بررسي تأثير تاريخ كاشت و زمان برداشت روي عملكرد، اجزاي كمي و خصوصيات كيفي بذر منوژم هيبريد چغندرقند در منطقه فيروزكوه

Effect of planting and harvesting dates on monogerm sugar beet seed yield and its quantitative and qualitative trials in Firozkouh

In order to evaluate the effects of different planting and harvesting dates on qualitative and quantitative characteristics of monogerm sugar beet seed bearing plants, this study carried out in Sugar Beet Elite Seed Production Station of Firozkouh at 2003. The experiment was based on Randomized Completely Blocks Design (RCBD) with four replications and split-plots. Planting date factor with three levels (including 19 March, 16 April and 30 April) and harvesting date factor with four levels (including 15, 30, 45 and 60 days after 50% flowering) composed main and sub-plots, respectively. After harvest and tresh pure seed yield, distribution pattern of seeds based on different diameter and thickness and laboratory seed viability were measured. According to the results, planting date had a significant effect on probability level of 1% on 50% emergency, bolting and flowering date based on days after planting and received growth-degree days (GDD), so that later planting date brought about a decrease in days until reaching 50% emergency, bolting and flowering. The main effects of planting and harvesting date and their interaction had a significant effect on the probability level of 1% on crude seed yield. The highest crude seed yield (1164 kg/ha) was obtain with sowing seed-bearing plants in 19 March and harvesting them at 45 days after 50% flowering. Late planting date caused a significant decrease in loss rate due to seed polish, while late harvesting date led to decrease in undersize seed portion because of its significant effect on undersize seed portion. According to the results, the studied factors did not have a significant effect on standard (with the diameter of 3.5-4.5 mm) and oversize (over 4.5 mm) seed percent. On the other hand, late harvesting date significantly led to the increase in germination rate of seeds, whilst planting date did not affect this characteristic. Key words: Sugar beet seed, planting date, harvesting date, seed yield, seed growth, Firozkouh.