Root system architecture plasticity in Vitis plants under progressive soil drying

Abstract

Prolonged water deficits driven by climate change are increasingly affecting the viticultural sector highlighting the need for drought-tolerant rootstocks. Rootstocks contribute to grapevine responses to water stress throughout the entire lifespan of the vineyard and represent a sustainable strategy to enhance cultivar adaptation while reducing reliance on additional agronomic practices. However, the availability of drought-tolerant rootstocks is limited, as only a few genotypes are widely used, and their genetic base is narrow. Exploiting the genetic variability within the genus Vitis could enable the selection of new drought-tolerant rootstocks. As the below-ground part of the plant, rootstocks and their root system architecture (RSA) play a central role in soil water foraging and regulating plant responses under water deficit. In particular, RSAplasticity to water-limiting conditions is considered a key trait for drought-adaptation. This study aimed to investigate the RSAof a large set of Vitis genotypes under progressive soil drying through a smartphone-based phenotyping approach. Plants were grown in rhizotrons under controlled conditions and water use and physiological responses at both aerial and root levels were monitored throughout the soil-drying cycle. Four groups exhibiting contrasting physiological responses to soil drying and distinct RSApatterns were identified. Number of lateral roots emerged as the most influential trait in group differentiation indicating its importance in RSAplasticity under decreasing soil water availability. Among the identified groups, Group 1 exhibited the most promising behaviour for drought prone environments combining reduced water consumption through tight stomatal regulation, with sustained growth under water deficit, and a well-developed root system. The adopted smartphone-based image acquisition system proved suitable for high-throughput phenotyping, allowing rapid and reliable root traits determination. These findings reinforce the central role of RSAplasticity in grapevine adaptation to soil drying and support future rootstocks breeding programmes that exploit the largely unexplored genetic variability within Vitis.