EFFECT OF SALICYLIC AND ASCORBIC ACIDS ON YIELD AND FRUIT QUALITY OF WONDERFUL POMEGRANATE TREES

AN experiment trial was carried out during 2017 and 2018 seasons on Wonderful pomegranate trees about 7 years old grown in sandy soil under drip irrigation system from well at private orchard located on Cairo-Alexandria desert road (about 50 km from Cairo), Egypt. Treatments of salicylic acid (50,100 and 150 ppm), ascorbic acid (500, 750 and 1000 ppm) and tap water control were foliar sprayed twice a year i.e. at full bloom and four weeks later. Abstractly, salicylic and ascorbic acid treatments enhanced leaf characteristics, yield and fruit quality traits as well as minimized sunburned and cracked fruit percentages. Ascorbic acid treatment at 1000 ppm proved to be most efficient treatment in this respect.


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Manfalouty pomegranate. Abdel Aziz et al. (2017) stated that foliar sprays of salicylic acid at 100 ppm improving growth, yield, fruit quality and reduced cracked fruits of Manfalouty pomegranate trees. On the other hand, Abada and Abd El-Hameed (2010) have worked on Flame seedless grapevines, Wassel et al. (2011) on Red Roomy grapevines. They mentioned that the application of salicylic acid enhanced yield and fruit quality.
Ascorbic acid is considered as a natural and organic antioxidant compound (Hafez et al., 2010). Ascorbate is a major metabolite in the plant. This antioxidant and its association with other components of the antioxidant system, protect the plant against oxidative damage resulting from aerobic metabolism, photosynthesis and range of pollutants (Abd-El Hamid, 2009 and Hassanein et al., 2009). It acts as a co-enzyme in an enzymatic cofactor and plant growth regulator (Gomez and Lajolo, 2008). Ascorbic acid has auxinic action. It has a synergistic effect on improving growth, flowering, yield and fruit quality of fruit crops (Ahmed et al., 1997 andBarth et al., 2006). It used instead of auxin and other chemicals for enhancing growth and fruiting of Washington navel orange trees (Ragab, 2002). Fayed (2010) found that the interaction of foliar application of compost tea with ascorbic and citric acids enhanced growth, yield and fruit quality of pomegranate trees. However, Ascorbic acid enhanced the yield and controlling the incidence of fruit disorders of apple trees (Ahmed et al., 1997). Abd-El-Rhman et al. (2017) reported that foliar spray ascorbic acid enhanced yield and fruit quality of Manfaloty pomegranate trees. Atef (2018) pointed out that foliar spray with a mixture of ascorbic acid improved growth, yield fruit quality of Wonderful pomegranate trees. The purpose of this work is to study the effect of salicylic and ascorbic acids on leaf characteristics, yield, fruit quality, sunburned fruit and fruit cracking of Wonderful pomegranate trees.

Material and Methods:-
An experiment was carried out during two successive seasons 2017 and 2018 at a private farm located on Cairo-Alexandria desert road about 50 km fromCairo(latitude 30°9′ 2.92″ N, longitude 30°40′ 31.75″ E), Egypt. Wonderful pomegranate trees (Punica granatum) aged 7 years old grown in sandy soil and spaced 3 x 5 m apart under drip irrigation system from well. Physical and chemical analysis of the experimental soil shown in Table 1, meanwhile the chemical analysis of used water from irrigation is recorded in (Table 2).  The experiment consisted of forty two trees healthy, nearly uniform in shape and size and productivity and received the same horticulture practices, were subjected to seven treatments as: control tap water, Salicylic acid as foliar sprays at 50 ppm, Salicylic acid as foliar sprays at 100 ppm, Salicylic acid as foliar sprays at 150 ppm, Ascorbic acid as foliar sprays at 500 ppm, Ascorbic acid as foliar sprays at 750 ppm, Ascorbic acid as foliar sprays at 1000 ppm. Tween-20 was added at 0.1% as a surfactant to spray solution including the control "tap water". Spraying was 1061 carried out using compression sprayers (5L solution/tree) at the previously mentioned dates. The experiment was designed as a randomized complete block design with three replicates for each treatment and each replicate was represented by two trees. Foliar spray of salicylic and ascorbic treatments were carried out at two times, the first foliar spray was done at full bloom and the second one was performed four weeks later, meanwhile, the control trees were sprayed with tap water at the previously mentioned times.
The response of Wonderful pomegranate trees to the tested salicylic and ascorbic treatments was evaluated through the following determinations.

Leaf characteristics
The area of leaves was determined by using portable area planimeter Mod Li3100 Ali (Li-Cor) while Leaf total chlorophyll content was determined by Minolta chlorophyll meter SPAD-502.

No. of fruits/tree and yield kg/tree
At harvest time, the number of fruits per each treated tree was counted and reported then yield (kg) per tree was weighed and recorded.

Cracked, sunburned fruits
Number of cracked and sunburned fruits per tree was counted and recorded. The percentages of cracked and sunburned fruits/tree were calculated.

Fruit physical and chemical properties Physical properties
Ten fruits were taken at harvest time from each treated tree for determination of the following physical and chemical properties. Fruit weight (g), fruit length (cm), fruit diameter (cm), weight of fruit grains (g), weight of 100 grains (g), juice volume (cm 3 ) per fruit, peel thickness (cm).

Chemical properties
Total sugar (%), total soluble solids (T.S.S.) were determined by Hand refractometer, total acidity in fruit juice (expressed as citric acid per 100 ml juice), TSS/ Acid ratio and ascorbic acid (mg ascorbic acid/100 ml juice) according to A.O.A.C. (1995).

Statistical analysis
The obtained data in 2017 and 2018 seasons were statistically analyzed by MSTAT-C soft-ware and means were differentiated using Rang test at the 0.05 level (Duncan, 1955).

Leaf characteristics Leaf area (cm 3 )
Table, 3 demonstrates that salicylic and ascorbic treatments enhanced leaf surface area in both seasons as compared with control treatment. Generally, 1000 ppm ascorbic treatment proved to be the superior treatment in this respect.

Leaf total chlorophyll content
All salicylic and ascorbic treatments succeeded in increasing leaf total chlorophyll content as compared with the control treatment in both seasons of study (Table, 3). Moreover, 1000 ppm ascorbic proved to be the superior treatment in this respect.
Means within each column followed by the same letter (s) are not significantly different at 5% levelThe enhancement effect of salicylic acid on leaf characteristics of pomegranate trees may be attributed that salicylic is a growth regulator which participates in the regulation of physiological processes in plants. Salicylic acid has a role in protecting the cells from senescence and preventing free radicals from the oxidation of lipids the components of the plasma membrane. Salicylic acid showed a synergetic effect like auxin and gibberellins (Sanaa et al., 2006).  16 A Means within each column followed by the same letter (s) are not significantly different at 5% level Salicylic acids have direct effect on plant growth, ions uptake, stomatal movement and reversing the effect of ABA on leaf abscission, (Romani et al., 1989). It was found also to accelerate the photosynthetic rate, modify the activity of important enzymes, increase the leaf area and dry mass production and to exhibit a rapid rate of root differentiation, (Singh, 1993  The enhancement effect of ascorbic acid on leaf characters may be attributed that ascorbic acid has positive action in catching all free radicals produced during plant metabolism (Alscher et al., 1997). Moreover, ascorbic acid has an auxinic action and synergistic effect on tree growth (Ragab, 2002). Ascorbic acid increased IAA content, which stimulates cell division as well as cell enlargement and this in turn in improved plant growth (Hassanein et al., 2009 and Abd-El Hamid, 2009). Ascorbic acid may serve as a potential growth regulator to enhance stress resistance in several species (Shalata andPeter, 2001 andKhan, 2006). Besides, foliar application of ascorbic acid had positive effect on growth parameter and increases in photosynthesis (Tarraf et al., 1999). The obtained results regarding the effect of ascorbic acid on leaf characteristics go in line with the findings of Fayed (2010) who mentioned that the interaction of foliar application ascorbic + citric acid enhanced leaf chlorophyll content of pomegranate trees. Moreover, El-Sayedet al. (2014) reported that ascorbic acid treatments enhanced leaf area and total chlorophyll of Manzanillo olive trees. Atef Abo-Ogiala (2018) stated that foliar sprays with ascorbic acid enhanced growth parameters of "Wonderful" pomegranate trees.

Number of fruits/tree and yield kg/tree Number of fruits/ tree
It is clear from Table, 4 that salicylic and ascorbic sprayed trees produced a higher number of fruits than those sprayed with tap water control in both seasons of study. Anyhow, 1000 ppm ascorbic treatment shows superiority in this respect.  Table 4 illustrates that salicylic and ascorbic treatments succeeded in improving tree yield as compared with the control in both seasons. Generally, 1000 ppm ascorbic sprayed trees showed to be the highest production trees (24 and 25 kg/tree) against (16.3 and 16.0 kg/tree) for tap water control sprayed trees in 2017 and 2018 seasons, respectively.

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The improvement effect of salicylic acid on yield of pomegranate trees may be attributed that salicylic acid increased the photosynthetic rate, modify the activity of important enzymes, and it increased leaf area and dry mass production (Hayat and Ahmed, 2007). On the other hand, salicylic acid treatment increased leaf chlorophyll content (Hayat et  The enhancement effect of ascorbic acid on yield may be attributed that ascorbic acid increased leaf chlorophyll content (Azzedine, et al., 2011). This led to an enhancement of photosynthesis process (Tarraf et al., 1999).which led to more carbohydrate production and that reflected in higher yield. Besides, ascorbic acid increased IAA content which stimulates cell division as well as cell enlargement (Hassanein et Table, 5 shows that all tested treatments reduced the number of cracked fruits/tree as compared with the control treatment in both seasons of study. Generally, 1000 ppm ascorbic sprayed trees recorded the lowest values cracked fruits/tree in this respect.  Table, 5 shows that all tested treatments reduced a number of sunburned fruits/tree as compared with the control treatment in the first season of study. Generally, 1000 ppm ascorbic treatment proved to be the most efficient treatment in reducing a number of sunburned fruits/tree in the first season. However, all salicylic, ascorbic and control treatments produced a similar effect on the number of sunburned fruits per tree in the second season. Table 5 shows that salicylic and ascorbic treatments decreased sunburned fruit percentage as compared with the control in the 2017 and 2018 seasons. Generally, 1000 ppm ascorbic treatment exerted a high reductive effect on sunburned fruit percentage as compared with other treatments in both seasons.

Sunburned fruit (%)
The positive effect of salicylic acid in reduced cracked and sunburned fruits may be attributed that salicylic acid has an important role in protecting the cells from senescence and preventing free radicals from the oxidation of lipids the components of the plasma membrane. Salicylic acid is also involved in minimized of the stresses through enhancing 1064 antioxidant system. It is responsible for enhancing natural hormones that play a key part in regulating plant growth and development as well as enhancing the biosynthesis of IAA and minimizing the unfavorable effects of different stresses on plant development (Senarataa et al, 2004). Salicylic acid has a significant role in plant water relations, photosynthesis, and growth in plants (Arfan et al., 2007). The positive effect of ascorbic acid in reducing cracked and sunburned fruits may be attributed that ascorbic acid has catched all free radicals produced during plant metabolism (Nichloas, 1996 andAlscher et al., 1997). Ascorbic acid increased IAA content, which stimulates cell division as well as cell enlargement and this in turn in improved plant growth (Hassanein et al., 2009 andAbd-El Hamid, 2009). Ascorbic acid may serve as a potential growth regulator to enhance stress resistance in several species (Khan, 2006). This led to reducing cracked fruit. Furthermore, Ma and cheng (2004) mentioned that fruit protected from photo oxidative damage by the central antioxidant system (the ascorbate -glutathione cycle). Ascorbic acid reduces sunburn damage in fuji apples (Andrews et al., 1999). The obtained results regarding the effect of ascorbic on fruit disorders go in line with the findings of Ahmed et al. (1997) showed that Ascorbic acid application was controlling the incidence of fruit disorders of apple trees. Abd-El-Rhman et al. (2017) pointed out that foliar spray with ascorbic acid reduced fruit cracked percentage of Manfalouty pomegranate trees.

Fruit physical and chemical properties Fruit weight (g)
It is clear from Table, 6 that salicylic and ascorbic sprayed trees produced higher fruit weight than those sprayed with tap water control in both seasons of study. Anyhow, 1000 ppm ascorbic treatment shows superiority in this respect. illustrates that the tested salicylic and ascorbic treatments exerted a positive enhancing effect on fruit length as compared with the control in both seasons. Shortly, 1000 ppm ascorbic treatment proved to be the most efficient treatments in this concern.
Fruit diameter (cm) Table, 6 indicates that salicylic and ascorbic treatments produced higher fruit diameter than those sprayed with tap water control in both seasons of study. Moreover, 1000 ppm ascorbic treatment shows superiority in this respect. Other tested treatments occupied intermediate positions in this sphere.

Weight of fruit grains (g)
Table, 6 demonstrates that salicylic and ascorbic treatments succeeded in improving the weight of fruit grains in both seasons as compared with the control treatment. Generally, 1000 ppm ascorbic treatment gave the highest weight of fruit grains (170.3 and 169.6 g) against (135 and 136 g) for the control treatment in both seasons respectively. Table, 7 indicates that all tested treatments scored higher values of the weight of 100 grains as compared with the control treatment in both seasons of this study. Generally, 1000 ppm ascorbic treatment induced the highest weight of 100 grains (38.0 and 39.3 g) against (31 and 32 g) for the control treatment in both seasons respectively.  Table 7 indicates that tested treatments produced a high positive effect on juice volume per fruit as compared with the control treatment both season. Generally, 1000 ppm ascorbic treatment shows superiority in this respect. Table 7 indicates that salicylic and ascorbic treatments produced a high positive effect on peel thickness in both seasons of this study. Generally, 1000 ppm ascorbic treatment gave a high positive effect on peel thickness as compared with the control treatment in this study. Table 8 reveals that salicylic and ascorbic treatments produced a high positive effect on fruit total sugar content as compared with control treatment in both seasons of study. Generally, 1000 ppm ascorbic treatment shows superiority in this respect.

Fruit T.S.S. (%)
The tested concentration of salicylic and ascorbic exerted a high positive effect on fruit T.S.S. content than the control treatment in both seasons of study (Table 8). Moreover, 1000 ppm ascorbic treatment proved to be the most efficient treatments in this concern. Other treatments showed an intermediate value in this respect. Fruit total acidity (%) Tabulated data demonstrate that salicylic and ascorbic treatments induced a pronounced reductive effect on fruit total acidity content as compared with the control. Briefly, 1000 ppm ascorbic treatment proved to be the most efficient treatment in reducing fruit total acidity content.

Fruit T.S.S. /acid ratio
Statistical analysis indicates that salicylic and ascorbic treatments scored significantly high values of fruit TSS/acid ratio as compared with the control treatment in both seasons of study. Generally, 1000 ppm ascorbic treatment proved to be the most efficient treatment in scoring the highest values (14.58 and 13.78) against (8.65 and 8.41) for the control treatment in the first and second seasons, respectively (Table, 8).

Fruit ascorbic acid content
Tabulated data illustrate that salicylic and ascorbic treatments induced a high positive effect on fruit ascorbic acid content as compared with the control treatment. Moreover, 1000 ppm ascorbic treatment gave the highest values of fruit ascorbic acid content as compared with the control treatment throughout the two seasons of study.
The enhancement effect of salicylic acid foliar spray on fruit quality may be attributed to the salicylic acid plays a vital role in plant growth and ion uptake and transport (Hayat et  The enhancement effect of ascorbic acid on fruit quality may be attributed that firstly, ascorbic acid increased leaf area and leaf chlorophyll content (Azzedine, et al., 2011). That is lead to enhancement photosynthesis process (Tarrafet et al., 1999).which reflected in more carbohydrate production and consequently improved fruit quality. Secondly, ascorbic acid increased IAA content which stimulates cell division as well as cell enlargement (Hassanein et al. 2009 and Abd-El Hamid 2009). Furthermore, auxin was increased fruit quality (Ragab, 2002). Thirdly, ascorbic acid mitigates the adverse effect on plant growth by enhanced proline accumulation (Azzedine, et al., 1997). The proposed function of the accumulated proline is osmosis regulation which has an adaptive mechanism to environmental stress (Aspinall and Paleg 1981). So that the increase in proline leads to enhancement leaf chlorophyll content and that reflected in more carbohydrate production through photosynthesis process and consequently improved fruit quality. The obtained results regarding the effect of ascorbic on fruit quality go in line with the findings of Atef (2018) on pomegranate. He mentioned that foliar sprays of ascorbic improved fruit quality of pomegranate fruit.

Conclusion:-
Briefly, Spray Wonderful pomegranate trees with ascorbic at 1000 ppm twice a year i.e. at full bloom and four weeks later to enhanced tree growth, yield and fruit quality as well as it minimized both fruit cracking and sunburned fruit percentage.