ANTIMICROBIAL PROPERTIES OF MICROMYCETES AND STREPTOMYCETES FROM MOLDOVAN SOILS

Abstract

All soil microorganisms influence on plants. Beneficial effect of microorganisms can be direct and indirect, for example, through suppression of growth or destruction of phytopathogens. The purpose of our researches was to identify the strains-antagonists of phytopathogenic bacteria and fungi among micromycetes and streptomycetes, isolated from soil samples from different zones of Moldova. Investigated strains showed different ability of suppressing growth of phytopathogens. There were no antagonists to E. carotovora and A. tumefaciens found among micromycetes of genus Penicillium. Metabolites of strain Streptomyces sp. 66 caused formation of inhibition zone of growth (diameter-18,0 mm). The investigated strains had similarly poor inhibition effect on X. campestris. The streptomycetes and micromycetes demonstrated increased antagonism against C. michiganense: 7 strains of streptomycetes and 2 strains of micromycetes (zones of absence of growth - 12,0-30,0 mm). The ability to retain yeast growth was found only in 1 strain of micromycetes - Penicillium sp. 17 and 10 strains of streptomycetes retained the growth of S. cerevisiae 11 and Rh. gracilis 3 (the diameter of zones - 18,0-25,0 mm). For B. cinerea one active fungal antagonist - Penicillium sp. 5 (zones of 30,0-35,0 mm) was found and 2 strains of streptomycetes which completely suppressed growth of this test - microorganisme. Two strains of Penicillium sp. 2 and Penicillium sp. 5 actively retained the growth of A. alternata and 4 strains of genus Streptomyces completely suppressed the growth of this test - microorganisme. Determination of the ability of micromycetes and streptomycetes to suppress the phitopathogens of genus Fusarium reveled that 5 strains of genus Penicillium retained their growth (diameter of zones 15,0-25,0 mm). From 24 strains of streptomycetes 14 strains retained growth of F. solani, F. oxysporum, F. graminearum. The most active strains of Streptomyces sp. 9, Streptomyces sp. 66 (zones 20,0-34,0мм) and Streptomyces sp. 10 completely suppressed the growth of F. graminearum. Thus, the results received by us have shown, that among the fungi of genus Penicillium the antifungal activity is shown in the greater degree, than the antibacterial one. There were identified streptomycetes with ability to cause full suppression of growth of phytopathogenic fungi. Strains of Streptomyces sp. 9 and Streptomyces sp. 66 has wide antifungal spectrum - 8 test-microorganisms (14,0-34,0 mm). The received data correspond with the literature data which emphasize perspectives of microbial antibiotics in plant protection.