MORPHOLOGICAL VARIATION IN PRATYLENCHUS-PENETRANS

  • 1 January 1976
    • journal article
    • research article
    • Vol. 8  (3) , 185-195
Abstract
Variability of morphological characters used to separate P. penetrans from other species of the genus was studied in a population originating from a single gravid female. Pronounced heteromorphism was observed and characterized. About 30% of females had a crenate-tail terminus. Several shapes of stylet knobs were characterized; 50% of them were anteriorly flattened to indented. The outer margin of the cephalic framework extended into the body from 1/2 of 2 annules. The shape of the spermatheca varied from round to oval. A 5th lateral line was observed in many specimens. Environmental factors, particularly the host plant, influenced morphometric characters such as body length, width, esophagus length, stylet length, V value, and a and b'' ratios, as well as qualitative characters such as tail terminus, growth of ovary and shape of median bulb. Nematodes reared on pea and cabbage had a higher percentage of females with a crenate-tail terminus than those from tomato, rye, beet and alfalfa callus culture. Nematodes from peas were longer and wider; they often had gonads that extended to esophagi, but they had shorter esophagi and stylets than those from callus culture. Populations from different geographical locations also exhibited variability in morphological characters, as did the Cornell population. The validity of many characters used in species identification is discussed, and the possibility that other related Pratylenchus spp. are conspecific with P. penetrans is suggested.