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Copyright 2005, Board of Trustees, University
Ft. Pierce ARC Research Repor-t-L-1 iJ 75-5 June 1975
SEPAL AND FRUIT INFECTION OF WALTER TOMATO ByrgMPHYLIUM FLORIDAMUM
R. M. Sonoa4af
Dark black lesions on a few sepalS tthe entA 4calyx 61 Walter tomato fruits
were noticed on a farm near Ft. Piec orida the spri f 1975. The lesions
were mostly confined to calyxes on\y fruit the upp part of the staked
plants. These fruit were formed late in the&oeason. tieen 21 and 48 of the
calyxes on young fruit in different pats of the fi~\Wer infected. Lesions were
present on a few of these fruits after they had rjpeed. There were a few dark
lesions on leaves near the fruits with diseased-=alyxes.
Isolation and Identification of the Pathogen
Conidia of a Stemphylium sp. were present on diseased sepals in the field.
Conidia of the Stemphylium sp. were also present on two infected fruit in the
field. Stempbylium sp. was consistently isolated from sepal lesions. Other fungi
isolated along with the Stemphylium sp., in mixed cultures from sepals, were
Alternaria solani and A. alternate. Stemphylium sp. was isolated from the margins
of lesions on the two diseased fruit. Twenty-four excised leaf lesions all yielded
A. solani cultures. Stemphylium spp., A. solani, and A. alternate conidia were
found on dead, dry leaves on the botton of the plants.
The Stemphylium sp. was classified as Stemphylium. floridanum Hannon & Weber
(S. ycopersici (Enjoji) Yamamoto) on the basis of criteria presented by Ellis
(5) and Hannon and Weber (3) and data reported by Leach and Aragaki (4). Conidia
obtained from host tissue resembled conidia formed at 12C and 190 in tests by
Leach and Aragaki (4). Conidia of single-spored isolates formed on potato dextrose
agar at room temperature (24c to 28C) resembled conidia produced at 26.5C. and 28C
in tests by Leach and Aragaki (4).
Fruit Incubation Tests
Only one of 800 ripe fruit with darkened sepals examined in the field had
S. floridanum fruit rot. To test the effect of the fungus as a post-harvest
pathogen, ripe fruit with darkened sepals were brought into the laboratory and
incubated in high humidity chambers at room temperature (240 to 280). Seven of
24 fruit with calyxes attached became infected after 10 days. S. floridanum was
isolated from three fruit, A. alternate from three fruit and A. solani from one
fruit. Fruit with calyxes detached did not become infected although conidia of
S. floridanum were formed on dead tissue at the point of attachment between fruit
and calyx. When 45 ripe fruit with diseased calyx attached and 45 with calyx
removed were stored on the laboratory bench for 10 days no infection occurred.
*The surface of S. floridanum lesions on the fruit was dark. The lesions in-
creased slowly in size. The tissue under the lesions was brown and dry in texture.
1/ Associate Plant Pathologist, University of Florida, Institute of Food and
Agricultural Sciences, Agricultural Research Center, Fort Pierce, Fla. 33450
This is the first report of S. floridanui as a tomato fruit pathogen.
Previously, the fungus has been reported only as a foliage pathogen (3). The
incidence of fruit infection was negligible in the field and in the humidity
chamber when diseased calyxes were removed or when fruit were placed on the
laboratory bench. Losses caused by the pathogen can occur if diseased calyxes
remain attached and the fruits are exposed to high humidity. Calyx removal,
however, is standard procedure before shipping and storage.
In leaf inoculation tests the tomato variety Walter has been reported to be
highly resistant to S. floridanum although not immune (1). S. floridanum was
not isolated from any leaf lesions during the current study. Results of attempts
to inoculate calyxes of detached green Walter tomatoes were inconclusive as
Alternaria sp. interfered with the tests.
1. Bashi, E., M. Pilowsky and J. Rotem. 1973. Resistance in tomatoes to
Stemphylium floridanum and S. botryosum f. sp. lycopersici.
2. Ellis, M. B. 1971. Dematiaceous Hyphomycetes. Commonwealth Mycological
Institute. Kew, Surrey, England. 608 pp.
3. Hannon, C. I., and G. F. Weber. 1955. A leaf spot of tomato caused by
Stemphylium floridanum sp. nov. Phytopathology 45:11-16.
4. Leach, C. M., and M. Aragaki. 1970. Effects of temperature on conidium
characteristics of Ulocladium chartarum and Stemphylium floridanum.