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Fig. S1 Comparison of infection structures formed by Phakopsora pachyrhizi on glass slides (in vitro) and soybean leaves (in vivo).

Fig. S2 Visualization and measurement of the optical path difference (OPD) by displacement of interference band patterns using a Mach–Zehnder double-beam interferometer.

Fig. S3 Fully turgid and empty appressoria of Magnaporthe oryzae imaged in bright field and Mach–Zehnder microscopy.

Fig. S4 GC-MS profiles of soluble material in fractions enriched with appressoria from Phakopsora pachyrhizi and Magnaporthe oryzae.

Table S1 Calculation details for the determination of the turgor pressure in appressoria of Phakopsora pachyrhizi and Magnaporthe oryzae

Table S2 Overview of the specific refractive index increment for different biological osmolytes