| Abstract | Područje delte rijeke Neretve sa svojim klimatsko-zemljopisnim uvjetima, predstavlja
jedinstveno područje obzirom na gotovo monokulturne nasade unšijske mandarine
(Citrus unshiu Marc.). Zbog nedovoljne istraženosti paše, kao i odlika meda od unšijske
mandarine cilj je istraživanja bio utvrditi skupljačku aktivnost pčelinje zajednice te sastav
nektara i meda. Istraživanje je bilo provedeno tijekom trogodišnjeg razdoblja od 2014. do
2016. godine na području Opuzena. Na četiri sorte (‘Kawano Wase‘, ‘Okitsu’, ‘Chahara’ i
‘Zorica’) bilo je praćeno izlučivanje nektara i koncentracija šećera na osnovu čega je
utvrđen i njihov medonosni potencijal. Analiza sadržaja mednog mjehura i peludnog tereta
bila je provedena prema metodi Soehngen i Jay (1974). Melisopalinološkom je analizom
bio utvrđen peludni spektar sadržaja mednog mjehura, peludnog tereta i meda. Od
fizikalno-kemijskih parametara su bili analizirani udio vode, električna provodnost, pH
vrijednost i aktivnost dijastaze. Mikroekstrakcijom vršnih para na krutoj fazi (HS-SPME) i
ultrazvučnom ekstrakcijom (USE) pomoću organskih otapala bili su utvrđeni isparljivi
spojevi u nektaru, sadržaju mednog mjehura i medu. Prosječno veću količinu nektara
izlučile su sorte ‘Okitsu’ (23,40 µL) i ‘Kawano Wase‘ (22,79 µL) u odnosu na sorte
‘Chahara’ (21,60 µL) i ‘Zorica’ (20,01 µL). Kod sorti ‘Kawano Wase‘ (20,66%), ‘Okitsu’
(20,35%) i ‘Chahara’ (20,17%) bila je utvrđena prosječno veća koncentracija šećera u
odnosu na sortu ‘Zorica’ (18,43%). Medonosni se potencijal kretao u rasponu od 301 do
361,5 kg/ha. Od obrađenih 10 470 skupljačica nektarni je teret utvrđen kod 1 079, peludni
kod 1 476, dok je nektarni i peludni utvrđen kod 40. Prosječno veći broj skupljačica s
punim mednim mjehurom (404) i peludnim teretom (622) je bio ustanovljen u 8:00 u
odnosu na one prikupljene u 13:00 i 18:00. U 8:00 je bila utvrđena prosječno najveća
masa peludnog tereta (8,47 mg), no ona se nije statistički značajno razlikovala od one u
13:00 (8,44 mg), dok je ustanovljena masa u 18:00 (7,67 mg) bila statistički značajno
manja u odnosu na prethodna dva praćenja. Analizirajući masu sadržaja mednog mjehura
utvrđeno je da se prosječna masa kretala od 20,22 mg u 8:00 do 21,88 mg u 13:00,
međutim, ustanovljeno je da nije bilo statistički značajne razlike. Prosječna se masa
ukupnog peludnog tereta prikupljenog skupljačem kretala od 5,18 g do 30,92 g, a prema
botaničkom podrijetlu utvrđene su 22 biljne vrste, među kojima su najzastupljenije bile
naranča (Citrus sinensis), dvogodišnji dimak (Crepis biennis) i česmina (Quercus ilex). U
peludnom je spektru sadržaja mednih mjehura pelud unšijske mandarine ustanovljena u
21% uzoraka. Osim mandarine utvrđeno je još 17 biljnih vrsta. U peludnom je spektru
meda osim peludi mandarine (C. unshiu), od nektarnih biljnih vrsta učestalije je bila
zastupljena pelud od pastirske torbice (Capsella bursa pastoris), biljaka iz porodice
glavočika (Asteraceae Taraxacum form), vazdazelene krkavine (Rhamnus. alaternus) i
naranče (C. sinensis), a od nenektarnih biljnih vrsta crni jasen (Fraxinus ornus), česmina
(Q. ilex), hrast (Quercus spp.), klupčasta oštrica (Dactylis glomerata) i maslina (Olea
europea). Prosječni se udio vode u uzorcima meda kretao od 17,1% do 18,1%, električna
provodnost od 0,20 mS/cm do 0,27 mS/cm, pH vrijednost od 3,82 do 4,06 te aktivnost
dijastaze od 7,78 do 12,02 DN. Analizom isparljivih spojeva je utvrđeno da su u nektaru
najzastupljeniji spojevi bili: 1H-indol, metil-antranilat, linalool, α-terpineol, fenilacetonitril,
1,3-dihidro-2H-indol-2-on i kafein. Linalool, α-terpineol, 1,8-cineol, 1H-indol, metilantranilat,
cis-jasmon, kafein, 1,3-dihidro-2H-indol-2-on i fenilacetonitril su bili
najzastupljeniji spojevi u sadržaju mednih mjehura, a fenilacetaldehid, fenilacetonitril,
linalool, 1H-indol, metil-antranilat, kafein i 1,3-dihidro-2H-indol-2-on u medu. Od utvrđenih
spojeva, 1H-indol, zatim 1,3-dihidro-2H-indol-2-on te fenilacetonitril do sada nisu bili
pronađeni u medu od agruma. |
| Abstract (english) | The Neretva river valley with its climatic and geographical conditions, is a unique area due
to the almost monoculture plantations of Satsuma mandarin (Citrus unshiu Marc.). Due to
insufficient pasture research and quality of honey from Satsuma mandarin, objective of
this study was to determine the foraging activity of honey bee colonies and the
composition of nectar and honey.
The three-year research was conducted from 2014 to 2016 in the Neretva valley in the
area of Opuzen. The amount of nectar and sugar concentration was monitored on four
varieties of mandarins, ‘Kawano Wase‘, ‘Okitsu’, ‘Chahara’ and ‘Zorica’ by sampling 10
open flowers for each variety in a single measurement. Six measurements per day were
performed at intervals of two hours (8:00, 10:00, 12:00, 14:00, 16:00 and 18:00). In the
final year of research, nectar secretion was monitored on flowers in the opening phase
and in the phase of a fully open flower. Nectar sampling was carried out using glass
capillaries with a capacity of 75 µL according to Corbet (2003). Based on the collected
data, the honey potential of investigated varieties was determined. Monitoring of
honeybee visits to mandarin was conducted in April 2016, according to Abrol (2007).
Flower visit is monitored by counting bees in the studied varieties. Two trees were
selected in each variety. On each of the trees, three branches were marked with the
uniform number of flowers. Visits are monitored by counting bees three times a day, at
10:00, 14:00 and 18:00 for 5 minutes per each branch. Floristic observations were
performed at selected locations and plant species listed that bloom at the same time as
the Satsuma mandarin. Foraging activity is determined using honey bee colonies of
Carniolan bees (Apis mellifera carnica, Pollmann, 1879). Returning bees were collected
on the hive entrance for the content of honey sac and pollen loads study. The analysis
was performed according to the method of Soengen and Jay (1974). Sampling of pollen
loads was conducted using outdoor pollen collector set on the hive entrance. From the
physico-chemical analysis of the collected samples of honey, the water content, electrical
conductivity, pH and activity of diastase, as well as qualitative melisopalynological
analysis were conducted. Analysis of volatile compounds was performed using
microextraction of headspace on a solid phase (HS-SPME) and ultrasonic extraction with
organic solvents (USE) on samples of nectar, honey sac contents and honey.
Mean values of the nectar quantity were larger and not significantly different in cultivars
‘Okitsu’ (23.40 mL) and ‘Kawano Wase‘ (22.79 mL), compared to the other two studied
varieties. Also, a statistically significant difference was found between the other two
varieties, where the average higher amount of nectar is found in variety ‘Chahara’ (21.60
mL) compared to ‘Zorica’ (20.01 mL). The range of the specified parameter in all the years
ranged from minimally 5 to maximally 75 µL. The lowest concentration of sugar (18.43%)
was found in variety ‘Zorica’ that was significantly different from the nectar of other studied
varieties. The mean values of the studied parameter in ‘Okitsu’ (20.35%), ‘Kawano Wase‘
(20.66%) and ‘Chahara’ (20.17%) were not significantly different. The mean values of the
quantity of secreted nectar in closed flowers of all varieties ranged from 18.96 to 21.03 µL
in open flowers, and are significantly different. Based on the mean values of the sugar
concentration, higher concentration was determined in open (21.62%) compared to the
closed flowers (19.04%), taking into account all the studied varieties. The honey potential
of investigated varieties ranged from 301 kg to 361.5 kg of honey per hectare. There is no
exact data on cultivated areas according to different varieties in the Neretva valley. The
estimation that different Satsuma mandarin varieties cover 1 700 hectares suggests that it
was possible to produce from 511.7 tons to 614.5 tons of mandarin honey in the study
period. The highest mean number of bees visits was determined on variety ‘Kawano
Wase‘ (12.89), followed by ‘Okitsu’ (11.56) and ‘Chahara’ (11.11), while the lowest (10.00)
visit was on the variety of ‘Zorica’.
Floristic research has identified a total of 78 taxa (species, subspecies, and varieties).
Based on the data on the flowering source, from the determined plants, nine of them were
the source of nectar only, 45 of nectar and pollen, while 24 were visited by bees
exclusively for pollen. Foraging activity of bee colonies was determined in the pasture
based on the analysis of foragers at the hive entrance. In total, 10,470 foraging bees were
processed, of which 2595 came with the load to the hive. Nectar was found in 1079,
pollen in 1476, however nectar and pollen loads together were found only in 40 bees.
7875 foraging bees returned to hive without load. The highest number of foraging bees
with nectar (404) and pollen load (622) was determined at 8:00, while the number of bees
at 13:00 and 18:00 was significantly lower. The average weight of the honey sac ranged
from 20.22 mg at 8:00 to 21.88 at 13:00, and the range was from 0.70 mg to 58.60 mg.
However, comparing the resulting average values, there were no statistically significant
differences among investigated wights per times (hours). Average maximum weight of
pollen loads was found at 8:00 am (8.47 mg) and was not significantly different from the
values measured at 13:00 (8.44 mg). The mean weights of pollen loads collected at 18:00
(7.67 mg) were significantly lower in comparison to two previous samplings. The range of
pollen loads weight ranged from 0.50 mg to 45.90 mg. The mean total weight of pollen
collected in external pollen collectors during 2014 was 30.92 g in the morning and 8.78 g
in the afternoon measurements, and was significantly different. In 2015, the average
weight of collected pollen in the morning was 10.55 g and was not significantly different
from pollen collected in the afternoon (5.18 g). In 2016, the average weight was higher at
the site of the Buk-Vlaka (19.79 g) in relation to the location Ušće (12.89 g).
According to the botanical origin, collected pollen originated from 22 plant species, among
which the most common were orange (Citrus sinensis), rough hawksbeard (Crepis
biennis) and evergreen oak (Quercus ilex). In the pollen spectrum of honey sac content,
pollen of Satsuma mandarin was determined in 21% of samples, while 79% of the
samples did not contain pollen from Satsuma mandarin. Apart from the mandarin, pollen
from additional 17 plants was found. In pollen spectrum of honey samples besides
Satsuma mandarin pollen the most common pollen of nectariferous plants was from
shepards purse (Capsella bursa pastoris), plants of the Asteraceae family (Asteraceae
Taraxacum form), evergreen buckthorn (Rhamnus alaternus) and orange (C. sinensis),
and of non nectariferous plants pollen of manna ash (Fraxinus ornus), holm oak (Q. ilex),
oak (Quercus spp.), orchard grass (Dactylis glomerata) and olive (Olea europea).
The average values of the water content in the samples of Satsuma mandarin honey
ranged from 17.1% to 18.1%, the electrical conductivity from 0.20 mS/cm to 0.27 mS/cm,
pH values from 3.82 to 4.06 and diastase activity from 7.78 to 12.02 DN.
The main identified compounds in volatile peaks in nectar headspace were: linalool, αterpineol,
1H-indole, methyl anthranilate and phenylacetonitrile. Relevant extracts
contained 1H-indole, methyl anthranilate, 1,3-dihydro-2H-indol-2-on, and caffeine. The
main headspace compounds in the honey-sac were: linalool, α-terpineol, 1,8-cineole, 1Hindole,
methyl anthranilate and cis-jasmon. The specific compounds of the honey sac
extract (USE) were: caffeine, 1H-indole, 1,3-dihydro-2H-indol-2-on, methyl-anthranilate
and phenylacetonitrile. However, the composition of the headspace of honey was
significantly different in comparison to the representation of phenylacetaldehyde and
linalool derivatives that have arisen as a result of conditions in the hive and honey bee
activity which is an original contribution to the knowledge of the transport of volatile
compounds from the nectar over honey sac to honey. Extracts (USE) of honey contained
higher aliphatic compounds as the main component, that are not useful for determining
the botanical origin of honey as may be derived from the hive. Traceability of Satsuma
mandarin honey is determined through chemical markers: phenylacetaldehyde,
phenylacetonitrile, linalool and linalool derivatives, 1H-indole, 1,3-dihydro-2H-indol-2-on,
and caffeine. 1H-indole, 1,3-dihydro-2H-indol-2-on and phenylacetonitrile that were found
as typical compounds of Satsuma mandarin honey, and not found in other types of Citrus
(Citrus spp.) honey. |
