Effects of girdling, nitrogen, zinc and auxin foliar spray applications on mandarin fruit “Nova” quality characteristics

Four treatments were applied in young mandarin trees, variety “Nova”, in order to assess their effects on fruit quality. The treatments comprised an untreated control, applications of zinc plus nitrogen, post-bloom auxin application and pre-bloom girdling. At harvest the physical quality characteristics of the fruits were measured (weight, diameter, length, peel thickness, juice content, peel color) along with juice quality characteristics (pH, total soluble solids, titratable acidity, phenolic compound content, antioxidant capacity and carbohydrates). Zinc and nitrogen as well as auxin application resulted in the heaviest fruits among treatments, while juice content was the lowest under control treatment. None of the treatments had a significant effect on maturity index of the fruit. Girdling slightly increased the antioxidant capacity of the juice while decreased peel color index. Sucrose, glucose and fructose concentration was highest in fruits from girdled scaffolds, resulting in the highest sweetness index, while the lowest was observed under zinc and nitrogen application. It seems that all treatments enhanced fruit quality, but girdling had a distinctive and significant effect on most of the fruit quality characteristics assessed.