STUDIES ON THE POLLINATOR FAUNA OF ONION (Allium cepa L.)
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Date
2022-01-26
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University of Agricultural Sciences GKVK, Bangalore
Abstract
The study was carried at the Departments of Apiculture and Horticulture, UAS, GKVK, Bangalore during January-April, 2022. Onion (var. Arka Kalyan) plants started flowering during February, which was 42-52 days after bulb sowing. The peak flowering was observed in March. The inflorescence is umbellate-cyme. The umbel consisted of 346±141.5 small flowers, which were dull or creamy-white. The life span of the flower was about 4 days. The production of nectar was relatively highest in the morning 06:00-08:00hrs. (12.26±1.76μl) and it gradually decreased towards evening 16:00-18:00hrs. (0.76±0.08μl). Totally, 57 insect species visited the umbels, among them, 28 species belonged to the order Hymenoptera, nine species to order Diptera, eight species each belonged to orders Hemiptera and Lepidoptera, two species to order Coleoptera, one species each belonged to the orders Mantodea and Anisoptera.
Among all the insect floral visitors, only seven Hymenopteran species foraged more frequently, they played a major role in pollination. The highest Shannon-Wiener diversity index was observed during 06:00-10:00hrs. in both the initial and peak blooming periods. Berger-Parker dominance index was higher in peak blooming period. A. dorsata was the most pre-dominant species, followed by A. florea, A. mellifera, T. iridipennis and A. cerana. Overall maximum time spent and highest flower visits was recorded during 08:00-10:00hrs. and 06:00-08:00hrs., respectively. Significantly higher quantitative and qualitative parameters of seed yield were recorded in the seeds obtained from open pollinated flowers (574.39kg/ha.), followed by plants enclosed with A. mellifera (519.69kg/ha.) and A. cerana (451.31kg/ha.) colony, as compared to other modes of pollination.