Abstract
Relationships of two populations of Pratylenchus neglectus, one from Parma, Idaho (IPN) and the other from Ontario, Canada (CPN) to Russet Burbank potato and Verticillium dahliae (Tid) were evaluated. Early egression of IPN and CPN was measured on a resistant potato cultivar (Butte). Egression of CPN from Butte roots was lower (79.4%) than that of IPN (93.7%). CPN reproduced faster and averaged twice the population size on cultivars Russet Burbank and Butte (P< 0.05) compared to IPN. IPN with Vd had an effect on tuber yield that was similar to the effect of Vd alone, while the interaction of P. penetrans (PP) or CPN with Vd was greater than that of Tid alone. Area under the disease progress curve (AUDPC) for plants grown in soil infested with P. penetrans plus Vd was higher (P < 0.05) than those for Vd alone or IPN plus Vd. AUDPC values produced by CPN plus Vd were not different from those produced by P. penetrans plus Vd (P> 0.05). IPN, CPN and P. penetrans did not affect root and shoot growth of Russet Burbank (P> 0.05) but tuber yield was reduced at inoculum levels of 10,000, or 20,000 nematodes of CPN per plant, and at 5 000, 10 000, or 20 000 nematodes of P. penetrans per plant (P< 0.05). At inoculum levels of 5 000 and 10 000, CPN reproduced more on potato than did IPN. At all inoculum levels, P. penetrans reproduced in significantly greater numbers than IPN or CPN. Based on these findings IPN and CPN appear to he distinct and differ in their behavior. PCR amplification of the ITS1 region of rDNA from individual IPN and CPN nematodes yielded fragments of different size suggesting a possible need for taxonomic reevaluation of this species.