Water relations and quality changes throughout fruit development and shelf life of sweet cherry grown under regulated deficit irrigation

The performance of 'Prime Giant' sweet cherry trees under three different irrigation regimes was examined during two consecutive seasons, 2015-2016 and 2016-2017. The irrigation treatments evaluated were: (i) a control treatment (CTL) irrigated at 110% of crop evapotranspiration (ETcd) to maintain non-limiting soil water conditions, (ii) RDM a regulated deficit irrigation treatment which applied a mild water stress during preharvest (90% of ETcd.) and a medium stress during postharvest (65% of ETcd) and (iii) RDS a regulated deficit irrigation treatment which applied a severe water stress (55% of ETcd.) during postharvest. There were significant differences during postharvest in soil and plant water indicators such as soil matric potential, midday stem water potential and maximum daily branch shrinkage between CTL and regulated deficit irrigation treatments (RD). However, only midday stem water potential was able to distinguish between RDM and CTL during preharvest. Fruit quality parameters such as fruit size, color, soluble solids concentration (SSC) were periodically measured during fruit developing as well as fruit water potential and osmotic fruit water potential. In 2016, there were no differences in any parameter between treatments. However in 2017 both deficit treatments led to fruits with a higher SSC and darker color than CTL. There were no differences in fruit yield or number of fruits per tree among treatments in either year of the study. When fruit quality was assessed in 2016, the color of the pedicels of fruits from the deficit irrigation treatments were greener than those from CTL after 20 days of cold storage at 2 degrees C and 90% relative humidity (RH) but and after 5 days of shelf-life simulation (15 degrees C and 65% RH) the differences between treatments disappeared.