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H-Gene-Mediated Resistance to Hessian Fly Exhibits Features of Penetration Resistance to Fungi

First, fourth, and sixth authors: Department of Entomology, NDSU Dept. 7650, P.O. Box 6050, and second, third, and fifth authors: Electron Microscopy Center, North Dakota State University, Fargo 58105; and seventh author: Institut de Biologie Moleculaire des Plantes, CNRS, Strasbourg, 67084, France (retired).

Features shared by host-specific phytophagous insects and biotrophic plant pathogens include gene-for-gene interactions and the ability to induce susceptibility in plants. The Hessian fly shows both. To protect against Hessian fly, grasses have H genes. Avirulent larvae die on H-gene-containing resistant plants but the cause of death is not known. Imaging techniques were used to examine epidermal cells at larval attack sites, comparing four resistant wheat genotypes (H6, H9, H13, and H26) to a susceptible genotype. Present in both resistant and susceptible plants attacked by larvae were small holes in the tangential cell wall, with the size of the holes (0.1 μm in diameter) matching that of the larval mandible. Absent from attacked resistant plants were signs of induced susceptibility, including nutritive tissue and ruptured cell walls. Present in attacked resistant plants were signs of induced resistance, including cell death and fortification of the cell wall. Both presumably limit larval access to food, because the larva feeds on the leaf surface by sucking up liquids released from ruptured cells. Resistance was associated with several subcellular responses, including elaboration of the endoplasmic reticulum–Golgi complex and associated vesicles. Similar responses are observed in plant resistance to fungi, suggesting that “vesicle-associated penetration resistance” also functions against insects.

Additional keywords:arthropod, electron microscopy, gene-for-gene resistance, Mayetiola destructor, Triticum aestivum.