Morphological and Biological Characters of Diagnostic Significance in Tylenchul Us and Trophotylenchul Us Species

Abstract

The presence of cuticular outgrowths around the excretory pore was a consistent and peculiar character of Tylenchulus graminis, T. palustris and T. semipenetrans adult females. Shape and size of these cuticular structures varied and their number ranged usually from 2 to 5. No cuticular outgrowths were observed around the excretory pore of Trophotylenchulus floridensis or Tropholylenchulus obscurus. Tylenchulus graminis and T. palustris are cortical feeders and their parasitic habits are similar to those of T. semipenetrans. 'Nurse' cells, the same size as normal cortical cells but with dense cytoplasm and hypertrophied nucleus and nucleolus, were detected in Andropogon virginicus, Baccharis halimifolia and Fraxinus caroliniana roots infected with these two species. Trophotylenchulus floridensis is a cortical feeder in roots of a noncultivated dicotyledon host in Florida and induces a syncytium characterized by dense cytoplasm, hypertrophied nuclei, cell wall thickening, and cell wall protuberances. These host responses to T. floridensis parasitism differed from those of a previous report, suggesting intraspecific variability in host response as shown by preferential feeding sites in the roots of different hosts by Trophotylenchulus.