The effects of seed moisture content and regional storage temperature on the longevity of two onion cultivars

Onion seeds are short-lived species in storage. This study was designed to test two onion cultivars ('Texas Early Grano' (TEG) and Banka) seed storage under different temperatures derived from the monthly mean values in five different regions of Turkey over 28 months with 7, 8, 9, 10, 11, and 12% seed moisture content. Every four months, samples were removed and seed germination was tested. Longevity differences were compared by changes in P-50 (the time to germination reduced to 50%). The longest longevity and highest P-50 values were obtained in Central Anatolia and the Black Sea and the shortest longevity was observed in the southeastern region of Turkey. The highest P-50 values were 17.5 and 17.9 months in TEG, and 23.6 and 23.8 months in the 'Banka' cultivars. P-50 values declined to 11.7 months in TEG and 13.8 months in 'Banka' cultivars in the southeastern region, respectively. Overall, the best longevity was seen in seeds stored at 7% moisture content, and 'Banka' had longer P-50 values than those of the TEG cultivar. In any region, the best storage can be drying seeds to 7% and storing seeds in ambient conditions no longer than 4-6 months.