Effects of cucumber root exudates on soil bacterial community structure under salt stress.

摘要

Effect of cucumber root exudates on rhizosphere bacterial community structure and soil microbial diversity were investigated by PCR-DGGE, in which JinChun5 (salt-tolerant) and JinYou1 (salt-sensitive) cucumber cultivars under different salt stress (0, 100, and 200 mmol.L-1) were used, and different root exudates were collected (0, 30, and 20 ml strain-1). Results showed that the types of soil bacteria reduced under salt-stress condition, as indicated by a decrease in the number of DGGE bands. Low concentrations of root exudates stimulated the appearance of some additional DGGE bands, but high concentrations of root exudates reduced the number of DGGE bands and further exasperated the negative effects of salt stress. Specific DGGE bands were sequenced, indicating that most of the soil bacteria were closely related (95-100%) to unculturable strains belonging to beta -Firmicutes, gamma -Proteobacteria, Actinobacteria and Sphingobacteria. As the duration of salt stress increased, the salt-tolerant cucumber variety demonstrated typical salt-tolerant characteristics. In the salt-tolerant variety soil, sequences similar to an uncultured Bacillus were found and another sequence closely matched an uncultured halophilic bacterium, which could resist dehydration and survive extreme environments. In the salt-sensitive soil, sequences similar to another uncultured Sphingobacterium, which could induce apoptosis, was found. These results significantly advance the understanding of biological resources and the molecular mechanism of cucumber salt-tolerance.