Actinobacteria as alternative agents for sustainable agriculture

Abstract

Four hundred and seventy-one actinobacteria were isolated from the soil sample and subsequently screened for indole acetic acid (IAA) production. IAA producers (15 only) were tested for phosphate solubilization, hydrogen cyanide (HCN) production, and antifungal activities against several phytopathogens such as Fusarium proliferatum, Fusarium oxysporum, and Alternaria solani. Isolates C4, W59, P97, and P112 were selected for performing other plant growth-promoting (PGP) activities such as ammonia production, potassium solubilization, nitrogen fixation, and hydrolytic enzyme production including proteolytic, cellulolytic, and chitinolytic enzymes. The four selected actinobacteria were applied to wheat and clover plants in greenhouse and field experiments. Streptomyces coelicoflavus strain H-112 and Streptomyces tricolor strain H-97 showed significant increases in all growth parameters during seed germination, plant growth, and yield production. Streptomyces tricolor strain H-97 was the most isolate-inhibited damping-off disease caused by Fusarium proliferatum on wheat plants since the treatment with this strain produced P97 produced 46 plants from 50 infected seeds. Therefore, the actinobacteria could be used as plant growth-promoting agents instead of chemical fertilizers and fungicides.