Servicios personalizados
texto en 
Inglés (pdf)
Articulo en XML
Referencias del artículo
Enviar articulo por email
Citado por SciELO 
Similares en
SciELO 
Permalink
INTRODUCTION
Sustainable agriculture is one of the major priorities of the 2030 Agenda, which contributes to poverty reduction through approaches in favor of the poor population, promoting the empowerment of family farming, women and youth; as well as the value chain, access to markets and social protection systems. The use of varieties of crops adapted to the conditions of the country and the analysis of production, harvesting and post-harvest processes notably help to develop precision agriculture, with a minimum cost, that guarantees the food demand of the world population.
The use and study of biostimulants and their effects is a practical alternative that contributes to the development of sustainable agricultural production systems. Biostimulants are defined as any substance or microorganism capable of increasing nutrition efficiency, tolerance to abiotic stress and the quality of crops (Du Jardin, 2015). According to Drobek et al (2019) they are preparations of natural origin that support the pro-ecological cultivation of vegetables and fruits, whose effects can be multifaceted. At the National Institute of Agricultural Sciences (INCA) of the Republic of Cuba, a group of bioproducts are developed in order to increase the growth and development of crops. Among these bioproducts is QuitoMax®, a liquid biostimulant based on chitosan polymers, obtained from the chitin present in the lobster exoskeleton, with beneficial results in development, yields and anti-stress protection in several important economic crops (Morales et al., 2016).
Horticulture is an attractive activity, mainly due to the growing demand for horticultural species with nutritional and/or medicinal value and high production volumes in small areas. Garlic (Allium sativum L.) is an annual horticultural plant of the Alliaceae family, which is used as a condiment and aromatic agent in food cooking, in addition to being used in the pharmaceutical industry, due to the chemical compounds it presents (Espinoza et al., 2010). In Cuba, the yields of this crop are very low, despite the fact that high volumes of mineral fertilizers and pesticides are applied in its production system (Pupo et al., 2016).
Scientific studies related to the use of QuitoMax® or other types of biostimulants in garlic cultivation are limited (Balmori et al., 2019). Similarly, those related to the modification of the parameters of quality of the agricultural fruit are insufficient. In this sense, the aim of this work was to evaluate the quality parameters of garlic (Allium sativum L.) obtained from two Criollo clones: 'Criollo-9' and 'Criollo-Víctor' treated with concentrations of QuitoMax®.
MATERIALS AND METHODS
Materials and Experimental Conditions
Garlic bulbs harvested from a field experiment developed with two Criollo clones were used: 'Criollo-Víctor' and 'Criollo-9' in the Farm 'La Jaula', belonging to San José de las Lajas Municipality, Mayabeque Province, during the period 2018- 2019. The field experiment was carried out in a Sialitic Brown soil, according to the classification of Cuban soils (Hernández et al., 2015), with pH = 7.80 and organic matter content (OM) of 5.59 %. The plantation was carried out in flower beds of (20 × 1.40 × 0.30 m) made up of soil and organic fertilizer. The cloves were planted manually with a planting density of 4 rows at 20 × 10 cm between plants.
Before planting, the cloves were soaked 24 hours in QuitoMax® solutions at concentrations of 1.0; 5.0 and 10.0 mg L-1 and in water (control treatment). At 50 days after planting (dap), foliar applications were made with the same doses of the biostimulant, keeping the group of control plants with water, for a total of four treatments for each clone. For the 'Criollo-Víctor' clone the treatments were designated as: CV-0, CV-1, CV-5 and CV-10, and for the 'Criollo-9' clone they were designated as: C9-0, C9-1, C9-5 and C9-10.
QuitoMax®, whose active ingredient is chitosan, was kindly provided by the Bioactive Products Group (GPA) of the National Institute of Agricultural Sciences (INCA). This liquid biostimulant is obtained by deacetylation of chitin extracted from lobster exoskeleton. Concentrations of 1.0, 5.0 and 10.0 mg L-1 of QuitoMax® were used, whose composition shown on the product's marketing label is presented in Table 1.
TABLE 1 Composition of QuitoMax®, a chitosan polymer produced by INCA
| Components | Quantity |
|---|---|
| Chitosan | > 4 g L-1 |
| Acetic acid | > 0,4 % |
| Potassium | > 0,07 % |
| Sodium benzoate | > 0,05 % |
Cultural attentions were developed according to the Organoponic and Orchards Intensives Manual (INIFAT, 2010). Irrigation was carried out on alternate days with a 10 L watering can and the removal of weed plants by manual weeding. The culture was harvested 120 days after planting and 20 bulbs were selected at random from each treatment for the evaluation of external quality parameters. The raw garlic extract from each of the treatments (5 extracts per treatment) was obtained by macerating 5 g of the skinless cloves and subsequent filtration through gauze.
Determination of Caliber, Firmness, Pungency and ºBrix of Garlic Plant Bulbs of 'Criollo' Clones Cultivated with Different Concentrations of Quitomax®
The caliber of bulb is a classification according to the equatorial diameter of the bulb. this work, the classification proposed by Burba (1997) was used which establishes caliber 3 (26-35 mm), caliber 4 (36-45 mm) and caliber 5 (46-55 mm).
The firmness of the bulb was performed using a CEMA C-08 Digital Penetrometer in the Laboratory of Quality and Metrology of the Faculty of Technical Sciences, UNAH. The firmness of the bulb was taken as the maximum force that the bulb supports up to the separation of the cloves, and is expressed in kg F. The ºBrix was measured using a manual refractometer placing 1 to 2 drops of the diluted garlic extract (1:10) in the prism of the refractometer, avoiding the formation of air bubbles. The measurement was made by holding the refractometer in sunlight. After each measurement (three replicates per treatment) the prism was cleaned and dried.
The pungency (pyruvic acid content) with spectrophotometer according to techniques modifications of Benklebia (2000), Espinoza et al (2010) and Grégrová et al (2013). At 2 aliquots of the diluted garlic extract (1:10) 2 aliquots of 5 % trichloroacetic acid were added for the inactivation of the enzyme alliinase and it was left to rest for 1 hour. Then it was centrifuged for 1 min and 1 mL of 2,4-dinitrophenylhydrazine (0.125 g in 1 L of 2 mol L-1 HCl solution) was added to 1 mL of the supernatant. It was incubated in a water bath at 37°C for 15 min. Subsequently, 5 mL of NaOH 24 g L-1 were added and stirred for 5 minutes. Absorbance readings were recorded at 490 nm.
Physical-Chemical and Chemical Properties of Garlic Extract from Plants of 'Criollo' Clones Cultivated with Different Concentrations of Quitomax®
The electrical conductivity (EC) and pH (active acidity) of the diluted garlic extract (1:10) were performed by conductimetry and potentiometry respectively, according to the Cuban standard NC 39: 1999. The total measured acidity corresponds to the total acid content in the extract and was determined by acid-base volumetry, using NaOH 0.025 mol L-1 as titrant and phenolphthalein as indicator. The results were expressed as a function of the organic acids with the highest content in fruit and vegetable juices: citric, malic and tartaric acid (Domene & Segura, 2014), as well as pyruvic acid. The calculation was made as a function of the molar mass of each acid taking into account the volumetric law and expressed as a percentage (Table 2).
The determination of the total protein content in the extract was made by the Biuret method. To an aliquot of the diluted extract, 1 mL of distillated water and 8 mL of the Biuret reagent (mixture of copper sulfate in basic medium that forms with the peptide bonds a blue complex) were added. The dilution was shaken and around 10 min were waited for good color development. Absorbance was read at 540 nm in UV-Visible spectrophotometer (Rayleígh-1601).
The reducing carbohydrate content in the garlic extract was determined on a Rayleigh-1601 UV-visible spectrophotometer and glucose standards (0.2 to 1 mg mL-1) were used. The reducing carbohydrate content was determined using 3 mL of 3,5-dinitrosalicylic acid and 1 mL of the garlic extract, 1:10 dilution according to the methodology described by Noelting & Bernfeld (1948).
TABLE 2 Expressions for the calculation of titratable acidity according to organic acid. Modified from Domene & Segura (2014) where Vg: volume spent on titration
| Acid | Molar Mass (g mol-1) | g of acid L-1 | % of acid |
|---|---|---|---|
| 192,12 | Vg*0,16 | Vg*0,016 | |
| 134,09 | Vg*0,17 | Vg*0,017 | |
| 150,09 | Vg*0,19 | Vg*0,019 | |
| 88,06 | Vg*0,22 | Vg*0,022 |
The data were processed using the Statgraph v 5.1 statistical package, a simple classification analysis of variance (ANOVA) was performed and the multiple comparison of means was achieved using the Tukey test at 95 % confidence.
RESULTS AND DISCUSSION
Determination of Caliber, Firmness, Pungency and ºBrix of Garlic Plant Bulbs of 'Criollo' Clones Cultivated with Different Concentrations of Quitomax®
The quality of the garlic bulb can be measured through various indicators such as caliber, firmness, color, pungency, total soluble solids content and phenol content (Argüello et al., 2006; Grégrová et al., 2013; Akan, 2019). Table 3 shows the results of the indicators of caliber, firmness and pungency of garlic bulbs from plants of the 'Criollo' clones treated with different concentrations of the non-microbial biostimulant QuitoMax®.
Table 3 Values of caliber, firmness and pungency of the garlic plant bulbs (Allium sativum L.) of the 'Criollo' clones cultivated with different concentrations of QuitoMax®. (Means of three repetitions)
| Treatments | Caliber (%) | Firmness (Kg F) | Pungency (mg L-1) | |
|---|---|---|---|---|
| 3 (26-35 mm) | 4 (36-45 mm) | |||
| C9-0 | 40 | 60 | 17.22 | 2.48 |
| C9-1 | 40 | 60 | 15.33 | 2.36 |
| C9-5 | 20 | 80 | 16.77 | 2.33 |
| C9-10 | 60 | 40 | 15.23 | 2.59 |
| ESx | 1.13 | 0.0045 | ||
| CV (%) | 9.84 | 6.43 | ||
| CV-0 | 100 | - | 16.38 | 2.49 bc |
| CV-1 | 40 | 60 | 15.66 | 1.93 c |
| CV-5 | 80 | 20 | 15.83 | 3.13 a |
| CV-10 | 40 | 60 | 16.02 | 2.97 ab |
| ESx | 1.08 | 0.0037 | ||
| CV (%) | 10.04 | 9.87 | ||
In none of the clones were obtained bulbs of 5 caliber (46-55 mm), this result could be justified by the fact that for the 'Criollo' clones the maximum caliber reached is 4. In the literature consulted, no reports were found of caliber (or equatorial diameter) of bulbs for 'Criollo' clones, with the exception of the 'Criollo-9' clone for which a range of values for the equatorial diameter of the bulb from 34 to 39 mm is reported (Izquierdo & Gómez, 2012).
Table 3 shows that the influence of the use of QuitoMax® on this indicator depends on the cultivar and the concentration of the biostimulant. While for the cultivar 'Criollo-9' the major amount of bulbs with caliber 4 are founded using the QuitoMax® concentration of 5 mg L-1, for the cultivar 'Criollo-Víctor' the major amount of bulbs with caliber 4 was obtained when QuitoMax® concentrations of 1.0 and 10.0 mg L-1 are used.
It is necessary to highlight that for this last cultivar ('Criollo-Víctor') the percentage of bulbs with caliber 4 only appears in plants treated with the doses of the biostimulant QuitoMax®, this could have an important commercial and economic implication once the bulb is the commercial attribute of this crop.
The increase in the diameter of the garlic bulb in plants cultivated with biostimulants has been reported by several authors (Balmori et al., 2019; Pupo et al., 2016; Shafeek et al., 2015; Paradjikovic et al., 2014; Denre et al., 2014; Anjum et al., 2014; Zaki et al., 2014). Shafeek et al (2015), in the study of the effect of foliar application of humic acid (HA) in garlic cultivation (Chinese cv.) under field conditions, found that plants treated with the highest concentration of HA produced bulbs of higher caliber. The results of this work indicate that the use of the highest concentration of the biostimulant (QuitoMax®) does not always lead to the production of larger diameter bulbs.
The results for bulb firmness are within the range of values reported by Balmori et al (2019), who used dilutions of a humic vermicomposting extract in the cultivation of the 'Criollo-9' clone as a biostimulant. No significant differences were found between the clones or between the QuitoMax® concentrations. The latter indicates the possibility that there is no influence of this biostimulant on the number of external cataphylls (protective leaves), which influences the ease of cloves separation (López et al., 2012).
For pungency (pyruvic acid content), which corresponds to the concentration of alliin, the precursor substrate and responsible for the smell and taste of garlic (Espinoza et al., 2010), significant differences were found between QuitoMax® concentration only for the 'Criollo-Víctor' clone, with the highest concentrations of the biostimulant, being those with significantly higher values. These results are in correspondence with those of Denre et al (2014), researchers who in the study of the effect of different concentrations (100, 200, 300 and 400 ppm) of a commercial humic acid on the pungency of the Gargajali variety of garlic, found a significant increase in this indicator as the concentration of the biostimulant increases.
ºBrix is an indicator used in the agri-food industry to measure the approximate amount of sugars, although in reality with this scale the content of total soluble solids is determined, the most abundant being sugars and organic acids (Domene & Segura, 2014). In Figure 1 it is observed that for the 'Criollo-9' clone the concentration of 1 mg L-1 of QuitoMax® was significantly higher than the rest of the treatments, while for the 'Criollo-Víctor' clone there were no significant differences between treatments.
The ºBrix values found in this work are slightly lower than those reported in the literature for this cultivar from 17.2 to 21.3 ºBrix (Izquierdo & Gómez, 2012), as well as those reported by other authors in other cultivars such as Pardo et al (2007) who report ranges from 25.1 to 29.4 ºBrix and Grégrová et al (2013) with reports from 31.6 to 38.7 ºBrix. However, they are within the range of values reported by Balmori et al (2019) who made foliar applications of dilutions of an extract of humic substances in the cultivar 'Criollo-9'. The results of ºBrix found in this work indicate that there should be no changes in the carbohydrate content due to the use of QuitoMax®.
FIGURE 1 ºBrix values of the extract of bulbs of garlic plants (Allium sativum L.) from clones 'Criollo-9' (A) and 'Criollo-Víctor' (B) cultivated with different concentrations of QuitoMax®. (Means of three repetitions. Different letters represent significant statistical differences according to Tukey for p < 0.05).
Physical-Chemical and Chemical Properties of Garlic Extract from Plants of 'Criollo' Clones Cultivated with Different Concentrations of Quitomax®
For both cultivars of 'Criollo' clone, the use of QuitoMax® does not significantly modify the indicators of electrical conductivity (EC) and pH, while the titration acidity in the case of the 'Criollo-Víctor' clone is significantly modified with the concentration of the biostimulant.
Electrical conductivity is an indicative of the content of total salts, as well as acidic and basic ionizable substances. Hydronium and hydroxyl ions are the ones that most contribution to the conductivity of a solution. The values found in this work are slightly lower than those of Balmori et al (2019), authors who did find significant differences between the dilutions tested of the humic extract and the control treatment.
The pH values, indicative of the concentration of H3O+ ions in the extract, which comes from the acidic compounds present in it, are between 6.50-6.59, a range that corresponds to those reported by Pardo et al (2007) in 14 garlic cultivars: five of purple type (Moraluz, Morasol, Moratop, Mulvico and Planasa), 7 of white type (Basic, Corail, Cristo, Garcua, Ramses, Supreme and Thermidrome) and two of Chinese type (Planasa and Sprint). Other authors such as Espinoza et al (2010) working with six garlic cultivars (Cincomesino, Barranquino precoz, Mapuri, Alfa suquia, Pata de perro and Barranquino tardío) found lower pH ranges, as did Akan (2019) who reported a range from 5.5-6.33 for four varieties of garlic: French cultivar harvested in the eastern region of France (Nice), Spanish cultivar called 'Ajo Spring Blanco', Chinese cultivar from the province of Shandong and the cultivar 'Taşköprü' from of the district with the same name located in the Black Sea Region, northern part of Turkey. According to this author, pH levels are mainly determined by irrigation, fertilization and ecological conditions. The EC and acidity values of the extract of garlic plant bulbs from the 'Criollo 9' and 'Criollo Víctor' clones treated with different concentrations of Quitomax® are presented in Table 4.
TABLE 4 Values of electrical conductivity (EC), active acidity (pH) and measurable acidity (% organic acids) in the extract of bulbs of garlic plants (Allium sativum L.) from 'Criollo' clones cultivated with different concentrations of QuitoMax®. (Means of three repetitions. Different letters represent statistically significant differences according to Tukey for p < 0.05)
| Treatments | EC (µS cm-1) | pH | % organic acids | |||
|---|---|---|---|---|---|---|
| Citric | Malic | Tartaric | pyruvic | |||
| C9-0 | 1631 | 6,56 | 0,37 | 0,40 | 0,44 | 0,51 |
| C9-1 | 1751 | 6,56 | 0,32 | 0,34 | 0,38 | 0,44 |
| C9-5 | 1660 | 6,59 | 0,32 | 0,34 | 0,38 | 0,44 |
| C9-10 | 1728 | 6,50 | 0,37 | 0,40 | 0,44 | 0,51 |
| Esx | 34,18 | 0,019 | 0,012 | |||
| CV (%) | 6,99 | 0,99 | 11,36 | |||
| CV-0 | 1869 | 6,53 | 0,32 b | 0,34 b | 0,38 b | 0,44 b |
| CV-1 | 1705 | 6,54 | 0,19 c | 0,20 c | 0,22 c | 0,26 c |
| CV-5 | 1855 | 6,56 | 0,42 a | 0,44 a | 0,49 a | 0,57 a |
| CV-10 | 1732 | 6,52 | 0,40 a | 0,43 a | 0,48 a | 0,55 a |
| Esx | 46,48 | 0,06 | 0,03 | |||
| CV (%) | 8,99 | 3,09 | 7,86 | |||
The titration acidity of the garlic extract expressed as a function of the organic acids: citric, malic, tartaric and pyruvic, is significantly different between the biostimulant concentrations only for the 'Criollo-Víctor' clone. The highest concentrations (5 and 10 mg L-1) of QuitoMax® significantly exceed the control treatment and the concentration of 1 mg L-1 of the biostimulant is significantly lower than the rest of the treatments, results that correspond to those obtained for the Pungency indicator presented previously (Table 3).
The content of organic acids influences on the taste of food, color, microbial stability and the quality of preservation, while the content of organic compounds such as proteins and carbohydrates, are related to culinary and medicinal properties of garlic (Espinoza et al., 2010). Figure 2 shows the results for the protein content in the garlic extract of both cultivars, observing that for the cultivar 'Criollo-9' there are no significant differences between the treatments, but in the cultivar 'Criollo-Víctor' the QuitoMax® concentration of 5 mg L-1 significantly exceeds the rest of the treatments.
FIGURE 2 Total protein content in the extract of garlic plant bulbs (Allium sativum L.) from clones 'Criollo-9' (A) and 'Criollo-Víctor' (B) cultivated with different concentrations of QuitoMax®. (Means of three repetitions. Different letters represent significant statistical differences according to Tukey for p < 0.05).
Increased protein concentration in plants cultivated with biostimulants has been reported by several authors (Anjum et al., 2014; Shafeek et al., 2015, Canellas et al., 2015). In the consulted literature, few investigations were found where the content of N in the agricultural fruit of plants treated with QuitoMax® is reported. Fawzy et al (2012) report an increase in protein and nitrogen content in bulbs of garlic plants (Chinese cv.) cultivated with foliar application of Chito-Care®, a commercial product of chitosan from Egypt. Authors such as Sabreen & Mohsen (2015) studying the effect of foliar application of chitosan concentrations at concentrations of 0.05 and 10 g L-1 in the pumpkin crop, found an increase of N content in the fruit when used the highest concentration of the biostimulant.
It is possible that the increase found in this study only for one of the concentrations in the cultivar ‘Criollo-Víctor’ is conditioned by the form and time of application of the biostimulant. In this work, an imbibition of the cloves and a single foliar application are performed at 50 dap, while for example in the work by Sabreen & Mohsen (2015) in pumpkin, the foliar applications of chitosan were carried out three times with intervals of 10 days beginning at 25 days after planting. Another possibility could be the kind of chitosan, authors such as Costales et al (2016) point out that the degree of deacetylation and molecular mass of chitosan influence their biological response, information that is not generally found in commercial chitosan-based biostimulants.
Figure 3 shows the results for the content of reducing carbohydrates in garlic extract from plant bulbs treated with QuitoMax®, showing significant differences between treatments. For the 'Criollo-9' cultivar, all the concentrations of the biostimulant significantly exceed the control and the concentrations of QuitoMax® 5 and 10 mg L-1 are significantly higher than 1 mg L-1. For the cultivar 'Criollo-Víctor' a similar behavior is found, all the treatments with the biostimulant concentrations are significantly higher than the control treatment with no significant differences between them.
FIGURE 3 Reducing carbohydrate content in the extract of garlic plant bulbs (Allium sativum L.) from clones 'Criollo-9' (A) and 'Criollo-Víctor' (B) cultivated with different concentrations of QuitoMax®. (Means of three repetitions. Different letters represent significant statistical differences according to Tukey for p < 0.05).
These results do not correspond to those of ºBrix (Figure 1) where no significant modifications were found, which is logical since it is not about the content of total carbohydrates, but only the content of carbohydrates that contain a potentially free carbonyl group (monosaccharides and reducing disaccharides). Polysaccharides are not quantified by this technique because although they have the carbonyl group, it is small in the macromolecule and does not react.
In order to establish a relationship between ºBrix and carbohydrate content, it would be necessary to determine the total carbohydrate content, and especially of fructanes, such as scodorose, reserve polysaccharide and more abundant in garlic that has been related to the quality of the bulb (Argüello et al., 2006). Another possible correlation would be from the identification of the carbohydrates present in the garlic extract by techniques such as high-performance liquid chromatography (HPLC). Investigations about the influence of QuitoMax® on carbohydrate metabolism were not found. Chitosan stimulates the physiological processes in the plant and increases the size of the cells, which makes the nutrients easier to be assimilated by the plant, increasing its growth, development and yields (Rodríguez et al., 2017).
Even though integral mechanization of garlic cultivation is not common in Cuba, machinery such as planters or harvesters can save time and field labor. Other machinery such as sorters contributes to increasing yields and quality (López et al., 2012). Knowledge of the physical, mechanical and chemical properties of garlic is of great importance for the mechanization of this crop and its commercial destination. The efficiency of the sheller / sorting machines depends on the caliber, firmness, number of fertile leaves, number and degree of humidity of external cataphiles. In addition, one of the most common errors in the use of planters is the poor calibration of the cloves (López et al., 2012). The elements described above and the quantification of the chemical compounds in the different varieties of garlic are important factors when selecting the cultivars with the best chemical characteristics for the food or pharmaceutical industry (Espinoza et al., 2010).
Several authors have justified the different values of the indicators evaluated in this study by the origin of the garlic, the type of soil where the planting was carried out, the cultural attentions provided and environmental factors. According to Akan (2019), the effect of the variety is significant in morphological indicators, but not in the case of biochemical indicators, suggesting that this latter behavior can be explained by genetic and environmental conditions. In this work, both cultivars were planted under the same experimental conditions, so the responses to the application of QuitoMax® would be conditioned by the type of cultivar.
CONCLUSIONS
With the use of biostimulants, not only to increase the size of the agricultural fruit is intended, but also to avoid an alteration to the detriment of the already established quality values for the fruit. In this work, there were no notable variations in garlic quality parameters for both clones, making it possible to use QuitoMax® in the production of this crop. The few modifications found in the quality indicators evaluated (size, pungency, % of organic acids, content of reducing carbohydrates and proteins) contribute to the increase in internal quality and depend on the concentration of the biostimulant and the variety.
