Near-isogenic lines for Triticum aestivum height and crop competitiveness

Near isolines of 'Nugaines' winter Triticum aestivum chat differed in heigh t were planted with and without Aegilops cylindrica to determine the effect of plant height on competition against A. cylindrica. The isolines had eit her 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 wi th or without competition from A. cylindrica. Plants with fewer reduced hei ght genes had the faster rates of height and weight gain, which are importa nt: traits for enhanced competitiveness. When growing in competition with A . cylindrica, the shortest isoline allowed the greatest amount of A. cylind rica 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. cylindr ica on a percent basis was the least when averaged over 2 yr. When competin g against A. cylindrica, the tallest isoline did not always have the larges t 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 tal ler plants and reduce the advantage gained by being taller than the surroun ding weeds.