Characterization of honeys from west and south Buenos Aires Province, Argentina

Pollen analyses were carried out on 33 honey samples from Espinal, Monte de Llanuras y Mesetas and Pampeana phytogeographical Provinces, collected during the 2000-2001 period. Sample processing as well as qualitative and quantitative analyses were performed according to standard techniques. Sixty-seven morphological pollen types were identif ied. The association of Eucalyptus sp. (E. camaldulensis Dehnh., E. viminalis Labill.), Centaurea sp. (C. solstitialis L., C. calcitrapa L.) and Diplotaxis tenuifolia DC. characterized these honeys. Twelve samples were unifloral: six from Eucalyptus sp., five from Helianthus annuus L., and one from Brassicaceae. Asteraceae and Fabaceae were the most representative botanical families.

The aim of this work was to study the botanical and geographical origins of honeys from these districts, which are located in the Caldén District of Espinal Province, a small area of Monte de Llanuras y Mesetas Province, and the Austral District of Pampeana Province (Burkart et al., 1999).

Resumen
Origen botánico de las mieles del oeste y sur de la provincia de Buenos Aires, Argentina

Preparation of samples and analyses
The pollen content of 33 honey samples obtained by centrifuging was studied: seven samples from Patagones District, seven from Villarino District, six from Puán District, nine from Adolfo Alsina District and four from Guaminí District.
Material preparing and analyses were carried out according to the methodology proposed by the International Bee Research Association (Louveaux et al., 1978).
Pollen types were identified up to species, genus, tribe, subfamily or family.A small list of potential species to which pollen could belong was added to some genera.
Frequency of occurrence of pollen grains, expressed as percentage, was determined by counting the number of honey samples in which pollen types appeared.Frequency classes of pollen grains were as follows: dominant pollen (D > 45%), secondary pollen (S = 16-45%), important minor pollen (M = 3-15%) and traces (T < 3%).Nectarless plant pollen was excluded when calculating percentages of frequency classes (Louveaux et al., 1978).
Generally, samples are classif ied as monofloral when a nectariferous pollen type, excluding honeydew elements, is ≥ 45% (Louveaux et al., 1978).However, this rule was not used for Eucalyptus sp. and Helianthus annuus honeys.Honeys were considered to be monofloral of Eucalyptus sp. when its pollen reached 70%, according to Resolution 274/95 (SAGPyA, 1998).Since the Argentinean legislation does not contemplate the conditions that honeys should fulfil to be considered monofloral of H. annuus, the Italian criterion was adopted (Accorti et al., 1986).Investigations carried out by Bedascarrasbure and Bailez (1987) and Andrada et al. (2004) showed that H. annuus pollen could be underrepresented (group I).For this reason, honeys were considered to be of H. annuus when its pollen reached 15%.
The number of honeydew elements was scarce in all samples; therefore the HDE/P index (ratio of the number of honeydew elements/number of pollen grains) was not calculated.

Results
Quantitative analyses (PAC-10) are presented in Figure 2.
Qualitative analyses, frequency of occurrence, frequency classes, pollen-plants, and pollen-nectar plants are given in Table 1 From the total samples, 36% were monofloral and 64% were mixed.Among monofloral samples, six were from Eucalyptus sp.(four group II and two group I), five from Helianthus annuus (group I) and one from Brassicaceae (group I).
Figure 3 shows the distribution of honeys in the studied districts according to their botanical origin.
Accompanying pollens of eucalyptus and sunflower honeys (frequency of occurrence > 50%) are presented in Figures 4 and 5.
Monofloral samples had a poor pollen content; 92% of them were eucalyptus and sunflower honeys.Considering Eucalyptus sp. as an over-represented pollen type, it should be classif ied in group III (Louveaux et al., 1978).However, results obtained in this work agree with values expressed by Aira et al. (1998) in Portugal.Results for Helianthus annuus honeys also agree with those obtained in Italy by Accorti et al. (1986).
Thirty four pollen types were identified in eucalyptus honeys; 79% of them belonged to pollen-nectar plants.Five taxa with important minor pollen frequency class were observed.Eucalyptus sp.honeys differed from those harvested in surrounding plains of Sistema Ventania (Valle et al., 2001) because they had other accompanying types: Schinus sp., Vicia sp., Mutisieae and Trifolium sp. (Fig. 4).
Thirty nine pollen types were identified in sunflower honeys; 82% of them belonged to pollen-nectar plants.Four taxa showed values ranging from 16 to 45% (S).This could be explained by the low pollen percentage established for sunflower honeys, according to Accorti et al. (1986).Sunflower honeys differed from those harvested in the southern Austral District of Pampeana Province (Valle et al., 2000) because of the presence of Asteraceae, Senecio sp., Vicia sp., Medicago sp. and Cichorium intybus (Fig. 5).
Accompanying pollen types of monofloral honeys come mainly from introduced species.
Honeys from Puán district were mixed and presented elements from Caldén District (Condalia microphylla, Prosopis sp. and Larrea divaricata) with frequency class values of secondary and important minor pollen (Andrada and Tellería, 2002).Similar characteristics were reported for La Pampa honeys (Tellería, 1996;Naab et al., 2001).

Figure 1 .
Figure 1.Geographical location of the studied districts.

Table 1 .
Frequency classes and frequency of occurrence of pollen types

Table 1 (
continued).Frequency classes and frequency of occurrence of pollen types