Near-isogenic lines for Triticum aestivum height and crop competitiveness

Near isolines of 'Nugaines' winter Triticum aestivum chat differed in height were planted with and without Aegilops cylindrica to determine the effect of plant height on competition against A. cylindrica. The isolines had either reduced height gene Rht(1), Rht(2), Rht(1) plus Rht(2), or neither Rht genes and averaged 73, 77, 51, and 101 cm tall, respectively, when grown with or without competition from A. cylindrica. Plants with fewer reduced height genes had the faster rates of height and weight gain, which are important: traits for enhanced competitiveness. When growing in competition with A. cylindrica, the shortest isoline allowed the greatest amount of A. cylindrica seed production but did not have the lowest T. aestivum yield. However, when compared to the A. cylindrica-free control, the shortest isoline had the greatest percent yield loss. The tallest isoline reduced A. cylindrica seed production the most, and T aestivum yield reduction due to A. cylindrica on a percent basis was the least when averaged over 2 yr. When competing against A. cylindrica, the tallest isoline did not always have the largest yield and yield parameters, and the shortest isoline did not always have the smallest yield and yield parameters. There is a cost to the T. aestivum plant to produce extra stem biomass that may reduce yield potential of taller plants and reduce the advantage gained by being taller than the surrounding weeds.