Genetic progress in grain yield and associated changes in spikelet and grain traits in historical set of Pannonian wheat cultivars

Changes in yield components and spike traits are associated with wheat grain yield genetic progress. The aim of this study was to determine variation in yield components, spike and individual grain traits, and their role in winter wheat grain yield genetic improvement under conditions of the Pannonian Plain. Therefore, two-year field trials were conducted in a southern Pannonian location (Novi Sad, Serbia) with ten winter wheat cultivars released between 1931 and 2015. The grain yield had a significant positive linear relationship with the year of cultivar release, showing the improvement rate of 46.4 kg ha-1 yr-1. Grain yield increase has been positively related to the improvement of spike grain weight. Spike grain weight improvement with a rate of 0.25 g yr-1 was followed by simultaneous rise of the individual grain number and grain weight at different positions within a spikelet. Compared to other grains at different positions within a spikelet, G3 grains showed the highest rate of grain weight and the grain number improvement with the year of cultivar release. On the other hand, there was a significant decrease trend of grain protein content in individual grains at different positions. Therefore, wheat breeders should be more focused on grain number and weight improvement of distal grains in order to regain higher grain yield genetic gain under conditions of the Pannonian Plain.