Author
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Smith, Garry |
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Campbell, Larry |
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Submitted to: Plant Breeding
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/13/1995 Publication Date: N/A Citation: N/A Interpretive Summary: Incorporating disease resistance while maintaining or increasing yield and quality is a constant challenge for commercial plant breeders. The task is especially difficult if the desired resistance is not simply inherited, as is the case with most sugarbeet diseases, including Cercospora leaf spot. This study examined the trade-off between Cercospora resistance and performance. Forty commercial sugarbeet hybrids, all recommended for Cercospora-threat areas, were grown at Fargo, ND (no Cercospora) and Ft. Collins, CO (inoculated with Cercospora) in 1991 and 1992. Statistical analyses indicated that root yields at Fargo (in the absence of Cercospora) increased 1.2 tons per acre for each increment increase in disease susceptibility (observed at Ft. Collins). However, under disease conditions, disease resistance reduced yield loss substantially. In spite of the difficulty in developing high-yielding resistant commercial hybrids, the demonstrated ability of Cercospora to produce fungicide resistant strains and the possibility that effective fungicides will not be available to producers are arguments for continued breeding efforts. Technical Abstract: This report documents the difficulty breeders have experienced in combining resistance to Cercospora leaf spot (causal agent: Cercospora beticola Sacc.) with high yield in sugarbeet (Beta vulgaris L.). Forty commercial hybrids, all recommended for Cercospora-threat areas, were grown in a Cercospora-free and a diseased (inoculated) environment in 1991 and 1992. A 2.9 Mg ha(-1) decrease in root yield associated with each increment increase in susceptibility confirmed that under a severe epiphytotic (1991) Cercospora resistance provided substantial protection. Under less severe disease conditions (1992) there was no apparent relationship between yield and resistance, suggesting the benefits of resistance were similar to the yield potential sacrificed to obtain the resistance. In the absence of the disease, root yields increased 2.7 Mg ha(-1) for each increment of increased susceptibility. There was no evidence of association between sucrose concentration and resistance in the Cercospora-free environment. In spite of the limited success in developing resistant hybrids, the demonstrated ability of Cercospora to produce fungicide resistant strains and the possibility that effective fungicides will not be available are arguments for continued breeding efforts. |
