Diversity of antifungal actinomycetes in various vegetative soils of Korea

Abstract

Diversity of actinomycetes and their antifungal activities against some plant pathogenic fungi were examined in various vegetative soils from 14 different sites in the western part of Korea. Actinomycete counts ranged from 1.17 x 10(6) to 4.20 x 10(6) cfu x g(-1) dried soil. A total of 1510 actinomycetes were isolated from the soil samples. Streptomyces was predominant in soils with a pH range of 5.1-6.5, 9.1-13.0% moisture, and 9.1-11.0% organic matter. Most Micromonospora, Dactylosporangium, and Streptosporangium were distributed in soils with pH 4.0-5.0, 2.0-9.0% moisture, and 4.0-7.0% organic matter. Actinomadura and nocardioform actinomycetes were abundant in soils with pH 4.0-5.0 and 13.1-20.0% moisture and with 9.1-11.0 and 4.0-7.0% organic matter, respectively. Populations of Streptomyces were predominant in all the soils, but were highest in grassland and lowest in mountain-forest soils. Micromonospora was most abundant in pepper-field soil and nocardioform actinomycetes were highest in rice paddy field soil. Dactylosporangium was predominant in lake-mud sediments and pepper-field soil, Streptosporangium in lake-mud sediments, and Actinomadura in mountain-forest soil. Antifungal actinomycetes were abundant in orchard soil and lake mud. More than 50% of antifungal isolates from most soils were classified as genus Streptomyces. Actinomycete isolates that showed strong antifungal activity against Alternaria mali, Colletotrichum gloeosporioides, Fusarium oxysporum f.sp. cucumerinum, and Rhizoctonia solani were predominant in pepper-field soils, whereas those against Magnaporthe grisea and Phytophthora capsici were abundant in radish-field soils.

Streptomyces koyangensis sp. nov., a novel actinomycete that produces 4-phenyl-3-butenoic acid

“…The isomers of DAP in the whole cell hydrolysates were analysed by TLC (Lee & Hwang, 2002). Cellular fatty acids were prepared and analysed using the method of Guckert et al (1991).…”

“…During the screening of antifungal metabolites for plant chemotherapeutic agents, we isolated a variety of actinomycete strains that are active against some plant-pathogenic fungi and oomycetes from vegetative soil in Korea (Lee & Hwang, 2002). Among them, Streptomyces sp.…”

Biocontrol of Botrytis allii Munn the Causal Agent of Neck Rot, the Post Harvest Disease in Onion, by Use of a New Iranian Isolate of Streptomyces

“…Soil sampling and isolation of Actinomycetes: Soil samples were collected from grasslands, orchards and vegetable fields in different localities of Kerman province, Iran. Several samples randomly were selected from mentioned localities using an open-end soil borer (20 cm in depth, 2.5 cm in diameter) as described by Lee and Hwang [5] . Soil samples were taken from a depth of 10-20 cm below the soil surface.…”

“…Streptomycetes are a group of Gram-positive bacteria which are mostly found in the soil; include some of the most common soil life. Streptomycetes produce different kinds of secondary metabolites and biologically active substances of high commercial value such as enzymes (which degrade the fungal cell wall directly) and antibiotics [5] . Species in the genus Streptomyces are of the major contributors to the biological buffering of soils and have roles in decomposition of organic matter conductive to crop production.…”

“…The level of inhibition at dual cultures was calculated by subtracting the distance (mm) of fungal growth in the direction of an antagonist colony (γ) from the fungal growth radius (γ°) of a control culture to give ∆ γ = γ°-γ. The ratings used were modified from those of Lee et al [5,8] , where ∆ γ: 5-9 mm, + (weak inhibition); ∆ γ: 10-19 mm, ++ (moderate inhibition); and ∆ γ>20 mm, +++ (strong inhibition).…”