Hybrid vigor (or heterosis) is the overperformance of a hybrid over its parents in a specific trait or a set of traits. As such, hybrid breeding serves as a tool to efficiently trigger gains in breeding programs.
In Swiss alpine swards, we observed frequent prevalence of triploid hybrids of Festuca pratensis x F. apennina with outstanding competitiveness relative to their parental species in the sites of sympatric occurrence. Observations of these highly vigorous hybrids prompted the study on their heterosis across various environmental conditions. Phenotypic observations during 3 years at four locations at different altitudes (from 200 to 1850 m a.s.l.) have shown heterosis for dry biomass production at all sites during the first and second year, reaching a maximum of + 508% for annual yield. This is by far the highest value of heterosis ever reported for annual dry matter yield of a forage grass.