Submitted to: American Journal of Enology and Viticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 11, 2012
Publication Date: June 1, 2012
Citation: Schreiner, R.P., Pinkerton, J., Zasada, I.A. 2012. Consequences of Mesocriconema xenoplax parasitism on ‘Pinot noir’ grapevines grafted on rootstocks of varying susceptibility. American Journal of Enology and Viticulture. 63:251-261. Interpretive Summary: A four-year field trial to investigate the long-term resistance of certain grape rootstocks to the ring nematode and the impact that this nematode pest has on below ground and above ground vine growth and physiology was conducted in microplots. Results showed that only one rootstock (420A) of three rootstocks previously identified as resistant to ring nematode in greenhouse trials remained resistant over a four-year period under high nematode pressure. We also showed that the first signs of nematode damage to vines occurs in fine root growth and colonization by beneficial, mycorrhizal fungi. Vines later showed reduced shoot growth, best indicated by dormant season prune weights of shoots. By the fourth year, an overall reduction in fruit yield due to ring nematode was also found. Effects of ring nematode on other vine physiological parameters (including measures of vine water and nutrient status) were generally weak or too small to reliably use as an indicator of damage. Based on these findings, only rootstock 420A can continue to be recommended for use in western Oregon vineyards with populations of ring nematode. In addition, monitoring of vine prune weights together with nematode populations in soil appears to be the most likely tool that viticulturists can use to manage infested sites.
Technical Abstract: Pinot noir grapevines grafted to five rootstocks (Vitis vinifera) and a self-rooted control known to vary in resistance to ring nematode (Mesocriconema xenoplax) were studied over four years in field microplots to 1) evaluate durability of resistance to ring nematode under conditions allowing for high population densities to develop, and 2) better understand how ring nematode parasitism affects below and above ground vine growth and physiology. Ring nematode populations in infested microplots of all three susceptible vines (self-rooted, 3309C, 1103P) increased rapidly during the second year and remained high throughout the study, while nematodes increased in two of the previously resistant rootstocks (110R, 101-14) during the third year reaching similarly high populations as susceptible roots in the fourth year. Only 420A remained resistant through the entire four-year period, with no net increase of ring nematode populations on this rootstock. The impact of ring nematode parasitism on vines was most apparent in the susceptible rootstocks and self-rooted vines with reductions in fine root growth and colonization by arbuscular mycorrhizal fungi (AMF) occurring as early as the second growing season. These reductions in both fine root production and AMF colonization due to ring nematode feeding were greater in subsequent years in the susceptible vines. The frequency of fine roots containing vesicles of AMF was reduced in all five rootstocks that supported a population increase of ring nematode (only 420A was unaffected). Ring nematode did not alter above ground vine performance until the third or fourth growing season, when shoot lengths and pruning weights were reduced in some or all of the three susceptible vines. Ring nematode did not alter shoot growth in any of the three resistant rootstocks, nor did it affect leaf gas exchange or leaf water potential in any vines in any year. However, by year four ring nematode reduced fruit yield as a main effect across all rootstock treatments.