Tomato is a highly perishable fruit given the fragility of its tissues and high metabolic activity, which requires additional methods for its appropriate conservation, aiming to reduce post-harvest losses (FERRAZ et al., 2012). Worldwide, a large part of the tomatoes produced are destined for the fresh consumer market, and the fruit’s visual appearance and quality directly influence the consumer's purchasing decision (BOTEON et al., 2020). In this sense, techniques to maintain fruit quality longer after harvest must be developed, increasing shelf life and reducing fruit losses or discards (MENEZES, 2017).
The main losses in post-harvest tomato quality are associated with physical damage, inadequate transportation, storage, and the action of pathogenic agents (CHITARRA, 2005). Such losses can be quantitative, in which a large part of the tissues is deteriorated and lost, or qualitative, where the visual aspect of the product is compromised, reducing its economic value (MACHADO et al., 2017), and culminating in a reduction in shelf life, making it difficult to sell. Although this waste can be used for processes like composting, this does not reduce the impact of disposing of the product as a nutritious and functional food, such as tomato fruit (ALENAZI et al. 2020).
Tomatoes are susceptible to several post-harvest pathogens, notably alternaria spot, which has a high destructive potential and is responsible worldwide for considerable economic losses in post-harvest tomatoes (AHMED et al., 2016; ARAH et al., 2015). The etiological agents, in Brazil, are fungi of the genus Alternaria (PEREIRA, PINHEIRO 2013), and control measures are taken using synthetic fungicides (BABI-PEÑA, 2006).
Reducing the incidence of post-harvest diseases is one of the biggest challenges to minimizing food losses, as in the case of tomatoes. This control has been currently done using heat treatments, humidity control, atmosphere modification, and alternative control with biological products, in addition to specific synthetic fungicides (MACHADO et al., 2017). However, the global advancement of sustainable vegetable production systems, which meets the demand for more natural products with reduced health risks, has increased the need to search for alternative products to conventional pesticides aimed at controlling pests and diseases in these cultivation systems to increase the production of high-quality fruits from a sanitary point of view and without residues of toxic products (PERON et al., 2018).
In this context, several studies have reported the potential of essential oils and plant extracts as an alternative for post-harvest treatment of fruits and vegetables, mainly due to their efficiency in controlling phytopathogens (PERES et al., 2017; CRUZ et al., 2010). Different essential oils and aqueous and/or ethanolic extracts of plants, containing specific active ingredients, have antimicrobial activity and have been studied in the control of diseases in tomatoes as well as inducing plant resistance to pathogens (NETO et al., 2016). The antifungal activity of an extract can be observed against one or several pathogens, and the determination of efficient concentration levels to inhibit them is imperative (ARAUJO et al., 2018).
In this sense, extracts or isolated metabolites, especially those from plants used as food like cloves (Syzygium aromaticum) and some species of cinnamon, such as Cinnamomum zeylanicum, have the advantage of being minimally or non-toxic to humans and the environment. These can be applied at effective concentrations as fungicides and are constantly associated with lower phytotoxicity and contamination risks compared to synthetic fungicides (CARMELLO, CARDOSO, 2018; STANGARLIN et al., 2011). However, extracts from parts of aromatic plants such as cinnamon bark and clove flower buds have been regularly associated with their natural antifungal and antibacterial activities on different species of plant and human pathogens (CARMELLO, CARDOSO, 2018; GOMES et al., 2018; KOWALSKA et al., 2021), and these extracts, when effective against fungi of agricultural importance, are called botanical fungicides (YOON et al., 2013).
Therefore, this study aimed to analyze the potential of cinnamon and clove extracts, applied alone or in combination, in controlling the phytopathogen Alternaria alternata, in in vitro conditions and post-harvest tomato fruit. This can result in an effective technique for controlling phytopathogens and reducing post-harvest losses caused by this fungus. Furthermore, the main active ingredients present in these extracts were studied, as well as the type of antifungal activity associated with these botanical fungicides.