Biocontrol and plant growth-promoting properties of Streptomyces isolated from vermicompost soil

Thirty isolates of Streptomyces like colony isolated from vermicompost soils were assessed for their antagonistic and plant growth-promoting (PGP) activities. Five isolates having the best inhibitory activity against five plant pathogenic fungi, Colletotrichum gloeosporioides, C. musae, Fusarium sp. TFPK201, Fusarium sp. Foc 1699 and Pestalotia sp. were subsequently identified by 16S rDNA analysis. The selected isolates were classified in the genus Streptomyces and given the name of Streptomyces spp. SEF1, SEF8, SEF47, SEF48 and SEF49, respectively. Then, their PGP and antifungal activities were evaluated. The results showed that the selected isolates were able to produce IAA, siderophore, and amylase. Production of IAA was ranged from 14.06 to 16.59 µg/mL. The highest siderophore production was found in the isolate SEF48. Only isolates SEF47, SEF48, and SEF49 showed amylolytic activity. The culture filtrate from the tested Streptomyces spp. inhibited the fungal mycelial growth and suppressed conidial germination, but their inhibition ability was different. Interestingly, the application of all selected culture filtrates before disease infection significantly decreased tomato Fusarium wilt disease incidence and severity. However, only Streptomyces sp. SEF47 could significantly reduce the disease incidence and severity when it was applied after the disease infection. Moreover, this research found the plant growth-promoting ability of the culture filtrate of selected isolates on tested tomatoes. The Streptomyces sp. SEF47 provided a significant ability for controlling all tested plant pathogenic fungi and promoting plant growth. Therefore, Streptomyces sp. SEF47 could be considerable biocontrol and PGP agent used in sustainable agriculture.