Image-based Appraisal of Woody Starch Reserves in Grapevine

Maintaining stable yield in a climate change scenario requires the implementation of adaptive strategies for vine and vineyard management. Knowing the level of starch stored in perennial vine organs may help to reduce the risk of environmental constraints. Therefore, the development of decision support tools is important to assist winegrowers. The aim of this work was to test the possibility of estimating the starch content in grapevine woody tissues using digital imaging analysis. A colorimetric index (CI) based on red (R), green (G), and blue (B) mean pixel values was proposed and compared with an existing spectrophotometric index (SI). Shoots of three grapevine cultivars were collected during the 2020 dormant season and forced to produce new rooted cuttings. From these cuttings, a total of 73 internodes were sampled and their woody sections stained with Lugol's iodine solution and CI and SI determined. In the three varieties, the CI well correlated with the SI (Spearman's test ranged from - 0.84 to - 0.93, p < 0.0001). The resulting CI-based model developed can accurately (R-2 = 0.84) predict the SI confirming it is a reliable method for the digital determination of woody reserves in grapevine, supporting management decisions in viticulture.