Before revision:  Then, we conducted a linear regression of the yield of hybrids against each stress metric, and classified the hybrids based on the slope  the regression line, since the slope of the regression line showed how sensitive a hybrid was to a specific environmental stress.
After revision:  Then, we conducted a linear regression of the yield of hybrid against each stress metric, and classified the hybrids based on the slope the regression line, since the slope of the regression line showed how sensitive a hybrid was to a specific environmental stress.