Impact of the introduction of
stingless bee colonies (Scaptotrigona aff. postica) on the
productivity of acai (Euterpe
oleracea)
Impacto da
introdução de colônias de abelhas sem ferrão (Scaptotrigona aff. postica) na produtividade de açaí (Euterpe
oleracea)
Impacto de la introducción de colonias de
abejas sin aguijón (Scaptotrigona aff. postica) en la productividad del açaí
(Euterpe oleracea)
Nilton Akio Muto
1; Renan Oliveira de Sousa Leite2; Daniel Santiago Pereira3; Hervé Louis Ghislain Rogez4; Giorgio Cristino Venturieri5
1Biomedicine
Doctor; Professor, Federal University of Pará, Center for
Valorization of Amazonian Bioactive Compounds; Belém, Pará, Brazil. E-mail: niltonmuto@ufpa.br; 2Biotechnologist; Master in Agro
Environmental Biotechnology - Federal University of Pará/Center
for Valorization of Amazonian Bioactive Compounds; Belem, Pará, Brazil. E-mail: renan_leite92@outlook.com; 3Agriculture and Livestock technician,
Agronomist, Doctor of Animal Sciences; Researcher in Sustainable Systems:
Beekeeping - Embrapa Eastern Amazon; Belem, Pará, Brazil. E-mail: daniel.pereira@embrapa.br; 4Agroindustrial Chemical
Engineer, PhD in Agricutural Sciences and Biological Engineering; Professor -
Federal University of Pará/Center for Valorization of Amazonian
Bioactive Compounds; Belem, Pará, Brazil. E-mail: herverogez@gmail.com; 5Agronomist, PhD in Ecology;
Pollination Ecology, Meliponiculture and Beekeeping, NATIVO Company; Brisbane, Queensland, Australia. E-mail: giorgio@venturieri.com
Recebido:
12/04/2020; Aprovado: 26/06/2020
Abstract: The acai palm is a typical palm tree of the
Amazonian estuary, especially important in the diet and extractive agriculture
economy of the Eastern Amazonia. Its fruit productivity is highly dependent on
cross-pollination. Meliponiculture has greatly advanced during the last
decades, however, the use of meliponines for the pollination of tropical fruit
trees is scarse. In this work, in an irrigated crop of Euterpe oleracea, the fruit yield was evaluated after the
introduction of colonies of Scaptotrigona
aff. postica (Latreille, 1807). Three
gradients, 0-50, 65-115 and 130-180 meters, was used as a methodology to
evaluate the productivity increase, from the central point where 30 colonies
were installed. The productivity rate was evaluated by fruit weight per bunch,
number of fruits per rachilla, average fruit diameter and weight of one hundred
sample fruits. A significant increase in the productivity could be observed,
reaching 2.5 times more, depending on the distance of the plant to the colonies
of bees. The highest productivity interval was the closest, from 0-50 meters.
Key words: Meliponiculture; Pollination; Acai
Resumo: O açaí é uma palmeira típica do estuário amazônico,
especialmente importante na alimentação e economia da agricultura extrativista
da Amazônia Oriental. Sua produtividade de frutos é altamente dependente da
polinização cruzada. A meliponicultura avançou muito nas últimas décadas, porém
o uso de meliponineos para a polinização de fruteiras tropicais é pouco usual.
Neste trabalho, em uma cultura irrigada de Euterpe oleracea, a produtividade
dos frutos foi avaliada após a introdução de colônias de Scaptotrigona aff.
postica (Latreille, 1807). Três gradientes, 0-50, 65-115 e 130-180 metros,
foram utilizados como metodologia para avaliar o aumento de produtividade, a
partir do ponto central onde foram instaladas 30 colônias. A produtividade foi
avaliada pelo peso do fruto por cacho, número de frutos por rachilla, diâmetro
médio do fruto e peso de cem frutos amostrados. Pôde-se observar um aumento
significativo na produtividade, chegando a 2,5 vezes mais, dependendo da
distância da planta às colônias de abelhas. O maior intervalo de produtividade
foi o mais próximo, de 0-50 metros.
Palavras-chave: Meliponicultura; Polinização; Açaí.
Resumen: El açaí es una palmera típica del estuario del
Amazonas, especialmente importante en la alimentación y la economía de la
agricultura extractiva en la Amazonía oriental. Su rendimiento de frutos
depende en gran medida de la polinización cruzada. La meliponicultura ha
avanzado mucho en las últimas décadas, sin embargo el uso de abejas Meliponini
para la polinización de frutales tropicales es inusual. En este trabajo, en un
cultivo de regadío de Euterpe oleracea, se evaluó el rendimiento de frutos
luego de la introducción de colonias de Scaptotrigona aff. postica (Latreille,
1807). Se utilizaron tres gradientes, 0-50, 65-115 y 130-180 metros, como
metodología para evaluar el aumento de productividad, desde el punto central
donde se instalaron 30 colonias. El rendimiento se evaluó por el peso de la
fruta por racimo, el número de frutos por división, el diámetro promedio de la
fruta y el peso de cien frutas muestreadas. Se pudo observar un aumento
significativo en la productividad, llegando a 2,5 veces más, dependiendo de la
distancia de la planta a las colonias de abejas. El rango de productividad más
largo fue el más cercano, 0-50 metros.
Palabras
claves:
Meliponicultura; Polinización; Açaí.
INTRODUCTION
Palm trees are predominantly pollinated by insects,
29% by beetles, 26% by bees, 8% by flies and 7% by wind, and there are many
other pollinators ranging from mammals to crabs (BARFOD et al., 2011). The Euterpe genus fits in the group of palm
trees pollinated by the group “bee-flies-wasps”, as reported by Henderson et
al. (2000).
Acai palm (Euterpe
oleracea Mart.) is native to Amazonian forests and has recently been
labeled as a super food, because of the high levels of anthocyanins and other
non-anthocyanin flavonoids in its fruits (RUFINO et al., 2010).
The acai culture is mainly concentrated in the state
of Pará (Brazil) in Eastern Amazonia, where 1 million tons of the fruit is
produced annually, generating approximately US $ 149 million for the economy,
representing about 31% of the national production of non-timber products (IBGE,
2015). Despite its high productivity, the monoecious species is
self-incompatible and mainly pollinated by bees and flies (VENTURIERI et al.,
2014; VENTURIERI et al., 2016; CAMPBELL et al., 2018).
In addition, the state of Pará has around 50
companies that sell the fruit to other states, whereas 60% of the total
production is consumed localy, 35% goes to other regions of Brazil and 5% goes
abroad, this amount injects into the state’s economy something around U$ 1.5
billion, however, this value corresponds only 3% of the Gross Domestic Product
(GDP) of the state (CONAB, 2019).
The acai palm flowering period occurs along
the year in the Amazon region, with a peak in the months from January to May,
coinciding with the period of greatest rainfall. The period in which the
harvest of the acai fruit decreases, followed by the harvest period six months
after the fertilization of the acai flowers (OLIVEIRA, 2002).
Acai palm flowers are brightly
colored, sessile, diclinous, often distributed in rachis in triads composed of
two male flowers and one female, except for the terminal part of the rachillas,
where male flowers predominate (HENDERSON; GALEANO, 1996). Male ones begin
their anthesis by offering more abundant and concentrated nectar than that
offered by female ones, which can be interpreted as an stimulus to keep
pollinators over the inflorescences and to make them to visit male flowers
first and then go to female flowers, whose climax of their offering nectar, in
its highest concentration of sugar happens just after the decline in the
production of nectar in male flowers, a period coinciding with the greatest
receptivity of stigma (VENTURIERI et al., 2014).
In order to generate fruit, the acai palm, being
a monoecious and protandrous species (dichogamy in which the male sexual organs
develop before the female ones) with a floral characteristic that favors
allogamy, (OLIVEIRA, 2002) thus needs cross-pollination, mediated by bees
(DORNELES et al., 2013; VENTURIERI, 2014; BEZERRA et al., 2020).
The importance of pollinators in
agriculture is well recognized, but the increase in crop yield by using of
cultivated tropical pollinators is still a technology poorly used (POTTS et
al., 2010; GIANNINI et al., 2015; QUEZADA-EÚAN et al., 2018; RAMÍREZ et al. 2018) and
concentrated in a few genera, in particular, Apis mellifera to saturate crop flowers with insect visitors (VIANA
et al., 2014; GARIBALDI et al., 2017; ISAACS et al., 2017).
Later and Venturieri (2015) reported a stingless
bee species of the genus Scaptotrigona sp. with high potential for directed
pollination of the acai tree. However, Scaptotrigones
represent only one species group among several existing bee species. The
pollination efficiency of this bee, in particular, would be enhanced by the
following factors: 1) compatible size with the reproductive structures of the
flower; 2) compatible size with floral rewards and 3) short flight range,
forcing this bee species to be contained among the flowers of the cultivated
species.
Ne’eman et al. (2010) and Stavert et al.
(2016) reported that the key in pollination ecology is that how like flower
visitors vary in their performance as pollinators as a product of both their
interaction frequency and functional traits that mediate the quantity and
quality of pollen deposited during single flower visits.
Several bee species, mostly of
the genus Melipona Illiger, are used
in meliponiculture in Brazil (CONTRERA; MENEZES; VENTURIERI) and Mesoamerica (VILLANUEVA-GUTIÉRREZ
et al., 2013). The
genus Scaptotrigona Moure is also an
important genus for stingless bee keeping with many species, well known for its populous
colonies, and production of good quality honey in large quantities, in
comparison to other meliponines (REYEZ-GONZÁLEZ et al., 2014; ALEIXO et al.,
2017; HURTADO–BURILLO et al., 2017). Scaptotrigona
species from the group S. postica
Latreille, thereafter called S. aff.
postica that occurs in the rain forest, state of Pará in the Brazil, and
commonly known as “canudo” or “tucanaira” is a commonly kept stingless bee
species in the Amazon region, as it has great honey production potential. In
addition, this species may be of significant value for use in the pollination
of native crop species (VENTURIERI et al., 2012), due to visiting a great
spectrum of plants, its tolerance of handling, populous colonies and the
possibility to be multiplied on a large scale (RAMALHO, 2004; MENEZES,
VOLLET-NETO, FONSECA, 2013).
Resources stored in the hives by bees may
present a diversity of pollens in their composition, depending on the
availability of flowering plant species near the hive. Melissopalinology
identifies the pollens present in honey of bees and allows to recognize the
floral relationship of bees, indicating their preferences in different
locations and types of vegetation, which may help in identifying the floral
origin (BARTH, 2013).
The use of native Amazonian bees can
contribute to the sustainable development of regional fruit culture, increasing
the productivity of fruits of the target crop and making use of local bee
biodiversity, generating income, and preserving native species through their
use.
In the present study, it was evaluated the
yield of fruits in irrigated crop system of Euterpe
oleracea under two situations, one under the influence of open pollination,
promoted by the natural insect population of the area and another by the
increase of Scaptotrigona aff. postica density, by the addition of
hive boxes.
MATERIALS AND METHODS
Experimental
Area
The work was carried out from January to
September 2017, in an acai plantation cultivated in Santa Maria city, Pará
State, Brazil (1o01'47.76” S and 47o35'08.95” W). The
planting was done under dryland conditions, in a Yellow oxisoil medium type,
irrigated with the water supply of 110 L/day/plant, with an application by
rainfall control, mixed fertilization (NPK, micronutrients, and cattle manure),
with a 3x3m spacing between clumps. The orchard was in the reproductive phase,
with 6 years of implantation, and with the height of the trees not exceeding
15m.
A second area of 30 hectares, in the
municipality of Igarapé-açu, State of Pará (1º01'46 "S 47º35'03" W),
also of monoculture of irrigated acai crop, in July 2015, was used to evaluate
the crop fidelity of forager bees of S.
aff. postica to the acai flowers.
Crop fidelity
For this experiment, 4 strong colonies were
placed in the center of the cultivation area. After 8 days on site, at the time
of greatest floral opening (9-10 am), the boxes had the entrance hole closed
with a mesh and replaced by empty boxes for the capture of the forager workers
that returned to the colony. Of the total foragers, of the 4 boxes, only those
with pollen load were evaluated, to verify the botanical origin.
To count the bees captured in the trap
boxes, CO2 gas was used to make the bees fall asleep, a white background with 4
divisions was placed at the bottom of these boxes, two repetitions for each
colony was done, photos were taken in high resolution for later counting on the
computer screen (Figure 1b). Two
repetitions for each colony was done, counting a total of 452 workers.
Microscope slides were made from samples of
pollen loads from the bee corbiculae. The pollen was identified using an
optical microscope, comparing it with the pollen slides made from acai anthers’
flowers (Figure 1d). After there was
no doubt about the visual identification of pollen loads, all bees that
contained whitish pink pollen basket were counting as acai origin (Figure 1a).
Figure
1. Use of of Scaptotrigona aff. postica to increase pollination of Euterpe oleraceae. a)
bee foragers arriving with acai pollen basket; b) bee sample in a trap box; c)
communal shelter (meliponary); d)
acai pollen from microscope slides and e)
acai yield from crop plantation where colonies have been placed.
Palynological
analysis from pots of Scaptotrigona aff. postica
The introduction of S. aff. postica
at the acai palm plantation was carried out in January, two months before the
beginning of the flowering of the plant, to adapt the colonies to the new
environment, recovering from the stress of environmental change. It was used
Vertical (Embrapa) hive model developed for housing Scaptotrigona aff. postica
colonies (JAFFÉ et al., 2015; LEÃO et al., 2016). The hives were organized in a
collective shelving system (Figure 1c).
We randomly selected 10 beehives of S. aff. postica, from 30, to
verify the occurrence of pollen of acai tree or other species present in the
environment. The palynological analysis was performed in triplicate from pollen
and honey collected from internal food pots from February to May 2017.
An evaluation parameter of pollen load of
pink-white color, proposed by Venturieri et al. (2014), as a visual indicator
for the evaluation of pollen recently collected in the corbicle of workers
returning to the colony.
Melissopalinological studies were performed
by standard methodology according to (LOUVEAUX et al., 1978), modified by Iwana e Melhem (1979),
followed by the acetolysis method for pollen sediments, according to (ERDTMAN,
1960) and subsequent assembly of blades.
The pollen grains were quantified using
light microscope (400x) on glycerin dispersion slides until the number of 500
pollen grains per sample.
The identification carried out by comparing
the shape and measurement of the pollen with pollen reference (ANGGADHANIA et al., 2020).
Fruit
yield evaluation
An area of 500 m2 of acai palm
plantation was measured through a fiberglass measuring tape where 30
colonies of S. aff. postica were installed at the center
of property. The area was divided into four quadrants with three concentric
ranges with the following distances: 1) from 0 to 50 meters, 2) from 65 to 115
meters and 3) from 120 to 180 meters from the central location where the hives
were arranged (meliponary) (Figure 1c,
Figure 2).
After 180 days of pollination, the
approximate period of formation of the ripe fruit (OLIVEIRA, 2002), the
productivity characters were evaluated. The sample counting was made from thirty
six plants randomly distributed in four quadrants and three ranges.
Figure
2. Layout of the study
area and strips in acai (Euterpe oleracea)
cultivation area: (f) ripe fruit collection.
For each mature bunch collected were
measured: The Total Weight of fruits per bunch (TWF), expressed in kg; Number
of Fruits per Rachilla (NFR), Average Fruit Diameter (AFD), expressed in
millimeters (mm); average weight of 100 fruits (W100), expressed in grams (g),
(n = 100); the total weight of ripe berries (WRB), the average weight of the
hydrated fruits (WHF) in grams (g), fruit yield / fruit dry mass (MSF) in g/g.
The pulping of the acai fruits was
performed according to the methodology of Rogez (2000) (Figure 3). The acai
pulp was obtained with the ratio (1: 2 v/w), volume (L) of mineral water, and
mass (kg) of the fruit. The dry matter content was quantified by drying (ADOLFO
LUTZ, 2008). About 2 to 5 g of the pulp obtained was used, in porcelain
crucibles and taken to the oven for 24 hours.
Figure 3. Pulping steps of acai fruits
Fruit
quality evaluation
The total phenolic content of acai fruits
was determined using the Folin-Ciocalteu colorimetric method (SINGLETON; ROSSI,
1965), adapted by Silva,
Rogez, Larondelle (2007). Phenolic content was expressed in milligrams
of gallic acid equivalent per 100 g sample (mg EAG / 100g). Quantifications
were performed in duplicates and calculations were based on the calibration
curve obtained with gallic acid (Extrasynthèse, Genay, France). Anthocyanin
quantification is based on the method of Askar and Treptow (1993) and optimized
by Rogez (2000) based on dilutions with 1.0 and 4.5 buffers at different
wavelengths 520 and 690 nm by differential spectrophotometry. The total content
of anthocyanins (AT) was calculated as cyanidin-3-glucoside (mg/l) equivalents.
Statistical
analysis
Firstly, the homoscedasticity and normality
of the variable fruit production were verified, respectively by the
Brown-Forysth test and the Lilliefors test, both at p <0.05. No significant
differences were observed, the ANOVA analysis of variance model was adopted,
and when in at least one of the tests a significant difference was observed,
the ANOVA - GLM and the t-student test were used (MYERS, 2012). To determine
which factors contributed to the distinction of means, the DMS test was applied
(p <0.05). The correlation between the variables was estimated through the
Spearman correlation index (AYRES et al., 2007).
RESULTS AND
DISCUSSION
The
crop fidelity of Scaptotrigona aff. postica to the flowers of Euterpe oleracea
Pollen of E. oleracea (Figure 4a,
4b) showed a predominance of 57.87%
indicating that the samples are of monofloral origin because they present a
quantity of pollens> 45%, Smilacaceae pollen - Smilax sp (Figure 4c) showed 26.37%, behaving as secondary
pollen. Euforbiaceae pollen (Figure 4d)
and Pollen of Psidium guajava (Figure 4e) showed 14.98% and 1.06%, respectively.
Figure 4: Pollens identified in honey samples from Scaptotrigona
aff. postica. (a and b) Pollen from Euterpe oleracea, in ventral and dorsal disposition, respectively; c)
Smilacaceae pollen - Smilax sp.; d) Pollen of Euforbiaceae species; e)
Pollen of Psidium guajava (Myrtaceae).
In the experiment where bee foragers
returning to the colony, during the pick of opening hours of male flowers, it
was found that 100% of the pollen loads were pollen from acai flowers (Figure 1a, 1b).
Increased productivity in weight and number of fruits
Based on the productive parameters of acai
palm, it was observed higher total weight of fruit (TWF) per bunch, number of
fruits per rachilla (NFR), average fruit diameter and average weight of one
hundred fruits for plants located in the nearest radius to the hives (f1: 0-50 m), showing that
pollination by S. aff. postica was very effective in a short
distance (Figure 2).
The average weight of the bunch was
significantly different (p <0.005) between the palm trees (f1) near the hives, compared
to the medium (f2) and
distant (f3), indicating a
significant increase in acai yield with the densification of S. aff. postica colonies near to plants. Acai fruit bunches with
pollination less than 50 m increased TWF and NFR by 3.30 kg and 35.8 fruits per
rachilla, compared to 1.12 kg and 1.35 kg, 24.43 and 20.19 fruits per rachilla
at 115 m and 180m respectively (Table 1, Figure 5, Figure 6).
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Figure 5. Productivity characters after Acai
pollination, according to the distance of the S. aff. postica colonies (f1:
0-50m, f2: 65-115m, f3: 130-180m). TWF -
Representative Average of the total weight of fruits per bunch; **p <0.001.
Figure 6. Differences in acai fruit production at
different distances from 30 colonies of S.
aff. postica where f1
= 0-50, f2 = 65-115 and f3 = 130-180m .
The statistically significant difference,
with p <0.0001, between the number of acai fruits/rachilla between the
nearby (f1) and medium and
distant (f2 and f3) palm trees of native
beehives, indicates greater pollination of stigmas per rachilla (Figure 7).
Qualitative
parameters of acai fruit size
Estimates of the qualitative parameters on
acai fruit are related to the development of average diameter per fruit (DMF)
(Figure 8) and the average weight of 100 fruits (P100) expressed in g (n = 100)
in irrigated acai tree (Figure 9). The influence of pollination showed
significant growth in the fruit size closest to the hives of S. aff. postica. Atlhough, the fruit size not necessarily implicate in
higher fruit yield, hence fruits can produce a large size with finer shell
pulp.
Figure
7. Productivity characters
after Acai pollination, according to the distance of the S. aff.
postica colonies (f1:
0-50m, f2: 65-115m, f3: 130-180m). NFR -
Number of fruits per rachilla; **p <0.001.
Figure 8. Productivity characters after Acai
pollination, according to the distance of the S. aff. postica colonies (f1:
0-50m, f2: 65-115m, f3: 130-180m). AFD -
Average fruit diameter; **p <0.001
Figure 9. Productivity characters after Acai
pollination, according to the distance of the S. aff. postica colonies (f1:
0-50m, f2: 65-115m, f3: 130-180m). P100
- Average weight of one hundred fruits. **p <0.001.
Fruit
yield, Total polyphenols, and Total anthocyanins contents
The levels of total anthocyanin and total
polyphenols of fruits were in accordance with those described by Rogez 2000.
Fruits collected in the different ranges showed no statistical differences
(Table 2).
The fruit dry mass yield obtained by
dissecting after pulping fresh pulp served as a parameter of productivity by
fixed weight (Table 2). Fruit dry mass yield (5 grams) did not differ
significantly (p>0.005). Although there is a tendency for the more distant
lumps to present a higher yield of fruit dry mass possibly due to the smaller
diameter of the lump.
The levels of total polyphenols and total
anthocyanins were not statistically different. The values determined are within
the normal levels (DIAS et al., 2012).
Pollination made by bees influences the
increase in yield of most tropical crops which needs cross pollination,
reducing the number of abortions and may also contribute to fruit size and
quality (EDLUND et al., 2004). The use of stingless social bee colonies for
pollination purposes was already known to pre-Columbian ancient civilizations,
such as the Mayans (AYALA et al., 2013).