The lichen Xanthoria parietina is the most abundant species infecting fruit trees in Sharkia Governorate, Egypt. Isolation and cultivation of the X. parietina symbionts (alga and fungus) are of great importance to plant pathologists, as they may help to increase attention toward lichens as potential plant pathogens, which have so far received limited consideration. Discharged spores from ascocarps proved to be the most reliable and accurate method for isolating the mycobiont (fungal partner). Spore germination percentage and germ tube length were assessed after 3, 6, 9, and 12 days of incubation. Five solid culture media were used for discharged spore germination: soil extract medium, citrus branch extract medium, malt yeast extract medium, Lilly and Barnett medium, and plain agar medium. The results clearly demonstrated that nutrient-poor media were more favorable for spore germination and germ tube development than nutrient-rich media. Among the tested media, plain agar and soil extract media were the most effective for promoting spore germination and germ tube growth. Conclusively, this study revealed that spore germination and germ tube growth of Xanthoria parietina were strongly affected by the type of culture medium and incubation time. Plain agar and soil extract media supported the highest germination percentage and longest germ tubes, while Malt-Yeast Extract medium showed the lowest effect. These results confirm that low-nutrient media are more suitable for early stages of lichen spore development. Xanthoria parietina, Mycobiont, Lichens, Isolation, Citrus.