with late blight are shrunken on the outside, corky and rotted inside. Click
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Bacteria Take on Late Blight, Sprouting and Dry
Rot in Potatoes By Jan Suszkiw September 27, 2004
Spraying potatoes with harmless bacteria that delay sprouting and
suppress dry rots may also shield the tubers from late blight disease,
according to Agricultural Research
Patricia Slininger and David Schisler at the ARS
National Center for Agricultural
Utilization Research, Peoria, Ill., and colleagues patented methods for
using 18 strains of Pseudomonas and Enterobacter bacteria to
stymie postharvest sprouting and dry rot. Caused by the fungus Fusarium
sambuciunum, dry rot costs $100 million in losses in stored potatoes, which
comprise 70 percent of the nation's $3 billion tuber crop.
Recently, at annual meetings of the Society for Industrial Microbiology and the
American Phytopathological Society, the
scientists reported their discovery that the spray-on bacteria also stymie
infection of stored spuds by Phytophthora infestans, the funguslike
organism responsible for late blight. This disease is a worldwide threat,
causing $400 million in losses in the U.S. potato crop alone. The emergence of
fungicide-resistant strains of late blight has exacerbated the problem,
according to Schisler, who is in the ARS center's
Crop Bioprotection Research Unit.
To determine the beneficial bacteria's potential as a fungicide
alternative, the Peoria team began by inoculating wounded potatoes with both
the bacteria and an infectious-spore stage of late blight. After storing the
potatoes for one week at 15 degrees Celsius and 90 percent relative humidity,
the team checked the spuds for the telltale signs of late blight: a shrunken
surface with irregular brown patches beneath. Their top bacterial
"picks"--three strains of P. fluorescens and one of E.
cloacae--reduced late blight by 25 to 65 percent.
In warehouse-simulation studies at the
Idaho-Kimberly, the team sprayed boxes of potatoes with mixtures of late
blight and the bacteria. In those studies, the bacteria curbed late blight by
35 to 91 percent.
The ARS team, together with University of Idaho scientists, will
collaborate with a commercial firm to conduct further tests under a cooperative
research and development agreement.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.