## 1 Introduction
This emerging problem of resistance leads to a considerable threat to the crop yield, especially in case of useful plants which are particularly threatened by fungi or which are difficult to implement in breeding methods in order to introduce resistance into the useful plant [26; 25]. Allicin has gained considerable interest for the development of new fungicides for crop protection. Figure 1: Enzymatic transformation of allin to allicin by the enzyme allinase which involves the conversion of allin to intermediates allysulfenic acid and dehydroalanine, followed by the condensation of two molecules of allysulfenic acid to yield allicin. There are numerous pathogens that persist in the soil and invade the plants resulting in several diseases. The wilting pathogen, _Verticillium_, is particularly notorious and of increasing importance and threat [27; 28]. The host spectrum of the genus _Verticillium_ is broad [29], including economically important crops, such as potatoes and other Solanaceous plants, and large trees [30]. Treating a disease that has already broken out with fungicides is hardly possible due to the way the fungus lives in the xylem of the plant. The only promising method that has so far been effective in the control of _Verticillium_ is soil disinfection with fumigants such as methyl bromide [31; 32]. The use of methyl bromide, however, is banned in the most countries worldwide due to its high toxicity to the environment and humans [33; 34]. The ban on methyl bromide utilization has initiated the search for new methods to control soil-borne pathogens, weed seeds and pests. Several chemical and nonchemical methods have been introduced to eradicate pests and plant pathogens. For instance, biofumigants, steam, biocontrol and crop rotation are some of the methods to control phytopathogens [35]. There are some attempts to apply green \"biological\" solutions such as the introduction of Brassicaceae plant residues [34; 36]. The isothi cyanates, present in these plants, have an inhibiting effect on the spores of the _Verticillium_ fungus that germinate in the soil. Since allicin is volatile and inhibits the fungal spores in their germination stage, it can be exploited as an effective alternative fungicide via fumigation [37]. _Botrytis cinerea_ represents another example of a plant fungus which is a major pathogen of cultivated vegetables, fruits and flowers. This pathogen causes grey mold on more than 240 plant species leading to major economic losses [38]. Similarly, plant pathogens of the genus _Alternaria_ cause damage to Cruciferous crops, including broccoli, cauliflower, mustard and turnip. Blight disease is one of the most common diseases caused by these pathogens, causing an average yield loss in the range of 32%-57% [39]. In previous studies, the antifungal activity of allicin has been explained by proposing a variety of mechanisms of action. However, the mechanisms and modes of action of allicin pertinent to its health benefits are not yet completely understood [40]. More than half a century ago, allicin was evident as an inhibitor of several thiol-possessing enzymes, and glutathione overturned the inhibitory effect of allicin, which simply elucidated the principle of a nonspecific mechanism of action of allicin that includes its covalent bonding with the thiol groups in enzymes [41]. With reference to previously described modes of action, another study confirmed the interaction of allicin with protein thiol groups and also reported the diffusion of allicin across lipid bilayers [40; 42]. Allicin has been reported to result in the widespread _S_-thioallylation in the human Jurkat cell proteome. Moreover, allicin affected the essential cellular functions of specific targets including those for cancer therapy [10]. Recently, the crucial role of copper and zinc in the antifungal mode of action of allicin was revealed by a mini haploinsufficiency profiling (HIP) and homozygous profiling (HOP) assays [43].