Leaf traits: a micro-morphological characterization of grapevine (Vitis sp. pl.) genotypes

The analysis of leaf structure provides important elements to ecological studies and useful information to evaluate the susceptibility or tolerance to biotic and abiotic stress. A number of histological studies have been carried out on grapevine cultivars, relating leaf traits to resistance against fungal pathogens (1), water stress response (2) and other environmental conditions (3). In the present work the leaves of 17 different grapevine genotypes, Vitis Berlandieri, Vitis vinifera ssp. sylvestris and cultivars of Vitis vinifera ssp. sativa from six different Italian Regions, have been observed at the Scanning Electron Microscope (SEM). The leaves of all genotypes showed stomata only on the abaxial surface and scattered in the epidermis, but with a great variability, in terms of stomatal density and size, occurring among species and cultivars: mean stomata density in fact ranged between 100 and 200 stomata/mm2. High values of stomata density (more of 200 stomata/mm2) were recorded in Nero d’Avola and V. Berlandieri. The lowest values occurred in wild grapevine and in Sangiovese but, concerning the size of stomata, these last genotypes showed significantly larger and wider stomata when compared to the others. Stomata density appears to be a very variable parameter, related to genotype (4), but also to many environmental conditions, i.e. water stress and light irradiance (5) and CO2 concentration (6). Furthermore, raised and sunken stomata were visible in the same leaf with different ratios. In Vitis Berlandieri more than 99% of the stomata was protruding from the surface of the epidermis while Nero d’Avola exhibited about 89% of sunken stomata. Density, position and types of trichomes differently characterized the leaves of studied Vitis accessions; prostrate and erect hairs were mainly observed on abaxial side but in some genotypes they were observed also on upper epidermis. Leaf hairs are morphological characters that are taken in consideration as ampelographic descriptors of Vitis species and cultivars but they play also an important role in pathogen resistance (7). In this study the analysis of leaf traits allowed to obtain a micro-morphological characterization of grapevine genotypes; some characters may be related with plant resistance to stress. References 1) Boso S., Alonso–Villaverde V., Santiago J.L., et al. (2010). Macro– and microscopic leaf characteristics of six grapevine genotypes (Vitis spp.) with different susceptibilities to grapevine downy mildew. Vitis, 49: 43-50. 2) Winkel T., Rambal S. (1993). Influence of water stress on grapevine growing in the field, from leaf to whole plant response. Aust J Plant Physiol, 20: 143–157. 3) Rogiers S.Y., Hardie W.J., Smith J.P. (2011). Stomatal density of grapevine leaves (Vitis vinifera L.) responds to soil temperature and atmospheric carbon dioxide. Aust J Grape Wine R, 17:147-152. 4) Boso S., Gago P., Alonso–Villaverde V.,et al. (2011). Variability at the electron microscopic level in leaves of members of the genus Vitis. Sci Hort, 128: 228-238. 5) Palliotti A., Cartechini A., Ferranti F. (2000). Morpho–anatomical and physiological characteristics of primary and lateral shoot leaves of Cabernet Franc and Trebbiano toscano grapevines under two irradiance regimes. Am J Enol Viticult, 51: 122–130. 6) Moutinho-Pereira J.M., Gonçalves B., Bacelar E.A.,et al. (2009). Effects of elevated CO2 on grapevine (Vitis vinifera L.): physiological and yield attributes. Vitis, 48:159–165. 7) Levin D.A. (1973). The role of trichomes in plant defence. Q Rev Biol, 48: 3-15.