Use of thiamine for controlling Alternaria alternata postharvest rot in Asian pear (Pyrus bretschneideri Rehd. cv. Zaosu)

The effects of thiamine (vitamin B1) against Alternaria rot caused by Alternaria alternata and its possible mechanism in harvested Asian pear fruit were investigated. Thiamine strongly inhibited spore germination and mycelial growth of A.similar to alternata in vitro. Thiamine at a concentration of 100 mm effectively inhibited the development of Alternaria rot, enhanced the activities of defence-related enzymes, such as phenylalanine ammonia-lyase (PAL), polyphenoloxidase (PPO) and peroxidase (POD), and increased the content of flavonoids, phenolics and lignin. Thiamine also affected reactive oxygen metabolism of the pear fruit by increasing its production and H2O2 content, and enhancing the activities of major detoxifying enzymes, such as superoxide dismutase (SOD). These findings suggest that the effects of thiamine on Alternaria rot in pear fruit may be associated with its direct fungitoxic property against the pathogens, and the elicitation of biochemical defence responses in the fruit.