Final answer:
Joseph Gottlieb Kolreuter's study of hybridization contributed the most to later studies of genetics.
Step-by-step explanation:
The area of Joseph Gottlieb Kolreuter's studies that probably contributed the most to later studies of genetics is hybridization.
Kolreuter was a botanist who conducted extensive research on plant hybridization in the 18th century. He crossed different varieties of plants to produce hybrid offspring and observed the inheritance patterns of traits in subsequent generations.
This research laid the foundation for Mendel's groundbreaking work on inheritance, which is the basis of modern genetics.