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Melanin is a dark-pigmented proteinaceous polymer that provides appressoria of numerous plant-pathogenic fungi with their characteristic dark brown/black appearance. There are two types of fungal melanin − which derive from two different precursor molecules, that is, DHN (dihydroxynaphthalene) or DOPA (3,4 dihydroxyphenylalanine). DHN melanin is found in the appressorium cell wall, where it is observed as a discrete electron-dense layer. Loss of melanin, either by genetic or chemical disruption of melanin biosynthesis, renders appressoria unable to penetrate plant tissues in M. oryzae and C. graminicola [67,68]. Here, the rupture of melanin-deficient appressoria [68] suggests that DHN contributes to cell wall rigidity. However, appressoria of the soybean rust fungus, Phakopsora pachyrizi, lack melanin, but, nevertheless, generate high turgor pressures (5–6 MPa) [69,70]. This suggests that phytopathogens have developed alternative strategies to withstand high pressures in their infection structures. Moreover, many plant-pathogenic fungi penetrate plant tissues via secretion of degradative enzymes (e.g., B. cinerea and Sclerotinia sclerotiorum), whilst others use a combination of enzymic degradation and turgor pressure (e.g., Blumeria graminis [22]). Where enzyme degradation alone breaches the plant surface, melanin-dependent fortification of the wall of the infection structure is not required. However, melanin was found surrounding the appressorial pore in the apple scab pathogen Venturia inaequalis [71]. The function of this melanized appressorial ring structure is not clear, but it was shown that melanin is required for pathogenicity in this fungus. This suggests additional, yet undiscovered roles for FCW localised melanin in fungal plant infection.