7 is Aeromonas aquariorum.The four strains were optimized for the culture medium,and 2% glucose bean sprouts juice medium was added as the basic medium.Through a single-factor test,the optimalcarbon source of CT1-7 was identified as rice bran,and the optimal nitrogen source was ammonium nitrate.The optimal inorganic salt is dipotassium hydrogen phosphate,the optimum carbon source of FJ06-10 is identified as wheat bran,the optimal nitrogen source is soybean meal,and the optimal inorganic salt is calcium carbonate,the optimal carbon source of K1 is determined as sucrose,the most The optimal nitrogen source is soybean meal,and the optimal inorganic salt is dipotassium hydrogen phosphate,the optimal carbon source for KFH3 is sucrose,the optimal nitrogen source is ammonium sulfate,and the optimal inorganic salt is dipotassium hydrogen phosphate.Orthogonal test was conducted to determine the optimum medium formulation.The results showed that the optimal medium ratio of CT1-7was 3% rice bran,1.5% ammonium nitrate,and 0.3% dipotassium hydrogen phosphate,the optimal medium for FJ06-10 The ratio is 3% of wheat bran,1.5% of soybean meal,0.3% of calcium carbonate,the optimum ratio of K1 is 3% sucrose,1.5% soybean meal,and 0.3%dipotassium hydrogen phosphate,the optimum medium ratio of KFH3 is Sucrose 3%,ammonium sulfate 1.5%,dipotassium phosphate 0.3%.Through the application of potential evaluation to study the application effect of a single strain.Four treatments were set up in the experiment,in which K1 was used as treatment 1,KFH3 was used as treatment 2,VJ06-10 was used as treatment 3,CT1-7 was used as treatment 4,and CK was not used as a control to measure the bacteria against strawberry leaves.Enzymatic activity,plant weight,and rhizosphere soil enzyme activity.The results showed that the four bacteria K1,KFH3,FJ06-10,and CT1-7 all contributed to the growth of strawberry seedlings.Compared with CK,the fresh weight and dry weight of strawberry plants reached significant difference.The dry weight of ground strawberry plants increased by18%,104%,76%,and 81%,respectively,and the above-ground parts increased by 23%.128%,82%,95%,respectively,the underground part increased 6%,76%,63%,61%.The activities of sucrase,urease and catalase in the soil were all increased compared to the control.At 50 days,the four treatments of catalase and malondialdehyde in the leaf could reach extremely significant with the control CK.Differences(p<0.01),extremely significant differences in superoxide dismutase between treatment 2,4 and control CK(p<0.01),significant difference from treatment 1(p<0.05),peroxidase activity CK There was a significant difference from treatment 1(p<0.05),and a significant difference from treatment 4(p<0.01),indicating an increase in soil fertility.