Grapevine (Vitis vinifera) is the most widely cultivated fruit crop in the world and the most important in economic terms. Crimson Seedless is a new late-season table grape recently developed by scientists at the USDA-Fruit Genetics and Breeding Research Unit, Fresno, California, USA. When properly mature, the fruit of Crimson Seedless is bright red and has excellent eating characteristics; its berries are firm and crisp and have good flavor. Grapevine is affected by several fungal and diseases such as grey mold (Botrytis cinerea), powdery mildew (Uncinula necator) and downy mildew (Plasmopara viticola). Gray mold (Botrytis cinerea) is the main postharvest decay problem of table grapes and limits their shelf-life.
Botrytis cinereais responsible for the gray mold disease on more than 200 host plants. This necrotrophic ascomycete displays the capacity to kill host cells through the production of toxins, reactive oxygen species and the induction of a plant-produced oxidative burst. Thanks to an arsenal of degrading enzymes, B. cinereais then able to feed on different plant tissues. Recent molecular approaches, for example on characterizing components of signal transduction pathways, show that this fungus shares conserved virulence factors with other phytopathogens but also highlight some Botrytis-specific features. The discovery of some first strain-specific virulence factors, together with population data, even suggests a possible host adaptation of the strains. The availability of the genome sequence now stimulates the development of high-throughput functional analysis to decipher the mechanisms involved in the large host range of this species (Choquer et al., 2007).
The teleomorph (sexual form) of Botrytis cinereais anascomycete, Botryotinia fuckeliana, also known as Botryotinia cinerea. A total of 356 field isolates of B. fuckeliana were collected from grapes (Vitis vinifera) growing at four locations in Champagne (Trepail, Bar-sur-Seine, Bour-sault and Plumecoq). The isolates were collected from three varieties of grape (Chardonnay, Pinot Noir and Pinot Meunier) and three organs (berry, leaf and stem). Two hundred fifty-nine of the 356 isolates were collected from separate lesions, sometimes on the same plant. The remaining 97 isolates were separate isolations from the same berries (Giraud et al., 1997). Sulfur dioxide (SO2) is traditionally used as an antimicrobial postharvest, in packages or storage rooms. Thus, practices such as postharvest fumigation with SO2 and carbon dioxide (CO2) have a beneficial effect in preserving quality attribute for table grape (Mitcham and Leesch, 2004). One of the problems associated with SO2 fumigation of grapes is the constant potential for injury to the berries andrachis. Injured tissue first shows bleaching of color, followed by sunken areas where accelerated water loss has occurred. Another problem with SO2 fumigation of grapes is the level of sulphite residue remaining at time of final sale. Concerns about harm to human health from SO2 encourage evaluation of alternatives. Considerable research has been conducted to find alternatives to SO2 treatments for grey mould control.
A new technology for plant disease control is based on the activation of the plant's own defense system with the aid of low molecular weight synthetic molecules.
β-aminobutyric acid (BABA), a non-protein amino acid and a derivative of carboxylic acid. It has a carboxyl group at the first carbon atom and an amino group positioned at the third carbon atom, thus the name (DL)\-3-aminobutyric acid (β-aminobutyric acid) (Fig. 1). BABA is able to potentiate signal transduction pathways in different plants against a broad spectrum of microbial pathogens (Conrath et al., 2002; Ton et al., 2005).
The first line of defense a pathogen will encounter during plant infection consists of structural preformed barriers such as the cuticle and cell wall. The cuticle layer represents the first barrier for the pathogen to penetrate directly through the cell wall (Kerstiens, 1996; Zimmerli et al., 2000) observed that the protective effect of BABA is due to a potentiation of natural defense mechanisms against biotic and abiotic stresses. Higher concentrations of BABA are required on leaves in contrast to small doses that are required when applied to the root system (Cohen and Gisi, 1994).
Tavallali et al. (2008) reports that BABA induced resistance in orange peel tissue against infection of Penicillium italicum in a concentration-dependent manner and the optimum concentration was 40 mM. Therefore, these data suggest that BABA probably acts as a plant growth regulator which is most effective when applied at an optimal concentration and not as a fungicide that usually becomes continually more effective as the dose increases.
|Fig. 1:|| Structure of β-aminobytyric acid
Thus, the main mode of action of BABA in reducing decay development on the fruit surface was through the activation of pathogen resistance mechanisms and not any possible direct antifungal effects.
However, Fischer et al. (2009) found direct effects on fungi, since BABA inhibited the mycelial growth of Botrytis cinerea and affected Saccharomyces cerevisiae growth in a concentration dependent manner. Application of BABA in fruit possesses promising results in the control of postharvest diseases as an alternative to traditional methods.
Recently it has become clear that BABA also can cause major alterations in plant amino acid balance, induce stress-responsive energy sensor protein kinases, induce anthocyanin accumulation and reduce vegetative growth in Arabidopsis (Wu et al., 2010).
The objective of the present study was to evaluate the inhibitory effect of BABA for maintaining quality and controlling decay of Crimson Seedless grape caused by grey mould (Botrytis cinerea), in the laboratory and nature after cold storage and through marketing.
MATERIALS AND METHODS
Isolation and identification of the pathogen: Botrytis cinerea was isolated from naturally infected Crimson Seedless grape. These isolates were the most aggressive one in our collection and produced the largest lesions on inoculated fruits. These fungi were purified and maintained on Potato Dextrose Agar (PDA) and stored at 4°C, with periodic transfers through citrus fruits to maintain its aggressiveness. Seedless grape were ready for examination under a stereoscopic binocular microscope (6-50 x) for the presence of fungi and to study their habit characters. When necessary the compound microscope was used for confirming the identification after having examined the morphology of conidia and conidiophores. Fungi presented on infested seeds were identified by means of comparison with the description sheets of Commonwealth Mycological Institute, Kew, Surrey, England (CMI), Danish Government Institute of Seed Pathology (DGISP) publications as well as publication of Ellis (1971).
Effect of BABA on growth of fungi isolated from Crimson Seedless grape and disease infection percentage
Linear growth: BABA was tested in vitro on the linear growth of the pathogenic fungi. Different concentrations were added to 10 mL of sterilized PDA before solidification and then poured in sterile Petri-dishes. After solidification, the plates were inoculated with fungal disc (5 mm) in the center of the plate and incubated at 27±1°C. Three plates for each particular treatment for each fungus were used as replicates; three plates were prepared to serve as control for each fungus. Linear growth was observed daily and diameter of fungal colonies were recorded when plates of any treatment were filled with the fungal growth.
Dry weight: One hundred mL of liquid PD medium in 250 mL Erlenmeyer flasks were amended with different concentrations of the tested compounds after autoclaving. Each flask was inoculated using two discs of 0.6 mm in diameter of fungal culture, then incubated at 20±2°C for 7 days. Control flasks contain no concentrations of these compounds. Three replicates were used for each concentration. At the end of incubation period, the mycelium was filtered off and washed several times with distilled water, then dried in an oven at 80°C for 48 h till constant weight (El-Morsy, 1993).
Field study: The present investigation was carried out during the two successive seasons of 2012 and 2013 on five years old Crimson Seedless grapevines grown in a private vineyard located at Aga city, Dakahlia, Governorate. The vines were grown in clay loam soil and planted at 1.5x2.5 m apart and trained according to cane pruning system. All vines received the recommended regular fertilizer and other horticulture practices. Thirty-six vines of nearly similar vigor and bud load were chosen for the spraying applications according to completely randomized block design with three replicates each one was represented by three vines. Two weeks before harvest, clusters of the selected vines were sprayed as follows:
|•||Control (spray cluster with tap water)
||Spray clusters with BABA 200 ppm
||Spray clusters with BABA 250 ppm
||Spray clusters with BABA 300 ppm
The surfactant super film as a wetting agent was added at the rate of 40 cm/100 L water to all spraying solutions in order to obtain best penetration results.
Harvest time was adjusted when the berry skin was full red color and SSC percentage in berry juice of the control treatment reached 18-19% in the two seasons. Clusters were picked at morning and immediately transported to the laboratory. Samples from each replicate were taken to study the effect of each treatment on clusters and berries quality at harvest time to determine the initial properties.
For storage study, clusters of all treatments were sorted to remove any infected and berry damaged then clusters were packed using perforated plastic bags. All bags with clusters were weighted and every six bags were put in ventilated carton box. The total numbers of carton boxes were 48 for all treatments. Clusters of each treatment were placed in 12 carton box, each box containing 6 perforated plastic bags (6 clusters). All boxes were stored 30 days at 0±1°C with 90-95% RH, then 3 carton boxes for each treatment were taken 10 days intervals to determine clusters and berry characteristics.
Disease infection: It was determined according to the following equation:
For shelf life study, after 60 days of cold storage three carton boxes for each treatment were held 3 days at room temperature conditions as shelf life at 20±2°C with 70-75% relative humidity to determine the following parameters.
Clusters and berries measurements
Cluster weight loss (%): It was calculated according to the following equation:
Berry decay (%): It was calculated according to the following equation:
Berry shatter (%): It was determined according to the following equation:
Total loss (%): It was calculated according to the following equation:
Berry adherence strength: It was measured as (gf) by using PHSH-PULL (Dynamometer Modle DT101).
Berry firmness: It was measured as (g cm-2) by using PHSH-PULL (Dynamometer Model DT101) with 3/16 inch plunger.
Soluble Solids Content (SSC): It was measured in berry juice by using a Carl-Zeiss hand refractometer according to (AOAC, 2005).
Total titratable acidity: Titratable acidity of berry juice was determined in terms of anhydrous tartaric acid percentage according to (AOAC, 2005).
SSC/acid ratio: It was calculated by dividing the value of SSC over the value of titratable acidity of each sample.
Total anthocyanin content: It was measured in berry skin at 535 nm using spectrophotometer according to Hsia et al. (1965). The content of total anthocyanin in berry skin was calculated using the following equation:
The E value for 1% solution at 535 nm is equal to 98.2. Therefore, the absorbance of a solution containing 1 mg is equal to 98.2 according to (Ranganna, 1979).
Total sugar: The extract was prepared by taking 0.5 g of fresh berries and extracting the same with 80% ethanol by centrifuging three times. The supernatant was collected and measured quantity of distilled water was added to it and heated until all ethanol got evaporated. Then volume of sample was made up to 150 mL by adding distilled water. The total sugar was estimated using anthrones reagent (Ranganna, 1979). The 1 mL of alcoholic extract was taken in a test tube and chilled. After a while 4 mL of anthrones reagent was carefully run down the walls of the test tube. The test tubes were thereafter immersed in ice water. The tubes were brought to ambient temperature and boiled in water bath for 10 min. After proper cooling, the absorbance was measured at 625 nm.
Statistical analysis: Data of both seasons of the study were designed and analyzed as completely randomized block design by using analysis of variance (ANOVA), with two factors; time and temperature. Differences among treatment means were statistically analyzed by using the least significant differences test (LSD) at p = 0.05%, means separation using the CoStat program.
RESULTS AND DISCUSSION
This study was to estimate the effect of postharvest treatments by BABA on fruits quality and decreasing decay of Crimson Seedless grape fruits during storage.
Effect of BABA on growth of fungi isolated from Crimson Seedless grape and disease infection percentage: Data in Table 1 show the effect of in BABA on linear growth and dry weight of Botrytis cinerea isolated from Crimson Seedless grape. It was noticed that the reduction in linear growth and dry weight were correlated to the increase in BABA concentrations. BABA at 300 ppm treatment completely inhibited the linear growth and dry weight of Botrytis cinerea. This result is in agreement with the finding of Latifa et al. (2011) on citrus who reported complete inhibition of mycelia growth of Penicillium itelicum which was generally associated with complete inhibition of sporulation by organic acids and salts.
Data in Table 2 showed the effect of BABA on disease infection of Crimson Seedless grape during cold storage conditions through 60 days at 0±1°C with 90-95% RH and 3 days as marketing at room temperature. In both seasons, prolonging the marketing stage resulted in decreased in disease infection with the increase of BABA concentrations. BABA at 300 ppm treatment gave complete reduction in disease infection caused by Botrytis cinerea.
Some fruits, apples among them, are usually stored after harvest. During cold storage, losses of economic importance are produced by several decays due to fungal rot. Penicillium expansum and Botrytis cinerea are well-known postharvest pathogens. They produce blue and gray rots, respectively (Calvo et al., 2007).
|Table 1:||Effect of BABA on linear growth and dry weight (g) of Botrytis cinerea isolated from
|Table 2:||Effect of BABA on disease infection percentage by Botrytis cinerea of Crimson Seedless grape stored for 60 days at cold storage during 2012 and 2013 seasons
|Table 3:||Effect of pre-harvest BABA applications on Crimson Seedless grape characteristics at harvest during 2012 and 2013 seasons
This result is in agreement with the finding of Troncoso-Rojas and Tiznado-Hernández (2007) on fruits and vegetables by chemical alternatives to conventional fungicides for postharvest disease control should be natural or synthetic compounds with known and minimal toxicological effects on mammals and the environment. The origin of these alternatives includes classifications such as food additives and substances listed as Generally Regarded as Safe (GRAS) by the United States Food and Drug Administration, natural compounds obtained from plants, animals or microorganisms, some volatiles and essential oils, phenolic compounds, plant extracts, peptides, alkaloids, lectins, antibiotics, propolis, latex or chitosan and other chemicals such as calcium polysulfide or ammonium molybdate.
Fungicide application is now the most efficacious method for controlling plant diseases caused by oomycetes and fungi. As legislation is limiting and reducing their use, this is strongly stimulating studies for the identification of additional and environmentally friendly approaches in the control of their associated diseases. Among these, induced resistance offers the prospect of long-lasting, broad-spectrum disease control through activation of the resistance defense machinery of the plant itself. At least three types of systemic induced resistance have been described that are effective against biotrophic and necrotrophic oomycetes and fungi: Systemic acquired resistance induced systemic resistance and β-aminobutyric-acid-induced resistance. The phytohormones salicylic acid, ethylene, jasmonic acid and abscisic acid are involved in the pathways that characterize these forms of resistance. Through crosstalk between the induced resistance pathways, it is likely that plants can minimize energy costs and create a flexible signaling network that allows fine tuning of the plant defense response to invaders. Possible resistance mechanisms to oomycetes and fungi during induced resistance are described here and some examples of the application of induced resistance for the control of field and postharvest diseases of plants are reported and briefly discussed (Buonaurio et al., 2009).
Effect on characteristics of Crimson Seedless grape at harvest: Regarding to the effect of pre-harvest BABA applications on Crimson Seedless grape characteristics at harvest during the two seasons of 2012 and 2013 data are presented in Table 3.
Berry adherence gram-force (gf): With regard to the effect on berry adherence, the data in Table 3 reveal that, all applied treatments gave significant effect in this respect during both seasons. However, berry adherence was significantly higher by sprayed clusters, BABA 300 ppm (892 and 887 gf) in the two seasons. While, BABA at 200 ppm application increased the berry adherence (868 and 858 gf) in both seasons than those applied with BABA at 250 ppm (853 and 848 gf) during both seasons.
Berry firmness (g cm-2): It is clear from Table 3 that BABA treatments gave significant differences on the berry firmness at harvest than the untreated clusters during both seasons Furthermore, BABA (300 ppm) gave higher berry firmness (840 g cm-2) than the other treatments used during both seasons. BABA at 250 ppm increased the firmness (836 and 830 g cm-2) in both seasons than those applied with at 200 ppm (832 and 826 g cm-2) during both seasons.
Soluble solids content (SSC) (%): Regarding the effect of pre-harvest BABA applications on SSC (%) of Crimson Seedless grape, data from Table 3 revealed that all treatments gave no significant values of SSC (%) in berry juice during both seasons. BABA at 300 ppm gave somewhat higher values of SSC in berry juice (19.60 and 19.26%) during the two seasons under the study. The data also disclose that, BABA 250 ppm application increased SSC (19.40 and 19.10%) than 200 ppm BABA (19.20 and 18.90%) in both seasons.
Titratable Acidity (TA%): Data from Table 3 demonstrate that no significant differences between BABA treatments or control on the value of juice acidity at harvest during both seasons. While, BABA at 300 ppm gave a higher value of total acidity in fruit juice (0.634 and 0.626%) than all treatments used during the two seasons under the study.
Total anthocyanin content: With regard to the effect on anthocyanin content, the data also in Table 3 reveal that, all treatments used gave a somewhat increment in the values of anthocyanin in berry skin than the control in both seasons. However, BABA at 300 ppm application gave higher significant anthocyanin content (109.0 and 110.0 mg/100 g fw) during both seasons, respectively. Also, clusters sprayed with BABA at 250 ppm increased anthocyanin content (105.63 and 107.66) than BABA 200 at ppm (101.30 and 105.60 mg/100 g fw) during both seasons under the study. From the obtained data it is obvious that a good relation between soluble solids and anthocyanin content, since, the treatment which increased soluble solids produced clusters with higher anthocyanin content.
Total sugar (%): The data also in Table 3 disclose that, all treatments increased the values of total sugars insignificantly than the untreated clusters during the two seasons under the study. While, BABA at 300 ppm application gave higher value of total sugar (17.30 and 17.0%) during both seasons, respectively. Also, clusters sprayed with BABA at 250 ppm increased sugar content (17.20 and 17%) than at 200 ppm (17 and 16.50%) during both seasons under the study.
Effect on characteristics of Crimson Seedless grape under cold storage and through marketing at room temperature:
Cluster weight loss (%): Data from Tables 4 and 5
showed that the percent of clusters weight loss significantly increased gradually
with the progress of storage period and during marketing. The data also disclose
that all applied treatments significantly reduced the percent of loss in fruit
weight than the control under cold storage or held at room temperature. Since,
the percent of loss in fruit weight at the untreated clusters were 5.36 and
5.73 after 60 days of cold storage and it were 8.33 and 8.07 after three days
as marketing in both seasons, respectively.
The lowest significant values of weight loss percentage were recorded by applications of BABA at 300 ppm ranged 3.91 and 4.11 after 60 days of cold storage and 4.12 and 4.81 after 3 days as marketing in the two seasons, respectively.
Grapes are non-climacteric fruits with a relatively low physiological activity and are subject to serious water loss and softening after harvest which can result in stem browning, berry shatter, wilting, shriveling of berries (Crisosto et al., 2002).
Water loss is strictly a physical factor related to the evaporative potential of the surrounding air. The higher the evaporative potential of the air surrounding the fruit, the more water is lost from the fruit. This relationship may be expressed directly as the vapor pressure deficit a term which indicates the combined influence of temperature and relative humidity (Ngcobo et al., 2012).
Berry decay (%): It is clear from Tables 3 and 4
that the most treated fruits did not present any decayed berries till 15 days
of cold storage except control clusters in the second season.
|Table 4:||Effect of pre-harvest BABA applications on weight loss, decay Shatter and total loss of Crimson Seedless grapes under cold storage during 2012 and 2013 seasons
Thus, the percent of decayed berries for the untreated clusters were 4.48 and 4.96% after 60 days of cold storage but it reached about 7.08 and 6.31% through marketing in both seasons.
Furthermore, clusters treated with BABA at 300 ppm gave a lower percent of decayed berries after 60 days of cold storage (0.93 and 1.38%) but it were 3.80 and 3.21% during marketing in both seasons, respectively. Zhang et al. (2011) instituted that the effects of BABA on blue mould caused by Penicillium expansum in apple fruit stored at 25°C were investigated. BABA provided an effective control and strongly inhibited spore germination, germ and tube elongation of P. expansum in vitro. Using Propidium Iodide (PI) staining combined with fluorescent microscopy, it was found that the plasma membrane of BABA-treated P. expansum spores was damaged and the leakage of protein and sugar was significantly higher in BABA-treated mycelia than in the control. BABA treatment induced a significant increase in the activities of chitinase, β-1, 3-glucanase and peroxidase in apple fruit.
|Table 5:||Effect of pre-harvest BABA applications on weight loss, decay, Shatter and total loss of Crimson Seedless grape 3 days at marketing in room temperature after 60 days of cold storage during 2012 and 2013 seasons
These findings suggest that the effects of BABA on blue mould in apple fruit may be associated with the direct fungitoxic property against the pathogens and the elicitation of defense-related enzymes in fruit.
Berry shatter (%): Berry shatter is mainly triggered by mechanical damage
occurring during harvesting, packaging and transportation. As shown in Tables
4 and 5 the berry shatter increased significantly with
the advanced in storage period. In all the cases, excessive water loss leads
to berry shatter. However, clusters sprayed with BABA at 300 ppm evaluated low
level of berry shattering (2.11-2.61%) closely followed by clusters treated
with BABA at 250 ppm (3.17-4.02%) after 60 days of cold storage during both
seasons, respectively. Whereas, berry shatter was very high in control clusters
presented 5.17 and 6.87%, respectively.
Additionally, BABA 300 at ppm reduced the percent of berry shattering (3.63 and 3.12%) significantly than all treatments used or the control, while the untreated ones gave 7.53 and 8.64% after 3 days during marketing in both seasons, respectively.
There appear to be three types of berry shatter; physiological, pathological and mechanical. The first is associated with the thickening and hardening of the pedicel and production of an abscission layer. The increase of berry shatter during shelf life has been recommended the pedicle and stalk of cluster behave in a climacteric process showing respiration and ethylene peaks (Fayed, 2010).
Total loss in cluster (%): Total loss in cluster is mainly due to the
cluster loss weight, berry shattering and decayed berries which are presented
in Tables 3 and 4 from these data, it is
clear that the total loss in cluster gradually increased as storage period advanced.
Moreover, all the applied treatments reduced the percent of total loss in cluster than the untreated clusters. Yet, the percent of total loss in untreated clusters were 15.01 and 17.56% under 60 days of cold storage and reached 20.98 and 23.03% after three days at marketing in the both seasons, respectively.
BABA at 300 ppm reduced the total loss in clusters than the other treatments used either at 60 days from cold storage or during marketing at the same time. Yet, the percentage of total loss in clusters due to use BABA at 300 ppm was about 6.95 and 8.10 after 60 days of cold storage but reached about 11.56 and 11.15% during marketing, respectively through the two seasons. Since, this treatment was more effective for reducing the percentage of decayed and shattering berries. Moreover, BABA at 250 ppm application was more effective in reducing the percent of total loss in clusters compared with BABA at 200 ppm during both seasons. The percentage of total loss due to this treatment was about 9.04 and 10.13% after 60 days of cold storage and reached 15.70 and 15.04% during marketing in both seasons, respectively.
A possible explanation that such a high concentration of BABA is needed to elicit disease resistance is probably that only a small portion of the compound is actually absorbed by the tissue and also that of the entire BABA compound mixture only a small portion of its R-anantiomer isoform was found to be active in inducing pathogen resistance (Cohen, 2001).
Soluble Solids Content (SSC) (%): Regarding to the effect of pre-harvest
BABA applications on SSC (%) of Crimson Seedless grape data from Tables
6 and 7 revealed that the percent of SSC in berry juice
was gradually increased as a storage period advanced either at cold storage
or during marketing. Since, all treatments gave somewhat higher values of SSC
in berry juice than the untreated fruit during the two seasons under the study.
The data also disclose that, BABA at 300 ppm increased SSC (%) (20.50 and 20.30%) than the other treatments used or the control during cold storage, while reached 20.90 and 20.70 during marketing, respectively through the two seasons.
Khan et al. (2012) confirmed that increase in TSS may be related with enzymes which are presented when amino acids enhanced the synthesis of different proteins, acids and sugars.
|Table 6:||Effect of pre-harvest BABA applications on SSC, titratable acidity and total sugar of Crimson Seedless grape under cold storage during 2012 and 2013 seasons
|Table 7:||Effect of pre-harvest BABA applications on SSC, titratable acidity and total sugar of Crimson Seedless grape 3 days at marketing in room temperature after 60 days of cold storage during 2012 and 2013 seasons
This explanation is in the line with using foliar application of green algae extract on superior grapes which significantly improved TSS synthesis (Abd El Moniem and Abd-Allah, 2008).
Titratable Acidity (TA) (%): The acidity level is a very important quality factor in table grapes and those used for wine production. Consumer acceptance of table grapes and grape juice is strongly influenced by the sweetness to acid balance.
Data from Tables 6 and 7 demonstrate that
the most treatments used gave a somewhat increment of total acidity in berry
juice than the control after 60 days of cold storage.
Application of BABA at 300 ppm increased the percent of titratable acidity in berry juice than the other treatments or the untreated ones especially in the first season that presented 0.709% after 60 days of cold storage and ranged 0.724 and 0.716% three days during marketing. Whereas, BABA at 250 ppm treatment produce a higher value of this trend at cold storage in the second season realized 0.703%. On the other hand, all treatments used gave a higher value of titratable acidity in berry juice than the control clusters through marketing conditions.
All treatments increased acidity in fruits due to amino acids enhanced synthesis of different acids. This finding is in agreement with exogenous application of BABA which increased acidity of treated fruits. Similarly, foliar applications of mixture of amino acids and Ascophylum nodosum (Seaweed) amino acids enhanced acidity in Perlette grapes (Khan et al., 2012).
Total sugar (%): Considering to the effect on total sugar, data in Tables
6 and 7 reveal that the values of total sugar were progressively
decreased by the storage period advanced from harvest till 60 days either at
cold storage or during marketing at room temperature.
With regard to the effect of these treatments on total sugar the data reveal that, clusters treated with BABA 300 ppm produced a higher value of total sugar at cold storage since the values averaged about 18.30 and 18.0% while during marketing application gave a higher value of this trend (18.80 and 18.50%) under the two seasons, respectively.
BABA at 250 ppm application increased the percent of total sugar in cluster juice (18.26 and 18.0%) than those treated with BABA at 200 ppm (18.0 and 16.96%) after 60 days of cold storage during both seasons.
|Table 8:||Effect of pre-harvest BABA applications on berry adherence, berry firmness and anthocyanin content of Crimson Seedless grapes under cold storage during 2012 and 2013 seasons
|Table 9:||Effect of pre-harvest BABA applications on berry adherence, berry firmness and anthocyanin content of Crimson Seedless grape 3 days at marketing in room temperature after 60 days of cold storage during 2012 and 2013 seasons
It was reported that the accumulation of sugars in grapes preceding the rise in anthocyanin content, thus a strong correlation is found between the accumulation of certain amount of sugars in the berries and formation of anthocyanin (Pirie and Mullins, 1980). Furthermore, it has been found that the percentage of sugar has a triggering effect on anthocyanin accumulation.
Berry adherence strength (gf): It evident from Tables
8 and 9 that berry adherence was gradually reduced significantly
as storage period advanced. Also, all sprayed treatments improved berry adherence
than the control. However, berry adherence was significantly higher at clusters
sprayed with BABA at 300 ppm that attained 726 and 713 gf till 60 days under
cold storage since reached 697 and 680 gf during marketing through both seasons,
While, the decrement value of berry adherence was found of control clusters which reached 653 and 647 gf after 30 days under cold storage but arranged 618 and 592 gf during marketing through both seasons, respectively.
BABA at 250 ppm offered higher berry adherence (706 and 701 gf) after 60 days under cold storage and 3 days during marketing (657 and 639 gf) than BABA 200 ppm in both seasons under the study.
BABA enhanced the activities of antioxidant enzymes and non-enzymatic antioxidants. Accumulation of ABA transcription and signaling factors in BABA-treated Arabidopsis might prime it for ABA accumulation (Jakab et al., 2005). According to Zimmerli et al. (2001), BABA primes Arabidopsis plants to respond quicker and stronger to biotic and abiotic stresses. Recent studies revealed that BABA enhances mRNA Accumulation of Abscisic Acid (ABA) and ethylene early signaling intermediates.
Berry firmness (g cm-2): Data in Tables 8
and 9 showed that all treatments had the highest effects on
berry firmness comparing with control. Since, berry firmness was gradually decreased
during marketing as storage period advanced. However, the reduction in berry
firmness was higher during marketing at room temperature than at cold storage.
Since, the values of berry firmness of the control clusters were 644 and 624
g cm-2 after 60 days under cold storage but reached 584 and 570 g
cm-2 during marketing through both seasons respectively.
Meanwhile, BABA 250 ppm application presented higher berry firmness than all treatments used or the control at 60 days of cold storage (770 and 741 g cm-2) or during marketing at room temperature which ranged 624 and 615 g cm-2 in both seasons. BABA 300 ppm treatment gave a higher significant increment in berry firmness (673 and 670 g cm-2) after 60 days of cold storage or 3 days during marketing (619 and 595 g cm-2) than clusters treated with BABA 200 ppm application (667 and 656 g cm-2) till 60 days under cold storage and 3 days during marketing (594 and 586 g cm-2) in both seasons.
Firmness of BABA is increased by increasing Ca2+ content. Probably, BABA activates ABA signaling and ABA stimulates the increases in cytosolic Ca2+ by inducing both Ca2+ influx from the extracellular space and Ca2+ release from intracellular stores. ABA-induced increases in the activities of a can be prevented by the antioxidant enzymes pretreatments with the Ca2+ chelator indicating the involvement of Ca2+ in ABA-induced antioxidant defense (Jakab et al., 2005).
Total anthocyanin content: Tables 8 and 9
showed the changes in total anthocyanin content in the skin of Crimson Seedless
grape were gradually reduced from harvest till 60 days either at cold storage
or 3 days at room temperature as marketing after cold storage. Also, all treatments
applied increased the content of anthocyanin in berry skin than the control
under cold storage or at room temperature.
Moreover, BABA at 300 ppm application significantly increased the content of anthocyanin in berry skin (90.50 and 93.83 mg/100 g fw) after 60 days under cold storage and 3 days during marketing (83.70 and 85.93 mg/100 g fw) than the other treatments used or the control during both seasons.
However, control clusters presented lower values of anthocyanin in berry skin (80.30 and 77.16 mg/100 g fw) after 60 days of cold storage or 3 days during marketing (66.50 and 72.10 mg/100 g fw) through the both seasons.
Anthocyanins are colored pigments, thus the manipulation of anthocyanin production in grapes, is potentially a mean of influencing the visual perception of color in the fruit (Mori et al., 2005). Also, anthocyanins are plant secondary metabolites providing pigmentation to flowers, fruits, seeds and leaves. Guidoni et al. (2002) reported that anthocyanin concentration of grapes is an important fruit quality parameter for marketing. Anthocyanins contribute to grape quality by effecting both color intensity and color quality.
Anthocyanin considers one of the important flavonoids classes. Red and black grapes owe their attractive color to their anthocyanin pigments. Moreover, anthocyanin levels and the other flavonoid classes in grape skin are parameters available for evaluating grape quality.
It has been shown, BABA stimulate anthocyanin biosynthesis by regulating the expression of CHS (chalcone synthase) and DFR (dihydroflavonol-4-reductase) (Wu et al., 2010).
Based on the results of this study, it can be concluded that, the foliar applications of BABA had more pronounced effect on berry quality of Crimson Seedless grape than the control during cold storage at 0±1°C with 90-95% RH and through marketing at room temperature. Spraying 300 ppm BABA gave the best results for reducing total loss weight percentage, keeping the quality of berry during cold storage and during marketing at room temperature compared with the other treatments used or the control. Application of BABA in table grape possesses promising results in the control of grey mold as an alternative to SO2 treatments.