The hybrid Richter-110 (Vitis berlandieri x Vitis rupestris) (R-110) has the reputation of being a genotype strongly adapted to drought. A study was performed with plants of R-110 subjected to water withholding followed by re-watering. The goal was to analyze how stomatal conductance (g(s)) is regulated with respect to different physiological variables under water stress and recovery, as well as how water stress affects adjustments of water use efficiency (WUE) at the leaf level. Water stress induced a substantial stomatal closure and an increase in WUE, which persisted many days after re-watering. The g(s) during water stress was mainly related to the content of ABA in the xylem and partly related to plant hydraulic conductivity but not to leaf water potential. By contrast, low g(s) during re-watering did not correlate with ABA contents and was only related to a sustained decreased hydraulic conductivity. In addition to a complex physiological regulation of stomatal closure, g(s) and rate of transpiration (E) were strongly affected by leaf-to-air vapor pressure deficit (VPD) in a way dependent of the treatment. Interestingly, E increased with increasing VPD in control plants, but decreased with increasing VPD in severely stressed plants. All together, the fine stomatal regulation in R-110 resulted in very high WUE at the leaf level. This genotype is revealed to be very interesting for further studies on the physiological mechanisms leading to regulation of stomatal responsiveness and WUE in response to drought.

The effects of viruses on grape production and must quality are not fully understood. In this study, the evaluation of the impact of different virus infections on performance of the main autochthonous grapevine varieties of Mallorca (Callet, Manto Negro and Moll) was pursued. Therefore, a large number of vines were observed in field conditions over 4 years and tested by enzyme‐linked immunosorbent assay for viruses listed by the international certification programmes. In each variety, some specific virus infections resulted to be more effective than the others in inducing losses in production. In Callet, yield (Y) reduction was over 20% in plants infected by Grapevine fanleaf virus (GFLV). In Moll, plants subject to more than one infection showed over 40% Y decrease. In Manto Negro, the most surprising results were obtained, because plants showed almost 40% Y reduction because of Grapevine leafroll‐associated virus‐1 (GLRaV‐1) infection. In addition, virus infections were linked to some must quality parameter increase in Manto Negro and Moll, but in the majority of cases it was an indirect effect, because the decrease in production parameters played a predominant role by producing an important concentration effect. However, in Manto Negro, anthocyanin content decrease was directly related to GFLV infection.