Biocontrol property of Streptomyces parvulus VRR3 in green gram plant (Vigna radiata L.) against Fusarium solani in greenhouse

Abstract

Actinomycetes are isolated from various habitats including, plants, rhizospheres of.plant roots, terrestrial environment, and marine sediments. These Actinomycetes produce various secondary metabolites with antifungal, antibacterial, anticancer and antidiabetic properties. In the present study, a total of 31 endophytic Actinomycetes strains were isolated from the root of Vigna radiata L. (green gram plant). The antagonistic property of all strains was tested in vitro against Fusarium solani. The mycelia growth inhibition varied between 10.5 ± 1.4 and 80.5 ± 4.2% by Actinomycetes, whereas, the crude extract showed 14.2 ± 1.1 and 78.4 ± 3.1% growth inhibition (p < 0.01). The selected twelve Actinomycetes produced extracellular lytic enzymes. The results revealed that Streptomyces parvulus produced protease (18 ± 2 U/mL), amylase (20 ± 1 U/mL), lipase (13 ± 1 U/mL) and cellulase (8 ± 0 U/mL) at high levels than other Actinomycetes (p < 0.01). In addition, the ability of the screened Actinomycetes to produce plant growth-promoting agents was analyzed. The results showed that S. parvulus and other strains produced Indole acetic acid (1.5 ± 0.3 to 34.1 ± 3.4 μg/mL), phosphate solubilisation ability (1.5–24.3 PO4−3 μg/mL). The thermostable and pH-stable secondary metabolite-producing organism was characterized as S. parvulus VRR3. The in vivo growth-promoting activity of the green gram plant was tested in the greenhouse. The results showed that the selected S. parvulus was able to improve the growth of green gram seedlings, showing enhanced shoot-, and root length (p < 0.01). In addition, the seedlings treated with S. parvulus showed a decreased incidence of Fusarium wilt disease symptoms, whereas the positive control developed >80% disease symptoms (p < 0.01). Hence, S. parvulus VRR3 has the potential to become an important biocontrol agent in modern agricultural practice.