Wheat/Hessian fly interactions: Obviation of resistance and response of the Wci-2 defense gene
Abstract
Plant-insect interactions are relatively simple and normally do not develop elaborate resistance mechanisms due to the mobility of the insect. However, the Hessian fly-wheat interaction is an exception due to the relative immobility of all larval stages. Wheat has evolved an R gene-mediated system of resistance that functions in a gene-for-gene manner, while the fly has co-evolved its virulence to cope with resistance. During the course of this co-evolution between pathogen and host, a relatively rare phenomenon of induced susceptibility has emerged whereupon virulent larvae can circumvent or obviate the resistance mechanism rendering otherwise genetically avirulent larvae virulent. Despite the potential locally induced resistance response posed by probing avirulent larvae, the greatest proportion of avirulent adults to emerge occurred when both genotypes were present simultaneously. Avirulent larvae can be rescued by virulent larvae if the time frame between the two infestations is five or fewer days. Moreover, there appears to be no systemic induced resistance response that causes damage to subsequent infestations of larvae, and survivability of the avirulent genotype increases as the time between infestations decreases. These results give insight about the mechanism of virulence. Due to the implication of the jasmonic acid mimic coronatine in another systemic-induced resistance response, a lipoxygenase gene in wheat was investigated further. In the study of molecular interactions of the Hessian fly with wheat, Wci-2, a plant lipoxygenase, was the only pathogenesis-related gene that responded to larval feeding. Further investigation has revealed that this gene is a general response gene to wounding stress of all types, likely leading to the formation of jasmonic acid or some other derivative, which is active in defense signaling.
Degree
Ph.D.
Advisors
Williams, Purdue University.
Subject Area
Agronomy|Organismal biology
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