Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/29/1999
Publication Date: N/A
Citation: Interpretive Summary: Symptoms of the disease Fusarium dry rot include a dark, tissue discoloration that can progress to form a dry, crumbly rot of the potato. The disease causes hundreds of millions of dollars of losses in tuber storage houses each year. There are no chemical control measures available for tubers stored for human consumption. We previously discovered and patented 18 strains of bacteria that are capable of controlling Fusarium dry rot in laboratory tests. In order to increase the likelihood that this discovery will be developed into a commercial product helpful to USDA-ARS customers, the present work was conducted to determine if the bacteria that control dry rot in laboratory experiments would also perform in experiments conducted in pilot scale and commercial storage house tests. We determined that several of our bacteria did control Fusarium dry rot disease under these conditions, reducing disease by 25-40% compared to potatoes that were enot treated. Bacteria also were far better at controlling disease than th only fungicide registered for use on potato tubers stored for consumption by humans. Our bacteria even reduced disease when applied to potatoes entering commercial storage houses and when the bacteria were produced in liquid culture as they would have to be if they were to be industrially produced as a commercial biological control product. These findings increase the likelihood of our discovery resulting in the development of a biological control product active against dry rot of potatoes. Once commercially developed, use of this product would decrease the amount of pesticide residues on potatoes and in the environment.
Technical Abstract: Lack of effective chemicals impedes control of Fusarium dry rot of stored potato tubers destined for processed and table stock use. Biological control of dry rot incited by Gibberella pulicaris (anamorph=Fusarium sambucinum) has been demonstrated in laboratory studies but not in commercial storage environments. Several Gram-negative bacterial strains that were efficacious and amenable to production in liquid culture in laboratory studies were selected for pilot studies in Idaho and for bin trials at commercial storage houses in Idaho and North Dakota. In the first year of pilot studies, fluorescent Pseudomonas strain S22:T:04 (~1 x 10**8 cfu/ml) decreased the level of dry rot caused by G. pulicaris when coinoculated with the pathogen compared to controls and the fungicide Mertect 340F. In second year studies, P. fluorescens strain P22:Y:05 and Enterobacter cloacae strain S11:T:07 (~4 x 10**8 cfu/ml) controlled disease eincited by G. pulicaris (25% and 17% avg disease decrease, respectively) when antagonists were applied after pathogen inoculum. Treatment effects on dry rot that developed from inoculation with Nectria haematococca (anamorph=Fusarium coeruleum) were variable and influenced by interactions between antagonists, a wetting agent and Mertect 340F. In commercial storage bin trials, E. cloacae S11:T:07 reduced naturally occurring levels of dry rot by an average of 21% compared to 14% for Mertect 340F, demonstrating significant microbial efficacy when the antagonist was produced in a liquid culture system compatible with industrial fermentation practices.