ISHS Acta Horticulturae 724: IX International Symposium on the Processing Tomato
INCREASING RESISTANCE OF TOMATO TO LEPIDOPTERAN INSECTS BY OVEREXPRESSION OF POLYPHENOL OXIDASE |
| Authors: | P. Thipyapong, S. Mahanil, A. Bhonwong, J. Attajarusit, M.J. Stout, J.C. Steffens |
| Keywords: | common cutworm, cotton bollworm, induction, Lycopersicon esculentum, PPO |
| Abstract:
Polyphenol oxidases (PPOs), which catalyze the oxidation of phenolics to quinones, have been reported to confer resistance to Pseudomonas syringae and are assumed to be involved in insect resistance. To assess the impact of PPO expression on resistance to 2 major lepidopteran insects, the common cutworm (Spodoptera litura (F.)) and the cotton bollworm (Heliothis armigera (Hübner)), we used transgenic tomato plants constitutively expressing sense- and antisense-oriented potato PPO genes. The transgenic plants expressing a sense PPO construct (overexpressing PPO [OP] plants) exhibited 2- to 5.3-fold higher PPO activity levels whereas the antisense PPO transgenic plants (suppressed PPO [SP] plants) exhibited 2.6- to 9-fold lower PPO activity levels than nontransformed controls. The growth rates of both common cutworm and cotton bollworm larvae were significantly correlated with PPO activity levels. The PPO-overexpressing transgenic plants clearly showed an increase in resistance; growth rates of common cutworm were up to 1.7 times lower than on controls and larvae consumed less foliage. In addition, increased PPO activity led to higher larval mortality. These results suggest a critical role for PPO-mediated phenolic oxidation in insect resistance. Manipulation of PPO activity could provide resistance simultaneously to both disease and insect pests, and therefore might be used as a component of effective integrated pest management for tomato production. | |
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