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Free Phenols and Root Necrosis in Nematex Tomato Infected with the Root Knot Nematode. Charles H. Brueske, Associate Professor, Department of Biology, Mount Union College, Alliance, Ohio 44601; Victor H. Dropkin, Professor, Department of Plant Pathology, University of Missouri, Columbia, Missouri 65201. Phytopathology 63:329-334. Accepted for publication 30 September 1972. DOI: 10.1094/Phyto-63-329.

Nematex tomato seedlings are known to be resistant to certain root knot nematodes at 27 C, and susceptible at 32 C. At the lower temperature, brown necrotic areas are usually associated with larval penetration of the roots; at the higher temperature, this necrosis is greatly reduced or is absent. Uninfected and infected seedlings, 4 to 7 days old, were analyzed for changes in free phenol content under both temperature regimes. In the resistant state (27 C), free phenol concentrations declined more rapidly in the infected seedlings than in the corresponding uninfected seedlings. In the susceptible state (32 C), the decline in the free phenol concentration appeared to be correlated with temperature rather than with infection, since free phenol concentrations declined rapidly in control and infected seedlings. Changes in phenolase activity in the roots were also measured in the susceptible and resistant states. An increase in phenolase activity was found in resistant-infected roots and in susceptible-infected and uninfected roots. There was no increase in phenolase activity in the resistant-uninfected roots.