Differentiation of Two New York Isolates of Pratylenchus penetrans Based on Their Reaction on Potato.

The behavior of two isolates of Pratylenchus penetrans on six potato clones was assessed to test the hypothesis that these nematode isolates from New York were different. Four potato cultivars (Superior, Russet Burbank, Butte, and Hudson) and two breeding lines (NY85 and L118-2) were inoculated with nematode isolates designated Cornell (CR) and Long Island (LI). Population increase and egression of nematodes from roots were used to distinguish resistance and susceptibility of the potato clones. Based on numbers of eggs, juveniles, and adults in their roots 30 days after inoculation, potato clones Butte, Hudson, and L118-2 were designated resistant to the CR isolate and susceptible to the LI isolate. More eggs were found in the roots of all plants inoculated with the LI isolate than with the CR isolate. The clones NY85 and L118-2 were inoculated with the CR and LI isolates in a 2 x 2 factorial experiment to assess differences in nematode egression. Egression was measured, beginning 3 days after inoculation, for 12 days. The rates of egression were similar for the four treatments and fit linear regression models, but differences were detected in numbers of egressed nematodes. More nematodes of the CR isolate than the LI isolate egressed from L118-2. Differences in egression of females was particularly significant and can be used as an alternative or supplement to reproduction tests to assess resistance in potato to P. penetrans and to distinguish variation in virulence.