THE PLANT CELL, Vol 2, Issue 7 643-649, Copyright © 1990 by American Society of Plant Biologists
Chimeric Tomato Plants Show that Aphid Resistance and Triacylglucose Production Are Epidermal Autonomous Characters
J. C. Goffreda, E. J. Szymkowiak, I. M. Sussex and M. A. Mutschler
Department of Plant Breeding and Biometry, Cornell University, Ithaca, New York 14853
Graft chimeras were generated using Lycopersicon pennellii and L.
esculentum to determine the contribution of the three meristem layers (L1,
L2, and L3) to trichome density, sugar ester production, and aphid
resistance. Sugar esters, in the form of triacylglucoses, have been
implicated in the aphid resistance of pennellii. One chimera possessed the
epidermal layer (L1) of pennellii and the internal tissues (L2 and L3) of
the aphid-susceptible esculentum. The second chimera had both the L1 and L2
of pennellii and the L3 of esculentum. Type IV trichome densities did not
differ significantly among the chimeras and pennellii. Both chimeras
accumulated sugar esters with similar sugar and fatty acid composition as
pennellii. The concentration of epicuticular sugar ester on the chimeras
was also comparable with that of pennellii. Leaf cage and feeding studies
demonstrated that both chimeras are as resistant to aphids as is pennellii.
The resistance could be reduced similarly on all three types of plants by
removal of the type IV trichome exudate. These results indicate that the
presence and density of the type IV trichomes and the amount and type of
sugar esters produced are features determined by the genotype of the
epidermis. These epidermal features are sufficient to account for the aphid
resistance observed in pennellii.
