Abstract:

Knowledge on genetic gain of yield potential and its associated traits is essential for understanding yield-limiting factors and developing strategies for future variety improvement. Yield potential trials, comprised of 10 landmark and newly released wheat cultivars (Triticum aestivum L.) from Beijing, were conducted, using a complete randomised block design with three replicates, under controlled environment during 2001–2002 and 2002–2003 seasons. Molecular markers were used to detect the presence of dwarfing genes and the 1B/1R translocation. The result showed that genetic gain in yield was 64.63 kg ha^-1 year-1 or 1.20% per year. The breakthrough on yield plateau occurred at the period of release of Fengkang cultivars in 1980. Fengkang 2 and Fengkang 8 were the first cultivars carrying 1B/1R and Rht-D1b released in Beijing. Yield genetic gain was slowed down after 1980. Newly released cultivars were characterized by early heading, reduced plant height, decrease of spikes per square meter, slight increase of kernels per spike, remarkable increase of thousand kernel weight and harvest index, with annual genetic gains of －0.10%, －0.70%, 0.35%, －0.50%, 0.63%, 1.12%, and 0.79%, respectively. Increasing the number of kernels per spike by reducing the number of sterile spikelets per spike and reducing the number of sterile florets per spikelet, increasing thousand kernel weight by increasing the rate of grain filling, then combining greater weight of grains per spike with higher number of spikes per squire meter, is one of the best approaches in breeding for further yield increase.

Key words: Bread wheat, Yield potential, Agronomic trait, Dwarfing gene, 1B/1R translocation