Introduction
Gray mold is a primary postharvest disease in floriculture crops (Ha et al. 2021), with Botrytis cinerea ranking second among the top 10 fungal pathogens affecting plants, following Magnapor theoryzae (Dean et al. 2012). Gray mold causes economic losses of millions of dollars worldwide (Lee and Kim 2019). During the distribution of cut flowers in Dutch flower auctions, gray mold causes losses in the market share of roses, gerberas, and lisianthus of 8-10%, 22-33%, and 50%, respectively (Vrind 2005). In Colombia and Kenya, economic losses due to gray mold in export-quality roses are 1.6% and 10-20%, respectively (Salgado-Salazar et al. 2018). Greenhouse-grown crops are especially at risk, particularly in Spain, Italy, Turkey, South Korea, and Japan (Rosslenbroich and Stuebler 2000).
Infection is frequently facilitated by high relative humidity (> 93%) and temperatures of 15-20°C during postharvest storage and transportation (Fanourakis et al. 2013;Williamson et al. 1995). The physical control of B. cinerea may include low-temperature storage, hot-water or heat treatment, radiofrequency and microwave exposure, low and high-pressure treatments, UV-C treatment, or the use of a controlled and modified atmosphere (Nicot et al. 1996;West et al. 2000). Physical control methods are easy to implement because they are not harmful to humans and demand no technological innovations or regulations, so many studies have been conducted using these methods in recent years (Fallik 2004).
Alternatively, chemical control involves treating plants with fungicides and pesticides (Roberts et al. 2003;van Jaarsveld 2018), while biological control options use Bacillus subtilis, Cladosporium cladosporioides, and Cladosporium oxysporum (Simone et al. 2020). Chemical control is relatively inexpensive, easily applied, and generally effective in preventing and controlling pathogens (Usall et al. 2016). However, the cost of chemical control to suppress gray mold on horticulture crops was in the millions of dollars, accounting for 10% of the global antifungal market share (Dean et al. 2012).
Although many review papers have been published on gray mold, no studies have used the R program to code for text mining analysis and have considered the thesis according to a specific Korean site in analyzing (Krasnow and Ziv 2022; Table 1). In this study, we conducted a study to identify what keywords the study of gray mold (Botrytis cinerea) was studied a lot using a text mining in R analysis that considered horticultural crops, environmental or physical treatments, and chemical or material factors.
Materials and Methods
Search and article selections
This study used text-mining techniques to understand domestic and international research trends on gray mold (Do et al. 2020). The data were collected from papers on B. cinerea in ScienceON (https://scienceon. kisti.re.kr). Data, including international and domestic articles, reports, and patents, could be sorted by year, journal name, researchers, research institutes, tables and graphs, and countries. Article abstracts comprised shorter sentences and succinct text, presenting only the most essential findings (Westergaard et al. 2018). These abstracts were extracted to form text from papers published between 1980 and 2021 and saved as Excel files. A total of 36,626 words were recognized in 7,342 paper abstracts.
Data analysis
Lim et al. (2014) proposed an unstructured data-cleaning model for text mining. To analyze the data related to B. cinerea, we conducted word extraction and preprocessing to analyze the 1,000 most common words, classifying inappropriate words, such as idioms, prepositions, adverbs, and units, into dictionaries and eliminating them (Lee 2020). With this model, the final dataset consisted of data not in the dictionary, and unnecessary words were removed using heuristic post-processing methods with R. The collected and post-processed data was interpreted through word cloud visualization (Fig. 1). Morphology analysis was performed through the text-mining package tm, provided by R (version 4.1.1, Sun et al. 2017).
The final dataset was created through heuristic post-processing of words from morpheme analysis, and the results were visualized through the R wordcloud package. Words with similar meanings were grouped and treated as one word. Words with higher frequencies were displayed in larger fonts and positioned closer to the center (Do et al. 2020). A word cloud was created using the dplyr and stringr packages, which extracted 500 words that were identified more than 100 times (Lu 2018).
Results and Discussion
The top 10 keywords on B. cinerea of horticultural crops were tomato, strawberry, grape, apple, cucumber, bean, kiwifruit, rose, pepper, and pear (Tables 2 and Fig. 1). The roses on horticultural crops were in the top 10. Ha et al. (2021) studied chemical control approaches, radiation, biological controls, resistance inducers, and ethylene inhibitors to control B. cinerea in rose flowers. Roses, gerberas, and chrysanthemums account for a high proportion of plants affected by gray mold due to environmental factors such as distribution time, temperature, relative humidity, ethylene, dry and wet transportation methods, the accumulation of bacteria in preservation solutions, and airborne spores (Hoogerwerf et al. 1989).
Previous research on B. cinerea through text mining analysis has been conducted to study environmental or physical factors. It included storage, temperature, cold, seasons, humidity, heat/hot, UV-C, sprays, films, and coatings (Table 2). The leading causes of B. cinerea postharvest losses are physical damage, poor packing, and issues related to transportation, storage, and handling (Nxumalo et al. 2021). The environmental and physical treatments to control gray mold that involves eco-friendly and residue-free technologies are particularly valued by consumers (Simone et al. 2020). However, these treatments could have low persistence, adversely affecting crop quality when commercially applied (Usall et al. 2016). Heat treatment is the most well-known physical treatment, typically involving hot water dips or rinsing and hot air (Usall et al. 2016). 50°C hot water dip treatment for 20-40 s was effective against gray mold in roses (Lee et al. 2016). Ultraviolet (UV) light is divided into long-wavelength UV-A (400-315 nm), medium-wavelength UV-B (315-280 nm), and short-wavelength UV-C (280-100 nm), which can be used to improve antioxidants and for sterilization purposes in horticultural crops (Lee and Kim 2018;Song and Lee 2012). The appropriate UV-C dosage for suppressing gray mold has been determined for roses (1.08 kJ·m-2) (Vega et al. 2020). Coatings inhibiting B. cinerea have been studied mainly with edible coatings in fruits rather than flowers.
Chemical or material words included fungicide, chitosan, ethylene, oil, ROS, ABA, VOC, glucose, carbon, and ethanol (Table 2). Fungicide applications are the easiest method to control gray mold in many horticultural crops. Lee et al. (2006) confirmed the importance of post-harvest fungicide treatment because gray mold is likely to occur after harvest if only pre-harvest fungicide treatments are made. Fillinger and Elad (2016) reviewed the significant fungicides active against gray mold, and these fungicides are divided by their mode of action on respiration, cytoskeleton integrity, osmoregulation, amino-acid synthesis, and the synthesis of sterols such as dichlofuanid, fluazinam, and carbendazim. Some alternative fungicides have been studied for controlling gray mold in horticultural crops, including treatment with NaOCl, ClO2, CaSO4, CO2, plant extracts, hot water dips, and hot air on cut flowers (Fillinger and Elad 2016;Ha et al. 2021;Lee and Kim 2020;Usall et al. 2016). Pulsed treatments of 400 μM methyl jasmonate (C13H20O3) provided systemic protection against Botrytis rot by inducing resistance mechanisms in cut roses without impairing flower quality (Meir et al. 1998). Chitosan is a linear polysaccharide composed of D-glucosamine and N-acetyl-D-glucosamine linked by a β-(1→4) bond obtained by treating the exoskeleton of arthropods with alkaline solutions. It is the second most abundant biopolymer (Simone et al. 2020). Chitosan natural polymers are non-toxic, biodegradable, and active against B. cinerea, damaging hyphal cell walls (Ghaouth et al. 1994). Many ethylene inhibitors or action inhibitors, such as aminoethoxyvinylglycine (AVG), aminooxyacetic acid (AOA), silver thiosulphate (STS), 1-methylcyelopropene (1-MCP), and nano silver (NS) have been studied for their potential to control gray mold (Ha et al. 2021). Plant essential oils have the potential to replace synthetic fungicides in the management of postharvest diseases (Vitoratos et al. 2013). In a test of 49 essential oils, Wilson et al. (2007) found that palmarosa (Cymbopogon martini), red thyme (Thymus zygis), cinnamon leaf (Cinnamomum zeylanicum), and clove buds (Eugenia caryophyllata) had the most antifungal activity against B. cinerea occurring constituents of D-limonene, cineole, β-myrcene, α−pinene, β−pinene, and camphor. Reactive oxygen species (ROS), abscisic acid (ABA), and volatile organic compounds (VOCs) were also included in the materials identified through text mining (Table 2). The ROS levels of horticultural crops were related to the activities of antioxidant enzymes (Romanazzi et al. 2016). One paper analyzed VOCs influencing horticultural crop quality related to gray mold infection (Guigon-Lopez et al. 2021). Salts such as sodium potassium carbonate and ethanol were tested as control agents of gray mold, with both preharvest and postharvest applications (Romanazzi et al. 2010).
In conclusion, the top 10 keywords on B. cinerea` of horticultural crops were tomato, strawberry, grape, apple, cucumber, bean, kiwifruit, rose, pepper, and pear. Roses were the only flower in the top 10 horticultural crops. Research has examined environmental or physical treatment factors such as storage, temperature, cold, seasons, humidity, heat, UV-C, sprays, films, and coatings. Chemical or material words included fungicide, chitosan, ethylene, oil, ROS, ABA, VOC, glucose, carbon, and ethanol.
