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 Title: Variation for root and shoot growth among wheat cultivars and the effects of barley yellow dwarf virus on growth Author(s): Hoffman, Thomas Karl Doctoral Committee Chair(s): Kolb, Frederic L. Department / Program: Crop Sciences Discipline: Crop Sciences Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): Agriculture, Agronomy Agriculture, Plant Pathology Abstract: Studies were conducted on eight soft red winter wheat cultivars to evaluate differences in root growth, to evaluate the effects of barley yellow dwarf virus (BYDV) on root and shoot growth, and to study the effects of a plant growth regulator on root growth of healthy and BYDV infected plants. Cultivars evaluated were Caldwell, Cardinal, Clark, Howell, IL 87-2834, Tyler, and Pioneer$\sp\circler$ brands 2548 and 2555. Studies on root growth were conducted in the greenhouse in an aeroponic mist box. Differences in root growth were found for root dry weight, root length, numbers of seminal and adventitious roots, and root to shoot ratio. Infection with BYDV caused noticeable symptoms in the roots prior to the shoots. Root length and root to shoot ratios were decreased by infection, but number of adventitious roots was often increased by infection. A plant growth regulator, PGR-IV, had little measurable effect on root growth of BYDV infected plants, but it increased root dry weight, number of lateral roots, and lateral root length in healthy plants. Effects of the virus on yield and growth rate were determined in the field in drill-planted plots. Plots were inoculated in the fall when seedlings were in the two leaf stage. BYDV-induced grain yield reductions of 21% to 36% were measured. Most yield loss resulted from a reduction in kernels per head. None of the cultivars tested exhibited a high level of tolerance to the virus and the highest yielding cultivars were often the ones that exhibited the highest grain yield reductions. Even so, highest yielding cultivars under control conditions were usually the highest yielding under BYDV-inoculated conditions. Growth rate throughout the season was measured by fitting the Richards function to dry weight data collected on a weekly basis. The reduced biomass production under inoculated conditions resulted from reduced relative growth rates rather than from a shortened period of growth. Relative growth rate was not related to a cultivars tolerance based on grain yield reduction, but relative growth rate in the early part of the season was positively related to grain yield per se under BYDV infection. Issue Date: 1996 Type: Text Language: English URI: http://hdl.handle.net/2142/21844 ISBN: 9780591198980 Rights Information: Copyright 1996 Hoffman, Thomas Karl Date Available in IDEALS: 2011-05-07 Identifier in Online Catalog: AAI9712308 OCLC Identifier: (UMI)AAI9712308
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