Yield Component Path Analysis of Okanagan Riesling Vines Conventionally Pruned or Subjected to Simulated Mechanical Pruning

Abstract

Okanagan Riesling grapevines (Vitis spp.; parentage unknown) were subjected over five seasons (1984-1988) to three training systems (mid-wire bilateral cordon; Hudson River umbrella; Lenz Moser) in combination with two pruning strategies [18 nodes per meter of row; simulated mechanical pruning (SMP)]. SMP consistently reduced weight of cane prunings, cluster weight, berries per cluster, clusters per shoot, berry weight, and °Brix and increased shoots per vine, yield, and clusters per vine. Yields of SMP vines were not significantly higher than those of their manually pruned counterparts in the final year of the trial. Path analysis showed large direct effects of clusters per vine and cluster weight on yield. Negative direct effects on yield came from berries per cluster and berry weight. Shoots per vine had a large indirect effect on yield via clusters per vine. Training system had minimal effects on all aspects of vine performance. A lack of a yield increase in the final year of the trial suggests that Okanagan Riesling vines subjected to mechanized pruning may require occasional cordon renewal to regenerate large volumes of fruitful nodes.