Evaluation of novel cold-hardy rootstocks for phylloxera and nematode resistance across contrasting environments

Abstract

Pest- and disease-resistant rootstocks are foundational to sustainable global viticulture, offering a strategy to mitigate edaphic stressors and climatic variability while optimizing scion performance. This study evaluated four elite grapevine rootstock selections (i.e., RT24, RT40, RT50, and GE0937-18) developed by the University of Minnesota for growth morphology, propagation efficiency, phylloxera resistance, and cold hardiness.

These selections, along with own-rooted Vitis vinifera ‘Chardonnay’ as a control, were established in a randomized complete block design with three replicates in two geographically distinct regions in the U.S.: Minnesota and Washington. Viticultural metrics, including stem diameter, pruning weights, and number of acceptable propagative units, were generally higher in the Washington trials. Among the selections, GE0937-18 consistently exhibited the lowest vigor and the greatest propagation difficulty.

Resistance to plant-parasitic nematodes was validated through controlled greenhouse inoculations using three nematode species: Meloidogyne hapla, M. incognita, and Mesocriconema xenoplax. Results demonstrated a high degree of resistance across the new selections compared to the control. For instance, own-rooted ‘Chardonnay’ supported average densities of 27,375 (M. hapla) and 85,373 (M. incognita) eggs per gram of root, whereas the most susceptible new selection (RT50) restricted densities to just 75 and 252, respectively.

A comprehensive data matrix will be presented, providing a framework for researchers to integrate these rootstocks into future scion-interaction trials and sustainable production systems.