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Morphology and Histochemistry of Soybean Roots Infected with Heterodera glycines. Burton Y. Endo, Nematologist, Crops Research Division, ARS, USDA, Beltsville, Maryland 20705; Joseph A. Veech, Plant Physiologist, Crops Research Division, ARS, USDA, Beltsville, Maryland 20705. Phytopathology 60:1493-1498. Accepted for publication 5 May 1970. DOI: 10.1094/Phyto-60-1493.

Morphological and histochemical observations were made on roots of susceptible, Lee, and resistant, Pickett, soybeans infected with the soybean cyst nematode, Heterodera glycines. Certain host enzymes were localized near the nematode stylet during penetration and migration of the infective larvae. Increased enzyme activity was observed in syncytia of both susceptible and resistant hosts during the early stages of disease development. As syncytia development progressed in the susceptible host, high enzyme levels were demonstrated in the dense cytoplasm. In the resistant host, syncytia were initiated and showed a slight increase in enzyme activity, but the syncytia shortly became necrotic and deteriorated. Cortical necrosis was common in both susceptible and resistant hosts as a result of intracellular migration of larvae. Enzyme stimulation and necrosis associated with cyst nematode infections are discussed in relation to similar studies previously reported for root-knot infections of the same host.