The Impact of Ring Nematode (Mesocriconema xenoplax) On Grapevines Grafted Onto Different Rootstocks in Field Microplots

Vine performance of Pinot noir grapevines grafted onto five rootstocks with known differences in susceptibility to the ring nematode (M. xenoplax), or self-rooted, was studied under field conditions in microplots to better understand the physiological effects of ring nematode parasitism and to further test durability of rootstock resistance. Ring nematode population densities increased the fastest on self-rooted vines followed by 3309C and 1103P rootstocks, similar to results from prior greenhouse trials. Little to no nematode population growth occurred in 110R, 101-14 and 420A rootstocks during the first two years, also consistent with previous trials.  However, in year three (2008) ring nematode population densities increased dramatically in 110R and 101-14 rootstocks and high population densities were sustained on these rootstocks through year four. Only 420A rootstock remained highly resistant to the ring nematode in this trial. The first effect of nematodes on plant or soil variables occurred below ground in year two (2007). Ring nematode parasitism decreased root growth and mycorrhizal colonization of roots in self-rooted vines and these effects were detected the next year in nematode-susceptible rootstocks (3309C and 1103P). Nematodes also increased soil respiration in self-rooted vines in year two. Effects of nematode parasitism on above-ground vine performance were not apparent until year three (2008), when shoot length was reduced in self-rooted vines at bloom and in 3309C vines at véraison. Dormant season pruning weights were reduced in both self-rooted and 3309C vines in 2008. Nematodes had no impact on vine nutrient  status in 2006, but had variable effects in 2007. By 2008, nematodes reduced potassium in leaves and petioles across all rootstocks and reduced copper in leaves and petioles in self-rooted and 1103P vines. Rootstocks affected vine nutrient status in 2007 and 2008 in a manner consistent with previous published research. The ring nematode did not alter vine N status, gas exchange, leaf water potential, or yield during the first three years of vine establishment. By year four (2009) shoot growth and yield were reduced across all rootstocks by nematodes (main effect), as only one rootstock (420A) out of six had suppressed ring nematode population increases throughout the study.