Jared Ali

Indirect defenses are well documented for the aboveground constituents of plants. Belowground signals that mediate multitrophic interactions are equally important. Entomopathogenic nematodes (S.diaprepesi) are attracted to herbivore-induced volatiles released from Swingle var. (P.trifoliate x C.paradise) citrus when fed upon by the root weevil, D.abbreviatus. Herein, we examined the extent to which belowground recruitment signals modify behavior of nematode species representing various foraging strategies, and trophic levels. We compared attraction to extracts of infested roots and non-infested roots from Swingle citrus rootstock and a parent line of the hybrid, P.trifoliate (Pt). Swingle roots infested by weevils attracted more nematodes than non-infested roots irrespective of nematode foraging strategy and trophic status. The parental line of the swingle rootstock, Pt, attracted all nematode species irrespective of insect herbivory. Dynamic in situ collection and GC-MS analysis of...

Aboveground mulitrophic interactions such as the attraction of natural enemies of herbivores to herbivore induced plant volatiles (HIPVs) have been extensively investigated. Recently, analogous HIPV mediated interactions below ground have been described for corn as well as for citrus seedlings damaged by root weevils. The HIPVs released by damaged citrus roots attract a plurality of entomopathogenic nematodes (EPNs) and its main constituent was identified as pregeijerene (1, 5-dimethylcyclodeca-1, 5, 7-triene). Release of this HIPV by citrus roots peaked 9-12 hr after initiation of larval Diaprepes abbreviates root feeding. In field assays, lab-collected citrus root HIPVs attracted native EPNs and increased mortality of beetle larvae compared with controls. In addition, field applications of 8ng/l of pregijerene isolated from Ruta graveolens caused similar results. Field collections of root volatiles from mature citrus trees proved that pregeijerene is released in the field in respo...