It tells you what the paragraph is going to be about.
An F1 hybrid (or filial 1 hybrid) is the first filial generation of offspring of distinctly different parental types. F1 hybrids are used in genetics, and in selective breeding, where it may appear as F1 crossbreed. The term is sometimes written with a subscript, as F1 hybrid.
F1 hybrid seeds refers to the selective breeding of a plant by cross pollinating two different parent plants. In genetics, the term is an abbreviation for Filial 1 â literally âfirst children.â It is sometimes written as F 1, but the terms mean the same.