Soil streptomycetes with in vitro activity against the yam pathogens Curvularia eragrostides and Colletotrichum gloeosporioides

Abstract

Yam (Dioscorea cayennensis Lam), an important crop in the Northeastern region of Brazil, is susceptible to the attack of several phytopathogenic fungi, such as Curvularia eragrostides (Henn.) Meyer and Colletotrichum gloeosporioides (Penz.), which cause leaf spot diseases. This work aimed to evaluate the effect of six actinomycete isolates (S. thermotolerans, S. griseus subsp. griseus, Streptomyces sp. N0035, S. purpurascens, and two isolates identified as Streptomyces sp.), as well as the effect of their secondary metabolites, on mycelium growth and spore germination of C. eragrostides and C. gloeosporioides, from yam plants, cultivar da Costa. Additionally, the chitinolytic activity of these actinomycete strains was determined in a minimum salt growth medium with chitin as the sole carbon source. There was significant interaction between the actinomycete isolates and the phytopathogenic fungi for spore germination and mycelium growth inhibition. Streptomyces sp. codified as AC 26 was more efficient in inhibiting spore germination of C. eragrostides, while S. thermotolerans and Streptomyces sp. N0035 were more efficient for C. gloeosporioides. Streptomyces sp. (AC 26) was the most efficient in inhibiting mycelium growth of both fungi, and the inhibitory effect was positively correlated to metabolite concentration. S. griseus subsp. griseus did not show chitinolytic activity and did not control mycelium growth of both fungi. The actinomycete strains evaluated in this study can be considered potential biological agents for controlling yam phytopathogenic fungi associated with leaf spot diseases.

Identification, isolation and optimization of antifungal metabolites from the Streptomyces Malachitofuscus ctf9

“…Therefore, currently, there is an immense need for antifungal agents. Several members of the streptomycetes family have been reported as potential biocontrol agents and as the potent producers of antifungal compounds (16,24), indicating that these filamentous bacteria possess a vast potential for producing antifungal metabolites. In search for antifungal agents, Streptomyces strains have been isolated from various types of soils, including rice paddy, lake mud and were filled in their respective jars and were connected to the fermenter.…”

Identification of an antifungal metabolite produced by a potential biocontrol Actinomyces strain A01

“…For determining the antimicrobial spectrum, spore suspensions from pathogenic fungi were prepared according to the method described by Soares et al (22) as follows. Plant pathogenic fungi were cultured on PDA slants (17) at 25-28ºC for 5-7 d. The fungal spores were harvested by washing with 5 mL sterilized distilled water and diluted into the suspension in the concentration of 10 6 spores mL -1 .…”

Effect of Actinobacteria and Pseudomonas spp. against Sclerotium rolfsii in Groundnut

“…257 actinobacteria were screened against S. rolfsii and 36 Actinobacteria showing best inhibition were further selected for secondary screening. In secondary screening (Soares et al, 2006) actinobacteria were streaked at the middle of plate containing Soya-Casein Digest Agar Medium (SCBA). Agar plugs of growth of S. rolfsii were placed on both sides of the streaked culture after four days using a cork borer.…”