Variety-driven effect of rhizosphere microbial specific recruit-ment on drought tolerance of M. ruthenica (L.)

As one of the environmental factors that seriously affect plant growth and crop production, drought requires an efficient but environmentally neutral approach to mitigate its harm to plants. Soil microorganisms can interact with plants and soil to improve the adverse effects of drought. M. ruthenica (L.) is an excellent legume forage with strong drought tolerance, but it is still unclear what the key role of microbes in resisting drought stress is. What kind of flora play a key role? Is the recruitment of such flora related to its genotype? Therefore, we selected three varieties of M. ru-thenica (L.) for drought treatment, analyzed their growth and development, physiological and biochemical characteristics, and performed 16S rRNA high-throughput sequencing analysis on their rhizosphere soils, in order to clarify the variety-mediated response of rhizosphere micro-organisms to drought stress. It was found that among the three varieties of M. ruthenica (L.), Mengnong No.2, Mengnong No.1 and Zhilixing were subjected to drought stress and showed a reduction in plant height increment of 24.86%, 34.37% and 31.97%, fresh weight of 39.19%, 50.22% and 41.12%, respectively, whereas dry weight was reduced by 23.26%, 26.10% and 24.49%, re-spectively.At the same time, we found that the rhizosphere microbial community of Mengnong No. 2 was also less affected by drought, and it was able to maintain the diversity of rhizosphere soil microflora stable after drought stress, while Mennong No. 1 and Zhilixing were affected by drought stress, resulting in a decrease in rhizosphere soil bacterial community diversity indices to 92.92% and 82.27%, respectively. Moreover, the rhizosphere of Mengnon No. 2 was enriched with more nitrogen-fixing bacteria Rhizobium than the other two varieties of M. ruthenica (L.), which made it still have a good ability to accumulate aboveground biomass after drought stress. In conclusion, this study proves that the enrichment process of microorganisms is closely related to plant genotype, and different varieties enrich different types of bacteria in the rhizosphere to help them adapt to drought stress, and the respective effects are quite different. Our results provide new evidence for the study of microorganisms to improve the tolerance of plants to drought stress, and lay a foundation for the screening and mechanism study of drought-tolerant bacteria in the future.