Effect of type of rootstock on yields of Carina grapevines (Vitis vinifera) and levels of citrus nematode (Tylenchulus semipenetrans Cobb)

Abstract

Carina grapevines grafted to the rootstocks Ramsey, Harmony, Schwarzmann, K51-32, 5BB Kober, or Richter 110 were compared with their own roots for resistance or tolerance to the citrus nematode (Tylenchulus semipenetrans Cobb). Ramsey was the only rootstock of those studied which was considered resistant to the citrus nematode in the field situation. Low numbers of citrus nematode were found on or near the roots (<254 larvae/500 g soil). Ramsey can also be considered to be tolerant to the citrus nematode as Carina vines on Ramsey rootstock had the highest yield over a 3-year period (30.7-38.8 kg fresh fruit/vine). While Harmony was not resistant, having large numbers of citrus nematodes on and about the roots (947-4919 larva/500 g soil), Carina vines on Harmony yielded well in this trial (25.0-28.3 kg fresh fruit/vine), suggesting tolerance to the citrus nematode. All other rootstocks and own rooted vines maintained similar levels of citrus nematodes. However, grafted vines produced higher yields than vines on own roots. This could be due to tolerance to the citrus nematode, or to rootstocks inferring greater root density or inherent vigour than own rooted Carina grapevines. Thus, in field situations, where citrus nematodes are known to be high, Ramsey rootstock gives the best yield and, because of its resistance to the citrus nematode, also reduces the level of this nematode in the soil. K51-32,5BB Kober, Schwarzmann, and Richter 110 would all perform satisfactorily under citrus nematode pressure but would not control the nematode levels in the soil. Harmony would be the least favourable rootstock in a citrus nematode infested vineyard as it increases citrus nematode populations.