Abstract

The purpose of this study was to assess the diversity and biocontrol potential of nematicidal actinobacteria from agricultural soils. Two hundred soil samples were collected from 20 provinces (autonomous regions or municipalities) of China, and 4000 actinobacteria isolates were obtained. Of the 4000 isolates evaluated, 533 (13.3% of total) and 488 (12.2%) respectively showed nematicidal properties to target nematodesPanagrellus redivivus and Bursaphelenchus xylophilus with nematicidal activities (NA) of more than 30%. The sum of strains with NAs of 90-100%, 80-90%, 60-80% and 30-60% was 55, 100, 127 and 251 to P. redivivus, while 37, 85, 111 and 255 to B. xylophilus, respectively. The most active isolates showed high host selectivity, in which only 101 isolates (5.1% of the total) were toxic to the both targets with NAs>30%. Additionally, 69 of the 101 isolates were randomly selected for species diversity analysis. Phylogenetic analysis placed the 69 actinobacteria in three families (Streptomycetaceae, Pseudonocardiaceae and Nocardiaceae) of the Actinobacteria with sequence similarity of 97.4-100%. The largest group was Streptomycetaceae, containing 58 isolates (84.1% of the total) that showed 97% to 100% sequence identity to 28 species of the generaStreptomyces (57 isolates, 27 species) and Kitasatospora (1, 1). The Pseudonocardiaceae group contained 7 isolates (10.1% of the total) showing 98.5-99.7% homology to Amycolatopsis lurida (4 isolates) and A. niigatensis (3). The Nocardiaceae group included 4 isolates (5.8% of the total) with 99-99.6% sequence identity to one species N. fluminea.

Key words: Nematicidal actinobacteria, nematode, biocontrol, phylogenetic analysis.