Isolation and identification of tomato-associated endophytic actinomyces and their potential for plant growth promotion

Abstract:

[Background] Endophytic actinomycetes are ubiquitous in all the plant species. The use of plant growth-promoting endophytes has become of great interest as a way to enhance plant growth. [Objective] Endophytic actinomyces that could effectively promote the growth of plant were isolated, screened and identified from the tomato root, laying a foundation for the development of biological fertilizer. [Methods] Endophytic actinomyces in the tomato root were isolated with tissue sand culture method and actinomyces isolation medium; bacterial strains with strong growth promotion characteristic were screened through Salkowski colorimetric method, Mo-Sb colorimetric method and CAS plate detection method, and their growth promotion effect was verified through the pot experiment of tomato and cucumber seedling. Bacterial strains were identified through analyses of morphology, physiological biochemistry, 16S rRNA gene sequence similarity and phylogeny. [Results] Endophytic actinomyces NEAU-D1 with an Indole-3-acetic acid (IAA) yield of 25.56 mg/L was isolated and screened, which could produce siderophore and had good dissolving effect on various insoluble phosphate. 16S rRNA gene sequence analysis showed that the bacterial strains were Streptomyces. Pot experiment of tomato and cucumber seedling showed that, compared with the control group, the root length, plant height, fresh weight and dry weight of the tomato seedling were significantly increased by 9%, 23%, 47% and 92% respectively, while those of the cucumber seedling were significantly increased by 43%, 47%, 134% and 58% respectively. [Conclusion] Streptomyces NEAU-D1 can be used as a potential growth promoting endophytic actinomyces for the research and development of multifunctional biological fertilizer for facility vegetables.