Effect of Sowing Dates and Day Hours on Nectar Production and Frequency of Honeybee Visits in Parental Lines of Sunflower Hybrid APSH-11¹

Abstract

A study was conducted using parental lines (CMS 7-1A and RHA 271R) of sunflower hybrid APSH 11 to know the effect of sowing dates and day hours on nectar production vis-a-vis frequency of honeybee visits on them. At peak of flowering period, volume of nectar, in florets of male and female lines, was measured at 0800, 1000, 1200, 1400 and 1600 h of the day using micropipettes (one lambda size) in the crops sown during mid-December, January and February. Frequency of honeybee visiting a capitulum during two minutes period, was recorded at the aforesaid five specified hours. Nectar production was higher in CMS 7-1A (0.81 µ1/5 florets) than RHA 271 R line (0.61 µl). Irrespective of dates of sowing, there was minimum nectar production at 08 h. Average nectar amount was highest in January sown crop (0.82 µl). Nectar production was higher in RHA 271R at 0800 h whereas in CMS 7-1A, nectar production was high during rest of the day. The frequency of honeybee visits was greatly influenced by temperature and relative humidity. The honeybee visits on male or female line were governed by date of sowing and floral rewards. The male line attracted more honeybees (4.71 and 7.46) than the female line (3.48 and 4.33 per 27 capitula during 1999-2000 and 2000-2001 respectively), in the December sowing. However, in the other two sowings, the female parent attracted more honeybees than the male parent. Thus, the study indicated that the female parental line produced more nectar and attracted more honeybees. The sowing dates greatly influenced the foraging preference of honeybees on male and female parental line.