Videira 'Syrah' sobre diferentes porta-enxertos em ciclo de inverno no sul de Minas Gerais

the objective of this work was to evaluate rootstock influence on agronomical, ecophysiological and qualitative characteristics of 'syrah' vines managed by double pruning. grapevines were grafted onto 'so4', '110 richter' and '1103 paulsen' rootstocks and trained in vertical shoot position, with no irrigation. ecophysiological characteristics, yield and composition of ripe grapes were evaluated in three crop seasons (2007, 2008 and 2010). rootstocks did not affect pre-dawn water potential, with values close to -0.2 mpa, indicating that there was no soil water deficit at the end of ripening (june). there was also no significant effect of rootstocks on yield. the rootstock '1103 paulsen' induced lower vegetative growth, lower photosynthetic rate and the best results for berry maturation for crop seasons with lower amount of rainfall. the rootstocks '110 richter' and 'so4' showed higher vigor under the meteorological conditions of 2010 and the greatest photosynthetic rates in the same period. meteorological conditions significantly affected technological and phenolic ripeness, with best results observed in drought years. the '1103 paulsen' rootstock provides better balance between vigor and yield, increasing grape quality.