Hj. Mcauslane et al., RESISTANCE IN GERMPLASM OF CUCURBITA-PEPO TO SILVERLEAF, A DISORDER ASSOCIATED WITH BEMISIA-ARGENTIFOLII (HOMOPTERA, ALEYRODIDAE), The Florida entomologist, 79(2), 1996, pp. 206-221
Elite breeding lines and susceptible varieties of Cucurbita pepo L. (z
ucchini and yellow crookneck squash) and accessions of two wild specie
s, Cucurbita ecuadorensis Cutler and Whitaker and Cucurbita martinezii
Bailey, were evaluated in spring and fall 1995 for resistance to silv
erleaf whitefly, Bemisia argentifolii Bellows & Perring, and to squash
silverleaf; a physiological disorder associated with feeding by B. ar
gentifolii. Populations of whitefly and severity of silvering were gre
ater in the spring season than in the fall. In general, the yellow squ
ash variety, 'Supersett', and the two yellow squash breeding Lines (A2
4-10 and K26-4) supported larger populations of whitefly than the zucc
hini variety, 'Elite', and A21-7 and Sunseeds 3, the zucchini breeding
lines. However, whitefly populations within the yellow squash cultige
ns or within the zucchini cultigens did not differ significantly. In c
ontrast, 'Elite' was severely silvered in the spring (average rating o
f 4.8 at the end of the season) while Sunseeds 3 never exhibited silve
rleaf and only one plant of A21-7 exhibited slight silvering (rating o
f 1). 'Supersett' was usually significantly more silvered than the yel
low squash breeding lines, but the lines nevertheless exhibited signif
icant levels of silvering (average rating of 3.2 compared to 3.9 for '
Supersett' at the end of the spring season). Four accessions of the tw
o wild species, C. ecuadorensis and C. martinezii, all supported moder
ate populations of whiteflies and developed silverleaf. In the case of
the zucchini breeding lines, silverleaf severity was not related to n
umbers of immature whiteflies. Resistance to silverleaf in the zucchin
i breeding lines may be due to some Form of tolerance to the effects o
f whitefly feeding.