#!/bin/bash
s='Continent1_Breed1_Ind-ID1 Continent1_Breed1_Ind-ID1 0 0 0 -9
Continent1_Breed2_Ind-ID2 Continent1_Breed2_Ind-ID1 0 0 0 -0
Continent2_Breed1_Ind-ID1 Continent2_Breed1_Ind-ID1 0 0 0 -9'
sed 's/^\([^_ ]*_[^_ ]*\)_[^_ ]*/\1/' <<< "$s"