Friendly Bacteria Help Fight Potato Rot
Fungi By Jan
June 12, 2002
Soil-dwelling bacteria are scientists latest weapon
against an unsightly post-harvest disease called dry rot that costs U.S. potato
growers as much as $250 million annually in tuber losses.
Service scientists Patricia Slininger, David Schisler and colleagues are
testing the bacteria as a biological alternative to thiabendazole (TBZ), a
chemical fungicide thats losing its effectiveness against Fusarium
sambucinum, the main culprit behind dry rot.
Through ARS, its in-house research agency, the
U.S. Department of Agriculture holds two
patents on the bacteria as biological dry rot control agents. A third patent
covers their use to inhibit sprouting, another costly potato storage problem.
The two scientists began exploring the bacterias
biocontrol potential in 1994, when a third ARS researcher--Ann
Desjardens--reported TBZ resistance in 90 percent of dry rot strains she
isolated from potato fields. At ARS National Center for Agricultural Utilization
Research in Peoria, Ill., Slininger and Schisler researched different
physical and nutritional conditions for mass-producing the bacteria in liquid
culture and keeping them viable during cold storage.
Lab tests and trial runs in potato storage houses indicate that
spraying tubers with the bacteria can diminish dry rot disease by 59 percent or
more. The six Pseudomonas and Enterobacter strains being tested
are harmless to humans, but form a living bandage around potato wound sites
that stymies dry rot infections.
The bacteria secrete natural antibiotics that suppress the dry
rot fungus. One such antibiotic, indoleacetic acid, may also help retard
sprouting on stored potatoes. Cultures of some of the biocontrol bacteria seem
to retard stored potato sprouting nearly as well as
1-methylethyl-3-chlorophenylcarbamate (CIPC). Although used on more than half
the U.S. potato crop, CIPC faces tighter regulation due to concerns over its
persistence in the environment and on the spuds.
Now that the patents are available for licensing, the Peoria
scientists are seeking a commercial partner to adapt the technology for market
use. A longer story about their work appears in the June issue of Agricultural