Suppression of Jasmonic Acid-Dependent Defense in Cotton Plant by the Mealybug Phenacoccus solenopsis

The solenopsis mealybug, Phenacoccus solenopsis, has been recently recognized as an aggressively invasive pest in China, and is now becoming a serious threat to the cotton industry in the country. Thus, it is necessary to investigate the molecular mechanisms employed by cotton for defending against P. solenopsis before the pest populations reach epidemic levels. Here, we examined the effects of exogenous jasmonic acid (JA), salicylic acid (SA), and herbivory treatments on feeding behavior and on development of female P. solenopsis. Further, we compared the volatile emissions of cotton plants upon JA, SA, and herbivory treatments, as well as the time-related changes in gossypol production and defense-related genes. Female adult P. solenopsis were repelled by leaves from JA-treated plant, but were not repelled by leaves from SA-treated plants. In contrast, females were attracted by leaves from plants pre-infested by P. solenopsis. The diverse feeding responses by P. solenopsis were due to the difference in volatile emission of plants from different treatments. Furthermore, we show that JA-treated plants slowed P. solenopsis development, but plants pre-infested by P. solenopsis accelerated its development. We also show that P. solenopsis feeding inhibited the JA-regulated gossypol production, and prevented the induction of JA-related genes. We conclude that P. solenopsis is able to prevent the activation of JA-dependent defenses associated with basal resistance to mealybugs

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Not AvailableOrnamental hosts and their significance in the management of cotton mealybug P. solenopsis were studied over two years. Twelve of the 24 documented ornamental hosts belonged to three families, viz. Asteraceae, Malvaceae and Euphorbiaceae. Higher number of ornamentals as off season hosts (9) outnumbering cotton season (3) at Central over North and South zones indicated the strong carryover of the pest at Central India. Helianthus debilis during cotton season, Vicoa indica during off season and Hibiscus rosasinensis and Withannia somnifera throughout the year are the preferential ornamental hosts with extreme severity. Role of roadside and backyard ornamentals in the spread of P. solenopsis was higher at South followed by North > Central zones. Removal and careful destruction of plants or plant parts of P. solenopsis infested ornamentals should be adopted for prevention of pest spread and to mitigate the loss to the crop of cotton.Not Availabl