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M. Sc. Dissertations

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20111
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Subject: Zoology × End date: 2011 × Start date: 2011 × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Studies on insect pollinators on onion (Allium cepa L.)
    (CCSHAU, 2011) Sunita Devi; Gulati, Rachna
    The studies on insect pollinators of onion (Allium cepa L.) revealed that a total of 25 insect species belonging to fourteen families of four orders were recorded from the umbels of onion at Hisar during March – April, 2010. Hymenopterans were the major floral visitors of onion umbels and were most abundant (60%) followed by Lepidoptera (20%) and Diptera (12%). Coleoptera were recorded as least abundant (8%) amongst the four families. All the four Apis species viz. A. dorsata, A. cerana, A. mellifera, A. florea were recorded as top workers on onion umbels as pollen and nectar gatherers. Data on abundance of bee pollinators revealed that irrespective of different day hours, significantly maximum numbers of Apis dorsata was recorded from onion umbels (5.24 bees/m2/5 min.) followed by A. mellifera (4.05 bees/m2/5 min.) and A. cerana (2.93 bees/m2/5 min.) and A. florea (1.79 bees/m2/5 min.). Irrespective different species, the mean population of bees was significantly more during 0800-1000 hours of the day (bees/m2/5 min.) followed by 1600-1800 h., 1400-1600 h and 0600-800 h (2.97 bees/m2/5 min.). Apis dorsata recorded maximum frequency of occurrence (39%) during blooming period followed by A. mellifera (31%), A. cerana (16%) and A. florea (14%). Among different bee species, A. dorsata initiated foraging on onion umbels little earlier (0630 h) than other bees in morning. Total foraging (activity) time was longest for A. dorsata (1170 h) with maximum abundance (5.24 bees/m2/5 min) suggested it to be an efficient pollinator of A. cepa umbels in the present investigation. Maximum and minimum temperature showed significantly positive correlation (r = 0.609 to 0.739) with bee species whereas evening relative humidity showed significant negative correlation (r = -0.644 to -0.736). The data on foraging speed i.e. time spent by different bee species on A. cepa umbels showed A. dorsata (3.33 seconds/ umbel) differed significantly from A. mellifera (2.96 seconds/ umbel), A. cerana (2.90 seconds/ umbel) and A. florea (2.65 seconds/ umbel).On the basis of abundance, time spent on umbels, umbels visited, loose pollen grains sticking to bee body and pollination index, A. dorsata was considered as the most efficient pollinator of onion seed crops followed by A. mellifera, A. cerana and A. florea under agro-ecological conditions of Hisar. The effect of different modes of pollination showed that seed set per umbel, seed weight, germination and seedling length were statistically comparable with each other in Open-pollination and Beepollination. The trend shows that bee strength of two and three frames was equally effective (statistically comparable) in seed setting and subsequent germination, seedling length, therefore, for 10 m × 10 m area, nucleus hive of two frame strength of A. mellifera population is sufficient for seed setting in onion seed crop.