study of sugar beet (beta vulgaris l.) monogerm hybrids seed quality changes during fruit development and maturation

background and objectives: the most important determining factor in sugar beet root yield is seed quality. seeds with germination percentage are lower; the germination is slow and non-uniform, will produce plants that initial growth is slow. according to various studies indicate that harvest time is an important factor influencing the quality of sugar beet seed. in the early harvest of sugar beet seed plants, germination and seed vigor is low and late harvest also led to an increase in losses due to seed loss. however, in the specified number of days after the first flowering, germination percentage in various cultivars may be significantly different. like other crops, harvest timing is essential for achieving high quality seeds of sugar beet. therefore, this study was to evaluate changes in seed quality during development and ripening in cytoplasmic male sterile (cms) lines of sugar beet and determine a stage of development where maximum seed quality was done.materials and methods: this study was conducted in ardabil agricultural research station (alarough) in 2012 and based on a completely randomized block design. the experimental treatments were five promising diploid cytoplasmic male sterile (cms) lines (7112×sb36, sb37×28874, 7112×436, 419×sb36 and 261×231) of sugar beet. each plot consists of eight lines planting and hybrid varieties were sown in strips in female: male ratio was 6: 2. to evaluate changes in the quality of sugar beet seed, 5 plants in each plot in the flowering stage were symptomatic and from 50 percent flowering until the end of the growing period, growing seeds were harvested at intervals of 7-5 days. after harvesting and calculate fresh and dry weight of fruits, was carried out germination test, accelerated aging and electrical conductivity.results: results indicated that there were significant differences among different female parent in respect to maximum seed dry weight. needed degree days (gdd) to attain the maximum seed weight after 50% flowering was 507.5, 563.3, 459.3, 499.7 and 492.7 for 7112×sb36, sb37×28874, 7112×436, 419× sb36 and 261× 231 lines, respectively. at the corresponding dates, the seed moisture content was 52.3, 40.8, 52.6, 44.4 and 42.5%, respectively. the maximum seed quality (maximum germination) for sb37×28874 and 261×231 occurred before, but for 7112×sb36, 7112×436 and 419×sb36 after the physiological maturity.conclusion: to achieve high quality seeds in sugar beet, harvesting must be done at 480-580 degree-days after 50% flowering. at this time, the moisture content of fruits was in the range of 40-52% and the fruits were red-colored.