Reaction of Grape Rootstocks to Ring NematodeMesocriconema xenoplax

Abstract

The reaction of grape rootstocks to the ring nematode <i>Mesocriconema xenoplax</i> was studied in glasshouse experiments and in a vineyard trial. Growth of one Oregon population of <i>M. xenoplax</i> differed among 20 rootstock and self-rooted cultivars grown in the glasshouse for eight months. The reproductive factor, Rf (final nematode density divided by initial nematode density), was ≤0.5 for 420A Mgt rootstock and ≤2.4 for 101-14 Mgt and 110R rootstocks; Rf values ≤1 indicate high nematode resistance. Other rootstocks had Rf values between 6.9 and 52.5. Root dry weights of all varieties except 420A Mgt were reduced by <i>M. xenoplax</i>. In another glasshouse experiment, 420A Mgt and 101-14 Mgt were found to be resistant to one Washington State and four Oregon populations of <i>M. xenoplax</i>, although both were moderately susceptible to a California population. A root-stock trial was planted in 1997 in a vineyard infested with <i>M. xenoplax</i>. After six and seven years, population densities of <i>M. xenoplax</i> were lowest in vines on 420A Mgt (≤0.08 g⁻¹ soil) and 101-14 Mgt (≤0.24 g⁻¹ soil) rootstocks. Population densities on other rootstocks ranged from 1.25 to 4.57 g⁻¹ soil. 420A Mgt produced good vine vigor and yield and showed the highest degree of <i>M. xenoplax</i> resistance. Rootstock 101-14 Mgt, which is widely used in Oregon, was also resistant but produced only average vigor and yield. Other common Oregon rootstocks, Riparia Gloire, 3309C, and self-rooted Pinot noir, were highly susceptible to <i>M. xenoplax</i> and were among the least vigorous vines.