Study on Quantitative and Qualitative Characters of Onion Cultivars and Determination of the Relation Between some Characters and Storability

In order to recognize and select Iranian onion cultivars with the best quantitative and qualitative characters such as yield, neck thickness, size, form, number of scales, storability, dry matter, total soluble solide, firmness and determine the relation of some characters on storability, this experiment was conducted at Karaj in 1999-2000. Field experiment was carried out based on Randomize Complete Block Design with four replications and five treatments Ghermez Azarshahr, Sefide Kashan, Sefide Qhom, Tarom Zanjan and Dorche Isfehan onion cultivars. For determination of the storage ability of Onion cultivars, a study was carried out in a factorial experiment based on completely randomized design with three replications in common storage conditions. Factors were cultivars with five levels and dates with eight levels. In a period of four months at 15 days interval, (8 distinct dates) losses were measured according to percentage of weight loss, sprouting and rotting. The rate of changes of some traits such as total soluble solids (T.S.S), dry matter (Dm), bulb firmness were also determined during storage. Results showed that in field experiment, the highest and lowest yields were obtained from Sefide Qum cultivar (60.82 tha-1) and Dorche Isfehan (32.03 tha-1) respectively. Sefide Qum cultivar had the lowest percentages of weight loss, sprouting and rotting during storage (15.33% and 11.72% respectively), which were not significantly different from those of Germez Azarshahr and Dorche Isfehan. Tarom zanjan cultivar had the highest weight loss, and Sefid Kashan had the highest bulb sprouting and rotting during storage period (23.06% and 55.46%, respectively). In storage period, some qualitative characters such as dry matter and total soluble solids increased slightly, but bulb firmness decreased. Sefid Qum cultivar had the highest total soluble solids, dry matter and bulb firmness (9.81%, 11.8%, 39.19 N, respectively), and Tarom Zanjan the lowest (8.37%, 9.29%, 34.3 N, respectively). A highly significant positive correlation (r =0.84) and linear regression equation (y = -2.472 + 1.424x) was found between total soluble solids and dry matter of bulbs. During storage, a significant negative correlation of (r = -0.592) and linear regression equation (y=101.515-1.863x) was found between bulb firmness and sprouting and rotting.