Manipulating fruit quality through foliar nutrition

C H A P T E R

29 Manipulating fruit quality through foliar nutrition Vasileios Ziogasa, Michail Michailidisb, Evangelos Karagiannisb, Georgia Tanouc, Athanassios Molassiotisb,* a

Institute of Olive Tree, Subtropical Plants and Viticulture, Hellenic Agricultural Organization (H.A.O.)—Demeter, Chania, Greece b Laboratory of Pomology, Department of Agriculture, Aristotle University of Thessaloniki, Thessaloniki, Greece c Institute of Soil and Water Resources, ELGO-DEMETER, Thessaloniki, Greece *Corresponding author. E-mail: [email protected]

O U T L I N E 1 Introduction

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8 Boron (B)

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2 Nitrogen (N)

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9 Cobalt (Co)—copper (Cu)—iron (Fe)

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3 Phosphorus (P)

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10 Zinc (Zn)

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4 Potassium (K)

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11 Manganese (Mn)—nickel (Ni)—selenium (Se)

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5 Calcium (Ca)

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12 Titanium (Ti)

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6 Magnesium (Mg)

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13 Conclusions and future perspectives

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7 Sulfur (S)

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References

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1 Introduction Due to life-supporting role of fruits in human diet, the study of fruit quality undergoes a great burst of knowledge (Fotopoulos et al., 2010). Fruit quality has been associated with various factors like genetics, microclimate conditions, cultivation practices, plant nutrition, proper pollination, harvesting method, and maturation index at harvest (Co^elho de Lima and Alves, 2011). Schreiner et al. (2013) described quality as “the sum of characteristics, properties, and attributes of a product or commodity which aims in fulfilling the established or presumed customer requirements” (by the International Organization of Standardization, ISO 8402, 1989). The external fruit parameters include color, shape, size, and lack of defects, while the internal are related with taste, texture, aroma, nutritional value, sweetness, acidity, and postharvest shelf life (Shewfelt, 1999; Kingston, 2010). Attributes like skin color, titratable acidity, and ratio of total solid content to titratable acidity are being considered important fruit quality factors at harvest time (Oosthuyse and Westcott, 2005). Meanwhile, total soluble solids, sugar content, firmness, shape, and external fruit appearance are closely related to fruit nutrient levels. The relation between the adequate nutritional status of the fruit tree and the overall fruit quality has been well documented (Dris et al., 1999). Several nutrients like nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) exert a notable influence upon several fruit quality parameters (Fallahi and Simons, 1996). The sufficient supply of macro- and micronutrients can be achieved via the use of soil surface application of fertilizers, fertigation, or even via foliar spray application (Nicola et al., 2009). Particularly, foliar A.K. Srivastava, Chengxiao Hu (eds.) Fruit Crops: Diagnosis and Management of Nutrient Constraints https://doi.org/10.1016/B978-0-12-818732-6.00029-0

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© 2020 Elsevier Inc. All rights reserved.

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29. Manipulating fruit quality through foliar nutrition

application has been characterized as the most appropriate method of nutrient application in fruit trees, providing rapid plant response and uniform distribution upon the foliage (Umar et al., 1999; Mengel, 2002). The most common macronutrients applied as foliar fertilizers are N (as urea, ammonium nitrate, and ammonium sulfate), P (as H3PO4, KH2PO4, NH4H2PO4, Ca(H2PO4)2, and phosphites), K (as K2SO4, KCl, KNO3, K2CO3, and KH2PO4), Mg (as MgSO4, MgCl2, Mg(NO3)2), and Ca (as CaCl2, Ca propionate, and Ca acetate). Also, the most commonly foliar applied micronutrients belong the B (as boric acid (B(OH)3), borax (Na2B4O7), Na octaborate (Na2B8O13), B-polyols, Fe (as FeSO4, Fe(III) chelates, and Fe complexes), Mn (as MnSO4, Mn(II) chelates), and Zn (as ZnSO4, Zn(II)-chelates, ZnO, and Zn organic complexes) (Tanou et al., 2017). In addition to this, foliar application has the potential to provide a higher status of nutrient bioavailability compared with soil application (Li et al., 2018). Micronutrient absorption has been proven of being a fruit species-dependent factor related with the thickness and the composition of the plant cuticle (Eichert and Goldbach, 2008). Great body of experimental data has focused upon the beneficial effect of foliar application of nutrients toward fruit yield and the improvement of the overall fruit quality (Eichert and Goldbach, 2008; Pacheco et al., 2014). This chapter outlines up-to-date progress in terms of the regulation of nutrient-mediated fruit quality with an emphasis upon foliar nutrition.

2 Nitrogen (N) Nitrogen is an essential ingredient for plant survival, as it participates in the formation of amino acids, and possesses a multiple principal role in plant metabolism (proteins, enzymes, storage compounds of nitrogen, etc.). Exogenous supply of N to trees via foliar spray application, to improve the fruit quality and yield, is mainly achieved by the use of urea and in combination with potassium, in the form of potassium nitrate (KNO3). Although N is an important element for plant nutrition, current knowledge is not able to fully support its role in fruit quality when applied in the form of foliage-sprayed nitrogen. Nitrogen prolonged the vegetative phase at the expense of ripening. In mango, N foliar spray prolonged green coloring of mature fruits reducing fruit quality (Nguyen et al., 2004). Evidence suggested that the increasing rates of foliar applied urea induced the soluble protein and ascorbic acid, total amino acids, titratable acidity, and alcohol acyltransferase activity, whereas it decreased soluble sugars in apples (Zhao et al., 2013) and in mandarins (Al-Obeed et al., 2018). Application of nitrogen via the foliar spray of KNO3 resulted also in the increase of titratable acidity in pomegranate (Pulla Reddy et al., 2011). In regard to productive parameters, urea foliar spray increased fruit size and yield of apples, pears, and mandarins (Dong et al., 2005; Sánchez et al., 2008; Curetti et al., 2013; Al-Obeed et al., 2018), but when it was applied postharvestly at apple trees, it didn’t affect the next year’s yield (Wojcik, 2006a). Previous data support the beneficial effects of applied foliage N in almond nuts on fruit weight, width, percentage of hard shells, protein content, and percentage of green shells (Bybordi and Malakouti, 2006).

3 Phosphorus (P) Phosphorus is a macronutrient that regulates a variety of cellular functions due to its participation to the ATP molecular structure. Foliar application of P at sweet persimmon increased fruit yield and decreased fruit dropping. On the other hand, in guava fruits, P did not affect fruit production, but it has been associated with disease control (Natale et al., 2002). Foliar P application apart from alleviating P deficiency may also contribute to the overall fruit quality at harvest and during postharvest period since a positive impact on fruit hardness and sugar content with parallel acidity decrease has been reported at sweet persimmon (Hossain and Ryu, 2009). The combined P, Fe, and Zn foliar application has been reported to exert significant influence on the morphophysical and qualitative parameters of guava fruits as it increased volume, weight, yield, sugars, acidity, ascorbic acid, and pectin content (Kanpure et al., 2016).

4 Potassium (K) Potassium is an essential macronutrient and exerts an important role in plant physiology since it provides the correct ionic environment for metabolic processes in plant cells (Leigh and Wyn Jones, 1984). There are several evidences showing that foliar K application has a positive impact in fruit quality and yield. Citrus, apples, pears, peach, plum, mango, and date palm trees sprayed with K exhibited a significant increase in yield (Abdi and Hedayat, 2010; Ashraf et al., 2013; Ben Mimoun and Marchand, 2013; Baiea and Moneim, 2015;

5 Calcium (Ca)

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Jawandha et al., 2017; Dbara et al., 2018) sometimes due to decreased fruit drop phenomenon after flowering (Baiea and Moneim, 2015; Oosthuyse, 2015). In olive trees, a notable effect in yield increase was observed only after 5 years of systemic K application (Ben Mimoun and Marchand, 2013). In terms of fruit quality parameters, many reports support the beneficial role of K foliar application as it increased fruit size/weight of orange (Hafez et al., 2017), pear (Gill et al., 2012), peach (Dbara et al., 2018), plum ( Jawandha et al., 2017), and mango (Baiea and Moneim, 2015); fruit firmness in apples (Solhjoo et al., 2017), pear (Gill et al., 2012), but not in peach (Dbara et al., 2018); the coloring percentage in orange (Hafez et al., 2017) and pear (Gill et al., 2012); the content of total soluble solids in orange (Hafez et al., 2017), apple ( Javaid et al., 2016), pear (Gill et al., 2012), peach (Ghanem and Ben Mimoun, 2010b; Dbara et al., 2018), plum (Ghanem and Ben Mimoun, 2010a), and mango (Baiea and Moneim, 2015); the ascorbic acid in orange (Hafez et al., 2017) and mango (Baiea and Moneim, 2015), and also olive soluble carbohydrates and anthocyanins (Zivdar et al., 2016). On the contrary, acidity was reduced at orange (Hafez et al., 2017), peaches (Ghanem and Ben Mimoun, 2010b), and plum ( Jawandha et al., 2017) or remained unaffected at pear (Gill et al., 2012) and peach (Dbara et al., 2018). It has been suggested that potassium may exert a beneficial effect toward physiological disorders as its foliar application has been shown to reduce fruit cracking and improve fruit quality of lemons (Devi et al., 2018), whereas oranges did not demonstrate any significant effect on fruit quality parameters (Ramezanian et al., 2018).

5 Calcium (Ca) Calcium is an essential macroelement for plant growth, and its absence, in certain content, leads to plant and cell malfunctions and eventually to cell death. On-tree Ca foliar spray is an effective way to increase Ca content in leaves and fruits. Calcium seems to be associated with fruit quality as reports indicate a beneficial impact on flesh firmness, accumulation of bioactive compounds, and prevention of physiological disorders, which are related to cell-wall consistency. Quality attributes, such as soluble solid content, acidity, mean weight, weight loss during storage, respiration, and ethylene production, undergo a controversial impact due to Ca foliar application, and this can be observed under several species of fruit trees. Several reports demonstrate that Ca foliar spray increases fruit flesh firmness at harvest and during postharvest period in a variety of fruits, including peaches (Alcaraz-López et al., 2004; Val and Fernández, 2011; Ekinci, 2018), apples (Wojcik, 2002; Kadir, 2005; Domagala-Światkiewicz and Blaszczyk, 2009; Wójcik et al., 2016; Ghorbani et al., 2017; Solhjoo et al., 2017), oranges (Ramezanian et al., 2018), strawberries (Wójcik and Lewandowski, 2003; Singh et al., 2007a,b, 2009; Bieniasz et al., 2012), plums (Plich and Wójcik, 2002; Alcaraz-Lopez et al., 2004), sweet cherries (Brown et al., 1996; Tsantili et al., 2007; Michailidis et al., 2017) kiwifruits (Shiri et al., 2016), papaya (Madani et al., 2015) olives (Tsantili et al., 2008), guava (Goutam et al., 2010), and pears (Frances et al., 1999). Νo significant shifts to fruit firmness were observed due to Ca foliar application, for some species like apples (Brown et al., 1998; Wojcik and Szwonek, 2002; Val et al., 2008), peaches (Crisosto et al., 2000), and strawberries (Toivonen and Stan, 2001), while a decrease of fruit firmness was observed for peaches (Val et al., 2010). It has been suggested that fruits treated with Ca solution at preharvest time exhibited a significant accumulation of pectin (Ekinci, 2018). On-tree Ca spray of fruits alleviated physiological disorders; skin cracking in sweet cherries (Brown et al., 1996; Michailidis et al., 2017), lemons (Devi et al., 2018), and pomegranates (Bakeer, 2016; Davarpanah et al., 2018); and scald incidents in apples (Kadir, 2005). During postharvest period, Ca foliar application alleviated the internal browning in peaches (Val and Fernández, 2011) and apples (Wojcik, 2002), the sensitivity of apples to bitter pit (Wojcik, 2002; Wojcik and Szwonek, 2002; L€ otze and Theron, 2006), and the severity of chilling injury in mandarins (D’Aquino et al., 2005). Application of Ca via the foliage is considered a potent method to increase total phenolic content of fruits at harvest and during postharvest storage for sweet cherries (Michailidis et al., 2017), oranges (Ramezanian et al., 2018), and strawberries (Xu et al., 2014). Furthermore, an increase in ascorbic acid and anthocyanin content in strawberries (Singh et al., 2007a,b, 2009; Xu et al., 2014), in ascorbic acid in guava fruits (Goutam et al., 2010), and in carotenoid content in kiwifruits (Shiri et al., 2016) was observed. The soluble solid concentration (° Brix) at harvest and during postharvest period was decreased following Ca foliar spray in peaches (Val an d Fernández, 2011), apples (Wójcik et al., 2016; Ghorbani et al., 2017), strawberries (Singh et al., 2007a,b, 2009), and papaya fruits (Mirshekari and Madani, 2018); by contrast, it was increased in strawberries (Wójcik and Lewandowski, 2003), apples (Solhjoo et al., 2017), kiwifruits (Shiri et al., 2016), mango (El-Razek et al., 2017), jujube (Mao et al., 2016), and guava (Goutam et al., 2010). In addition to this observation, an increase in fruit acidity was observed in peaches (Val and Fernández, 2011), strawberries (Wójcik and Lewandowski, 2003; Singh et al.,

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29. Manipulating fruit quality through foliar nutrition

2007a,b, 2009), papaya fruits (Mirshekari and Madani, 2018), and apples (Domagala-Światkiewicz and Blaszczyk, 2009) in Ca-sprayed fruits at harvest and after cold storage. It has been reported that foliar spray of Ca decreases weight loss during postharvest storage in peaches (Ekinci, 2018) and kiwifruits (Shiri et al., 2016). Moreover, Ca application resulted in an increase of fruit weight during harvest in apples (Kadir, 2005; Solhjoo et al., 2017) and mango (El-Razek et al., 2017). Fruit skin redness improved in apples as a result of Ca applications (Kadir, 2005), while the respiration rate and ethylene production were decreased in papaya fruits (Mirshekari and Madani, 2018).

6 Magnesium (Mg) Macroelement magnesium (Mg) has a multifunctional role in plants, but its function in fruit quality has not been fully elucidated. Reports indicated that foliar spray of Mg had no impact on firmness and color index of peaches and plums (Alcaraz-Lopez et al., 2003; Alcaraz-López et al., 2004), while a lower fruit juice pH was reported with no parallel effect upon the acidity of peaches (Ekinci, 2018) at harvest and during postharvest period. Recent studies demonstrate that Mg has a positive function upon litchi pericarp color index. At molecular level, these reports indicate an increase of anthocyanin content in the pericarp that contributes to the red color of the pericarp and boosted the overcome of the stay-green phenomenon. Moreover, Mg foliar spray is linked with several transcripts that are associated with flavonoid biosynthesis, anthocyanin biosynthesis, and the ABA signaling pathway. Magnesium could contribute to the accumulation of anthocyanin content via the increase of ABA concentration in fruits (Wang et al., 2017a,b).

7 Sulfur (S) The effect of foliar sulfur (S) application in fruit quality is difficult to study, since S exists in its anionic form (
2SO4) and participates as a stabilizer of cationic elements, such as magnesium (MgSO4), manganese (MnSO4, (Ekinci, 2018)), iron (Fe2SO4, (Song et al., 2016)), calcium, and nitrogen. Elemental sulfur with proven fungicidal activity could be used to clarify the effect of sulfur in fruit quality. Indeed, foliar sprays with S increased pecan nut weight under perennial open field experiments (Wells et al., 2014), thus amplifying the need for a deeper understanding of S-controlled metabolic processes of fruit at harvest and postharvest period.

8 Boron (B) Boron (B) has long being considered an essential nutrient for higher plants (Marschner, 1995), since it has been associated with reproductive processes affecting flower development, pollen germination, and pollen tube elongation (Loomis and Durst, 1992). B deficiency is associated with malformed fruits, which reduces overall fruit yield and negatively affects fruit quality (Sharma et al., 2004). Cracking, shriveling, deformation, internal and external browning, and corking near the pit or into the flesh are notable signs of B deficiency (Wojcik and Wojcik, 2006). Application of boron via the soil may cause phytotoxicity, since the limit between deficiency and toxicity is rather narrow in many fruit crops (Gupta, 1979). Therefore, it has been proposed that foliar application is more effective than soil application (Singh et al., 2007a,b). Several studies have demonstrated that B foliar application could have a positive outcome to the overall fruit yield of strawberry (Singh et al., 2007a,b), olive (Larbi et al., 2011), raspberry (Wojcik, 2005), and pistachio (Acar et al., 2016). However, B application in sweet cherry (Wojcik and Wojcik, 2006) and hazelnut (Silva et al., 2003) did not have any significant physiological effect. The foliar application of B has a variable effect in total fruit yield, and there is no clear rule between the applied concentration and yield response (Sotiropoulos et al., 2006). Foliar application of B could contribute to the qualitative characteristic of fruit firmness. Studies indicate that there was a positive correlation of B foliar spray and fruit firmness in raspberry (Wojcik, 2005) and pear (Wojcik and Wojcik, 2003), while B spray in apples (Peryea and Drake, 1991; de SÁ et al., 2014) had no effect. It has been proposed that total firmness is a marker of fruit ripeness, and foliar application of B sustained the firmness of the applied fruit (Wojcik and Wojcik, 2003). Fruit quality traits are linked and determined by the content of various attributes like vitamins, phenols, anthocyanins, starch, and the antioxidant capacity of the fruit extract (Molassiotis et al., 2013). Foliar application of B increased

9 Cobalt (Co)—copper (Cu)—iron (Fe)

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the concentration of vitamin C in mandarins (Al-Obeed et al., 2018). Also, the foliar application of B increases the anthocyanin content of sweet cherry fruits (Wojcik and Wojcik, 2006), while when applied upon pomegranate plants the fruit concentration of anthocyanins remained unaffected (Davarpanah et al., 2016). Furthermore, foliar spray of B in pomegranate plants did not exhibit any significant difference in the concentration of total phenols and total antioxidant activity of fruit extracts (Davarpanah et al., 2016). Moreover, external B applied in apple trees (de SÁ et al., 2014) reduced the starch content of fruits. A similar trend of reduction was also observed in olive fruits (Saadati et al., 2013), where the foliar application of B also resulted in a reduction of soluble carbohydrates. The foliar B application increased total soluble solid content in sweet cherry (Wojcik and Wojcik, 2006), raspberry (Wojcik, 2005), pomegranate (Davarpanah et al., 2016), and mandarins (Al-Obeed et al., 2018), while the TSS content remained unaffected in apples (Peryea and Drake, 1991; de SÁ et al., 2014) and strawberry (Wójcik and Lewandowski, 2003). Several reports proposed that foliar B treatment could increase the titratable acidity of pear fruits (Wojcik and Wojcik, 2003) but could provoke a decrease in apples (de SÁ et al., 2014) and pomegranate fruits (Davarpanah et al., 2016) while had no significant effect concerning this attribute in sweet cherry (Wojcik and Wojcik, 2006), apples (Peryea and Drake, 1991), tart cherries (Wojcik, 2006a,b), and strawberry (Wójcik and Lewandowski, 2003). The foliar application of B was positively correlated with the increase of total sugars in mandarin fruits (Al-Obeed et al., 2018), but not in pomegranate (Davarpanah et al., 2016). It has been shown that B element is linked with internal fruit characteristics, like fruit malformations, cracking, split nut ratio, internal browning, length and diameter values, internal tissue structure, and dietary fiber content. In this regard, foliar application of B exhibited an effect toward these quality parameters through a significant increase in B concentration into the core and inner cortex of apples (Peryea and Drake, 1991) and increase in volume, length, and diameter when applied to mandarins (Al-Obeed et al., 2018). Also, the foliar application of B could increase the mean nut mass and kernel mass of hazelnuts (Silva et al., 2003) and decrease internal cracking events in mango fruits (Saran and Kumar, 2011), decrease internal membrane permeability in pear (Wojcik and Wojcik, 2003), decrease of the split nut ratio and split kernel ratio in pistachio fruits (Acar et al., 2016), and reduce the appearance of fruit malformation in strawberry fruits (Singh et al., 2007a,b). However, foliar application of B in strawberry fruits could not influence albinism appearance or the appearance of gray mold (Singh et al., 2007a,b). Also, foliar application of B was not effective toward the sensitivity to fruit cracking in cherry fruits (Wojcik and Wojcik, 2006). A body of scientific data indicate that B foliar application could pose a positive effect toward the oil content from olive fruits and increase the ratio of monounsaturated fatty acids to saturated ones during olive oil extraction (Saadati et al., 2013). Moreover, foliar B application did not have any effect to the fat content in avocado fruit (Abdel-Karim et al., 2015). Scientific data also pinpoint the fact that B foliar application was able to decrease the activity and expression level of certain enzymes related to the postharvest shelf life. In detail, the activity and expression level of polygalacturonase, pectinesterase, and β-galactosidase were decreased in B-treated orange fruits (Dong et al., 2009).

9 Cobalt (Co)—copper (Cu)—iron (Fe) Cobalt (Co) application plays a regulatory role in plant metabolic cascades. Application of Co significantly inhibited ethylene biosynthesis in plants (Yang and Hoffman, 1984). The alleviated floral malformation syndromes were attributed to the ability of Co to exert an inhibitory effect in ethylene biosynthesis (Singh et al., 1991) via the prevention of the oxidation of 1-aminocyclopropane-1-carboxylic acid to ethylene (Singh et al., 1994). In the work of Singh et al. (1994), Co foliar feeding prior to flower bud differentiation was evaluated for its effect in mango fruit quality. Data indicated that total and nonreducing sugars were adversely affected by the foliar application of high levels of Co; however, total soluble solids or reducing sugars were not affected. Scientific data highlight the role of copper (Cu) toward disease resistance due to its ability to participate in enzymatic activities, reactive oxygen species (ROS) production, regulation of gene expression, and processes linked with the biosynthesis of pathogen-related proteins and phytoalexins (Evans and Solberg, 2007). The effect of Cu foliar spray in cherry and apple fruit quality was studied by Brown et al. (1996). Post bloom application of Cu, in the form of copper hydroxide, was applied to sweet cherry trees after 6 weeks of flowering and in apple trees following 8 weeks of flowering in the presence or in the absence of Ca treatments. Results indicated that only when Cu was applied in tandem with calcium the formula was able to improve fruit resistance to cracking and to increase fruit firmness. The combination of Cu and Ca was also able to improve the flesh firmness of “Golden Delicious” apples (Brown et al., 1996) and minimize significantly the rain-induced fruit cracking in sweet cherry (Brown et al., 1995).

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29. Manipulating fruit quality through foliar nutrition

In fruit tree cultivation, iron (Fe) is an indispensable cation required for mineral nutrition (Chouliaras et al., 2004). Iron deficiency consists a major nutritional problem when trees are cultivated to calcareous or alkaline soils, affecting fruit quality parameters and overall yield (Chouliaras et al., 2004). Foliar spray of compounds containing Fe favorably improved fruit quality in several tree cultivations (Song et al., 2016). Foliar application of compounds containing Fe, under calcareous soils, could favor the fruit yield, the Brix index, and the titratable acidity in pomegranate fruits (Mirzapour and Khoshgoftarmanesh, 2013). Also, the beneficial effect of Fe-containing compounds in foliar spray was studied in the work of Song et al. (2016), where foliar spray in peach fruits increased fruit firmness, total soluble solid content, and Fe tissue concentration and enhanced the activity of succinate dehydrogenase (SDH) and aconitase (ACO).

10 Zinc (Zn) Zinc (Zn) in plant nutrition is considered a microelement that generally linked with important roles in fruit set and retention, fruit yield, and fruit quality. Notably, Zn is essential for the activation of different enzymes, including dehydrogenases, aldolases, isomerases, transphosphorylases, and DNA and RNA polymerases and to its implication to the biosynthesis of tryptophan, cellular division, maintenance of cell membrane integrity, and photosynthesis (Marschner, 2012). In response to Zn foliar application, the overall fruit yield was increased in pomegranate (Davarpanah et al., 2016) while remained unaffected in mango fruits (Bahadur et al., 1998). Specific physical parameters of fruits were also influenced after foliar application of Zn solutions in several types of fruit trees. In this sense, Zn foliar applications provoked a significant increase of fruit weight, pulp weight, fruit juice, fruit volume, and circumference/diameter ratio in mandarin fruits (Ashraf et al., 2013; Al-Obeed et al., 2018) while remained unaffected in pomegranate (Davarpanah et al., 2016) and mango fruits (Bahadur et al., 1998). Zinc foliar treatments altered the quality characteristics of the fruit related with acidity and soluble solids. In detail, foliar sprays with Zn increased the content of total soluble solids and titratable acidity in pomegranate (Davarpanah et al., 2016), mango (Bahadur et al., 1998), and mandarin fruits (Ashraf et al., 2013; Al-Obeed et al., 2018), while these ripening features remained unaffected in apples (Rasouli and Koushesh Saba, 2018). Foliar Zn feeding increased total sugars in mandarins (Al-Obeed et al., 2018) while reduced the levels of starch in apples (Rasouli and Koushesh Saba, 2018) and the soluble carbohydrates in olive fruits (Saadati et al., 2013). However, no effect of Zn in sugars, total phenols, and total anthocyanins was observed in pomegranate (Davarpanah et al., 2016); in addition, total phenolic content in apple (Rasouli and Koushesh Saba, 2018) and sugar in mango fruits (Bahadur et al., 1998) were unaffected under Zn exposure. The ability of Zn foliar application to interfere with antioxidative fruit parameters was evaluated by several groups. Foliar spray of Zn-containing solutions increased vitamin C in apple fruits (Rasouli and Koushesh Saba, 2018) and mandarins (Ashraf et al., 2013; Al-Obeed et al., 2018), while the antioxidative activity of the fruit extract was increased in apples with parallel increase of the enzymatic activity of superoxide dismutase (SOD) (Rasouli and Koushesh Saba, 2018). This effect could be attributed to the role of Zn as a constituent of SOD enzyme, thus facilitating its inhibitory effect upon free radical generation (Cackam and Marschner, 1988). Foliar sprays of Zn failed to provoke a significant increase to the antioxidant activity of fruit extracts from pomegranate (Davarpanah et al., 2016) and decreased enzymatic activity of polyphenol oxidase in apples, resulting to the decreased levels of enzymatic browning (Rasouli and Koushesh Saba, 2018). Furthermore, foliar spray of Zn in olive fruits increased the oil content of the drupe and favored the ratio of monounsaturated fatty acids to the saturated ones (Saadati et al., 2013). This increase was estimated that could be attributed to the continued activity of the triglyceride-forming biosynthesis pathway until the fruit reaches full maturation (Dag et al., 2011). Also, Zn foliar spray increased the maturation index of apples (Rasouli and Koushesh Saba, 2018) and the pH of fruit juice extracted from pomegranate (Davarpanah et al., 2016) and mandarins (Al-Obeed et al., 2018).

11 Manganese (Mn)—nickel (Ni)—selenium (Se) Scientific data related with the impact of manganese (Mn) foliar application on various quality parameters from fruit species are rather limited. In the work of Ekinci (2018), Mn foliar application in peach trees increased polygalacturonic acid (pectin) content followed by a decrease of fruit weight loss. Additionally, foliar spray of Mn in citrus plants

13 Conclusions and future perspectives

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(grape fruits and oranges) had no significant effect to the overall fruit yield, fruit number, or the average fruit weight (Swietlik and LaDuke, 1991). Experimental data have highlighted the fact that Ni is part of the active center of urease (Dixon et al., 1975), and the activation of urease is the most important attributed function of Ni in the plant metabolism (R€ omheld, 2011). Scientific reports indicate the positive effect of Ni application in plant growth, fruit yield, and seed germination ( Jamali et al., 2013). In the work of Eshghi and Ranjbar (2015), foliar application of Ni-containing compounds in strawberries increased the crown number at the studied fruits. Selenium (Se) is not an essential element for plants, although it can benefit their growth and survival in some environments (Kápolna et al., 2009; Pacheco et al., 2014). The concentration of Se in plants mainly depends upon the vegetal species and the form that Se is supplied to the plant (Kápolna et al., 2009). Data indicate that foliar Se application has a higher bioavailability than soil sprayed (Li et al., 2018). In the work of Jing et al. (2017), foliar application of various Se compound in winter jujube resulted to the increase of vitamin C content, soluble sugars, and total flavonoid content and favored the sugar-to-acid ratio and had a beneficial effect in the fruit weight and overall yield. Beneficial effects of foliar applied Se were also recorded by Li et al. (2018) in blueberries. The foliar spray of Se-containing compounds resulted in augmentation of Se concentration to the pomace of the fruit, the internal anthocyanin content, and favored the intact rate fruit rate, thus resulting to fruits with improved quality characteristics.

12 Titanium (Ti) Titanium (Ti) is considered a beneficial element for plant growth. Ti applied via roots or leaves at low concentrations has been documented to improve crop performance; however, the physiological role of Ti in higher plants has not been clarified. In the work of Pais (1983), it was stated that Ti has an impact upon tissue development similar to auxins, while the foliar application of Ti upon paprika pepper improved the photosynthetic activity of the plant (Carvajal and Alcaraz, 1998). Wócik et al. (2010) found that foliar application of Ti in apple trees resulted to a significant increase of overall apple fruit yield. Furthermore, the foliar Ti spray did not provoke any significant change to the mean apple weight, firmness of the pomace, total soluble solid concentration, and titratable acidity. Although Ti application in apples did not alter the coloring of the fruits (Wócik et al., 2010), however, foliar Ti increased the color formation in plum (Alcaraz-Lopez et al., 2003) and peach (Alcaraz-López et al., 2004). Also, Ti foliar application was correlated positively with the increased ability of plum (Alcaraz-Lopez et al., 2003) and peach (Alcaraz-López et al., 2004) and with the ability to store increased quantities of Fe, Cu, Zn, and Ca into the peel of the fruit. This work further indicated that Ca assimilation to the flesh and skin of the fruits after Ti foliar spray application is attributed to the enhanced absorption, translocation, and assimilation procedures into the fruit of plum (Alcaraz-Lopez et al., 2003) and peach (Alcaraz-López et al., 2004). Furthermore, Ti foliar application was related with the ability of plum and peach fruits to delay ripening procedures and exert an overall decreased ripening status (Alcaraz-Lopez et al., 2003; Alcaraz-López et al., 2004).

13 Conclusions and future perspectives Scientific data indicate and support the fact that foliar application of macro- or micronutrients can act as a beneficial factor toward the improvement of fruit quality, an action that is closely related with the chemical formula of the element, the applied dosage, and the number of repeated applications (Tables 29.1 and 29.2). Summarizing current scientific knowledge of foliar applied nutrients, data indicate that the most profound effect was established after the application of Ca, K, and B. The foliar spray of these elements exerted significant positive effect and beneficial effect toward fruit quality parameters. Lack of specific scientific data linked with the mode of action of other macro- or micronutrients upon fruit quality attributes does not allow the extraction of clear and specific results for the rest of the elements. Also, another factor that needs attention is the diversity that is related with the interpretation of the results. Specific quality attributes do not always have the same meaning in all types of fruits. For example, in some cases like citrus, the increase of acidity might be a positive attribute, but to other species like fig, a decrease of acidity is called a positive result. An in-depth molecular, metabolomic analysis could shed light to the metabolic cascades that are controlled and influenced by the foliar application of each macro- or microelement, providing a holistic approach toward the understanding and manipulation of fruit quality via the usage of foliar nutrition.

408 TABLE 29.1

29. Manipulating fruit quality through foliar nutrition

Effect of macroelement foliar application in fruit quality characteristics.

Formula

Fruit

Dose

Sprays

Increase

Decrease

Ref.

CaCl22H2O

Papaya

0.5%, 1%, 1.5%, 2%

6

Firmness, trititable acidity

Respiration rate, ethylene production, soluble solid concentration

Madani et al. (2014)

Apple

0.5%

6 in 4 seasons

Fresh weight, firmness, starch concentration, soluble solid concentration

Ghorbani et al. (2017)

0.5%

5

Fresh weight, firmness, anthocyanin concentration, soluble solid concentration

Solhjoo et al. (2017)

8.971 kg Ca/ha

1–8

Fruit size, fresh weight

Scald

Kadir (2005)

6–9 kg/ha

6

Firmness

Soluble solid concentration, starch concentration

Wójcik et al. (2016)

1%, 2%

4

Yield, fruit quality

Fruit cracking

Bakeer (2016)

1%, 2%

2

Fruit cracking

Davarpanah et al. (2018)

Kiwifruit

1.5%

3

Trititable acidity

Weight loss of fruit, decay

Shiri et al. (2016)

Strawberry

10, 20, 50 mM

Every 4 days AP

Total phenol concentration, anthocyanin concentration

1.5 kg Ca/ha

5

Firmness

Decay

Wójcik and Lewandowski (2003)

2 kg Ca/ha

5

Yield, firmness, trititable acidity, ascorbic acid concentration

Decay, physiological disorders, soluble solid concentration

Singh et al. (2007a,b)

0.4%

3

–

–

Toivonen and Stan (2001)

Olive

58.5 mM

3

Firmness

Tsantili et al. (2008)

Guava

0.5%, 1%, 1.5%

1

Firmness, soluble solid concentration, ascorbic acid concentration

Goutam et al. (2010)

Sweet cherry

0.5%

2

Skin penetration, stem removal, total phenol concentration

Fruit cracking

Michailidis et al. (2017)

0.5%

3

Firmness

Fruit cracking

Erogul (2014)

22.5, 45, 58.5 mM

2

Firmness, stem removal

1.5%

4

Firmness

Weight loss of fruit

Ekinci (2018)

0.5%, 1%

5

Firmness

Physiological disorders,

Val and Fernández (2011)

1.1%

3

decay

Sugar and Basile (2011)

Pomegranate

Peach

Pear

Xu et al. (2014)

Tsantili et al. (2007)

409

13 Conclusions and future perspectives

TABLE 29.1 Effect of macroelement foliar application in fruit quality characteristics—cont’d Formula

Fruit

Dose

Sprays

Ca(NO3)2

Sweet cherry

0.5%

3

Apple

0.4%, 0.8%

4

5–8 kg/ha

6

0.2 M

3

3%

2

Ca(OH)2

Sweet cherry

Increase

Decrease

Ref.

Fruit cracking

Erogul (2014)

Firmness, trititable acidity

Physiological disorders, decay

DomagalaŚwiatkiewicz and Blaszczyk (2009)

Firmness

Physiological disorders

Wojcik (2002)

Fruit cracking

Erogul (2014)

Firmness

Fruit cracking

Brown et al. (1996)

Firmness

Physiological disorders

Val and Fernández (2011)

Fruit cracking

Erogul (2014)

Hemicellulose, total pectin, water-soluble pectin

Dong et al. (2009)

Calcium propionate

Peach

0.5%, 1%

5

Calcium caseinate

Sweet cherry

0.5%

3

–

Orange

0.3%

5

Cellulose, protopectin

–

Plum

4 mg Ca/L

3

Compression resistance, penetration resistance

Alcaraz-Lopez et al. (2004)

–

Jujube

0.2%, 0.4%

4

Soluble solid concentration

Mao et al. (2016)

MgSO4

Peach

2%

4

Firmness

MgCl2

Litchi

1.5%

1

Flavonoid biosynthesis transcripts, anthocyanin biosynthesis transcripts, ABA signal pathway transcripts

Wang et al. (2017b)

Lychee

1.5%

2

Anthocyanins concentration, ABA concentration

Wang et al. (2017a)

–

Plum

0.103 mM

3

Penetration resistance

Alcaraz-Lopez et al. (2003)

–

Peach

0.103 mM

3

KNO3

Apple

0.25%

3

Fresh weight, anthocyanin concentration, soluble solid concentration, trititable acidity

Solhjoo et al. (2017)

Mango

2%, 4%

1–2

Yield

Oosthuyse (2015)

2%

4

Yield, fresh weight, soluble solid concentration, ascorbic acid concentration

Trititable acidity

Baiea and Moneim (2015)

Plum

1%, 1.5%, 2%

2

Yield, fresh weight, soluble solid concentration

Trititable acidity

Jawandha et al. (2017)

Clementine

5%, 8%

2–3

Fresh weight, fruit size

Hamza et al. (2015)

Pear

1%, 1.5%, 2%

1–3

Fresh weight, fruit size, firmness, soluble solid concentration

Gill et al. (2012)

Weight loss of fruit

Weight loss of fruit

Ekinci (2018)

Alcaraz-López et al. (2004)

Continued

410

29. Manipulating fruit quality through foliar nutrition

TABLE 29.1 Effect of macroelement foliar application in fruit quality characteristics—cont’d Formula

Fruit

Dose

Sprays

Increase

Decrease

Ref.

K2SO4

Apple

0.25%

3

Fresh weight, anthocyanin concentration, soluble solid concentration, trititable acidity

Solhjoo et al. (2017)

Peach

143 g/tree

3

Yield, fruit size, soluble solid concentration

Dbara et al. (2018)

Citrus

1%

4

Yield, fresh weight

Ashraf et al. (2013)

Olive

0.1%, 0.2%

2

Soluble solid concentration, anthocyanin concentration

Zivdar et al. (2016)

Clementine

2.5%, 4%

2–3

Fresh weight, fruit size

Hamza et al. (2015)

Pear

1%, 1.5%, 2%

1–3

Fresh weight, fruit size, firmness, soluble solid concentration

Gill et al. (2012)

KCl

Apple

0.25%

3

Fresh weight, firmness, anthocyanin concentration, soluble solid concentration, trititable acidity

Solhjoo et al. (2017)

KH2PO4

Mango

2%

4

Yield, fresh weight, soluble solid concentration, ascorbic acid concentration

Trititable acidity

Baiea and Moneim (2015)

K2HPO4

Mango

2%

4

Yield, fresh weight, soluble solid concentration, ascorbic acid concentration

Trititable acidity

Baiea and Moneim (2015)

B(OH)3

Strawberry

160 g B/ha

3

–

–

Wójcik and Lewandowski (2003)

150 g B/ha

3

Yield

Singh et al. (2007a,b) Mao et al. (2016)

–

Jujube

0.2%, 0.4%

4

Soluble solid concentration

MnSO4

Peach

1%

4

Polygalacturonic acid content

NH4NO3

Mango

0.75%

4

Physiological disorders, green color

Nguyen et al. (2004)

CO(NH2)2

Apple

0.5%

7

Yield, fruit size

Dong et al. (2005)

0.2%, 0.5%, 0.8%

Ca (H2PO4)22H2O

Ascorbic acid concentration

Fruit weight loss

Soluble solid concentration

Ekinci (2018)

Zhao et al. (2013)

Pear

5%

1

Fruit size

Curetti et al. (2013)

Mandarin

0.1%

2

Yield, fresh weight, fruit size, soluble solid concentration, pH

Trititable acidity

Al-Obeed et al. (2018)

Sweet persimmon

7.5, 10, 20 ppm P

Yield, soluble solid concentration, firmness

Trititable acidity

Hossain and Ryu (2009)

411

13 Conclusions and future perspectives

TABLE 29.2

Effect of microelement foliar application in fruit quality characteristics.

Formula

Fruit

Dose

Sprays

Increase

Decrease

Ref.

B(OH)3

Strawberry

8%

3

Fruit yield

Fruit deformation

Singh et al. (2007a,b)

Sweet cherry

8%

2

Titratable acidity, total anthocyanins

Wojcik and Wojcik (2006)

Raspberry

8%

4

Fruit yield, firmness, titratable acidity

Wojcik (2005)

Tart cherry

8%

3

Apple

0.3%, 0.6%

2

Pear

0.2, 0.8 B/ha

10

Olive tree

0.25%

Mandarin

Solubor

Wojcik (2006a,b) Starch content, titratable acidity

de SÁ et al. (2014)

Ca content, firmness, titratable acidity, internal browning

Membrane permeability

Wojcik and Wojcik (2003)

2

Oil content, MUFA/ PUFA ratio

Soluble carbohydrates

Saadati et al. (2013)

300 mg/L

2

Volume length, fruit diameter, total soluble solids, juice pH, total sugars, ascorbic acid content

Al-Obeed et al. (2018)

Olive tree

300 mg/L

2

Fruit yield

Larbi et al. (2011)

Solubor

Hazelnut

300, 600, 900 mg/L

4

Nut mass, kernel mass

Silva et al. (2003)

Polybor

Apple

0.30, 0.60 g B/L

1

Core boron, cortex boron, fruit color

Peryea and Drake (1991)

Tarimbor fertilizer

Pistachio

0.1% 0.2% 0.3%

2

Fruit yield

Split nut ratio, split kernel ratio

Acar et al. (2016)

B

Orange

3 g/kg

5

Tissue structure, segment membrane, dietary fiber content

Polygalacturonase activity, Pectinesterase activity, β-galactosidase activity

Dong et al. (2009)

Nano-B-chelate fertilizer

Pomegranate

3.25, 6.5 mg B/L

1

Total soluble solids, maturation index, fruit juice pH

Titratable acidity

Davarpanah et al. (2016)

Bormit

Strawberry

160 g/ha

3

Microelement concentration

Na2B8O134H2O

Mango

0.05%, 0.0075%, 0.1% tree
1

3

Internal cracking

Saran and Kumar (2011)

CoSO4

Mango

250, 500, 1000, 1500 ppm

1

Nonreducing sugars

Singh et al. (1994)

Cu(OH)2

Sweet cherry

50% Cu 100 L/tree

1

Resistance to cracking, firmness

Brown et al. (1995)

FeSO47H2OFeSO47H2O

Pomegranate

2 g/L

2

Fruit yield, total soluble content

Mirzapour and Khoshgoftarmanesh (2013)

Aminoacid-Fe compound fertilizer

Peach

1000 mg/kg

2

Firmness, total soluble solids, Fe concentration, succinate

Song et al. (2016)

Wójcik and Lewandowski (2003)

Continued

412

29. Manipulating fruit quality through foliar nutrition

TABLE 29.2 Effect of microelement foliar application in fruit quality characteristics—cont’d Formula

Fruit

Dose

Sprays

Increase

Decrease

Ref.

Fruit weight loss

Ekinci (2018)

dehydrogenase activity, aconitase activity MnSO4

Peach

1%

4

Polygalacturonic acid content

NiSO4

Strawberry

150, 300, 400 mg/L

2

Crown number

Eshghi and Ranjbar (2015)

SeSO4

Winter jujube

25, 50, 100, 200 mg/L

3

Ascorbic acid content, soluble sugars, total flavonoids, sugar/acid ratio, fruit weight, fruit yield

Jing et al. (2017)

Na2SeO3-Na2SeO4

Blueberry

200 mg/L

2

Se concentration, pomace storage, anthocyanin content, intact fruit rate

Li et al. (2018)

C24H32O24Ti

Apple

3 g Ti/ha

6

Fruit yield

Wócik et al. (2010)

C24H32O24Ti

Plum

0.0042 mM, 5 L/tree

3

Resistance to compression, resistance to penetration, color formation, peel and flesh Fe-Cu-Zn concentration, absorptiontranslocation and assimilation of Ca

Weight, ripening status

Alcaraz-Lopez et al. (2004)

C24H32O24Ti

Peach

0.0042 mM, 2 mg Ti L/tree

3

Resistance to compression, color formation, peel Fe-Cu-Zn, Peel and flesh Ca absorption, translocation and assimilation process

Ripening status

Alcaraz-Lopez et al. (2003)

ZnSO4

Olive tree

0.25%

2

Oil content, UFA/SFA ratio

Soluble carbohydrates

Saadati et al. (2013)

ZnSO4 Nano-Zn-chelated fertilizer

Mango

0.25%, 0.50%, 1.0%

1

Zn pulp concentration, total soluble solid content

Bahadur et al. (1998)

Mandarin

0.5 g L/tree

2

Fruit weight, fruit pulp, fruit juice, fruit volume, fruit lengthdiameter, total soluble solid content, acidity, fruit juice pH, total sugars, ascorbic acid content

Al-Obeed et al. (2018)

Mandarin

1%

4

Circumference/ diameter, fruit juice content, juice total soluble solids, ascorbic acid content, total soluble solids/acid ratio

Peel thickness, citric acid content

Ashraf et al. (2013)

413

References

TABLE 29.2 Effect of microelement foliar application in fruit quality characteristics—cont’d Formula

Nanochelated Zn

Fruit

Dose

Sprays

Increase

Pomegranate

60, 120 mg Zn L/tree

1

Fruit yield, titratable acidity, total soluble solids, maturation index, fruit juice pH

Apple

0.13%

1

Ascorbic acid content, total antioxidative activity, superoxide dismutase activity

Decrease

Ref. Davarpanah et al. (2016)

Starch content, polyphenol oxidase activity

Rasouli and Koushesh Saba (2018)

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