Screening, Identification, and Functional Study on Drought-tolerant Endophytes in Sugarcane

  Objective   Endophytes in sugarcane were screened for drought resistance to serve as microbial and germplasm resources.

  Methods  Drought-tolerant microbes were isolated from a collection of 329 sugarcane endophytes at the Sugarcane Research Institute, Yunnan Agricultural University. In a simulated experiment, target strains were screened under the artificial draught condition created by using 0-45% PEG6000. Potential candidates were identified based on the morphological, physiological, and biochemical characteristics as well as 16sDNA sequences of the microbes. Optimal culture conditions for the growth, nitrogen fixation ability, and IAA secretion of the identified isolates were determined.

  Results   Two strains that exhibited significant drought-tolerance were identified. K5 was a Kocuria sp. with an accession number of OP737815, and ZM a Bacillus sp. with an accession number of OP740361. Withstood the stress exerted by 40% PEG6000 or 100 g·L⁻¹ sodium chloride, they could grow stably at 50 ℃ in wide ranges of pHs and temperatures but optimally under an initial pH at 5.0 for K5 and 6.0 for ZM. ZM was stronger than K5 in fixing nitrogen. Within a limited timeframe, the IAA secretion of the two strains increased with prolonged culture.

  Conclusion   Both K5 and ZM displayed significant drought-resistance with the abilities of nitrogen fixation and IAA secretion. They could be potential candidates as a microbial agent, and their carrier sugarcane a valuable germplasm.