SUMMARY

Sunflower (Helianthus annuus L.) breeding programs typically target het-erogeneous regions, where large genotype × environment interactions (GEI) complicate genetic progress. Some understanding of the underlying factors, nature and repeatability of GEIs can help to accommodate their effects. This review summarizes the findings of a series of studies conducted in Argentina with the goals of understanding the effect of GEIs on sunflower yield progress and design breeding strategies aimed at impacting on future rates of genetic advance. Pattern analyses revealed that the central and northern subregions are different mega-environments (ME), which suggests that yield gains in the northern ME would have been reduced if selection had been done in central environments and vice versa. Photoperiod and minimum temperature during the reproductive phases are the main environmental factors underlying the observed GEIs. Genetic gain analyses indicated clear and continuous improve-ments in oil yield due to plant breeding during 25 years and confirmed the pre-diction about lack of yield gains under the northern ME from selection done i