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Histopathology of and Oxidative Enzyme Patterns in Wando Peas Infected with Two Populations of Ditylenchus dipsaci. R. S. Hussey, Research Assistant, Department of Botany, University of Maryland, College Park 20742, Senior author is now Research Associate, Department of Plant Pathology, North Carolina State University, Raleigh 27607; L. R. Krusberg, Associate Professor, Department of Botany, University of Maryland, College Park 20742. Phytopathology 60:1818-1825. Accepted for publication 23 July 1970. DOI: 10.1094/Phyto-60-1818.

Nematodes of the Waynesville, North Carolina (WNC), population of Ditylenchus dipsaci induced a hypersensitive reaction in epidermal tissues of Wando pea seedlings, and did not further penetrate the tissues. Cortical cells adjacent to the necrotic lesions divided and gave the appearance of cork formation. Nematodes of the Raleigh, North Carolina (RNC), population of D. dipsaci penetrated Wando pea and caused tissue disruption characteristic of the susceptible response observed in other host species. The resistant response (necrosis) was preferentially expressed over the susceptible response (galling), as demonstrated by cross-inoculation. Oxidative enzyme patterns from RNC nematode-inoculated, WNC nematode-inoculated, and noninoculated Wando pea seedlings were compared. Differences in peroxidase isoenzymes were detected between inoculated and noninoculated tissues. No differences were detected between RNC nematode-inoculated and WNC nematode-inoculated tissues. Peroxidase activity, determined histochemically, was greater in inoculated than in noninoculated tissues. In RNC nematode-inoculated stems, high peroxidase activity was localized in parenchymatous cells directly associated with nematode-induced cavities in the cortex. In WNC nematode-inoculated stems, high peroxidase activity was associated with cortical cells adjacent to necrotic lesions in the epidermis.