Evaluation of viticultural practices to delay maturity in the disease resistant variety Solaris

Abstract

Global warming advances ripening of grapes to warmer months of the growing season, impacting fruit physiology and threatening wine typicity. Late pruning, early leaf removal or anti-transpirant application have been shown to be able to delay vine phenology and ripening depending on genotype and growing region. New disease resistant varieties represent a sustainable alternative to reduce pesticides in viticulture but are often unfortunately very precocious and their physiological responses to agronomic treatments have barley been addressed. In this ongoing study with the disease resistant cultivar Solaris several source-sink manipulation strategies are performed to test their capacity to delay maturity. Hedging and defoliation were compared against a control group in a randomized block design. Leaf surface area was decreased by 50 % 10 days after flowering and maintained throughout ripening. Berry weight, hexoses, organic acids (HPLC) were monitored weekly until harvest. Nitrogen (N-tester), Photosynthesis (LICOR 6400XT) and pruning weight were measured. Grapes were harvested, vinified and then analysed using the sensory discrimination triangle test. Low leaf surface decreased both berry weight and sugar accumulation from veraison till harvest; however, sensory analysis did not show significant differences in 2016. Malic acid accumulation was higher in control until the lag phase but reached similar levels at harvest. Photosynthesis confirmed the plant’s capacity to compensate for lost exposed leaf area. These preliminary results will be confirmed and further analysed in subsequent years on the Solaris variety taking into account reserves, reproductive organs (inflorescence initiation flowering and fruit set) and the perennial structures of the vine.