Abstract Low fruit set and quality are the most important problems in temperate fruit trees, especially in pear after harvest. These effects can be alleviated by some chemical compounds such as polyamines and self-incompatibility control substances (SICS). The treatments—chemical compounds putrescine (Put; 0.1 and 0.25 mM), spermine (Spm; 0.05 and 0.25 mM), and spermidine (Spd; 0.05 and 0.25 mM) as well as SICS (1 and 2 mg/L)—were applied during two years. The results showed that Spd (0.05 mM), SICS (2 mg/L), and Put (0.25 mM) resulted in a significant increase in June fruit set percentage. Final fruit set was enhanced by use of SICS (1, 2 mg/L). The highest index of maturity was observed in Put (0.25 mM), followed by SICS (1 mg/L) and Spd (0.05 mM). Spd at 0.25 mM gave higher values in total sugar, antioxidant, anthocyanin, and phenol in comparison to control. SICS at 1 and 2 mg/L gave the greatest values in phenol and total sugar contents, respectively.

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