Location:2009 Annual Report
1a. Objectives (from AD-416)
Objective 1: Evaluate, characterize, and utilize available sugarbeet genetic resources and ascertain the diversity (genetic, proteomic, morphological, and pathogenic) within and among sugarbeet and sugarbeet pathogen populations to fulfill the objectives below. This objective is an important part of the ARS NPGS Beta germplasm collection, which is available to public and private breeders and geneticists. Sub-objective 1a: Determine the spatial scale of genetic differentiation among populations of B. nana. Objective 2: Characterize the interaction of major sugarbeet pathogens (esp. Beet necrotic yellow vein virus, Cercospora beticola, Rhizoctonia solani, and Fusarium oxysporum) with sugarbeet. Sub-Objective 2a: Apply proteomics protocols to understand Beet necrotic yellow vein virus-sugar beet interactions. Sub-Objective 2b: Using comparative proteomics, determine the degree of conservation of defense response against a variety of Fusarium spp. Sub-Objective 2c: Determine role of ubiquitination and the proteosome pathway in activation of plant defense. Objective 3: Develop and distribute enhanced germplasm with novel stress resistance genes.
1b. Approach (from AD-416)
Objective 1 A multidisciplinary approach combining traditional genetics, molecular biology, and biochemistry will characterize variation among sugarbeet wild relatives and cultivated beets. Understanding the diversity within the NPGS Beta PI collection is necessary to both intelligently manage and utilize the germplasm stored in this collection. Understanding of the diversity contained in our commercial lines is necessary to most effectively introduce new diversity into them. Understanding the genetic variability of pathogen populations is extremely important to maintaining durable host plant resistance. The same classical and molecular tools will be used to gain the knowledge of genetic diversity in the pathogens, which is critical for selecting the number and pathotype of organisms to use in resistance screening. Objective 2 This multidisciplinary approach combining traditional genetics, molecular biology, and biochemistry will be used for identification of key genes or proteins involved in the sugar beet pathogen interaction. Characterization using varied techniques provides a better understanding of plant defense against disease and identifies candidate genes and novel sources of resistance to move into sugar beet germplasm. Furthermore, this greater knowledge of sugar beet pathogen interaction opens up avenues for creating novel selection tools, including exploitation of polymorphisms and use of biomarkers. The same analyses can be used to understand and better manage pathogens of sugar beet, creating novel, more effective disease control strategies. Objective 3 The basis of the breeding program is the formation of long range breeding populations through the introgression of resistant germplasm from “exotic” sources of the primary Beta germplasm pool (Beta vulgaris ssp. maritima, fodder beet, table beet, Swiss chard, foreign sugar beet landraces from the PI collection, etc.). This breeding scheme provides great flexibility to accommodate the genetic background of the germplasm and the disease resistances being chosen. The development of breeding populations will be accomplished using methods that produce genetically defined sub populations, which are useful for resistance gene mapping, marker development, exploring sugarbeet-pathogen interactions, and gene discovery.
3. Progress Report
This is the FY09 report for Project 5402-21220-007-00D, which began its 5 year duration March 11, 2008. Some of this research is continued from Project 5402-21220-006-00D Progress was made in breeding populations with resistance to sugarbeet cyst nematode, cercospora leaf spot, fusarium yellows, and rhizoctonia root rot. Breeding and disease evaluation nurseries were planted and inoculated. The inoculated nurseries were to screen for resistance to rhizoctonia root rot and fusarium yellows. Eight resistant germplasms are being prepared for ARS release and registration in the Journal of Plant Registrations. Fusarium Yellows, caused by Fusarium oxysporum f. sp. betae, occurs throughout the primary sugar beet production areas of the United States and can lead to significant reduction in root yield, sucrose percentage and juice purity. F. oxysporum isolated from sugar beet are known to be highly variable in pathogenicity (ability to cause disease on sugar beet) and little is known about regional population diversity and potential host range. To more fully understand host range, symptom development and range of virulence, isolates of F. oxysporum isolated from sugar beet were collected from several U.S. sugar beet production regions and pathogenicity tests performed on three hosts commonly found in crop rotation, (sugar beet, dry edible bean, and onion). Vegetative compatibility testing will more fully characterize genetic relatedness of this population of F. oxysporum. Rhizoctonia root rot, caused by Rhizoctonia solani continues to be a significant root associated disease for most sugar beet growing areas in the United States. Proteomic separation analysis has been started to identify proteins that potentially contribute to host resistance to Rhizoctonia and to characterize the proteomic expression profile in different parts of the sugar beet plant. This research addresses Problem Statement 3C, Germplasm Enhancement/Release of Improved Genetic Resources and Varieties of the NP301 Action Plan. Genes, proteins, and gene pools from both wild and cultivated relatives of sugarbeet will be evaluated, characterized, and introgressed into adapted germplasm. Genomic and proteomic approaches will be used to identify and characterize host plant resistance to disease, and identify gene or protein biomarkers to increase the efficacy of the development of resistance germplasm. A pre-breeding program will release enhanced germplasm.
1. Long term preservation of a collection of Rhizoctonia solani, using cryogenic storage. The fungus Rhizoctonia solani Kühn is an important plant pathogen on a number of crops and maintaining an extensive collection of reference isolates is important in understanding relationships of this pathogen with multiple hosts. After 5 years of storage at -160°C in liquid nitrogen vapor phase, only one isolate had a significant decrease in viability as compared to the percent growth 60 days after initial storage. After 10 years, 35 out 109 isolates did have a significant decrease in percent growth, 10 isolates had less than 10% growth, but only 1 isolate had no growth. Cryogenic storage methods, which allow easy long term storage of important reference isolates, are well suited for the preservation of R. solani culture collections. This will reduce the time and effort necessary to maintain these isolates.
2. Long-term Survival of Cryopreserved Sugarbeet Pollen. In a heterozygous crop such as sugarbeet, it is difficult to preserve superior, individual genotypes developed in plant breeding programs, and to collect wild relatives of cultivated plants when there is insufficient seed to fully represent the total genetic diversity present. We demonstrated that pollen, stored for 17 years in Liquid Nitrogen was able to pollinate sugarbeet and produce viable seed. In plant breeding, stored pollen could be used as a long term tester population or, from an individual genotype, as the parent in a recurrent scheme for genetic analysis. Collection and storage of pollen could be a way to obtain a more representative sample of the genetic diversity in wild populations. Additionally, with restrictions on the international transport of seed becoming increasingly stringent, pollen could be an alternate way to distribute Beta germplasm.
Lewellen, R.T., Panella, L.W., Harveson, R. 2009. Introduction - Botany of the Beet Plant. Pages 2-3 In: Compendium of the Beet Diseases and Insects, edited by R.M. Harveson, L.E. Hanson, and G. O. Hein, eds. APS Press. St. Paul, MN pp.140.