Microvine ::a new model to study grapevine growth and developmental patterns and their responses to elevated temperature

The use of standardized plant material grown in a controlled environment can facilitate disentangling the many impacts of climate change on grapevine production and quality. Microvine is a natural gibberellic acid-insensitive mutant showing dwarfism and early, continuous flowering along the vegetative axes. Microvine was initially proposed as a plant model for genetics. Here, we examined its suitability for characterizing grapevine vegetative and reproductive growth and development patterns and responses to elevated temperature. A series of experiments was performed in the greenhouse and in growth chambers under either standard (25/15°C day/night) or contrasting (from 22/12°C to 30/25°C) thermal conditions for several weeks. Under standard conditions, temporal patterns of leaf and berry growth were similar among several phytomers along the main axis, allowing temporal growth patterns to be estimated from the spatial distribution of organ size. These patterns were consistent between independent experiments under similar thermal and irradiance conditions. When plants were exposed to contrasting thermal conditions, the leaf emergence rate was linearly related to average daily temperature, enabling a thermal time-based model of development to be derived. Under cool conditions (22/12°C), the temporal evolution of biochemical parameters was similar to that typically reported for grapevine. However, exposing plants to a temperature increase of 8°C for 450°Cd revealed strong changes in thermal time-based development, 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 show the potential of Microvine for studying grapevine responses to climate change