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Improvement in Genetic Yield Potential of Semi-dwarf Wheat in the Great Plains of the USA

Battenfield, Sarah
Recently, private companies and public entities have made significant investments in and improvements to their wheat (Triticum aestivum L.) breeding programs. Because of this increased interest, recent genetic improvements made in wheat through traditional plant breeding need to be analyzed. Many studies have noted the significant yield improvement from tall cultivars to semi-dwarf cultivars, but no studies have documented improvements made from the earliest semi-dwarfs to present-day cultivars. Thirty cultivars were tested including 2 tall varieties (Kharkof, 1921 and Triumph 64, 1964), and 28 semi-dwarf cultivars spanning the period from 1971 (TAM 101) to 2008 (Jackpot and TAM 401). Cultivars were tested in 2010 and 2011 at eleven locations across Oklahoma, Kansas, and Texas with adequate disease protection and fertilizer. Experimental design was a split-plot design with fungicide treatment as the main plot and cultivar as the sub-plot with three replications per location. Yields for cultivars protected by fungicide treatment were higher than those without fungicide at most locations. A significant yield increase of 13.68 kg ha-1 yr-1 or 0.93% per year of Kharkof yield was obtained across all locations with the tall cultivars included. When gain was restricted to only semi-dwarf cultivars (1971 to 2008), yield gain was reduced to 11.65 kg ha-1 yr-1 or 0.46% per year of TAM 101 yield. Yield gain among semi-dwarf cultivars in locations with significant fungicide effect was only 10.51 kg ha-1 yr-1 or 0.37% per year of TAM 101 yield, which more accurately represents gain in genetic yield potential made excluding defensive breeding efforts. No evidence of a yield plateau was found.