Effects Of Endophytic Actinomycetes And Arbuscular Mycorrhizal Fungi On Growth And Volatile Oil Accumulation

The volatile oils of Atractylodes lancea (Thunb.) DC. (Asteraceae), an herbaceous perennial with a long history of clinical use as a traditional Chinese medicine, include a unique component of endophyte origin. The endophytes also affect the development, composition, and accumulation of pharmaceutically-active ingredients of plant origin. The plant is difficult to cultivate, and whether its growth and essential oil accumulation are affected by endophytic actinobacteria and arbuscular mycorrhizal fungi (AMF) has not been extensively researched.Because they live within plant tissues, endophytic actinomycetes not only have adequate nutritional supplies, but they are also protected from the external environment. Additionally, they need not compete with soil and rhizosphere microorganisms, and was beneficial to the biological control effect. In this paper, endophytic actinobacteria were isolated from roots, stems, and leaves of A, lancea using different types of media. We isolated a total of 77 strains and phylogenetically analyzed 16S rDNA sequences of seven strains; all seven belonged to the genus Streptomyces. The 77 isolated strains were subjected to antifungal screening. The results showed that 31 strains (42.3%) inhibited the growth of Fusarium oxysporum. Thus, antifungal strains accounted for a sizeable proportion of actinobacteria strains.To investigate the effects of endophytic actinobacteria on the growth, disease resistance, and essential oil accumulation of A. lancea, plantlets were inoculated under sterile conditions with one of five treatments:uninoculated control (CK), inoculated with F. oxysporum only (F), or inoculated with F. oxysporum and one of three endophytic actinobacteria (Ⅰ, Ⅱ, and Ⅲ). Groups Ⅰ, Ⅱ, and Ⅲ had higher levels of cellular defense enzymes, cytohydrolist, and antioxidant enzymes than the CK. Endophytic actinobacteria also changed the percentages of hinesol, β-eudesmol, and atractylodin in the essential oil; the proportion of β-eudesmol increased.To investigate the effects of AMF on survival rate, growth, and essential oil accumulation of A. lancea, plantlets were inoculated with different AMF strains using hardening-seedling technology after transplantation in greenhouse condition. The four treatments included the uninoculated CK and plantlets inoculated with either Glomus etunicatum (1#), Glomus tortuosum (2#), or Glomus mosseae (3#). The activities of phenylalanine ammonia-lyase, polyphenol oxidase, peroxidase, (3-1,3-glucanase, superoxide dismutase, and catalase, and the contents of chlorophyll (a+b) and soluble protein were measured periodically, while plant growth and essential oil content were measured after 35 days. Results showed that the mycorrhizal infection rate of treatments 1#,2#, and 3# were 42.41%,47.81%, and 63.39%, respectively. Most growth indices of the AMF-inoculated treatments were higher than in the CK; treatment 3# had the highest average number of leaves and plant height. The activities of cellular defense enzymes, cytohydrolist, and antioxidant enzymes were also higher than in the CK. AMF-inoculation changed the relative contents of hinesol, P-eudesmol, and atractylodin in the essential oil, increasing the proportion of β-eudesmol.In summary, endophytic actinobacteria and AMF can stimulate A. lancea plantlets to produce effective cellular defenses. Using endophytic actinobacteria, AMF, and endophytic fungi might improve the cultivation of A. lancea for medicinal purposes.