**1. Introduction**

Pomegranate (*Punica granatum* L.) belongs to the order of Myrtales, but the family type is uncertain between Punicaceae and Lythraceae [1]. Regarding the binomial name, the genus *Punica* reflects the feminized Roman name of Chartage, instead the species epithet *granatum* referred to the seeded arils; the common English name "pomegranate" describe its anatomical features of "grainy apple" [2, 3]. The Transcaucasian-Caspian region [4] is the center of diffusion of pomegranate shrubs, which early spread in the Mediterranean basin and then gradually reach the New World. Being a heliophilous plant, pomegranates tolerate temperature until 45**–**48°C with hot wind, even though temperatures below **−**18°C are harmful [1]. Pomegranate cultivation is promoted by the cool winter and hot summer; these features match with Mediterranean climate, although these shrubs are fully spread in tropical and sub-tropical areas too [2].

## **1.1 An outline of botanical features**

Some botanical features of pomegranate plants are relevant in plant pathology. First and foremost, flower biology. Being an andromonoecy shrub, it brings both hermaphroditic and functionally male flowers to the same plant [5]. Male flowers bloom earlier than bisexual ones and have a *vexillum* function attracting insects, and a selective advantage improving the genetic variability related to cross-pollination instead of self-pollination [5]. Fertile hermaphrodite flowers have well-developed *gynoecium* and *androecium*, urceolate vase-shaped calyx, and prominent U-shaped ovary; often they show big ovary and long style, the *stigma* emerges at the same height as the anthers or above them. On the other hand, male flowers are smaller, since the *androecium* is well-developed, but the *gynoecium* (including ovary and ovules) is rudimental: the style is shorter than anthers; the calyx is bell-shaped and the ovary is V-shaped. Furthermore, several intermediate flower forms exist that may be more or less close to the chief sexual forms showing different degrees of anatomical functionality [1, 4, 5]. Usually, hermaphroditic flowers (and occasionally a few intermediate forms) are fertilized [1, 5]. This is a delicate phase because latent fungal pathogens infect fruit during this stage passing through the open connection with the ovary [6]. According to the cultivar, between 5 and 8 months after fertilization and fruit set, pomegranate fruit, named *balausta*, ripen [4]. The most significant morphological feature of this berry-like and fleshy fruit is the persistence of the residues of the thick floral calyx [1] creating optimal ecological niche for fungal settlement and growth. In addition, the persistence of necrotic stamens acts as secondary source chiefly for wound fungal pathogens [6]. The leathery and woody rind and the richness in polyphenolic compounds guarantee physical and chemical protection from pathogenic fungi to a certain degree [1]. Internally, the carpel, made of light yellow and spongy tissue, as the mesocarp, acts as preferential way for latent fungi diffusion. Internally the *balausta* is reparteed in asymmetrical chambers, called "*locules,*" by membranes made of papery tissue [1, 2, 4]. Arils, attached to the carpel and wrapped by membranes, are the edible portion of pomegranates, constitute 40**–**60% of fruit weight, and are the most susceptible part of the fruit. Over time, pathogen diffusion happens chamber by chamber. Pomegranate is a non-climacteric fruit, so it must be harvested at the optimum maturity stage [4].

#### **1.2 An outline of horticultural features and disorder prevention**

Few horticultural characteristics are important to control disorders, improve disease resistance, and enhance healthy fruit production which is the key point for extended storage. Pomegranates could grow in different soils but prefer fertile and humus-rich ones with a medium-deep density and well-drained avoiding water stagnation [1]. During the dry season, especially in arid and semi-arid environments, pomegranate plants need a regular daily irrigation to prevent water stress; also considering reduction of groundwater resources, drip irrigation is one of the favorite techniques [7]. Furthermore, within 0.5% of soil mass, pomegranate is a saline-tolerant plant: sodium, chlorine, and potassium are accumulated in root tissues, preventing diffusion of toxic salts [1, 4]. Also, fertilization is important to prevent both pomegranate disorders, like cracking, and related diseases due to wound pathogens; nitrogen and calcium are the most involved chemical elements. Soil application of watery nitrogen enhances vegetative growth, fruit size, and yield; in addition, foliar application of potassium chloride, potassium sulfate, and

*Pomegranate: Postharvest Fungal Diseases and Control DOI: http://dx.doi.org/10.5772/intechopen.109665*

microelements improves both yield and growth of pomegranate [4, 8]. Among foliar treatments, calcium application is the most significant; it induces physiological resistance and stabilization of the cell membrane, preventing low-quality production and supporting postharvest storage [9]; in addition, if applied at the blooming stage and 1 month later, it prevents fruit cracking [10]. Indeed, nitrogen and calcium are key chemical elements for disease prevention; also pruning practices may influence disorder and disease development. In some parts of the world, multiple trunk method is the traditional growing practice for pomegranates, from three to five main trunks are developed and branches are open-vase pruned. This favors the branch maintenance year-after-year and allows the replacement of diseased one [4]. The single stem method provides a single trunk of up to 30 cm in height, after which divided into three or four main branches; this way ensures better vase-shape maintenance and adequate penetration of light that is fundamental for pomegranate veraison [4]. However, sunrays surplus could cause sunburn damaging fruit, indeed the perfect light balance is noticeable [1].

#### **1.3 An outline of pomegranate trade**

In the last decades, pomegranate cultivation increased worldwide to face consumer requests; pomegranates display nutraceutical properties due to the high content of active secondary metabolites (i.e.*,* alkaloids, terpenoids, and polyphenols). These compounds are well-known for both antimicrobial and antioxidant properties, and therapeutic ones that feed this trade [11]. Consequently, the request for fresh fruit and related processed products is rapidly growing reaching a global production of about 8.1 million tons [12]. In the world, the chief producers are India, China, and Iran which produced 70% of pomegranates [12], although official data are not available. Particularly, Indian production represents 41% of the global trade having 288,000 ha of pomegranate orchards and producing 3,256,000 tons of fruit gathered in the Maharashtra state and in the Solapur district [13]. In India, the most spread cultivars are Bhagwa and Arakta available throughout the year; these pomegranates support export to European, Middle East, and Asian countries, especially during the production gap (December, January, and March) [14]. Even though China is the second worldwide producer, 70% of produced soft-seeded 'Tunisia" pomegranates are headed to the national markets [14]. A similar scenario distinguishes the Iran market, which mainly aspires to internal commerce of "Malas Yazdi" pomegranates due to export troubles [14]. Regarding Europe, the main producers are Spain and Italy, detailing Spanish production aims at export, instead Italian is not enough to satisfy internal requests [12]; indeed, Italy imports 4% of the global production of pomegranates. Being high-quality, flavorful, and royalty-free cultivars [15], chiefly cultivated plants belong to the Israeli "Akko," the American "Wonderful" and the Spanish "Mollar de Elche," this last is featured by sweetness and herbaceous seeds. These cultivars, such as their wide-spread clones, sequentially ripening in September and October, so are available almost till January [4, 16]. Most updated Italian data referred to 2021 when pomegranate orchards are 1420 ha and have a total production of 192,485 [17]. As displayed in **Table 1**, comparing 2011 and 2019 production years, the present production is about 800- and 3600-fold increased, respectively. Almost the entire production happens in southern Italy, especially in Apulia and Sicily regions, where the Mediterranean climate is favorable. Pomegranate cultivation is promoted by the cool winter and hot summer, although these shrubs are spread in tropical and sub-tropical areas too [2]. Being a minor crop, worldwide analysis of


#### **Table 1.**

*Pomegranate Italian production. Pomegranate surface (ha) and fruit production (q) are compared in different years.*

pomegranate market is lacking due to both the absence of consistent and updated data and grouping within a single Harmonized Code1 (HS code) [18].

#### **1.4 An outline of yield and economic losses**

Yield losses caused by fungal postharvest rots may significantly reduce pomegranate production [19] partially justifying differences between produced and harvested amount of fruit (**Table 1**). Yield losses are reflected in economic ones. Particularly, fruit losses are distributed among the field, wholesale, and retail sites referring to related transportation too; similar data are obtained for Indian [20, 21] and South African markets [22, 23]. In the field importance of injuries, cracking, and fungal infections is highlighted rather than secondary infections and physical damages (dehydration, overripening, etc.) mainly involved during the other phases [20, 21]. In India, 10% of yield losses occur in the field and wholesale and 15% are in retail [20, 21], whereas, in South Africa, the percentages involved are 18, 23, and 21%, respectively [22, 23].

#### **2. Postharvest pomegranate diseases**

A careful eye in presenting postharvest fungal diseases of pomegranates is needed, according to the mode of infection that gives rise to "latent" infections and "wound" ones. In the field, latent pathogens infect the future fruit during the blooming stage and remain latent until environmental and physiological optimal conditions let them to develop; usually, this happens during postharvest stages. Chief diseases ascribable to this group are gray mold, black heart and black rot, soft rot, and anthracnose, which represent around 65% of total infections [6]. The remaining percentage belongs to wound pathogens that penetrate pomegranate rind and infect fruit following traumatic events caused by bad handling (i.e., no close-cropped peduncle), pests (i.e., borers), weathering (i.e., hail and rain), and abiotic damages (i.e., cracking) occurring from the field till the retail. Blue mold and aspergillosis are the main diseases related to these events [6]. Both groups of pathogens may be responsible also for secondary infections, generally related to nesting or infected stamens. Treatments to control primary and secondary infections, as well as good agronomical practices (i.e., debris and mummy removal) are needed to reduce yield and economic losses [19]. To this aim, a reliable identification of the chief genera and species of fungi is needed to face them with specific/ effective substances. Pathogen/disease characterization is primarily based on fruit symptom evaluation, followed by pathogen isolation and observation of their

specific macroscopic/microscopic structures on a broad spectrum medium, such as potato dextrose agar (PDA). Finally, molecular analyses are applied to univocally confirm their identity.
