Guava (Psidium guajava L.) rhizosphere Glomus mosseae spores harbor actinomycetes with growth promoting and antifungal attributes

A total of eight actinomycetes were isolated from Glomus mosseae spores predominant in the rhizosphere of guava (Psidium guajava L. cv Arka Mridula) orchards in Karnataka State, southern India. Five isolates were identified using RNA polymerase β-subunit gene primers as Streptomyces fradiae, S. avermitilis, S. cinnamonensis, Leifsonia poae and Streptomyces canus. All the isolates were tested for beneficial attributes like growth promotion, production of growth hormones like IAA and GA3, phosphate solubilization, siderophore production and antagonistic activity against pathogens including chitinase activity. S. canus recorded increase in guava height and plant dry matter (25.58%, 30.89%) over control followed by S. avermitilis (20.75%, 30%) and S. cinnamonensis (14.05%, 22%) and L. poae (11.09%, 20%) in 10 month-old P. guajava seedlings grown with actinomycetes cultures mixed in coco peat growth medium at 10−8 cfu g−1 substrate. All the isolates produced growth hormones at varying levels. S. canus produced 10.1 μg ml−1 of IAA and 12.0 μg ml−1 of GA3, the highest, compared to others. S. avermitilis, S. canus and L. poae exhibited higher activity of phosphate solubilization, siderophore production and chitin degrading activity out of the five isolates. All the isolates tested in dual culture possessed strong antifungal activity against Fusarium oxysporum and Alternaria solani. The findings from this current study clearly indicated the possibilities of using mycorrhizae associated actinomycetes as bioinoculant for growth promotion, nutrient mobilization and biocontrol agent in guava seedling production.

► Guava is the most important perennial fruit crop rich in vitamins, and antioxidant.
► Actinomycetes isolated from G. mosseae were identified as Streptomyces sp.
► All the five isolates exhibit beneficial attributes to facilitate the plant growth.
► The findings of this study indicated the benefits of actinomycetes as biofertilizer.