Relative susceptibility of selected cultivars, of potato to Pratylenchus penetrans.

Pratylenchus penetrans suppressed the tuber yields of potato cultivars 'Katahdin', 'Kennebec', and 'Superior', but did not affect yields of 'Russet Burbank'. In comparison with noninfested controls, all initial nematode densities (P(i)) of P. penetrans (P(i) = 38, 81, 164, 211/ 100 cm(3) of soil) suppressed yields of Superior; a moderate P(i) (81/100 cm(3) soil) suppressed yields of Kennebec; and on Katahdin, a moderate P(i) enhanced yields, but higher P(i)'s caused a marked loss. In general, yields were related to the tolerance of the cultivars to nematode colonization. Highest nematode densities were found in the roots of Russet Burbank; the next highest, in succeeding order, were found in roots of Kennebec, Katahdin, and Superior. Symptoms of nematode invasion were confined to losses of tuber yield and root weight.