Variability of the stomata among 'Albariño' (Vitis vinifera L.) clones and its relationship with susceptibility to downy mildew

Abstract

Introduction: In grapevines the stomata are located on the abaxial epidermis of the leaves, arranged in no specific order. As in other plants, they regulate the communication between the internal tissues and the external atmosphere, playing a critical role in both photosynthesis and transpiration processes. Moreover, stomata are the main entrance for pathogens such as Plasmopara viticola (Berk & Curt.) Berl. & de Toni, the causal agent of downy mildew, one of the most widespread fungal diseases of grapevines. Due to this and the fact that downy mildew causes large losses in yield and quality of grapes, there is a great interest to determine the causes of the different degree of susceptibility to this pathogen. Some authors have searched for anatomical features that might be related to the penetration and development of P. viticola in the mesophyll of grapevine leaves, such as the density of leaf hairs (KORTEKAMP and ZYPRIAN, 1999) or the ultrastructure of stomata (JURGES et al. 2009). Other authors have examined the differences concerning the number of stomata in different grapevine cultivars (DURING 1980, PALLIOTTI et al. 2000, BEN SALEM-FNAYOU et al. 2005), but none had evaluated the differences for this aspect between clones of the same cultivar. Recently some authors have found a strong correlation between the number and size of stomata and the susceptibility to downy mildew (LU et al. 2010). The aim of this work is to determine whether different clones of 'Albarino' differ in terms of their number and size of stomata and its possible relation with the different susceptibility to P. viticola of these same clones.