| Yield components of semi-dwarf and tall spring wheat1)
A. L. DIEHL and J. R. WELSH2) Department of Agronomy, Colorado State University, Fort Collins, Col., U.S.A. Abstract Yield components were evaluated for three semi-dwarf spring wheat (Triticum aestivum L. em. THELL) cultivars and two tall cultivars. The average yields of the semi-dwarfs were greater than the average yields of the tall cultivars. Tall cultivars produced equal or larger numbers of spikes per unit area compared with the semi-dwarfs. The semi-dwarfs Pitic 62 and Nadadores 63 consistently had more kernels per spike than the tall cultivars. Numbers of spikelets per spike and kernels per spikelet in Pitic 62 and Nadadores 63 were larger than the same characters in the tall cultivars Chris and Waldron. The semi-dwarf Ciano Sib was consistently greater than all other cultivars for kernel weight. Introduction The development of wheat (Triticum aestivum L. em. THELL) cultivars with shorter stature have received considerable attention from plant breeders. According to BRIGGLE and VOGEL (1968) most of the semi-dwarf wheats grown in their area of adaptation in the United States have higher yield potential than the standard commercial varieties. The greater yield potential of semi-dwarfs has been attributed to their ability to respond to high levels of cultural management, such as nitrogen fertilization, and to their inherent yield potential. Yield component studies of hard red winter semi-dwarfs by PORTER et al. (1964) and JOHNSON, SCHMIDT and MEKASHA (1966) have attributed higher yields to larger numbers of kernels per spike. An evaluation of semi-dwarf spring wheat selections by MCNEAL, BERG and KLAGES (1960) shows that yield and tiller number of the semi-dwarfs were similar to the standard types. The objectives of this study were to establish the components of yield advantages of semi-dwarf spring wheat cultivars over standard height cultivars and to investigate the stability of these components over environments. Materials and methods Two tall cultivars, Chris CI 13751, and Waldron CI 13958, and three semi-dwarf cultivars, Pitic 62 CI 13927, Nadadores 63 CI 13931, and Ciano Sib S 4017 CO 691, were selected from the Colorado spring wheat variety test in 1969 and in 1970 for the yield component study. Irrigated nurseries were grown at Fort Collins, Center, Grand Junction, and Hesperus, Colorado, for this study. A split-plot design with nitrogen fertilizer levels as main plots and varieties as subplots was used. Each set of three equally spaced nitrogen levels was replicated three times, resulting in a total of 9 replications for varieties. At all locations except Grand Junction, plots were four rows wide with a 30.5 cm spacing between rows. The Grand Junction nurseries were seeded in two-row irrigation beds with a 30.5 cm spacing between rows and 38.1 cm spacing between beds. Plots were either 3.04 or 6.08 m in length, depending upon location. Seeding rates of 68 and 79.5 kg/ha were used in 1969 and 1970, respectively. Yield was determined by harvesting the two center rows in each plot at maturity, and yield components were measured from the remaining border rows. Spikes per unit area were measured by culm count of one uniform section 0.91 m in length in each plot in 1969 and two 0.91 m sections in each plot in 1970. Kernels per spike, spikelets per spike, and 1,000 kernel weight were determined from a random sample of 30 seed-bearing spikes per plot. Kernels per spikelet were calculated from kernels per spike and spikelets per spike. Analyses of variance of individual yield components for each location were made. Since unequal variance between locations and years restricted pooled analyses, only means for each characteristic measured for the eight trials are reported. |
| 1) Published with the approval of the Colorado State University, Experiment
Station as Scientific Series No. 1698. 2) Former Graduate Research Assistant and Associate Professor of Agronomy, Colorado State University, Fort Collins, Colorado, 80521, U.S.A., respectively. |
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