M. Rezaee - Department of Agricultural Mechanization, Faculty of Agriculture, Science and Research Branch, Islamic Azad University, Tehran, Islamic Republic of Iran.
M. Almasi - Department of Agricultural Mechanization, Faculty of Agriculture, Science and Research Branch, Islamic Azad University, Tehran, Islamic Republic of Iran.
A. Majdabadi Farahani - Department of Agriculture, Agricultural and Medical Nuclear Research Center, Karaj, Islamic Republic of Iran.
S. Minaei - Department of Agricultural Machinery, College of Agriculture, Tarbiat Modares University, Tehran, Islamic Republic of Iran.
M. Khodadadi - Department of Onion and Potato Research. Seed and Plant Institute, Karaj, Islamic Republic of Iran.

Storage of potatoes is very important because fresh potatoes are available only for a few months in a year. Thus, any treatment such as irradiation that controls sprout growth and extends shelf life of potatoes could be beneficial. In this study, potato sprout inhibition and tuber quality after treatment with various levels of Gamma Irradiation (۰, ۵۰, ۱۰۰ and ۱۵۰ Gy) on different dates (۱۰, ۳۰ and ۵۰ days after harvest) were studied during prolonged storage at ۸ and ۱۶°C using tubers of Agria variety. A factorial experiment based on a randomized split plot design with three replications was carried out. There was minimum sprout development (۴.۸۳±۰.۰۱ g/۳kg tuber) in tubers from early irradiation date (۱۰ days after harvest). This study indicated that early irradiation and higher irradiation levels significantly decreased sprouting, percent weight loss and specific gravity of tubers. The loss of ascorbic acid and the contents of reducing and non-reducing sugars significantly increased by delay in irradiation whereas the content of sugars and ascorbic acid level decreased by irradiation. The loss of firmness became clearer during five months storage in non-irradiated tubers. Higher storage temperature (۱۶°C) caused greater loss of ascorbic acid (۲۰.۳۴%). In other words, tubers stored at ۱۶°C showed greater metabolic changes as indicated by sprouting, weight loss, and changes in sugars and ascorbic acid contents. The ۵۰ Gy irradiation treatment on the ۱۰th day after harvest resulted in complete sprout inhibition of tubers at ۸°C storage and ۱۵۰ Gy dose while inhibiting sprouting at ۱۶°C, caused greater loss of ascorbic acid. Tubers irradiated with later after harvest were subject to greater loss of ascorbic acid in response to higher doses of irradiation and higher storage temperature. Consequently, to reduce undesirable changes in Agria potato tubers, delay in irradiation and storage at high temperature are not recommended.

Potato, storage, Different Dates, γ-Irradiation, Sprouting