Screening Of Saline-tolerant Bacteria And Effects Of Biological Fertilizer On Saline-alkali Crops

Saline-alkali land resources are important land resources in China.The area of saline-alkali land is huge,so how to develop and use it has always been a hot issue.Microbial fertilizers made from plant growth promoting rhizo bacteria(PGPR)play an important role in improving the utilization of saline-alkali land.This study not only enriches the rhizosphere-promoting bacteria resource bank of saline-tolerant plants but also increases the knowledge of rhizosphere-promoting bacteria in saline-alkali tolerant plants,which has laid the foundation for the development of new microbial fertilizers suitable for saline-alkali land.The thesis has studied the effects of microbial fertilizers applied to saline and alkaline land on corn and wheat yields as well.In this experiment,the rhizosphere-promoting bacteria of 6 existing saline-tolerant plants were numbered 6CW15,6WW6,30-04J-2,6R3,6R8,and 30-04J-1.Preliminary identification using 16 S rDNA sequences,six strains are Bacillus safensis,Bacillus altitudinis,Bacillus siamensis,Bacillus velezensis,Bacillus subitis and Serratia rubidaea.Determining the saline-alkali resistance of each strain,I drew a conclusion that the 6WW6 and 6CW15 strains have the strongest resistance to salt and alkalinity,which can grow in medium with pH=9 and 11% sodium chloride.In the pot experiment,every strain had different effects on corn traits in different salt concentration soils.In different saline-alkali soils,strains had the most significant effect on the fresh and dry weight of above-ground and below-ground corn,as well as increased the germination rate of corn seeds significantly at the same time.The fresh weight of above-ground maize plants treated with 6CW15 in soil but not treated with saline-alkali mixed solution increased by 62.92%,above-ground dry weight increased by 43.63%,reaching a very significant difference level(p<0.01),so it has the best effect.The fresh weight of underground corn plants treated with 6R8 increased by 33.67%,and the dry weight of underground plants treated with 30-04J-1 increased by 52.90%,reaching a significantdifference level(p<0.05).In the soil treated with 40 mmol / L mixed saline-alkali solution,the fresh weight of above-ground corn plants treated by 30-04J-1 increased by 56.96%,the dry weight of above-ground corn plants increased by 40.28%;the underground fresh weight of6WW6 treated plants increased by 31.87%,and the underground dry weight increased by43.45%,reaching a significant(p<0.05)or extremely significant(p<0.01)difference level.In the soil treated with 120mmol/L saline-alkali solution,the fresh weight of above-ground corn plants treated by 6R3 increased by 137.93%,and the dry weight of above-ground corn plants increased by 102.79%,reaching extremely significant differences(p<0.01).The fresh weight of the underground corn plants treated with 30-04J-2 increased by 94.52%,and the underground dry weight increased by 61.11%,reaching a significant level of difference(p<0.01).According to the potted results and the salt and alkali tolerance characteristics of the strain,Bacillus altitudinis 6WW6 was selected for whole genome sequencing analysis to dig out its functional genes such as salt tolerance and growth promotion.A gene related to the production of IAA,eight genes related to the production of acid and phosphorus,nine genes related to the iron-producing carrier,twelve genes related to the promotion of plant salt tolerance and thirteen Genes related to their own salt tolerance were detected in the genome of6WW6DZCD-2 bacterial fertilizer can increase crop yields effectively.The yields of corn treated with DZCD-2 fertilizer were the highest among the treatment groups.In the 3 ‰?4‰and5‰ salt plot,the yield of corn treated with DZCD-2 bacterial fertilizer increased a lot when compared with no fertilization and conventional chemical fertilizer application,reaching a significant difference(p <0.05).In the 5 ‰ salt plot,the yield of corn treated with DZCD-2 bacterial fertilizer increased by 111.06% compared with the non-fertilized treatment,reaching a significant difference(p <0.01).Also it increased by 10% compared with the conventional fertilizers,increased by 22.06% compared with the common organic fertilizer,and increased by 17.5% compared with the fertilizer treated with DZCD-1 bacterial.In the5 ‰ salt plot,the yield of wheat treated with DZCD-2 bacterial fertilizer increased by103.32% compared to the yield of wheat without fertilization(p<0.01).It was found that the proportion of Proteobacteria in soils with different saline-alkaliconcentrations was the largest in the analysis of bacterial community diversity in wheat rhizosphere soil.The Chao index of soil treated with DZCD-2 bacterial fertilizer increased significantly,increasing the diversity of soil flora.The Hirschia,Nitrospira,and Terrimonas in soil treated with DZCD-2 bacterial fertilizer in low-salt-alkali soils increased significantly compared with other treatment groups.The Iamia,Flavobacterium,Marinicella,Haliangium,Illumatobacter and Pedomicrobium in soil treated with DZCD-2 bacterial fertilizer in high-salt-alkali soils increased significantly compared with other treatment groups.