In vitro Screening for Biocontrol Potential Abilities of Ohio Bacterial Isolates over Tomato Pathogens
Creators:Raudales, Rosa E.
Advisor:McSpadden Gardener, Brian B.
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Series/Report no.:Plant Pathology. Graduate student poster competition, 2008
In vitro inhibition of pathogen growth by other microorganisms can be used to initially select isolates with biocontrol potential. We set out to identify spore-forming bacteria with the potential to control diverse tomato pathogens. Using a novel isolation strategy, 1500 spore-forming isolates were obtained from corn and soybeans grown in different Ohio soils. From this collection 167 isolates were selected based on their ability to inhibit the growth of Fusarium spp. Phylogenetic analysis of 16S rDNA sequences revealed that 51% of the isolates belong to one species (A), 42% were another species (B) and the remaining 8% belong to other two species (C or D). Haplotype analyses were used to select 23 distinct genotypes. Based on inhibition over Botrytis cinerea and their genotype, 8 different isolates were selected for further studies. These were screened for inhibition activity against six other tomato pathogens (Alternaria solani, Colletotrichum coccodes, Fusarium oxysporum, Phytophthora capsici, Xanthomonas campestris and Pseudomonas syringae). Isolates A1, A2, A3, B2, and D1 each inhibited the growth of three or more pathogens (P<0.05). Additionally, fermentation products of strains A2, B2, and D1 inhibited X. campestris growth (P<0.1); while those of strains A2 and B2 inhibited P. syringae (P<0.1). Similarly, extracts of strains A2, A3, B2 and D1 inhibited Fusarium oxysporum growth (P<0.05) and only extracts of strain A3 inhibited P. capsici (P<0.05). Thus, from a collection of 1500 bacteria we selected 5 candidate strains with broad-spectrum antimicrobial activities for further testing and formulation development.