Morphology and morphometrics of Pratylenchus brachyurus and P. zeae II influence of environmental factors

Unfavourable host, overcrowding and high temperature decreased the body size of Pratylenchus brachyurus and P. zeae. Nematodes of both species, from host roots grown on White's nutrient medium, were larger than those on Krusberg's or Carew's media. Other characters like head to excretory pore distance, total oesophageal length, gonad and tail length also tended to vary in the same way as the body size in both species, though oesophageal and tail lengths varied less than the body size. Stylet length varied little. DeMan ratios a, b, b, c, and Geraelt's ratio (M.B.) varied widely and did not consistently exhibit strong relationship. By contrast, deMan V ratio and a new ratio designated ‘P.O.’ varied little and showed strong reiationship.