A morphological approach for the early selection of grapevine rootstocks tolerant to water stress

Abstract

Over the past two decades, grapevine rootstock breeding programs have increasingly favored genotypes with a tendency toward anisohydric behavior, which are better adapted to hot and arid conditions. However, drought tolerance is a complex trait that is difficult to evaluate during the early stages of selection. In this context, the present study investigates whether specific morphological traits can predict hydraulic behavior in Vitis spp., thereby supporting the identification of new parental genotypes.

Nine rootstocks from the University of Milan collection (four anisohydric and five isohydric) were analyzed by evaluating ten anatomical traits potentially associated with drought response, including leaf absorbance spectrum, shoot xylem area, leaf surface hydrophobicity, and stomatal density. Traits were examined individually through analysis of variance (ANOVA) and jointly through multivariate discriminant analysis.

ANOVA identified four traits that differed significantly between the two physiological classes: mean shoot xylem lumen area, petiole diameter, leaf area, and areole size. These parameters allowed the construction of a significant discriminant function, achieving an accuracy of 83% in correctly classifying genotypes as isohydric or anisohydric.

The resulting model enables the rapid discrimination of genotype hydraulic behavior using a limited set of easily measurable morphological traits. It is currently being validated on an independent collection of American progenies not yet characterized for their response to water stress. This approach represents a relevant advancement for the selection of resilient rootstocks and for the development of more efficient breeding programs.

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