Effects of drought stress on rhizosphere microbial diversity of spring wheat with different genotypes

Drought is the most important natural disaster affecting crop growth and development. Crop rhizosphere microorganisms can affect crop growth and development, enhance the effective utilization of nutrients, and resist adversity hazards. In this paper, six spring wheat varieties were used as research materials in the dry farming area of the western foot of the Greater Khingan Mountains, and two kinds of water control treatments were carried out: dry shed rain prevention (DT) -regulated water replenishment (CK). The phenotypic traits, physiological and biochemical indexes, drought resistance gene expression, soil enzyme activity, soil nutrient content, and the response of potential functional bacteria and fungi under drought stress were systematically analyzed. The results showed that compared with the control (CK), the leaf wilting, drooping, and yellowing of six spring wheat varieties were aggravated under drought (DT) treatment. The plant height, FW, DW, Pn and Gs, soil TN, MBC, MBN, MBP, SOC, and S-ALP contents were significantly decreased, while the soil TP, TK, and S-CAT contents were significantly increased (P < 0.05). TaWdreb2 and TaBADHb genes were highly expressed in T.D40, T.L36, and T.L33, and were lowly expressed in T.N2, T.B12, and T.F5. Soil TN and TP are the most sensitive to drought stress, which can be used as the characteristic values of drought stress. Based on this, two drought-tolerant varieties (T.L36) and drought-sensitive varieties (T.B12) were selected to further analyze the changes of rhizosphere microorganisms. Drought treatment and cultivar differences significantly affected the composition of the rhizosphere microbial community. Drought caused a decrease in the complexity of the rhizosphere microbial network, and the structure of bacteria was more complex than that of fungi. The Shannon index and network modular number of bacteria in the drought-tolerant varieties (T.L36) increased, with rich small-world properties. Actinobacteria, Chloroflexi, Firmicutes, Basidiomycota, and Ascomycota were the dominant bacteria under drought treatment. The beneficial bacteria Bacillus, Penicillium, and Blastococcus were enriched in the rhizosphere of T.L36. Brevibacillus and Glycomyce were enriched in the rhizosphere of T.B12. In general, drought will significantly affect the growth and development of spring wheat, and spring wheat can resist drought hazards by regulating the expression of drought-related genes, regulating physiological metabolites, and enriching beneficial microorganisms.