Eco-physiological changes in sorghum hybrids released in Argentina over the last 30 years

• Argentinean sorghum hybrids released during the last 30 years showed significant yield variation, but genetic yield progress was only 8.7 kg ha−1 year−1 (or 0.1% year−1).
• Breeding has improved grain filling attributes.
• High-yielding hybrids showed differential physiological strategies behind yield determination, suggesting potential room for trait piramidization.

The development of single-cross hybrids during mid-1950s was important for sorghum [Sorghum bicolor (L.) Moench] improvement worldwide. Within the hybrid era, however, there is limited information on sorghum genetic progress. Our main objective was to evaluate the genetic gain for grain yield and other phenotypic traits for grain sorghum commercial hybrids released in Argentina from 1984 to 2014. A second objective was to describe common attributes behind high-yielding hybrids. A total of 43 hybrids were grown at three different environments. Evaluated traits were grain yield, yield components (grain number m−2 and individual grain weight), phenology, plant height, stay-green, crop growth rate around flowering, reproductive biomass partitioning, grain set efficiency, biomass at maturity, harvest index and post-anthesis source/sink ratio.Yield across environments varied from 8.1 to 10.8 t ha−1. Genetic progress for grain yield was 8.7 ± 2.9 kg ha−1 year−1 (p < 0.01) across environments. This progress represented only 0.1% of the experiments mean grain yield. Modern hybrids set more grains per unit of reproductive biomass (p < 0.10), have more stay-green (p < 0.10), and showed higher post-anthesis source/sink ratio (p < 0.10) when compared to older ones. By clustering hybrids irrespective of the year of market release, three groups were conformed showing important grain yield differences. Common traits among high-yielding hybrids were high grain number, low grain size, later flowering time, intermediate height and stay-green trait. Within the high-yielding cluster, hybrids showed significant variability in crop growth rate around flowering, biomass at maturity, reproductive biomass partitioning, grain set efficiency, harvest index and post-anthesis source/sink ratio that could be exploited in breeding programs, describing opportunities for sorghum improvement in temperate environments.