Response to early generation selection for grain yield and harvest index in bread wheat (T-aestivum L.)

The availability of a reliable selection criterion for the identification of the most productive genotypes in early generations represents a crucial point in many breeding programs. The findings reported in the literature concerning the effectiveness of early generation testing for grain yield (GY) or harvest index (HI) are contradictory. In this work, we measured the response to selection for GY and HI applied in different generations, from F-2 to F-6, in nine segregating populations previously screened in F-2 by means of visual selection. Genetic variability for HI and GY was found in most of the segregating populations. However, GY of spaced plants in F-2 and F-3 generations was weakly correlated with yield of F-4 and successive generations grown at normal seed density. HI was of limited value as an indicator of yield potential.