October 26, 2007
Source:
Plant Disease
magazine
October 2007, Volume 91, Number 10
Pages 1288-1292
DOI: 10.1094/PDIS-91-10-1288
Published by The American
Phytopathological Society
http://apsjournals.apsnet.org/doi/interp/10.1094/PDIS-91-10-1288
Identification of Fusarium solani f. sp. cucurbitae Race 1
and Race 2 with PCR and Production of Disease-Free Pumpkin Seeds
H. L. Mehl and L. Epstein, Department of Plant Pathology,
University of California, Davis 95616
ABSTRACT
Fusarium solani f. sp. cucurbitae
causes a seedborne fruit rot of cucurbits and is classified into
two races that are actually distinct species: F. solani f. sp.
cucurbitae race 1 (Fsc1), which can infect the crown, roots, and
fruit; and race 2 (Fsc2), which only infects fruit. Here, we
report a polymerase chain reaction assay for rapid
identification because cultures of Fsc1 and Fsc2 are not easily
distinguished morphologically, and symptoms only on the fruit do
not indicate that a F. solani f. sp. cucurbitae isolate is Fsc2;
indeed, only Fsc1 was isolated from pumpkin fruit in California
in fields in which growers observed symptoms only on the fruit.
Planting of uninfected seed is critical for disease control.
Because pumpkin seeds in the United States typically are
purchased “as is,” without assurance that the seed is
uninfected, recommendations that growers plant clean seed is
scientifically sound but not helpful; contact fungicides such as
thiram control the pathogen in F. solani f. sp.
cucurbitae-infested seed, but do not control it in F. solani f.
sp. cucurbitae-infected seed. In this article, we present
evidence that cucurbit seed producers could restrict F. solani
f. sp. cucurbitae-infected seed from their seed lots simply by
visually examining fruit used for seed, and then excluding fruit
with dry rot symptoms. In a 2-year study, no F. solani f. sp.
cucurbitae-infected seed were recovered from fruit in which the
surface was lesion-free or in which a lesion extended less than
midway through the fruit flesh. Consequently, a rapid, visual
inspection and exclusion of symptomatic fruit should be
sufficient to obtain uninfected seed, even in infested fields.
Source:
http://apsjournals.apsnet.org/doi/interp/10.1094/PDIS-91-10-1288 |
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