Location: Northwest Irrigation and Soils Research2010 Annual Report
1a. Objectives (from AD-416)
Objective 1: Develop molecular genetic markers linked to sugarbeet chromosomal regions that confer improved resistance to pathogens. Objective 2: Develop agronomically-superior sugarbeet germplasm with resistance to Beet severe curly top virus (BSCTV). Objective 3: Determine the distribution and diversity of sugarbeet root rot organisms. Objective 4: Determine the effects of pathogens on sugarbeet post-harvest quality and storability. Objective 5: Develop innovative disease management options for BSCTV and root rot organisms.
1b. Approach (from AD-416)
Establish a sugarbeet research program in genetics and plant pathology using classical and molecular approaches to improve the sugarbeet genetics pool and disease management options, and enhance crop quality, productivity, yield, and profitability of production. Formerly 5368-21220-002-00D (5/08).
3. Progress Report
Objective 1: New sugarbeet DNA markers were developed using Diversity Array Technology (DArT) and used for genotyping new and elite USDA germplasm and commercial varieties. Three doubled haploid populations were developed to be used in the breeding program and for developing parental lines. New populations will be screened for curly top, rhizomania, and other important sugarbeet diseases. Thirty sugarbeet hybrids were produced from selected parental lines targeting curly top and rhizomania resistance. Progenies will be used for backcrossing, and the segregating populations will be evaluated for target traits. Progenies, including advanced “inbred” lines, will be screened in the field for diseases, and selection of mother plants will performed. Selected sugarbeet germplasm and progenies will be genotyped by DNA markers for specific traits. Mapping populations will be advanced to recombinant inbred lines. Objective 2: Germplasm screening for response to various important sugarbeet diseases is a continuous process to search for novel sources of genetic resistance. New plant introductions from cultivated and wild sugarbeets were screened in the curly top and rhizomania nurseries. Breeding lines and populations were evaluated for field performance and for selection of mother plants. Additionally, an enzyme-linked immunosorbent assay (ELISA) assay was developed to allow for the detection of two curtoviruses in sugarbeet and bean tissue. The assay was tested and recently published. Objective 3: Rhizoctonia isolates that had double peaks in the initial sequencing were cloned and resequenced. These data are in the process of being submitted for publication. The influence of strip tillage on both Rhizoctionia root rot and bacterial root rot was investigated. A process was initiated to establish the vegetative compatibility grouping for the Verticillium isolates collected from diseased sugarbeet. Leuconostoc root rot petri dish assay was developed and published for screening bacterial root rot. A greenhouse assay that is easier to conduct for Leuconostoc resistance is currently being investigated. Objective 4: The influence of storing rotted sugar beet roots with healthy sugar beet roots was investigated. Sugarbeet plants protected from pests and diseases in the field through the use of insecticide seed treatments were evaluated in storage. Objective 5: Isolates of bacteria were characterized and sequenced to investigate the interaction between manure applications and Rhizoctonia solani. The samples are currently being quantified using real-time polymerase chain reaction. Seed treatment trials were conducted to test the efficacy of seed treatments and host resistance in controlling curly top and pests in sugarbeet.
1. Sugarbeet Genetic Linkage Map. Curly top is a viral disease problem that can lead to complete sugarbeet crop loss if plants do not contain resistance. However, transferring a high level of resistance to newly developed commercial cultivars can take 10 years. ARS researchers at Kimberly, Idaho, developed breeding populations and extensive genetic linkage maps to identify DNA markers linked to curly top resistance. These data will reduce the time it takes to incorporate high levels of curly top resistance in commercial sugarbeet varieties.
2. Sugarbeet Selection for Bacterial Root Rot Resistance. Bacterial root rot caused by Leuconostoc can lead to 70% or more loss of sugarbeet root mass in the field. Therefore, developing cultivars with good host resistance to bacterial root rot would be a valuable disease management tool. An assay to screen sugarbeet cultivars for resistance to bacterial root rot was developed by ARS researchers at Kimberly, Idaho, with the cooperation of the Amalgamated Sugar Company. By incorporating host resistance to bacterial root rot into commercial sugarbeet cultivars, bacterial root rot should be substantially reduced in the field and possibly in storage.
3. Sugarbeet Root Rots at Harvest. Sugarbeet root rot can lead to yield losses of more than 50%. To identify the cause of these losses in the Intermountain West, fungi and bacteria were isolated from sugarbeet roots at harvest and consequently evaluated in pathogenicity tests by ARS researchers at Kimberly, Idaho. In greenhouse assays Rhizoctonia solani led to the most root rot, but in the field this fungus typically infest only 3 to 5% of the root mass. However, lesions created by Rhizoctonia solani allowed bacteria to infested 6 to 78% of the root mass, depending on the year. This research identified the importance of including bacterial root rot in sugarbeet breeding programs rather than only focusing on fungal root rots.
4. Curly Top Assay for Sugarbeets. Curly top caused by any of three Curtovirus species can lead to complete sugarbeet crop loss if plants do not contain resistance. The lack of an enzyme-linked immunosorbent assay system is one of the factors hampering development and screening for curly top resistance in sugarbeet germplasm. A joint effort between University of Idaho and ARS researchers at Kimberly, Idaho, developed an assay to reliably detect curtoviruses in plant tissue. This new assay is now available to assist breeding efforts to improve host resistance in sugarbeet and other crops.
5. Identifying Sugarbeet Varieties in Storage Piles. Harvested sugarbeets from numerous fields are mixed together in large piles until they can be processed. Significant sugar losses can occur during storage due to root rot and other factors, but the sugarbeet varieties associated with the rotted area cannot be identified. ARS researchers at Kimberly, Idaho, identified four DNA markers to differentiate the commercial sugarbeet varieties approved for production in Idaho, Oregon, and Washington. These markers provide a valuable research tool for evaluating differences in sugar losses among sugarbeet varieties during storage.Strausbaugh, C.A., Eujayl, I.A., Foote, P. 2010. Commercial Sugar Beet Cultivars Evaluated for Resistance to Bacterial Root Rot in Idaho, 2008. Plant Disease Management Reports. 4:FC010.