293 Improving the Postharvest Characteristics of Table Grape by Preharvest Application of Polyamines S.H. Mirdehghan a , S. Rahimi and M. Esmaeilizadeh Department of Horticultural Sciences Faculty of Agriculture University of Rafsanjan Vali-e-Asr Iran Keywords: putrescine, spermidin, microbial activity, pigments Abstract Although table grape is a non-climacteric fruit with low physiological activity, it is however prone to weight loss, softening and fungal infection during postharvest period. The whole vine especially fruits were sprayed with putrescine (put; 0, 1, 2 mM), spermidine (spd; 0, 1, 2 mM) at 40 and 20 days before harvest. Different fruit characteristics were analyzed after harvest and remaining fruits were stored at 1.5±1°C and 90±5% RH for 25 and 55 days. Different concentrations of polyamines significantly increased firmness of grapes at harvest. Firmness was also retained and decreased weight loss of fruit during storage. Table grape storability could be extended by put and spd treatments due to their significant effect on delaying the softening, water loss, fungal infection and senescence. INTRODUCTION Table grape (Vitis vinifera L.) is one of the most important horticultural crops in Iran and all commercial cultivars in Iran belong to this species. Although this fruit is classified as non-climacteric (Mullins et al., 1992), it has short shelf-life after harvest due to loss of firmness, increased fungal decay and weight loss. The most effective ways to control losses of this crop is to use sulfur dioxide but this chemical is harmful to humans and also to the environment. Polyamines are groups of natural compounds with aliphatic nitrogen structure that play important roles in many cellular processes such as flowering, fruit development, fruit ripening and senescence (Evans and Malmberg, 1989; Bouchereau et al., 1999). Exogenous application of polyamines has shown beneficial effects such as maintenance of fruit firmness, delayed color changes, reduced mechanical damage and increased shelf-life for climacteric and non-climacteric fruits (Serrano et al., 1996; Martinez-Romero et al., 2002). Zokaee-Khosroshahi et al. (2007) showed that storage life of perishable fruits like strawberry was significantly increased by putrescine due to its decreasing the ethylene production thus preventing softening. Also putrescine- treated fruit had less fungal infection than untreated ones and maintained the fruits’ very good appearance. Similar results were obtained in the use of putrescine on table grape ‘Sefide bidane’ and decay of berry was decreased in putrescine-treated (0, 1 and 2 mM) compared with the control (Asghari et al., 2010). Therefore, improving the quality of table grape by preharvest foliar spraying of polyamines was studied. MATERIALS AND METHODS This experiment was carried out in a commercial grape orchard where the trees were spaced 2.5 and 2.5 m between and along the rows. Entire trees, including fruits and leaves were sprayed with putrescine (1 and 2 mM) and spermidine (1 and 2 mM) at two stages that is, at 20 and 40 days before harvest. Foliar spraying with distilled water in these stages served as control. Fruits were picked at commercial maturity and transported to the laboratory immediately. Fruit quality at harvest was analyzed and berries were then a mirdehghan@vru.ac.ir, shmirdehghan@yahoo.com Proc. 7 th International Postharvest Symposium Eds.: H. Abdullah and M.N. Latifah Acta Hort. 1012, ISHS 2013