Microvine: A New Model to Study Grapevine Growth and Developmental Patterns and their Responses to Elevated Temperature

Growing standardized plant material in controlled environment can facilitate the disentangling of the many impacts of climate change on grapevine production and quality. Microvine is a natural gibberellic acid insensitive mutant showing dwarfism, early and continuous flowering along the vegetative axes. It was initially proposed as a model for genetics. In this study, we questioned its suitability to facilitate and hasten the characterization of grapevine vegetative and reproductive growth and development patterns as wells as their responses to temperature elevation. A series of experiments were performed in the greenhouse and in growth chambers under either ‘standard’ (25/15°C days/night) or contrasted (from 22/12°C up to 30/25°C) thermal treatments for several weeks. Under ‘standard’ thermal condition, measured temporal patterns of leaf and berry growth were similar among several phytomers along the main axis allowing us to estimate temporal growth patterns from spatial distribution of organ size. These patterns were stable between independent experiments under similar thermal and irradiance conditions. When plants were exposed to contrasted thermal treatments, leaf emergence rate was found linearly related to average daily temperature allowing us to derive a thermal time based model of development. Under cool thermal conditions (22/12°C), the temporal evolution of biochemical parameters was similar to that classically found for grapevine. However, exposing plants to a + 8°C thermal treatment for 450 °Cd revealed strong alterations of the thermal time based developmental program with either acceleration (leaf and internode growth) or delay (flowering, sugar accumulation in berries), as well as major uncoupling between growth and storage in internodes. These results reveal the potential of Microvine to study grapevine responses to the many facets of climate change