Influence of nectar sugar content on foraging activity of Apis mellifera L. in different crops and physico-chemical properties of its floral honeys and propolis
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Date
2022-04
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
The investigations entitled “Influence of nectar sugar content on foraging activity of Apis mellifera L. in different crops and physico-chemical properties of its floral honeys and propolis” were carried out at G.B. Pant University of Agriculture and Technology, Pantnagar during the year 2019-20 to 2020-21. A. mellifera bees showed significantly highest foraging intensity, foraging rate and foraging speed in all the plant species at 1300-1500 hours except in Brassica rapa var. toria where peak activity was observed at 1000-1200 hours. Foraging modes with maximum nectar and pollen foraging and composite foraging for both varied in different plant species viz. mustard (4th,5th, 7th SW); coriander (13th and 14th SW); berseem (18th-19th, 21th , 20th - 21st SW) and sunflower (25th; 25th ,21st - 24th SW), respectively. Among the three species of mustard, highest total sugar content (0.384±0.018 mg/flower) was recorded at 24 hours of flower opening in B. rapa var. yellow sarson, while minimum total sugar content was recorded just after opening of flowers (0 hours). Mean sugar concentration per flower was highest (33.34 per cent) in B. rapa var. toria, whereas least (27.26 per cent) in B. juncea. The total energy present per flower per day was highest in B. rapa var. yellow sarson with 0.37; 6.43; 8.63 and 4.58 J/flower/day at 0; 24; 48 and 72 hours respectively, and least in B. rapa var. toria with 0.25; 4.84; 3.88 and 2.75 J/flower/day at 0; 24; 48 and 72 hours. Furthermore, highest mean nectar sugar composition of glucose (51.33±0.41) was recorded in B. rapa var. toria, fructose in B. rapa var. yellow sarson (44.27±0.35) and highest sucrose concentration was found in B. juncea (0.605±0.047). Among the other eight bee forage plant species, berseem flowers were found to be richest floral nectar resource with highest total sugar content (0.672±0.009 mg/flower), total nectar sugar concentration (38 per cent), energy per flower per day (11.24 J at 72 hours) and carbohydrate composition with glucose (53.12±0.015), fructose (36.21±0.179) and sucrose concentration (4.29±0.006). In melissopalynological studies, a total of 64 pollen types belonging to different families were identified from 20 honey samples with 8 predominant, 3 secondary and 53 important minor and minor pollen types. In physico-chemical studies of 20 honey samples, 6 were recorded as extra light amber, 4 extra white, 3 amber, 4 white, 2 light amber and 1 was water white. Different physical properties like moisture content (litchi honey: 16.30±0.12 per cent), pH (coriander honey: 3.56±0.01), EC (multifloral honey: 0.412±0.015) and HMF content (mustard honey: 0.441±0.019) was lowest and were at par with quality parameters in different tested honeys. Whereas highest RI (1.583±0.008) was recorded in curry tree honey although highest TSS (82.9±0.06%), viscosity (0.128 ± 0.013), specific gravity (1.92 ± 0.19) and ash content (0.23±0.01%) was found in multifloral honey. Among the important minerals present in honey, highest amount of K and Fe was observed in litchi (482.31 and 18.93mg/kg), Na in jamun (203.15 mg/kg), Ca in curry tree (98.32 mg/kg), Mg in berseem (73.80mg/kg). In chemical properties of various honey, highest total sugar content in mustard (73.75 ± 1.16%), fructose in litchi (39.68±0.12 g/ 100g), glucose in multifloral (39.65 ± 0.37 g/ 100g) and lowest sucrose content was found in Eucalyptus (1.01 ± 0.16). The honey samples were compared using FTIR–ATR spectroscopy based on spectral differences, the characteristic bands of major monosaccharide absorption (glucose, fructose) and disaccharide (sucrose) absorption were present between 1400 and 900 cm-1. The physico-chemical properties of propolis from A. mellifera hive contained average moisture content (8.51 ± 0.04 per cent), average insoluble substance (42.06 ± 0.35 %) and soluble substance (56.36 ± 0.12 %), pH (4.18 ± 0.021), EC (1.67± 0.003 ms/cm), ash percentage (1.82 ±0.005 per cent), amount of wax (6.60 ± 0.17 per cent), total phenol content (19.02 ± 0.58 mg/ml), flavonoid content (65.23 ± 0.42 mg/ml) and protein content1.12 ± 0.002 mg/g).