Fourth International Bemisia Workshop International Whitefly ...

Journal of Insect Science | www.insectscience.org ISSN: 1536-2442
percentage and female fecundity were greater at both
30 and 25 °C and lower at 15 °C. The temperature
threshold (t0) and thermal accumulative effect
(degree-days) were also calculated. The laboratory
studies were confirmed by field applications
examining the relationship between seasonal
temperature and insect populations. The study
demonstrates that T. ricini can, in otherwise unlimited
conditions, persist and increase in number within the
range 20–30 °C. Therefore, the pest is well adapted to
high temperatures and may extend its distribution if the
mean world temperatures increase because of global
warming. Regarding the plant host species, the castor
bean was the preferred host followed by papaya, while
the sweet potato was not preferred. Host plant species
had a significant effect on egg hatching, nymphal
survival, female fecundity and the duration of the life
cycle of T. ricini.
Squash Vein Yellowing Virus, A Novel
Ipomovirus, Isolated from Squash and
Watermelon in Florida
Scott Adkins 1 , Susan E. Webb 2 , Diann Achor 3 ,
Chandrasekar S. Kousik 4 , Pamela D. Roberts 5 , and
Carlye A. Baker 6
1 USDA-ARS, Fort Pierce, FL, USA.
Correspondence: SAdkins@ushrl.ars.usda.gov
2 University of Florida, Gainesville, FL, USA
3 University of Florida, Lake Alfred, FL, USA
4 USDA-ARS, Charleston, SC, USA
5 University of Florida, Immokalee, FL, USA
6 FDACS-DPI, Gainesville, FL, USA
A novel whitefly-transmitted member of the family
Potyviridae was isolated from a squash plant
(Cucurbita pepo) with vein yellowing symptoms in
Florida. The virus, for which the name Squash vein
yellowing virus (SqVYV) is proposed, has flexuous
rod-shaped particles of ~840 nm in length. SqVYV
was transmitted by whiteflies (Bemisia tabaci, biotype
B) but was not transmitted by aphids (Myzus persicae).
The experimental host range was limited to species in
the Cucurbitaceae, with the most dramatic symptoms
observed in squash and watermelon, but excluded all
tested species in the Amaranthaceae, Apocynaceae,
Asteraceae, Chenopodiaceae, Fabaceae, Malvaceae
and Solanaceae. Initial greenhouse and field screening
of watermelon germplasm with SqVYV has identified
potential sources of resistance and experiments are in
progress to confirm these preliminary observations.
Infection of squash and watermelon by SqVYV
induced inclusion bodies visible by electron and light
microscopy that were characteristic of members of the
family Potyviridae. Comparison of the SqVYV coat
protein gene and protein sequences with those of
recognized members of the family Potyviridae indicate
that it is a novel member of the genus Ipomovirus. A
limited survey revealed that SqVYV was present over
the five most recent growing seasons in watermelons
suffering from a mature vine decline and fruit rot
observed in southwest and west central Florida.
Inoculation of greenhouse-and field-grown watermelon
plants with SqVYV at different stages of growth was
sufficient to induce these symptoms, suggesting that it
is the likely cause of this disease.
Making a Friend from a Foe: Expressing a
GroEL Gene from the Whitefly Bemisia
tabaci in the Phloem of Tomato Plants
Confers Resistance to Tomato Yellow Leaf
Curl Virus
F. Akad 1 , A. Eybishtz 1 , D. Edelbaum 1 , O. Dar-Issa 2 ,
N. Iraki 2 , and H. Czosnek 1
1 The Otto Warburg Minerva Center for Agricultural Biotechnology
& The Robert H. Smith Institute for Plant Science and Genetics in
Agriculture, The Hebrew University of Jerusalem, Rehovot, Israel.
Correspondence: akad@ufl.edu, czosnek@agri.huji.ac.il
2 UNESCO Biotechnology Center, Bethlehem University,
Bethlehem, West Bank, Palestinian Authority
Breeding for virus resistance in transgenic crop plants
is based on a variety of strategies such as expressing
pathogen-derived genes or on RNA-mediated gene
silencing. The strategy used in the present research is
based on a totally new concept. It takes advantage of
the fact that some, and perhaps all, plant viruses
transmitted by their insect vectors in a circulative
manner interact in the insect haemolymph with GroEL
homologues produced by the vector endosymbiotic
bacteria. It has been suggested that GroEL-virus
interaction could be a mechanism shared by plant
circulative viruses to avoid destruction in the
haemolymph. In this study, we have exploited this
phenomenon to generate transgenic tomato plants
expressing the whitefly GroEL in their phloem. We
expected that once inoculated by their vector,
phloem-limited circulative viruses will be trapped by
GroEL in the plant phloem, thereby inhibiting invasion
of phloem-associated cells and long distance
movement, rendering the plants resistant to the virus.
A gene encoding a GroEL homologue from the
whitefly B. tabaci was cloned in an Agrobacterium
binary vector under the control of an Arabidopsis
phloem-specific promoter, which was used to
transform two tomato genotypes. GroEL was
expressed in the two genotypes, during two
consecutive generations. All the twenty four To
GroEL-transgenic tomato plants obtained (but one and
its progeny) exhibited good levels of resistance to
whitefly-mediated inoculation of TYLCV, exhibiting
mild or no disease symptoms. The transgenic progeny
of the resistant plants expressed GroEL and were as
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