Submitted to: Phytopathology
Publication Type: Abstract only
Publication Acceptance Date: 10/23/2005
Publication Date: 4/6/2006
Citation: Lakshman, D.K., and Wanner, L.A. 2006. Screening and characterization of streptomyces isolates for biocontrol of Rhizoctonia solani and other plant pathogens. Phytopathology. 96:S63. Interpretive Summary:
Technical Abstract: Rhizoctonia solani, a ubiquitous soilborne fungal plant pathogen, is responsible for economic losses of agricultural, forestry, horticultural and ornamental crops worldwide. Soil actinomycetes are known to enhance fertility and possess antimicrobial properties against various plant pathogens. One hundred Streptomyces isolates, collected from diverse geographic locations within the United States and previously determined to be non-plant pathogenic, were screened in vitro for antagonism to two fungal (R. solani, AG-4, isolate RS23A, and Fusarium oxysporum fsp. gladioli) and two bacterial (Ralstonia solanacearum and Xanthomonus campestris) plant pathogens. Streptomyces isolates showed differing antimicrobial activities; i.e., some were anti-fungal, some anti-bacterial, and others were both anti-fungal and anti-bacterial. Antagonistic specialization was also noticed both within anti-fungal and anti-bacterial Streptomyces isolates. The majority of the anti-fungal isolates originated from Alaska and northeastern states like Maine and New York, whereas most of the anti-bacterial isolates came from northwestern states like North Dakota and Idaho. The ability to hydrolyze chitin has been correlated with antifungal properties. However, in-plate chitinolytic assays of the Streptomyces isolates demonstrated that not all anti-fungal isolates were efficient chitinase producers and some of the high chitinase producers were not anti-fungal in a dual-culture bioassay. The biocontrol potential of chitinolytic and antibiotic producing Streptomyces isolates, individually or in combination, will be investigated for control of R. solani on selected ornamental and vegetable plants in the greenhouse.