Effects of exogenous growth regulators on agrobiological, technological and physiological characteristics of an interspecific grapevine cultivar

ABSTRACT The use of interspecific grapevine cultivars offers new perspectives for sustainable viticulture. Although the application of exogenous plant hormones has become widespread in recent years, data regarding the response of interspecific grapevine cultivars to treatments with biostimulants are scarce. The aim of the study was to evaluate the effect of different doses of gibberellic acid (GA3) (25, 50 and 100 mg L−1), applied by spraying the inflorescences in the late flowering phenophase, and of the complex product Cropmax® (1.0, 2.5 and 5.0 mL L−1) applied by spraying the leaves in three different phenophases, on the phenology, fertility, physiological characteristics, grape yield and quality of the interspecific table grape cultivar Moldova (Guzal kara × Seyve-Villard 12-375), growing in temperate climate conditions (N-E Romania). The application of GA3 at 50 mg L−1 increased the plant productivity (36%), promoted fruit growth and rachis elongation, improved the percentage of the marketable yield (by 5.5%), balanced the sugar/acidity ratio, but affected the synthesis of phenolic compounds. Foliar application of Cropmax® at 2.5 mL L−1 significantly improved the berry diameter, and sugar and anthocyanin accumulation, but grape acidity remained high. All treatments allowed the normal development of plant phenophases and grape maturation, but GA3 application slightly extended the number of days of the annual biological cycle of the Moldova hybrid cultivar (up to 5.5 days), probably due to a temporary variation in the physiological parameters (except for stomatal conductance), as determined in mature leaves after the application of the exogenous growth regulator.