Non-destructive simple model to estimate the leaf area through midvein in cultivars of Vitis vinifera

Abstract Mathematical models are indirect and non-destructive methods for estimating the leaf area (LA), an important parameter associated with canopy vigor in Vitis viniferavineyards. This work aims to adjust and test mathematical models for estimating LA using the midvein length of the Vitis vinifera cultivars conducted in horizontal and vertical training systems in the Serra Gaúcha region, Brazil. Leaves were collected in ‘Chardonnay’, ‘Cabernet Sauvignon’ vineyards conducted in trellis and lyre training systems, and in ‘Merlot’ vineyards conducted in trellis and espalier systems. Models were tested for establishing the correlations among the parameters LA and midvein length, considering the cultivar/training system and the general data set. For validation, linear regression between the observed and estimated LA was defined. The relationship between the midvein length and LA was defined by non-linear potential equations (R2aj 0.95-0.98). The performances of the specific and general models were similar regardless of the cultivar/training system. The adjusted models showed excellent results in the validation step (correlation 0.95-0.98; Wilmott index >0.97 and confidence index>0.92). It is possible to estimate the LA of Vitis vinifera Chardonnay, Cabernet Sauvignon, and Merlot cultivars using a simple non-destructive model that employs one single measurement of the leaf blade, to optimize the vegetative canopy quantification in vineyards.摘要 数学模型是估算叶面积（Leaf Area, LA）的间接无损方法，而叶面积是酿酒葡萄（Vitis vinifera）葡萄园冠层活力相关的重要参数。本研究旨在针对巴西南塞拉地区（Serra Gaúcha）采用水平与垂直整形方式的酿酒葡萄品种，通过测量其叶中脉长度来校正并测试叶面积估算数学模型。研究采集了采用棚架（trellis）与竖琴架（lyre）整形方式的霞多丽（Chardonnay）、赤霞珠（Cabernet Sauvignon）葡萄园，以及采用棚架与篱架（espalier）整形方式的梅洛（Merlot）葡萄园的叶片。本研究分别针对品种与整形方式组合以及整体数据集，构建了叶面积与叶中脉长度的相关性模型。验证环节采用观测叶面积与估算叶面积间的线性回归分析。叶中脉长度与叶面积的关系通过非线性势函数方程确定，校正决定系数（adjusted R-squared, R²aj）为0.95~0.98。无论品种与整形方式差异如何，专用模型与通用模型的表现均无显著差异。校正后的模型在验证阶段表现优异：相关系数为0.95~0.98，威尔莫特指数（Wilmott index）大于0.97，置信指数大于0.92。仅需单次测量叶片叶中脉长度，即可通过本研究提出的简易无损模型估算酿酒葡萄霞多丽、赤霞珠与梅洛品种的叶面积，从而优化葡萄园冠层营养生长的量化工作。