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Agrociencia
versión On-line ISSN 2521-9766versión impresa ISSN 1405-3195
Agrociencia vol.51 no.5 Texcoco jul./ago. 2017
Crop Science
Genotype and environmental effects on physical and chemical qualities of mexican varieties of Hibiscus sabdariffa L. flowers
1Posgrado en Recursos Genéticos y Productividad, Fisiología Vegetal, Colegio de Postgraduados, Campus Montecillo. km 36.5 carretera México-Texcoco. 56230, Montecillo, Estado de México.
2Laboratorio de Calidad de Cultivos para Uso Humano y Pecuario, Campo Experimental Centro Altos de Jalisco, INIFAP. km 8 Carretera Tepatitlán - Lagos de Moreno. 47600, Tepatitlán de Morelos, Jalisco.
This study evaluated 53 red color-contrasting genotypes of Hibiscus sabdariffa L. of dehydrated calyces grown in a traditionally producing regions of Colima, Guerrero, Nayarit, Oaxaca and Puebla states in Mexico. The objective was to quantify the effects of genotype (G), environment (A, location) and interaction (G×A) on color variables (luminosity, hue and saturation), total anthocyanin content (CTA), total soluble phenols (FST), pH and titratable acidity (AT) in dehydrated calyces and aqueous extracts. The three factors had significant effects (p≤0.01) on calyx quality and extracts. But the genotype factor influenced more calyx color (60 to 81 %), CTA (72 %) and FST (44 %), while calyx color tone was mostly explained (62 %) by the interaction G×A. pH and AT were affected more by location (56 and 52 %) and by the G×A interaction (22 y 24 %). Nineteen genotypes were classified as dark red calyces, which contained higher total soluble anthocyanins and phenols levels; these variables showed higher expression at the Nayarit location. The remaining light-red calyx genotypes (34) were highly acidic, and the acidity increased when grown in Nayarit. Although the three effects of genotype, location (environment) as well as their interaction G×A had significant effects on the quality of hibiscus calyces, the genotype factor was the most relevant to CTA and FST, whereas the environment factor explained most of the variation of AT and pH of aqueous extracts.
Key words: Hibiscus sabdariffa; calyx; color; total anthocyanin content; total soluble phenolic compounds; titratable acidity
En este estudio se evaluaron 53 genotipos de jamaica (Hibiscus sabdariffa L.), con coloración roja contrastante en sus cálices deshidratados, cada uno de ellos crecidos en una región productora de Colima, Guerrero, Nayarit, Oaxaca y Puebla, estados con tradición en el cultivo de jamaica en México. El objetivo fue cuantificar los efectos de los factores genotipo, ambiente y su interacción G×A, en las variables de color (luminosidad, tonalidad y saturación), contenido total de antocianinas (CTA), fenoles solubles totales (FST), pH y acidez titulable (AT), en cálices deshidratados y extractos acuosos. Los tres factores tuvieron efectos significativos (p≤0.01) en la calidad de los cálices y extractos de jamaica, pero el efecto del genotipo fue más determinante en las variables de color (60 a 81 %), CTA (72 %) y FST (44 %), y la tonalidad de los cálices fue explicada en 62 % por la interacción G×A. El pH y la AT fueron afectados en mayor proporción por la localidad (56 y 52 %) y por la interacción G×A (22 y 24 %). De los genotipos, 19 se clasificaron por cálices de color rojo oscuro, por mayor contenido de antocianinas y fenoles solubles totales, variables que tuvieron mayor expresión en la localidad de Nayarit. Los 34 genotipos restantes, de cálices color rojo claro, sobresalieron por su alta acidez, que fue mayor cuando crecieron en Nayarit. Aunque los efectos de los factores genotipo, ambiente y su interacción G×A tuvieron efectos significativos en la variación de la calidad de los cálices, el genotipo fue el factor más importante en el CTA y FST, mientras que el efecto de ambiente fue el principal responsable de la variación en AT y pH de los extractos acuosos.
Palabras clave: Jamaica; cálices; color; contenido total de antocianinas; compuestos fenólicos solubles totales; acidez titulable
Introduction
Roselle or jamaica (Hibiscus sabdariffa L.) (Malvaceae) is a plant species native to Africa. During the colonial period, it dispersed to other tropical and subtropical regions suitable for its cultivation (Morton, 1987). In Mexico, it adapted to a wide territorial extension, where it is commercially grown. The national annual production of dehydrated calyces is 6950 t mostly harvested in the states of Guerrero, Michoacán, Oaxaca, Puebla and Nayarit (SIAP, 2015).
Roselle calyces are the most valued elements of H. sabdariffa because of their antioxidant, pigment and organic acid content; these compounds largely determine its commercial value (Patel, 2014). In Mexico, calyces are mainly used for production of refreshing beverages by extraction (cold, infusions and decoctions) due to its attractive color, palatability (Fasoyiro et al., 2005), antioxidant effects (Tsai et al., 2002; Prenesti et al., 2007), and medicinal properties (Reyes-Luengas et al., 2006; Herrera-Arellano et al., 2007).
Jamaica calyces contain high levels of anthocyanins, organic acids and other flavonoids (Sindi et al., 2014; Fernández-Arrollo et al., 2011), and their antioxidant properties were tested in vitro and in vivo (Ojeda et al., 2010; Herrera-Arellano et al., 2004). Also, the food, pharmaceutical and cosmetic industries are interested in H. sabdariffa genotypes with specific characteristics of color, acidity and phytochemicals content (Patel, 2014).
As an introduced plant species, genetic variation studies mainly describe variety performance in each cultivation region; however, growing interest in outstanding varieties for color and flavor has promoted the creation of breeding programs. These programs focus on generation of new higher-yielding jamaica genotypes of better quality traits, both in dehydrated calyces and in aqueous extracts (Borrás-Linares et al., 2015; Salinas-Moreno et al., 2012).
Borrás-Linares et al. (2015) and Christian and Jackson (2009) reported that the genotype factor influences color characteristics, phytochemical content and antioxidant activity of the calyces. Juliani et al. (2009) also showed that the phytochemicals content in jamaica calyces is affected by the production site. However, in studies performed in Mexico the genotype×environment interaction has not been elucidated, as Ottai et al. (2004) did with jamaica varieties and locations in Africa; they measured quality traits such as anthocyanin content, total acidity, pH, total soluble solids, amino acids and sugars. These authors showed that production site affects calyx quality at different levels of magnitude among genotypes and demonstrated the importance of the genotype×environment interaction on roselle quality.
The objetive of this research was to characterize 53 Mexican jamaica genotypes grown in five Mexican sites located at the top-producing states. The measured variables were color characteristics (luminosity, hue and saturation of color), anthocyanins content, total soluble phenols content, pH, and titratable acidity in dehydrated calyxes and aqueous extracts. The data allowed for quantification of the magnitude of the effects of genotype, environment, and the genotype×environment interaction. We postulated this method would allow identification of outstanding-quality jamaica varieties, optimal environments that improve quality, and the best genotype×environment combinations.
Materials and Methods
Dehydrated calyces were harvested from 53 jamaica genotypes contrasting in calyx color (light red and dark red) at five locations representative of the top producing jamaica states in the country, grown according to local methods. The five locations were: Ayutla de Libres, Guerrero (16° 57’ 57” N and 99 ° 05’ 38” W, 400 masl, 28.0 °C annual mean temperature, 1400 mm annual rainfall); Los Limones, San Miguel Chimalapa, Oaxaca (16° 01’ 34.27” N and 97° 29’ 34.95” W; 280 masl; 26.8 °C annual mean temperature; 1150 mm annual rainfall); Chiautla de Tapia, Puebla (18° 17’ 57’’ N and 98° 36’ 10’’ W; 900 masl; 24.8 °C annual mean temperature; 900 mm annual rainfall); Comala, Colima (19 ° 18’ 19.36” N and 103° 45’ 12.03” W, 610 masl, 26.4 °C annual mean temperature, 1118 mm of annual rainfall); and Xalisco, Nayarit (21° 27’ 2.71” N and 104° 53’ 55.94” W, 960 masl, 23.0 °C annual mean temperature, 1232 mm annual rainfall). Weather data were taken from the National Meteorological Service at the CONAGUA website (http://smn1.conagua.gob.mx/index.php?option=com_content&view=article&id=42&Itemid=28). The environmental variation studied here included climatic, edaphic, pre-harvest, and post-harvest differences.
Preparation of the aqueous extracts
The extraction for each sample was done according to the method established by Galicia-Flores et al. (2008): 2.5 g of dried calyces were placed in a 600 mL beaker and 100 mL of distilled water were added; the mixture was boiled 15 min, and the extract was removed from the calyces by decantation. The extraction procedure was repeated under the same conditions, and the two resulting extracts were mixed. Distilled water was added to the extract to complete 200 mL total volume. This mixture was filtered with Whatman No. 4 filter paper. All color, phytochemical and chemical determinations were done on the prepared aqueous extracts.
Color
Sample color was measured directly on the surface of the dehydrated calyces in five repetitions with a Hunter Lab MiniScan XE Plus (model 45/0-L) in the CIE scale L*, a* and b*, with D65 illuminant and a 10° angle. Prior to each measurement, calyces were introduced into a black plastic bag to prevent light interference. With the values of a* and b*, the values of hue (hue) and color saturation (chroma) were calculated as described by McGuire (1992). In the aqueous extracts color was measured in four repetitions of 50 mL in a glass beaker (accessory No. 04-7209-00) containing a black ring that held a 90 % reflectance white disk (accessory No. 02-4579-00) at the top. Then the glass cup was covered with a light trap (accessory No. 04-7209-00), and the reading was taken with the Hunter Lab MiniScan XE Plus colorimeter with a D65 illuminant calibration and a 10° angle. Calculations of hue and color saturation were performed in the same way as for dehydrated calyces.
Total anthocyanins content (CTA)
CTA was measured in four repetitions of the aqueous extracts by the absorbance recorded on an Epoch plate spectrophotometer (BioTek Instrument®) fitted with 96-well microplates (Costar®). The method proposed by Galicia-Flores et al. (2008) was modified to use 300 µL of the diluted extract and its absorbance read at 510 nm. CTA was calculated using a linear regression equation obtained from the cyanidin 3-glucoside (Polyphenols®, Nw) standard curve. CTA was expressed in equivalent mg of cyanidin 3-glucoside per 100 g of dry sample (mg EC3G 100 g-1 MS).
Total soluble phenols (FST)
FST were quantified in four repetitions using a modified Folin-Ciocalteu method (Singleton and Rossi, 1965) to adapt color measurements on microplates. The method is described below: 15 µL of the extract to be analyzed were added to 240 µL of distilled water and 15 µL of Folin-Ciocalteu reagent (Sigma Aldrich®) 0.25 N. The mixture was allowed to react for 3 min in the dark; then neutralized with 30 µL of 1 N sodium carbonate (Na2CO3, J. T. Baker®). The sample was allowed to stand at room temperature for 2 h in the dark, and absorbance was measured in the plate spectrophotometer at 765 nm. Gallic acid was used as standard, from which a standard curve for the quantification of the FST content expressed in mg equivalents of gallic acid per 100 g of dry sample (mg EAG 100 g-1 MS) was created.
Titrable acidity (AT) and pH
AT was determined twice by the AOAC method (1984). The method required a 10 mL aliquot in a 600 mL beaker; 200 mL of distilled water were then added to dilute the sample color to allow identification of the phenolphthalein change. Titration was done with 0.1 N NaOH (J.T. Baker®). The calculated percent of AT (AT) was expressed in milliequivalents of citric acid (0.064). pH was determined twice with a Denver Instrument UB10® potentiometer, calibrated with buffer solutions (J.T. Baker®) at pH 4 and 7.
Statistical analyses
A combined analysis through environments was performed with data of each variable, to quantify the effects of genotype (G), environment (A) and the interaction (G×A). In addition, genotypes and locations were submitted to mean tests (Tukey, p≤0.05) to identify the most outstanding ones. Univariate statistical analyzes were done with SAS System Version 9.0. Principal component analysis (PCA) and cluster analysis (AC) techniques were applied on variable means by the full bond method using Euclidean distances, to group the 53 genotypes according to their color characteristics, followed by CTA, FST, PAT and pH values to identify outstanding genotypes. Minitab® 17.1.0 was used for multivariate analyzes.
Results and Discussion
All the variables changed significantly (p≤0.01) as a result of genotype (G), environment (A) and interaction (G×A) effects (Table 1). It is notable that the contents of antioxidant compounds, CTA and FST in the calyx were influenced by genotype: this factor explained 72 and 44 % of the variation due to treatments, respectively. The interaction G×A caused 19 and 29 % of the total variation in the same variables, so that this interaction stands out as the second most important factor in the accumulation of these phytochemicals in jamaica calyces. Environmental effect alone only represented 9 and 27 % of the treatment variation.
Table 1 Estimated sum of squares by combined statistical analysis of 53 genotypes of Hibiscus sabdariffa L. grown in five environments (locations). The percentages were calculated with respect to the treatments sum of squares.
**p≤0.01. CTA: total anthocyanins content; FST: total soluble phenols; AT: titrable acidity; SDC: color saturación.
Ottai et al. (2004) reported a much stronger effect of genotype (94 %) on CTA, while the remaining 6 % depended on the environment (A) and the interaction G×A. Such a high dependence on genotype could be attributed to few genotypes in the study (three genotypes: a light red, a dark red and a white one lacking anthocyanins) possibly grown at scarcely contrasting environments. For FST, no published information was found relating its concentration to the genotype, environment and the G×A interaction.
In contrast, variables related to flavor or palatability, pH and AT were mainly affected by the growing environment (represented here by five locations) in magnitudes of 56 and 52 %, respectively (Table 1). The genotype and the G×A interaction affected in similar proportions these two traits. That is, the two variables related to acidity and taste are characteristics more dependent on the environment and the interaction than on the genotype. The results obtained by Ottai et al. (2004) do not agree with the present study regarding pH; these authors reported a greater dependence on genotype (53 %) than on production site (40 %). The difference between results in the two studies could be explained by the lesser number of genotypes and environments evaluated in Africa than in Mexico. Instead, the results do agree for AT considering that the environment effect was the most important on AT variation.
In the aqueous extracts the genotype factor represented effects ranging from 74 to 81 % in color luminosity, hue and saturation (Table 1). In the dehydrated calyces, the genotype effect on the percentages of luminosity and color saturation ranged from 72 to 76 %, while tone values were more dependent on the interaction G×A (62 %). That is, in color traits the genotype effect is highly dominant, meaning that color characteristics are highly heritable and stable through environments.
The former information suggests that for extracting phytochemicals from jamaica calyces, a greater gain may be achieved by selecting the darker red genotypes, taking into account that they are outstanding in synthesis and accumulation of both CTA and FST. In order to obtain calyces with the highest titratable acidity, it is more convenient to produce them in environments where the genotypes express a higher synthesis of organic acids.
Color variation in dehydrated calyces and aqueous extracts
Both the principal components analysis (ACP) and cluster analysis (CA) allowed to classify the 53 genotypes into two contrasting color groups: dark red and light red (Figure 1). The groups corresponded exactly with visual color classification of calyces. Borrás-Linares et al. (2015) classified calyces of H. sabdariffa into five groups according to their anthocyanin content. It is more common to classify genotypes depending on calyx colors, and frequently calyces are classified visually into three color categories: dark red, light red and green-yellow. However, genotypes with green-yellow chalices are less frequent than red ones (Juliani et al., 2009; Christian and Jackson, 2009; Babalola et al., 2001). The close relationship between anthocyanin content and flower color in jamaica was evidenced by Wrolstad (2004).
The dark red group (GCRO) included the following 19 jamaica genotypes (Figure 1): Tempranilla Negra, Jersey Acriollada, Negra UAN, Criolla Morada, Negra Quiviquinta, China, Morada×Roja, UAN 5, UAN 12-1, UAN 16 2, UAN 17, UAN 18, UAN 21, UAN 23, UAN 29, UAN 31, 6Q6, 7Q7 and 10. This group is characterized by having a luminosity interval of 12.5 to 14.8 % in their dehydrated calyces, with an average value of 13.7 %. The tonality values oscillated between 17.6 to 26.2°, with an average value of 21.5°. Color saturation ranged from 6.3 to 10.4 units, with an average of 8.3 units. In their extracts, the variation in luminosity was very similar to that observed in the dehydrated calyces.
Figure 1 Grouping of 53 Hibiscus sabdariffa L. genotypes according to luminosity, hue and color saturation values both in dehydrated calyces and in aqueous extracts.
The 34 jamaica genotypes included in the light red group (GCRC) were: 2MQ2, 3Q3, Colima, Coneja, Criolla Huajicori, Criolla Precoz, Criolla Precoz Puebla, Criolla Roja Violeta, Criolla Super Precoz, Q12, Tempranilla Flor, Tempranilla Roja, UAN 10 -1, UAN 10-2, UAN 11, UAN 12, UAN 13, UAN 15, UAN 16, UAN 19, UAN 20, UAN 21-1, UAN 22, UAN 24, UAN 24-1, UAN 25, UAN 26 , UAN 27, UAN 30, UAN 6 Novillero, UAN 6 Puga, UAN 6-1, UAN 7 and UAN 8 (Figure 1). In this group, the luminosity in dehydrated calyces varied from 15.7 to 22.2 %, with an average of 18.5 %. The tonality ranged from 19.9 to 24.9°, with an average of 22.2°; and a color saturation oscillating from 11.5 to 23.2 units, with an average value of 16.3. The aqueous extracts showed similar ranges of values in luminosity, hue and saturation.
Although there were less genotypes in the group of dark red calyces, the dispersion in Figure 1 shows that the variation between genotypes was greater than that observed in the light red genotypes, in terms of the tonality of their dehydrated calyces and color saturation in aqueous extracts. This is interesting for breeding programs since these genotypes could express a larger genetic variability since they have a greater diversity of color tones in the calyces and in extracts.
The significant effect (p≤0.01) of the environment on the color descriptors of dehydrated calyces and aqueous extracts of Hs, is shown in Table 2. The luminosity of dehydrated calyces showed the lowest values for genotypes grown in Nayarit (15.0±3.0 %), compared to the other four localities. In the aqueous extracts, we detected differences in luminosity between the five environments evaluated, and those from Colima variety (21.9±7.0 %) were the most luminous, in contrast to varieties from the State of Guerrero that were the darkest (19.1±7.0 %).
Table 2 Environment effect on luminosity (L), tonality (T) and color saturation (SDC) of dehydrated calyxes and aqueous extracts of 53 Hibiscus sabdariffa L. genotypes, each grown in five locations.
Values with different letter in a column are statistically different (p≤0.05). DMS: Least significant difference.
The jamaica calyces produced at the Nayarit, Oaxaca and Puebla (20.4±4.0 to 21.1±4.6°) had a more defined red tonality, compared to those from Colima and Guerrero (23.6±4.6 and 23.6±4.0, respectively). Color saturation of calyces and extracts was higher in Oaxaca (15.0±5.1), followed by Colima (14.3±5.8) and Puebla (13.9±5.4), while in Nayarit the lowest values were recorded (11.3±4.6). In the aqueous extracts, the tonality was more defined in the genotypes cultivated in Oaxaca (34.4±6.2) and Guerrero (32.4±7.6).
Phytochemical characteristics
Genotypes with the highest total anthocyanin content (CTA) were dark red colored (Table 3): UAN 18, Negra UAN, UAN 17, UAN 21, UAN 12-1, UAN 29, UAN 5 and 10, with a variation of 608±206 to 757±178 mg EC3G 100 g-1 MS. Varieties UAN 30, UAN 25, UAN 15, UAN 19, UAN 27, Tempranilla Roja, UAN 6-1, UAN 6 Novillero, Tempranilla Flor and Criolla Super Precoz, with clear calyces, were the ones that registered the lowest content in this phenolic fraction (163±51 to 228±74 mg EC3G 100 g-1 DM). Similar values were reported in national varieties of Hs from Guerrero and Oaxaca (Salinas-Moreno et al., 2012; Galicia-Flores et al., 2008).
Table 3 Average content of anthocyanins, total soluble phenolics, pH and titratable acidity in aqueous extracts of 53 Hibiscus sabdariffa genotypes of red calyces grown in five environments (locations). In each column, the bold numbers mark the maximum values of each variable, while the minimum values are underlined.
Values with different letter in a column are statistically different (p≤0.05). DMS: Least significant difference. CTA: total anthocyanins content; FST: total soluble phenols; AT: titratable acidity; AC: citric acid. 1Tempranilla Negra; 2Tempranilla Flor; 3Jersey Acriollada; 4Criolla Roja Violeta; 5Criolla Huajicori; 6Negra UAN; 7Criolla Morada; 8Criolla Súper Precoz; 9Criolla Puebla Precoz; 10Criolla Precoz; 11Negra Quiviquinta; 12UAN 6 Puga; 13UAN 6 Novillero; 14Morada×Roja; 15Tempranilla Roja.
The genotypes UAN 21, Jersey Acriollada, UAN 12-1, UAN 17, UAN 18, UAN 5, 10, 7Q7, Negra Quiviquinta, UAN 16-2, Criolla Morada, UAN 31, China and UAN 29 (Table 3), outstand in this study because of their high content of total soluble phenols (FST) (3640±828 to 2871±362 mg EAG 100 g-1 MS). Particularly, the Jersey Acriollada and UAN 21 varieties showed contents similar to those reported for the Sudan genotype (3650 mg EAG 100 g-1 DM) which is acknowledged in Mexico for its high accumulation of antioxidants (Reyes-Luengas et al., 2015).
The light-red calyx jamaica genotypes had the lowest FST contents, especially Criolla Huajicori, Criolla Rojo Violeta, UAN 21-1, UAN 6-1, UAN 6 Novillero, 3Q3, Colima, Tempranilla Flor, Tempranilla Roja and Criolla Super Precoz (2220±321-1647±259 mg EAG 100 g-1 DM). The top genotypes in CTA content are not necessarily the highest in FST, and vice versa, as was also reported by Christian and Jackson (2009). These results show that genotypes that do not stand out in CTA content, could do so in FST. But there are also genotypes that are high in both antioxidants, such as UAN 21, Jersey Acriollada, UAN 12-1, UAN 17, UAN 18, UAN 5, 10, 7Q7 and Negra Quiviquinta.
The FST contents in the 53 Mexican jamaica genotypes evaluated here are similar to other previously reported (Reyes-Luengas et al., 2015) and also to genotypes grown in Jamaica (Christian and Jackson, 2009). The cultivar Acriollada Jersey was the most variable through out locations (±1408 mg EAG 100 g-1 DM), in contrast to the Chinese, Morada×Roja, Tempranilla Negra and UAN 23 genotypes, which varied between ±199 and ±300 mg EAG 100 g-1 DM, and thus were more stable. The variation in the clear genotypes was from ±179 to ±811 mg EAG 100 g-1 DM, where Tempranilla Flor, 2MQ2 and UAN 26 were the most unstable genotypes across locations. These results show that the dark red genotypes contain more antioxidant phytochemicals than the light red ones, with 2.3 times more CTA and 1.3 times more FST.
The two important palatability variables in aqueous extracts of jamaica calyces, pH and titratable acidity, were significantly different (p≤0.05) among genotypes (Table 3). pH values fluctuated from 2.40±0.18 to 2.86±0.26, which are convenient values for preserving the structural stability of the cation flavilium in anthocyanins and confer the bright red hue in aqueous extracts (Prenesti et al., 2007; Wrolstad, 2004). Extracts of the genotypes UAN 10, UAN 12-1, 7Q7, UAN 15, Criolla Morada, UAN 24-1, UAN 24, UAN 26 and UAN 11 were the most affected by environment, since changes in standard deviation of pH values from ±0.34 to ±0.22 sometimes caused pH of 3.0 or higher, which reduced the stability of the bright red color in aqueous extracts.
The genotypic variation in AT expressed as percent of citric acid fluctuated from 14.2±4.3 to 23.2±3.3 % (Table 3). Genotypes with the highest percentages and thus the most palatable, were Colima, Criolla Huajicori, Q12, Criolla Rojo Violeta, UAN 10-2, 2MQ2, Criolla Super Precoz, Tempranilla Flor and 3Q3, with values ranging from 20.3±3.13 and 23.2±3.26 %. The varieties with the lowest percentages of AT were 10, UAN 21, UAN 5, UAN 24, UAN 15, 7Q7, UAN 24-1 and Criolla Morada (16.0±3.4-14.2±4.3 % citric acid). The average AT values of the dark red (17.0 %) and light red (18.9 %) varieties showed close averages. The higher values of standard deviation observed in AT show that the environmental effect was higher in this variable, with variation across locations from ±0.68 to ±5.71 % of citric acid. In this variable, genotypes UAN 15 and UAN 6-1 were the most unstable, showing high standard variations (±5.0 and ±5.71 %); in contrast, genotype Coneja was the most stable throughout environments since the standard deviation of acidity was ±0.7 %.
Genotype classification by physicochemical quality
When the 53 genotypes were grouped according to their antioxidant and acidity characteristics by application of ACP for CTA, FST, pH and AT, it was found that the first two components explained 94.0 % of the variance detected in the aqueous extracts. The first component (CP1), constituted by FST and AT, explained 68.8 % of the total variance; CP2 contributed 25.2 % of the remaining variance due to CTA and pH. With conglomerate analysis, the 53 genotypes of H. sabdariffa were classified into six categories (Figure 2).
Figure 2 Grouping of 53 genotypes of Hibiscus sabdariffa L. according to total content of anthocyanins, total soluble phenols, pH and titratable acidity.
Cluster 3 (Negra UAN, China, UAN 17, UAN 19 and UAN 18) and Cluster 6 (Jersey Acriollada, UAN 5, UAN 21, UAN 12-1, 7Q7 and 10) grouped genotypes with higher CTA and FST content. But genotypes of cluster 3 had greater AT than cluster 6 (Table 4). On the other hand, genotypes in group 1 (Tempranilla Flor, Colima, Criolla Violeta, Criolla Huajicori, Criolla Super Precoz, Tempranilla Roja, UAN 10-2, 2MQ2, 3Q3 and Q12) recorded the highest TA, although their CTA and FST were the lowest among the 53 genotypes. Most genotypes grouped in cluster 2 (Criolla Puebla Precoz, Criollo Precoz, UAN 6 Puga, UAN 6-1, UAN 6 Novillero, UAN 25, UAN 7, UAN 23, UAN 8, UAN 27, UAN 12, UAN 20, UAN 22, UAN 10-1, UAN 19, UAN 30, UAN 16, UAN 21-1 and Coneja) showed low content of CTA and FST and intermediate values of AT.
Table 4 Comparison of total anthocyanins content (CTA), total soluble phenols (FST), pH and titratable acidity (AT) in six groups of Hibiscus sabdariffa L.
Values with different letter in a column are statistically different (p≤0.05). DMS: Minimum significant difference.
Cluster 4 (Tempranilla Negra, Negra Quiviquinta, UAN 31, UAN 16-2, Morada×Roja y 6Q6) had intermediate values of CTA and FST, with low acidity percentages. The genotypes included in Cluster 5 (Criolla Morada, UAN 11, UAN 24, UAN 13, UAN 26, UAN 15 and UAN 24-1) had low values in CTA and AT but intermediate FST values.
Among locations (environments), Nayarit was noted to induce the highest accumulation of CTA (492±224 mg EC3G 100 g-1 DM) and FST (3114±747 mg EAG 100-1 DM), compared to the other locations (Table 5). The lowest CTA contents were obtained in Colima and Guerrero (327±180 and 322±172 mg EC3G 100 g-1 DM), and the lowest FST occurred in Colima and Puebla (2296±551 and 2281±476 EAG 100 g-1 DM, respectively).
Table 5 Effect of environment (location) on total anthocyanin (CTA), total soluble phenols (FST), pH and titratable acidity (AT) on 53 Hibiscus sabdariffa L. genotypes.
Values with different letter in a column are statistically different (p≤0.05). DMS: Minimum significant difference.
PH and AT were the variables most strongly affected by the production environment (p≤0.01) (Table 5). At pH, the variation across environments was from 2.31±0.11 to 2.76±0.19, in Nayarit and Colima, respectively. AT varied from 15.7±3.2 % in Guerrero to 24.0±2.9 % in Nayarit. Unlike phytochemical variables, pH variation was higher in Colima, followed by Guerrero and Puebla. In AT, the highest variation was in Guerrero, and the lowest in Oaxaca.
Conclusions
Among the 53 evaluated varieties of jamaica, var. UAN 21 stands for its high soluble phenol content and total anthocyanins, which are antioxidant compounds, and low titratable acidity. With high titratable acidity and high contents of anthocyanins and FST, genotypes with dark-colored calyces have higher phytochemical content than those with light red calyces, while the latter show a higher percentage of titratable acidity. Among production environments, Xalisco, Nayarit stands out for promoting calyces with highest values of CTA, FST and AT, compared to the other field locations compared here. The genotype, environment and G×A interaction have significant effects on the calyx quality of H. sabdariffa, but genotype stands out as the most important factor in CTA and FST, while the effect of the environment (location) was the main factor responsible for the variation in the acidity of the aqueous extracts
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Received: July 2016; Accepted: April 2017
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