Vol.:(0123456789) 1 3 Journal of Plant Diseases and Protection https://doi.org/10.1007/s41348-020-00302-4 ORIGINAL ARTICLE Effect of hot water treatments on apple fruit rot caused by Fusarium spp. Mladen Petreš 1  · Jelena Kalajdžić 1  · Biserka Milić 1  · Nenad Magazin 1  · Aleksandra Stankov 1  · Jelena Vukotić 1  · Mila Grahovac 1 Received: 18 November 2019 / Accepted: 24 January 2020 © Deutsche Phytomedizinische Gesellschaft 2020 Abstract Hot water treatments of apple fruits prior to long-term storage have a high potential as a physical measure against apple fruit storage rot caused by plant pathogenic fungi. Fusarium species are increasingly found as causal agents of postharvest apple fruit rot. The effect of high temperatures on casual agents of Fusarium fruit rot, F. avenaceum and F. graminearum, was tested in this article. In in vitro assay, spore suspensions of F. avenaceum and F. graminearum were exposed to high temperatures (ranging from 45 to 90 °C) at different duration (ranging from 30 s to 20 min) and the treatments that significantly inhibited mycelial growth of the isolates (53 and 57 °C for 3 and 5 min) were tested in vivo by hot water treatment of inoculated apple fruits of Fuji cultivar. The obtained results showed that the most promising hot water treatment should be between 53 and 57 °C and between 3 and 5 min of the exposure period. Keywords Apple · Fusarium · Hot water treatment · Postharvest Introduction Apple fruit possesses the ability for long-term storage, and due to this characteristic, it is available on markets all year round. During storage, quality of apple fruits can be affected by many factors and plant pathogenic fungi, being one of these, can cause significant postharvest losses during stor- age, ranging from 5 to 25% in developed countries and even up to 50% in developing countries (Ewekeye et al. 2013). The most significant fungal species that cause losses in apple storages are Penicillium expansum Link, Monilinia fructi- gena Honey, Botrytis cinerea Pers., as well as Alternaria spp., Mucor spp., Rhizopus spp., Botryosphaeria spp., etc. (Grahovac et al. 2011, 2012; Petreš et al. 2017a). Besides mentioned species, Fusarium avenaceum and Fusarium graminearum are also present as causal agents of apple fruit rots in storages, particularly in novel storage types in Serbia and in some European countries and in the USA (Sever et al. 2012; Kou et al. 2014; Wenneker et al. 2016; Petreš et al. 2017b). Although Fusarium species are not among dominant causal agents of apple fruit rot, they are still of high impor- tance because of their capability to produce mycotoxins in infected fruits (Sørensen et al. 2009; Petreš et al. 2018a), as well as their continual occurrence, at lower rates, in sam- pled rotten apple fruits in Serbia in the period from 2012 to 2018 (Tarlanović et al. 2017; Krsmanović et al. 2018). The presence of these species on stored apple fruits, even at small rates, can result in high mycotoxin contamination of fruits and apple products. Therefore, monitoring of these species on stored apple fruits is of high importance. Keep- ing in mind that postharvest use of synthetic pesticides is not allowed in Serbia and in many other countries, there is a need for finding alternative strategies for apple fruit rot con- trol. Hot water treatments may be a very effective alternative method for rot control, particularly in organic production (Maxin et al. 2006; Gasser et al. 2015). According to Maxin et al. (2012) and Maxin (2012), there are three modes of action of hot water treatments: washing-off the inoculum from fruit surface, heat inactivation of spores and activa- tion of defense response in fruits (stress-induced transcrip- tion of heat shock proteins—HSP). It is necessary to find an adequate combination of temperature and exposure period that will successfully suppress fruit rot and at the same time will not have a detrimental effect on the fruit. * Mladen Petreš mladen.petres@polj.uns.ac.rs 1 Faculty of Agriculture, University of Novi Sad, Trg Dositeja Obradovića 8, Novi Sad, Serbia