Genetic improvement of sunflower in Argentina between 1930 and 1995. I. Yield and its components

Historic sets of sunflower cultivars released in Argentina between 1930 and 1995 were compared in two field experiments to identify contributions of b reeding to the improvement of yield potential. Three yield components were considered: grain number; grain weight; and grain oil concentration. Both g rain and oil yield were positively associated with year of cultivar release . There was a clear discontinuity in yield trends, however, with a marked s tep around 1970, when the first hybrids were released. No improvement in yi eld potential was apparent during long periods before and after this turnin g point. On average, hybrids outyielded open-pollinated cultivars by 23% fo r grain and 36% for oil. More grains that are slightly lighter and of great er oil concentration accounted for most of the variation in grain and oil y ield between open-pollinated cultivars and hybrids. Increased grain number resulted from greater floret production, rather than enhanced floret fertil ity: variation in grain weight was associated with variation in rate rather than duration of grain filling. Further increase in yield potential could be achieved by maintenance of gra in number ca, 7500 m(-2) and increasing grain weight and oil concentration. The trade-off between grain weight and oil concentration deserves special attention, Targeting yield components in this way may accelerate the rate o f improvement in grain and oil yield potential. (C) 1999 Elsevier Science B .V. All rights reserved.