Interactions between XXXX and Bradysia impatiens: a role for phytoecdysteroids.

@entity27456 @entity19086 @entity11088 @entity2772
Plant produced insect molting hormones, termed phytoecdysteroids (PEs), are thought to function as plant defenses against insects by acting as either feeding deterrents or through developmental disruption. In @entity2772 ( @entity2772 ), @entity11088 (20E) concentrations in the roots rapidly increase following root damage, root herbivory, or @entity19086 (MJ) applications. In this inducible system, we investigated the plant defense hypothesis by examining interactions of roots, 20E concentrations, and larvae of the dark-winged fungus gnat (Bradysia impatiens). Root herbivory by @entity27456 larvae resulted in a 4.0- to 6.6-fold increase in root 20E concentrations. In paired-choice tests, increases in dietary 20E stimulated @entity27456 feeding deterrency. @entity27456 larvae preferred control diets, low in 20E, to those constructed from induced roots and those amended with 20E (25 to 50 micro g/g wet mass). When confined to 20E-treated diets, concentrations as low as 5 micro g/g (wet mass) resulted in significantly reduced @entity27456 survivorship compared to controls. The induction of root 20E levels with MJ resulted in a 2.1-fold increase in 20E levels and a 50% reduction in @entity27456 larval establishment. In a paired-choice arena, untreated control roots were damaged significantly more by @entity27456 larvae than MJ-induced roots that contained 3-fold greater 20E levels. Based on dietary preference tests, the 20E concentrations present in the MJ-induced roots (28 micro g/g wet mass) were sufficient to explain this reduction in herbivory. Interactions between @entity2772 roots and @entity27456 larvae demonstrate that PEs can act as inducible defenses and provide protection against insect herbivory.
