The intrinsic and extrinsic traits of citrus fruits change throughout their developmental process, and, therefore, to ensure the highest quality, fruit must be harvested at an appropriate stage of maturity. In a 2-year study, mandarin (Citrus reticulata Blanco) cultivars (Kinnow and Feutrell’s Early) grafted on rough lemon (C. jambheri Lush) rootstock were selected to analyze the effect of harvest time on their physicochemical characteristics and antioxidant potential in two consecutive growing seasons in the Multan region of South Pakistan, which has a subtropical climate. Fruits were harvested from commercial citrus groves at intervals of one month (from September to February). The results showed that different maturity stages/harvesting dates have a significant effect on the fruit quality and yield characteristics of mandarin cultivars. An increase in fruit weight, juice content, total soluble solids, ripening index, juice pH, and total sugar content was observed with the advancement of fruit maturity, while juice acidity, antioxidant capacity, total phenolic content, and vitamin C content had a decreasing trend towards fruit maturity. Overall, both cultivars showed similar profiles to the change in fruit quality traits during growth and development, but their amounts showed great variation. Based on the comprehensive consideration, Kinnow attained the maximum fruit quality and yield values from mid-January to February, whilst Feutrell’s Early attained the maximum values of these parameters from mid-December to mid-January, attributing to higher consumer acceptability. This study demonstrated that harvest time plays a key role in controlling the fruit quality and yield of mandarin cultivars. In practice, harvest time should be highly considered for the fresh and processed citrus market and industry.

Fruit orchards are frequently irrigated with brackish water. Irrigation with poor quality water is also a major cause of salt accumulation in soil. An excess of salts results in stunted growth, poor yield, inferior quality and low nutritional properties. Melatonin is a low molecular weight protein that shows multifunctional, regulatory and pleiotropic behavior in the plant kingdom. Recently, its discovery brought a great revolution in sustainable fruit production under salinity-induced environments. Melatonin contributed to enhanced tolerance in Zizyphus fruit species by improving the plant defense system’s potential to cope with the adverse effects of salinity. The supplemental application of melatonin has improved the generation of antioxidant assays and osmolytes involved in the scavenging of toxic ROS. The tolerance level of the germplasm is chiefly based on the activation of the defense system against the adverse effects of salinity. The current study explored the contribution of melatonin against salinity stress and provides information regarding which biochemical mechanism can be effective and utilized for the development of salt-tolerant germplasm in Zizyphus.

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