Tracking Virus Resistance Genes in Watermelon Made
Easier with New Molecular Markers By
December 28, 2009
Finding watermelon genes that confer resistance to the devastating
zucchini yellow mosaic virus (ZYMV) has just been made easier, thanks to
molecular markers developed by Agricultural
Research Service (ARS) scientists and university and international
ZYMV, a member of the Potyvirus family, seriously affects the
commercial production of cucurbit crops like watermelon worldwide. Potyviruses
are the largest of the 34 plant virus families currently recognized, most of
which are transmitted by aphids. Cucurbit plants infected with ZYMV lose their
ability to photosynthesize, resulting in yellow mosaic on leaves, stunted plant
growth, unmarketable and deformed fruit, or even early plant death.
In the United States, spraying watermelon fields with insecticides is
the most common practice to reduce the presence of aphids that spread the
virus. Still, the development of commercial varieties that are resistant to the
virus is the most economic and effective method for controlling the disease.
ARS plant virologist
Ling and geneticist
Levi, with the agency's
Vegetable Laboratory in Charleston, S.C.; geneticist
Harris, now with the ARS
Genetics and Breeding Research Unit in Tifton, Ga.; and geneticist
Havey, with the ARS
Crops Research Unit in Madison, Wis., collaborated with scientists in
France and at North Carolina State
University to sequence and clone a gene called eukaryotic translation
initiation factor 4E (eIF4E), which the scientists believe confers resistance
to ZYMV in watermelon.
The scientists have also identified single nucleotide polymorphisms
(SNPs, pronounced "snips") that are potentially responsible for resistance to
ZYMV in watermelon. SNPs are variations in DNA sequences that can affect
protein sequence and functions and, in this case, how a plant responds to ZYMV.
Based on these SNPs mutations, two molecular markers, named CAPS-1 and
CAPS-2, have been developed to help facilitate watermelon breeding through
marker-assisted selections. Currently, advanced watermelon breeding lines with
resistance to ZYMV are under development at the ARS Charleston laboratory for
future public releases.
Details of this study, which was partially funded by the
U.S. Department of
Agriculture's (USDA) National Institute
of Food and Agriculture (NIFA), can be found in the scientific journal
and Applied Genetics.
ARS is USDA's principal intramural scientific research agency. The
research supports the USDA priority of promoting international food security.