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ARS Home » Southeast Area » Fort Lauderdale, Florida » Invasive Plant Research Laboratory » Research » Publications at this Location » Publication #196470
Title: IMPACT OF CHEMICAL ELICITOR APPLICATIONS ON GREENHOUSE TOMATO PLANTS AND POPULATION GROWTH OF GREEN PEACH APHIDS

Author
item Boughton, Anthony
item HOOVER, K - PSU,DEPT. ENTOMOLOGY
item FELTON, G - PSU,DEPT. ENTOMOLOGY

Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2006
Publication Date: 9/15/2006
Citation: Boughton, A.J., Hoover, K., Felton, G.W. 2006. Impact of chemical elicitor applications on greenhouse tomato plants and population growth of green peach aphids. Entomologia Experimentalis et Applicata. 120:175-188.

Interpretive Summary: Over recent decades, research in the field of chemical ecology has revealed that plants have natural defensive responses that are activated by insect feeding or plant pathogens. Activation of these defensive pathways can reduce the impact of insect feeding or pathogen infection on plants. Recent research has improved understanding of these plant defensive pathways making it possible to apply chemicals, called "elicitors", to plants that activate these defensive pathways. This manuscript describes studies in which four elicitors, benzothiadiazole (BTH), harpin, ethephon and methyl jasmonate (MJ) were applied to tomatoes to evaluate their potential for managing populations of a common greenhouse pest, the Green Peach aphid, Myzus persicae. Studies evaluated elicitor toxicity to plants, induction of plant defensive proteins, and effects on population growth and reproduction of green peach aphids. Ethephon and MJ treatments caused varying degrees of toxicity to tomato plants. Ethephon caused pronounced changes in plant growth form and severe, negative impacts on growth and flowering of tomato plants. Effects with MJ were milder, but still caused temporary slowing of development, leading to smaller tomato plants and delayed flowering. The commercial elicitors BTH and harpin did not cause detectable plant toxicity. MJ treatments significantly increased leaf levels of the enzymes peroxidase and polyphenol oxidase, which are associated with increased resistance to feeding by insect herbivores. Populations of green peach aphids grew significantly more slowly on plants treated with BTH or MJ than on control plants or plants treated with harpin or ethephon. Slowed aphid population growth on BTH-treated plants was due to significant reductions in the production of aphid offspring, although this was independent of changes in time to onset of reproduction or the lifespan of adult aphids. Aphid fecundity was also reduced on MJ-treated plants relative to controls, but this difference was not statistically significant, suggesting that other mechanisms are involved in slowing aphid population growth on MJ-treated plants.

Technical Abstract: Recent advances in the understanding of plant signaling pathways have opened the way for using elicitor-induced plant resistance as a tactic for protecting plants against arthropod pests. Four common elicitors of induced responses in tomato, Lycopersicon esculentum Mill., were evaluated with regard to phytotoxicity, induction of plant defensive proteins, and effects on population growth and fecundity of a common pest, the green peach aphid, Myzus persicae (Sulzer) (Homoptera; Aphididae). Ethephon and methyl jasmonate (MJ) treatments caused varying degrees of phytotoxicity. Ethephon caused pronounced changes in plant growth form and severe, dose-dependent negative impacts on plant growth and flowering. Effects with MJ were milder, but still caused temporary inhibition of development, leading to smaller plants and delayed flowering. The commercial elicitors benzothiadiazole (BTH) and harpin did not cause detectable phytotoxicity. The highest doses of ethephon and MJ significantly increased leaf peroxidase (POD) levels but only MJ treatments significantly increased polyphenol oxidase (PPO) levels. BTH and harpin had no detectable effects on POD and PPO. Populations of green peach aphids grew significantly more slowly on plants treated with BTH or MJ than on control plants or plants treated with harpin or ethephon. Slowed aphid population growth on BTH-treated plants was due to significant reductions in aphid fecundity, although this was independent of changes in time to onset of reproduction or time to death. Aphid fecundity was also reduced on MJ-treated plants relative to controls, but this difference was not statistically significant, suggesting that other mechanisms are involved in slowing aphid population growth on MJ-treated plants. Growth of aphid populations on plants treated with a MJ-BTH mixture was reduced almost as much as with treatments of MJ alone, suggesting that JA-dependant and SA-dependent plant signaling pathways do not interact antagonistically with regard to induced defenses against aphids.