Management Strategies for Botrytis Rot in Strawberry

Abstract

Strawberry is major horticultural fruit crop grown across the globe. The crop is basis of a multibillion dollars food product industry and a major employer of the global population. Gray mold disease caused by pathogen Botrytis cinerea is responsible for massive pre-harvest and post-harvest losses in the crop making it a major challenge for the overall health of the industry. Furthermore, infected fruits are equally disliked by commercial buyers and domestic consumer resulting in to major losses for the growers. Rising populations and climate change factors are crucial in this aspect as well, because they have a negative impact on the overall yield of crop and can also lead to rapid mutations in pathogen genome making it more resilient to multiple climatic conditions. In this chapter we are going to discuss fundamentals of this issue, basic biology of the pathogen followed by conventional and modern approaches for disease control and future perspective.

1. Introduction

Strawberry is a globally important fruit crop with significant financial value for growers across the globe. Currently, almost 400,000 hectares of land is cultivated with strawberry crop plant with estimated global market value of about 19 billion USD [1]. China and US are the biggest producers of the crop with US market worth about US$ 2.5 billion [2]. Most common commercial cultivar of the plant has originated some 300 years before in response to hybridization between four different global cultivars (F. viridis, F. iinumae, F. nippiconica and F. vesca) [3]. Current domesticated crop is an allo-octoploid crop (2n = 8x = 56) and its overall genomic complexity has often led to the use of diploid relatives as model crops to better understand the genomic complexion of crop.

Commercial cultivars of the crop found their origin about 3 centuries ago in accidental hybridization of Fragaria chiloensis and Fragaria virginiana cultivars. Evidences has shown that Thomas Knight made some of the earliest efforts for crossing and breeding of strawberry cultivars in his personal gardens during 1817 in Britain [4]. Similarly, growers from north American region also began making efforts for newer and better cultivars of the crop, and these efforts played an important in overall technological production advancement and breeding efforts of the crop over the next 2 centuries. Strawberries and other berry fruits (i.e. blueberries, raspberries, blackberries, etc.) are well known for their high crop nutritional profile and are often added in to diet plan for patients of various cardo-vascular diseases [5]. Strawberry is among the group of so-called super fruit group that often tend to enhance overall body metabolism and bio-chemical setup with an additional supply of minerals and anti-oxidants. According to an estimation made by the UNFAO, overall production of strawberry plant has increased by more than 80% over the last two decades with nearly 3/4th of the produced berries being consumed as fresh products while remaining being taken in by industries as processed foods.

In general strawberry are perennial plants with an herbaceous growth pattern, and denser leave system. It produces a complex fruit called the achenes which are single-seed fruit, and the receptacles that are similar to floral meristem tissues [6]. Strawberries are source of various vitamins and minerals that are essential for proper functioning of human body. Strawberry fruit also contain good amount of dietary fibers that help in maintenance of blood sugar levels, and healthy fatty acids helps in metabolism stability.

Strawberry crop is infected by a number of pathogens including Fungal, bacterial, viral and nematode based infections. Among these most damaging of all are fungal pathogens that result in major losses for the crop [7]. Fungal pathogens are capable of damaging all parts of the plant including stem, root, leaf and fruit, in addition to this these pathogens are responsible for causing on field as well as post-harvest losses of the crop. Among all the fungal pathogens gray mold or the botrytis disease is the most damaging one caused by ascomycetes Botrytis cinerea, as it is responsible for significant on field yield losses as well as post-harvest losses [8]. The pathogen has severe economic implications for the growers and causes senescing of plant fruit and vegetative tissues. Disease prevalence is more dominant under wet, humid conditions, with some infection leading up to 80% losses (Table 1).

Ploidy	Species	Indigenous Area	Fruit Characters
Diploid	Fragaria nubicola	Himalayas	Bright red appearance with raised seed
	Fragaria viridis	Central Europe/ Eastern Europe	Small and firm fruit with Pink-red appearance
	Fragaria daltoniana	Himalayas	Elongated and bright red fruit with no taste
	Fragaria iinumae	Japan	Ovoid in appearance with sunken achenes
	Fragaria vesca	Japan	Bright red appearance with raised seed
Tetraploid	Fragaria mounpinensis	China—Tibet region	Small fruit with similarity to F. nilgerrensis
	Fragaria orientalis	Korea and Siberia regions	Soft fruit, with slight aroma and sunken seed
Hexaploid	Fragaria moschata	North Europe	Light to Dark purplish red color, ovoid shape, raised achenes
Octoploid	Fragaria virginiana	North America	Double than the size of F. vesca with soft fruit and light to deep red in color appearance
	Fragaria chiloensis	North America, Chile, Argentina	Red brownish furit color with white flesh
	Fragaria ovalis	Western coast to Rocky Mountains	Round small sized fruit with pink color
	Fragaria inturupensis	North Japan	Oval shaped fruit

Table 1.

Species diversity of strawberry plant (Fragaria spp.).

2. Botanical aspects of strawberry cultivars

One of the earliest efforts made to answer several mysteries of strawberry plant and discussing its botanical efforts were made by French researchers Antoine Nicolas Duchesne and Bernard de Jussieu, and their findings were later on published in their book during 1766 in France [9]. In their book Duchesne discussed basic aspects of strawberry plant and concluded that the current commercial cultivar of the crop is hybrid made in North America from two South American cultivars of the crop (i.e. F. virginiana and F. chiloensis) [10]. The genus Fragaria belongs to family Rosaceae that also contains a large number of commercially significant fruit crops and ornamental plants in it. Fragaria genus is added in to sub-family group Rosoideae that has about 20 difefernet species of the plant added in to it, with some of those being diploid, tetraploid, hexaploid and octaploid varieties [11]. The sub-family also consists a number of wild relatives of the crop such as, Fragaria nubicola and Fragaria vesca which are diploid wild relatives of commercial strawberries. Strawberry plants are normally perennial herbaceous plant that have trifoliate, membranous leaves, pitted leaflets and whitish flowers. The petals are normally obovate, short, scrabbled and numerous distinct pistils borne on elevated convex receptacles. These receptacles later on provide space for berry like fruits to grow on, with minute seed like achenes formed over the fruit [12].

An important aim of modern breeding programs is to improve growth potential of the plant as well as betterment of nutritional profile. These features are controlled and manipulated by genetic and epigenetic elements of the plant with some changes being permanently added in to the plant while other being a temporary addition in to their nutritional profile due to influence of favorable conditions [13]. Several quality traits are greatly influenced in strawberry plants owing to genetic basis as well as climatic factors associated with growing practices of plant, these traits include size of the fruit, it shape, color, rigidity of the fruit pulp and overall color formation on fruit surface. Over the time growing awareness among consumers is pushing people worldwide to add more proportion of food in their daily intake for healthy and balanced diet. For this purpose, small berry fruits are a major contender owing to its higher concentration of numerous vitamins, minerals, phenolic compounds, flavonoids, iso-flavonoid etc. Owing to this major health benefit associated with the crop it has become an important target for researchers to identify cultivars with relatively higher concentration of beneficial bio-compounds and subject these varieties for breeding programs. Strawberry fruit has a diverse and heathy nutritional profile, among the most important of this are phenolic compounds which play an important role in biochemical activities, growth and survival of plant under different growing conditions. Basic structure of phenolic compounds consists of one or more benzene ring in it with increased solubility owing to attached sugar molecules with it. Flavonoids, tannins, and phenolic acids are the most significant biochemicals of the category essential for optimum growth of plants and stable functioning of human body (Table 2) [14].

Class	Group	Compound
Flavonoids	Anthocyanins	Cyanidin-3-glucoside
		Cyanidin-3-malonylglucoside
		Pelargonidin-3-galactoside
		Pelargonidin-3-arabinoside
		Pelargonidin-3-malyloglucoside
		Pelargonidin-3-acetylglucoside
	Flavonols	Quercetin-3-glucuronide
		Quercetin-glucoside
		Quercetin-glucuronide
		Kaempferol-glucunoride
Phenolic acids	Hydroxycinnamic acids Ellagitannins	Ellagitannin
		Bis-HHDP-glucose
		Methyl-EA-pentose conjugate
		Ellagic acid
		Sanguiin H-6

Table 2.

Biochemical profile of strawberry fruit.

Phenolic compounds are produced in response to plant biochemical activity, they are essential for normal growth and survival of plants [15]. Evidence shows that these compounds are bio-actively important in humans as well owing to consumption of berry fruit. Several groups of phenolic compounds are important in this regard including flavonoids, hydrolysable tannins, phenolic acids, and condensed tannins. Anthocyanin is an important hydrophilic pigment associated with strawberry fruit and it has a varying color ranging from reddish to slight purple in color, this varying pigmentation in fruit is attributed to growing pH conditions of plant [16]. These anthocyanin compounds have a higher concentration of anti-oxidant compounds increasing overall antioxidant capacity of plant. Berry fruit also contains fair amount of carbohydrate molecules in it, including fructose, glucose and sucrose, also various organic acids such citric acid, malic acid etc. are all present in strawberry.

3. Disease pathogen

B. cinerea has a wide range of host and is capable of causing infection on hundreds of plant species having significant food and ornamental value [17]. Many horticultural crops (fruits and vegetables) have been reported to accumulate millions in yield losses owing to B. cinerea pathogen infestation. The pathogen has a necrotrophic mode of nutrition that grows on host plant vegetative tissue ultimately causing death of plant. Pathogen spores are predominantly present in different growing locations that emerge out of infected plant parts which serve as primary inoculum for causing infection. Initially spore gain entrance inside plant system via several natural openings or wounds [18]. Although it has been reported to cause significant damage in mature, ripped plants, infection rates are observed to be lower in unripen plants. Often in unripe plants pathogen has been reported to cause slow infection either in of delayed germination of conidia, as symptomless endophytic infection or colonization of abscising plant organs where growth arrests. Often under mild infectious conditions, pathogen enters a small asymptomatic phase during initial stages of the cycle. Followed by this pathogen initiates a more severe necrotrophic cycle in ripening plant tissues that leads to cellular breakdown and decay of these tissues [19].

Owing to modern sequencing technologies and OMIC approaches, more information is now available regarding bio-chemical basis of the plant as well as the corresponding pathogen species [20]. Reference genome analysis for the botrytis pathogen has shown that pathogen produces a variety of virulence factor which promote overall susceptibility of the pathogen [21]. During initial stages of the infection the pathogen is known to secrete a variety of effector proteins molecules and sRNA’s that enable suppression of cell death under stress and restrict immuno-response of the plant [22]. This provides favorable condition for plant to further grow in plant tissues and gradually establish infection in plants. Establishing fungal hyphae also secrets dicer like protein molecules DCL1 and DCL2 which penetrates in to the host cell and inhibit its RNAi mechanism limiting host defense ability in response to the infection [23]. Several pathogen enzymes including toxins and reactive oxygen species (ROS) producing enzymes cause immediate death of host cell. Another key activity involves synthesis of oxalic acid that lowers pH level of host cell, creating a suitable environment for enhanced fungal activity. Pathogen produces several enzymes including pectinases, protease and laccase that result in cellular degradation [24]. Pathogen also cause accumulation of Ca²⁺ which leads to lower structural integrity of pectin in cell wall and restrict callose deposition in cellular structures. Furthermore, pathogen also secrets cell wall degrading enzymes which causes cell wall to loosen and lysis of cell. Fungal pathogen also secrets a variety of hormonal biochemical which interfere with normal cellular functioning of host cell.

4. Pathogen infection mechanism

Infection in strawberry plants is caused by invading fungal pathogen, in primary infection invading pathogen hyphae tend to infect the host plant specially during the flowering stage, grow in to receptacle during flowering stage. Pathogen often tend to overwinter by forming sclerotia or by infecting surrounding plants with mycelial extension. Pathogen growth is restricted after initial infestation of unripe receptacle and a symptomless quiescent phase occurs. Estimates has shown that inhibition of earlier infection in unripe plants is nearly 50% in comparison to just 8% in ripen plant fruit. This is attributed to the presence of proanthocyanins in unripe fruit which restrict the activity of fungal enzymes necessary for rapid infection of plant [25]. Similarly, anthocyanin content has also been associated with lower infection in early growth stages of plant.

In secondary infection the source of conidia is diverse and it initiate necrotrophic phase without any quiescence. Secondary infection takes place at a rapid pace with initial symptoms appearing within 16 hours of primary infection and significant biomass appearing in almost 48 hours of initial infection [26]. Early responses of strawberries to infection include higher expression of the defense genes FaPGIP and FaChi 2–1 (Class II Chitinase), whereas lower expression of the reference gene DNA Binding Protein – FaDBP indicates extensive cell death induced by B. cinerea at late stages of infection [27].

Research evidence suggests that ripening process tend to increase the overall susceptibility of strawberry fruit to Botryits cinerea infection. In unripe form berry fruit is resistant to fungal infection as it causes pathogen quiescence. Initiation of ripening process tend to increase it susceptibility, this is due to sveral transcriptional regulator molecules associated with ripening process that increase disease risk of strawberry [28]. OMIC analysis has shown that significant changes takes place during trnastion from large green to white phase; this includes alteration in cell wall composition, biochemical profile, plant hormones, pigmentation, carbohydrate metabolism and antioxidant profile [28]. This result in relatively lower oxidative phosphorylation during ripening ultimately disrupting a variety of biochemical and physiological processes. Research has shown strong evidence suggesting that pathogen infection interferes with biosynthetic mechanism of plant hormone synthesis including; ethylene, ABA, etc., that tend to act as virulence factor by promoting fruit ripening and senescence process (Figure 1) [29].

Figure 1.

Influence of ripening phenomenon on overall susceptibility of strawberry fruit to B. cinerea infection.

Pathogen also tend to introduce several physiological and cellular changes in the crop for facilitating infection process. Cell wall degradation assist higher infection severity as the physical barriers to pathogen invasion are weakened. In berry fruit, cell wall begins to disassemble as the fruit enters in to ripening phase, this solubilization of cell wall increases overall available sugar contents as polysaccharides continue to breakdown. Down regulation of pectin lyase (PL) gene has shown a higher degree of fruit firmness during ripening and a lowering overall severity of disease. Invading pathogen targets polysaccharide compounds in cell wall by secretion of a variety of cell wall degrading enzyme, pathogenicity gene such as Bcpg (endopolygalacturonases gene) gene plays an important role in infection prevalence [27, 30]. Similarly, cuticle is another major barrier to prevent pathogen invasion, and this barrier get compromised during ripening phase as expanding fruit tend to create small cracks on fruit surface and relatively thinner cuticle. In addition to this pathogen secret cuticle degrading enzyme which further increase overall penetration and infection causing ability of pathogen [28].

5. Management strategies for botrytis rot in strawberry

Owing to the overall quantitative and qualitative importance of the strawberry fruit crop, management of pathogen is a crucial task in this regard. Historically, little information was available regarding pathogen survival, overwintering in other crops, mode of action and optimum growing conditions that limited the potential of control measures. Owing to this lack of information regarding disease spread the disease was mainly managed via conventional or cultural practices. During the late 19th to early 20th century discovery of pathogen species, formulation of new chemical compounds and the green revolution enabled application of synthetic chemicals as well as certain biocontrol agents for disease management. Recent progress in the availability of OMIC’s data owing to rapid progress in sequencing technologies are now enabling researchers to introduce resistance capabilities in to the genome of plant to overcome the invading pathogen. Latest genetic engineering technologies like the CRISPR/CAS technology has enabled knocking-out of susceptibility genes in plant and virulence genes in pathogen, making it difficult for disease to affect the plant. Also, massive data sets regarding climatic conditions has added in to our better understating of optimum growth conditions of both the plant and pathogen which can be used for managing infections in post-harvest and controlled growing environments. Following are some of the key management strategies used for managing Botrytis rot infection.

5.1 Conventional management techniques

Historically botrytis infection has been contained by adopting certain management strategies focused on constraining inoculum buildup of pathogen. Similarly, second most common approach used involves the practice of keeping pathogen away from the fruit by avoiding fruit contact with soil, infected plant parts or contaminated farm equipment. It is important to avoid contact of fruit with soil surface as certain conidia are present on the surface of soil and tend to germinate quickly upon connection with fruit and under relatively higher soil moisture [31]. Owing to pathogen dependence on higher soil moisture content it is also important to better manage the field irrigation system. In this regard, drip irrigation system, micro-sprinklers and smart sensors-based irrigation system plays an important role in maintaining stable soil moisture as well as restricting over irrigation of field to avoid prevalence of conidial germination [32]. Shady environment also tends to aid fungal infection and for this purpose proper thinning and pruning of trees tend to reduce infection initiation probability. Furthermore, application of moderate to lower dosage of nitrogen fertilizers is recommended during infection season to avoid excessive shoots and leaves growth. Similar to canopy issue, close spacing in plants also tend to promote infection and can be avoided with appropriate spacing among fruit plants. Another common practice for reducing fungal infestation is to grow plant under tunnels, in this case a relatively lower level of air inoculum is able to invade host which in turn reduces overall rate of infection. Although beneficial, tunnel-based approaches are challenging as well, the tend to increase risk of powdery mildew infection and create issues with fruit harvesting process [33]. Conclusively, the conventional approaches have shown significant results in the past and still plays a prominent role in management of disease.

5.2 Fungicide/chemical based control strategies

Demand for increase of crop production has always been a major challenge for human race, in an effort to satisfy increasing food demands of rising global population. This effort has often faced plant disease as a major challenge that tend to restrict fruitful outcomes of such efforts. In this regard application of various pesticide or insecticide chemicals has been utilized as a major source to restrict the pathogen activity and ensure higher crop yields [34]. Like many important plant diseases (such as powdery mildew disease, downy mildew, rice blast disease etc.) botrytis rot of strawberry is also manage heavily these days via synthetic pesticide chemicals. In order to secure effective outcomes from pesticidal application it is important to take in account for number of applications and time span for applying chemicals to diseased or susceptible plant [35]. furthermore, use of multiple fungicide is also important to control such pathogens that requires multi-mode of actions for growth inhibition. Botrytis rot has been heavily managed by the use of such chemicals with fungicides from the FRAC (Fungicide resistance action committee) groups and captain being most prominent group of chemicals overall [34]. Recently resistance development to fungicide application in pathogen has been a major challenge in plant disease management owing to changing resistance profile of invading pathogens in a single growing season (Table 3).

FRAC Chemical	Target site	Target action	Resistance risk profile
Dicarboximides	Hisitidine kinase	Signal transduction	Medium to high risk
Succinate dehydrogenase inhibitor	Succinate dehydrogenase	Respiration activity	Medium to high risk
Benzimidazole	Tubulin assembly	Cytoskeleton	High rsik
Phenylpyrroles	Hisitidine kinase	Signal transduction	Low to medium risk
Sterol bio-synthesis inhibitor	Keto reductase in C4 de-methylation	Inhibition of sterol synthesis	Low to medium risk
Anilinopyrimidines	Methionine synthesis	Protein synthesis	Medium risk

Table 3.

List of synthetic fungicide chemicals to control botrytis disease.

Efforts have been made recently in order to develop resistance profile of several B. cinerea isolates, a study conducted in the Louisiana state of USA involved resistance profiling of nearly 13 fungal isolates with each of them showing lower to moderate level resistance against FRAC 1 pesticidal chemicals. These isolates were later on further tested against FRAC 2 type of pesticide chemicals with a few isolates showing some degree of resistance to them. Another study including assessment of more than 1800 B. cinereaisolates was carried out in 2015, isolates from 10 different American states were subjected to resistance profiling, results indicated that multiple isoaltes have developed resistance against all single action sites of FRAC group chemicals [36]. A positive correlation was also observed between overexpression of efflux transporters, modification of fungicide target site and increased resistance level of pathogen against chemicals. B. cinerea also possess a diverse range of transposable elements in its genome, along with heterokaryosis and sexual reproduction process that enables pathogen to gain multiple resistance related mutations in a single growing season. This increased resistance in fungicide action sites indicates a prevailing nascent demand for more innovative approaches in disease management strategy. Efforts are now under way to produce new type of fungicide chemicals that will interfere with pathogen growth patterns at RNA level and inhibition of transcription-translation phases in plants, enabling targeted growth reduction and containment of pathogen infestation [37]. These approaches are in early development phase and far from large scale commercial availability. Meanwhile, mixed application and rotation of different fungicide chemicals can assist better management of disease along with avoiding risk of resistance development.

5.3 Biological control approaches for B. cinerea

Although synthetic chemicals have been utilized heavily for disease containment, many of the negative aspect of aforementioned approach has raised questions regarding its effectiveness. For example, many copper based or other type of pesticide chemicals are causing respiratory, dermatological issues as well as heavy metal contamination in agricultural fields [38]. Therefore, evaluation and application of other eco-friendly sustainable approaches has become a priority now. In this regard use of biocontrol microbes has been under extensive studies to make commercially viable eco-friendly products out of it. Several microbial species including Bacillus subtilis, Colletotrichum gloeosporioides, Epicoccum purpurascens, Gliocladum roseum, Penicillium sp., Trichoderma spp. have been tested to contain botrytis infection in controlled conditions [39]. Earlier studies have indicated that in many cases bio-control agents tend to reduce disease severity much higher than the synthetic chemicals, with up to 90% disease reduction in stamens and more than 75% reduction in fruits.

Bio-control agents utilizes multiple mode of actions to contain pathogenic microbe growth, this includes competition for primary growth nutrients, secretion of several growth inhibiting bio-molecules (such as anti-biotics), and influencing host plant biomechanism to produce pathogen growth restricting molecule such as chitinases and peroxidases, as well as certain PR proteins [40]. A combination of bio-control microbes is recommended to for application to infected plant so that pathogen growth contained via multi-mode of action strategy. Also, use of certain bio-control volatile compounds and extracts from these microbes has shown some potential to resolve pathogenicity issue [41]. Overall microbes and microbes-based bio-compounds have shown significant growth inhibiting properties, but their large-scale commercial application remains under question due to high degree of pathogen diversity at sub-species and variant levels, as well as overall commercial cost that is needed to incurred in order to produce commercial scale quantity of microbial compounds for disease management.

5.4 Genomic approaches for disease management

Over the last three decades huge number of genomic information data sets have been generated related to various crop plants and disease pathogens. These data sets have enabled a better understanding related to genes responsible for susceptibility in plants and utilization of this information for better management of disease. Earlier efforts were mainly the transgenic approaches that involved Agrobacterium mediated cellular transformation for disease related traits. Several factors affecting transformation efficiency in strawberry have been determined, that the leaf discs from in vitro cultures proliferating in the presence of 2.21 μM kinetin were the best explant for transformation. Furthermore, it was observed that the transformation efficiency for antibiotic-sensitive F. vesca and Fragaria semperflorens could be improved by using antibiotic carbenicillin for selection and suitable Agrobacterium strain. They achieved optimal transformation efficiency (15%) by the appropriate use of explant type and age, leaf-disc orientation, inoculation time, and phenolic compounds for bacterial virulence induction [42]. Incubation of A. tumefaciens with acetosyringone and indole acetic acid, age of explant, pre-culture, and pre-selection on antibiotic-containing medium were the other key factors to affect the transformation efficiency in strawberry.

Studies have shown significant results obtained by transgenic techniques for management of botrytis rot in strawberry. Schestibratov and Dolgov (2005) introduced thaumatin II protein via Agrobacterium-mediated transformation in multiple strawberry plants, with transformed platns with higher level of thau II expressed proteins exhibiting resistance against botrytis infection [42]. Vellicce et al. focused on strengthening of cellular defense mechanism in plant by transforming such genes in to plants. Two genes were targeted for this purpose; ch5B gene responsible for chitinase synthesis in plant and gln2 gene encoding for glucanase. Ch5B gene is responsible for degradation of cell-wall structures in pathogen resulting in to reduced growth of the pathogen and lesser infection severity [43]. In addition to this, modern CRISPR/CAS based genome editing has also enabled better management of disease; studies have shown that CRISPR mediated knock-out of SIMAPK3 gene susceptible for gray mold has shown a higher degree of resistance to the disease [44]. This is mainly due to increase in production of certain defense related secondary metabolites as well as synthesis of reactive oxygen species (ROS). In another study targeted mutagenesis of FaPG1 gene was carried out, this resulted in up to 70% increase in firmness of strawberry fruit, ultimately enhancing its shelf life and making less vulnerable to pathogen attacks (Figure 2) [45].

Figure 2.

CRISPR gene editing approach for resistance development in strawberry against B. cinerea infection.

5.5 Post-harvest management of disease

The pathogen also causes major challenges during post-harvest handling of the crop ultimately resulting in major losses. Efforts are also made to alter storage conditions in a manner to reduce overall infection, berry fruit is stored immediately below 3 degree temperature which inhibits the chance of pathogen to regrow. Fruit is also kept in an environment that is higher in carbon dioxide concentration and lower in oxygen, so that metabolism of fruit is restricted [46]. Relative humidity during storage is usually kept around 85–90% to prevent dehydration of fruit, but limit fungal growth [47]. A novel approach for post-harvest management of this disease includes the application of protective coatings on fruit surface, that prevents loss of water from the fruit and at the same time restrict growth of fungus owing to presence of anti-fungal compounds. Application of chlorine mist in storage facilities also has the potential to reduce pathogen infestation and disease severity [48, 49]. More recent approaches includes use of ultraviolet radiation as a treatment method to kill any microbial spore that might be present on surface of harvested fruit or inside the storage facility.

6. Conclusion

Many aspects of botrytis disease development are still not properly understood, technological advancement will play an important role in better understanding genetic diversity of pathogen and various bio-chemical pathways crucial for pathogen cellular growth. Similarly, better understanding of plant defense mechanism and reasons associated with its failure will also assist in development of effective disease management strategies. Furthermore, current disease management needs to be re-evaluated to cope with increasing restrictions and lack of efficacy of fungicides. Investigations on biocontrol approaches and pre- and postharvest treatments are necessary to manage gray mold. Research related to study of such natural mutations taken place in strawberry that enabled better resistance against pathogen attack can also assist in this regard. Also, massive information regarding climatic data can be used for better studying of climatic factors supporting pathogen growth so that a disease forecasting model can be developed which can later be used for better management of disease.

Conflict of interest

The authors declare no conflict of interest.