Cucurbit Genetics Cooperative Report 7:61-62 (article
A Preliminary Report on Screening Watermelons for Resistance to
Watermelon Mosaic Viruses 1 and 2
Munger, H.M., T.A. More, and S. Awni
Cornell University, Ithaca, NY 14853.
About 150 watermelon seed lots planted in November, 1982, were
inoculated as 3-week seedlings with WMV-1 and WMV-2. Except for
about 10 entries, all were PI's supplied by the Regional Plant
Introduction Station at Experiment, Georgia. For most entries 5
or 6 seedlings were inoculated with each virus.
Following inoculation mottling appeared on the leaves of nearly
all the seedlings and differences were not readily apparent
initially. In a few weeks certain entries showed much greater
growth and diminished mottling. The best plant in each of the
best entries was selected for transfer to a pot and carried
through the winter. Most selected plants survived until May,
1983, when they were rated for resistance and several cuttings of
each rooted. The surviving entries and their ratings are shown
in Table 1.
Table 1. Watermelons planted Nov. 10, 1982, 6 plants inoculated
with WMV1 and 6 with WMV2 on Dec. 2. Best plant saved from each
entry below and held for field planting in 1983.
Cornell test no.
Resistance rating (May 1983)
O.P. seed from WMV2 isolation
WM5-4 (Webb's sel. from Egon)
1Rotted but flesh color suggested a commercial variety.
212% soluble solids. Field assistant took it home to eat.
3Only seed produced in WMV1 isolation.
From 1 to 4 cuttings from each plant selected in the WMV-1 test
were planted in one isolated field, and from the WMV-2 test in
another, in single long rows. Plants were allowed to open-
pollinate with the thought that natural crossing might lead to
greater resistance through transgressive segregation.
Unfortunately, the WMV-1 selections were in an unfavorable
location and most did not survive transplanting in a hot, dry
period. Most of the WMV-2 selections grew and set fruit
normally, showing little evidence of virus disease. Part of the
seed from each selection will go to Egypt for testing since virus
diseases are limiting watermelon production there. There is
adequate seed to share with other watermelon breeders interested
in evaluating virus resistance.
These are highly preliminary results; larger samples of the more
promising entries should be re-tested and more care given to
getting seed, particularly from survivors of WMV-1 inoculation.
In the collection tested, 75 entries came from India, 15 from
Japan, 15 from South Africa, 10 from USSR, 10 from Central and
South America, and 7 from tropical parts of Africa. The
survivors from India had the best horticultural features but none
had high resistance to both viruses. Entries with the best
combined resistance to the 2 viruses came from Africa, but none
was really edible.