Growth regulators in chestnut shoot galls infected with oriental chestnut gall wasp, Dryocosmus kuriphilus (Hymenoptera: Cynipidae).
The potentially devasting impact of Dryocosmus kuriphilus on nut productivity of Chinese chestnut (Castanea mollissima) prompted an assessment of the role of endogenous phytohormone-like growth regulators in gall development. Enzyme immunoassays for several growth regulators associated with developing galls indicated the probable presence of t-zeatin (Z), t-zeatin riboside (ZR), dihydrozeatin (DHZ), dihydrozeatin riboside (DHZR), dihydrozeatin riboside (DZHR), indoleacetic acid [IAA] and abscisic acid (ABA) in gall tissues. Levels of these regulators were similar in amount and seasonal abundance to that in nongalled shoots; however, ABA- and DZHR-like substances were much higher in developing stem galls. All of these regulators (except ABA-like substances) were detected in developing cynipids within the stem gall, but levels within the insect were much lower than in stem-gall tissue. It is suggested that these particular regulators may not be the growth controlling factors that inititate gall development. Pupae contained high levels of IAA- and DHZR-like substances, while larvae contained only high levels of a DHZR-like factor, indicating these substances may have a role in insect morphogenesis.