Understanding the genetic determinism of phenological and quality traits in ‘Corvina’ grape variety for selection of improved genotypes

Abstract

Downy and powdery mildew are major issues in grapevine cultivation, requiring many phytosanitary treatments to ensure yield and quality. Climatic changes are also challenging grape cultivation in several areas, leading to anticipation of phenological events and increasing impact of temperature on grape quality. Beside disease resistance, adaptation of varieties to changing climate is thus an additional breeding target, which includes the selection of late ripening varieties that may escape the warmer summer conditions, while preserving distinctive performance and wine quality. With the aim to increase our understanding of the genetic determinism for phenological and quality traits, we have crossed the autochthonous cv. Corvina, typical of the Verona province area, to previously identified divergent varieties. Segregating cross populations of Corvina x Solaris and Cabernet-Sauvignon x Corvina including a high number of seedlings were developed, propagated and grown in field conditions for mapping of traits. High-density genetic maps based on SNPs obtained through hybridization to an Illumina Vitis18KSNP chip are produced. Field phenotyping includes the evaluation of the main phenological stages (budbreak, flowering, veraison and ripening) together with the assessment of some morphological and quality traits at harvest on all progenies with the final purpose of QTL mapping. Moreover, the introgression of resistance sources from cv Solaris is assessed in the relative cross. Response to Plasmopara viticola is investigated especially in selected resistant genotypes under field conditions or following inoculation of leaf discs and shows different degrees of resistance in some Corvina offsprings differing in the number of inherited Rpv loci. Based on resistance gene introgression as well as on phenotypic parameters, some selections are being propagated for a deeper characterization. New markers derived from the characterization of Corvina-crosses are expected to further assist future selections. Altogether, the described approaches will improve our understanding of the genetic control of phenology and berry quality traits, thus assisting breeding in this important local variety.