Location:2012 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 FY12 report for Project 5402-21220-007-00D. Progress was made in addressing the Problem Statements 3A, Genetic Theory and Methods of Crop Improvement and 3C, Germplasm Enhancement/Release of Improved Genetic Resources and Varieties and of the NP301 Action Plan. Objective 1: We were able to analyze the data allowing us to determine the spatial scale of genetic differentiation among populations of B. nana. We showed that, although the species is extremely inbred, there is genetic diversity but it is all among populations separated on mountain tops in Greece. This has implications for the Greek government’s plans to provide in situ conservation for this threatened species. Additionally, diversity in sugarbeet genetic resources was ascertained through screening for rhizoctonia root rot in field nurseries. We were able to finish experiments to further characterize genetic diversity within Fusarium oxysporum f. sp. betae (FOB). We found that FOB is variable in pathogenicity, morphology, host range, and symptoms. Utilizing sequence data from ß- tubulin, EF1a, and ITS, we determined that FOB diversity was not necessarily tied to geographic origin nor pathogenicity. Parsimony bootstrap and Bayesian MCMC analysis of individual and combined datasets revealed three unique clades. Objective 2: Progress has been made in understanding the interaction of Fusarium yellows (FOB), a fungal disease, with sugar beet. We also finished experiments testing the impact of air temperature on the severity of Fusarium yellows in greenhouse and growth chamber experiments. We have found that once temperatures reach 26oC, that disease severity does not increase with increasing air temperatures. Additionally we found that resistant varieties remain effective as temperatures increase. We are also completing the third year of a 3-year field study to characterize Fusarium yellows development and severity in the field and correlating those symptoms with relevant environmental conditions. Additionally, through preliminary proteomic investigation of Rhizomania (BNYVV) roots and leaf tissues, we have gained insight into sample preparation, protein extraction and methodology development that in FY2013, we should be able to begin mass spectrometery and data collection allowing us to gain insight(s) into the underlying cause of symptom development and resistance. Objective 3: Progress has been made in developing and distributing enhanced germplasm with novel stress resistance genes. Breeding populations with resistance to sugarbeet cyst nematode, cercospora leaf spot, fusarium yellows, and rhizoctonia root rot have been advanced. Four rhizomania and cercospora leaf spot resistant germplasms were released a registration manuscript has been submitted to the Journal of Plant Registration. More germplasm with resistance to rhizomania and novel sources of resistance to cercospora leaf spot are being prepared for ARS release.
1. Further characterization of the genetic diversity of Fusarium oxysporum f. sp. betae. Fusarium yellows of sugar beet (caused by Fusarium oxysporum f. sp. betae), can lead to significant reduction in yield and genetic resistance and cultural practices are the major management tools; there are no effective chemical protectants. F. oxysporum isolates were collected from symptomatic sugar beets throughout production areas in the United States by ARS researchers at Fort Collins, CO and East Lansing, MI. These isolates were characterized utilizing pathogenicity and phylogenetic analysis. Based on the findings from these studies, the pathogen populations have many diverse origins and most likely cannot be classified into distinct races. Potentially, however, local groups can be described, which will aid in screening and developing resistant lines for particular production regions.
2. Release of FC1028, FC1036, FC1037, and FC1038 multigerm sugarbeet germplasm. Sugar beet diseases remain an important source of pre- and post-harvest crop and sugar losses throughout the United States. Sugar beet germplasms FC1028’, ‘FC1036’, ‘FC1037’, and ‘FC1038’ were developed at Fort Collins, CO, Salinas, CA, and East Lansing, MI, in cooperation with the Beet Sugar Development Foundation, Denver, CO. All four germplasms are multigerm sugarbeet populations segregating for the Rz1 gene, which confers resistance to some strains of rhizomania (caused by Beet necrotic yellow vein virus). They all showed some tolerance to cercospora leaf spot (caused by Cercospora beticola Sacc.), and exhibited some tolerance to aphanomyces root rot or black root (caused by Aphanomyces cochlioides Drechsl.), and all of the germplasms except FC1036 were moderately tolerant of curly top (caused by Beet severe curly top virus). Both FC1037 and FC1038 demonstrated some tolerance to rhizoctonia root and crown rot (caused by strains AG-2-2 of Rhizoctonia solani Kühn). These populations are released to seed companies and public research from which to select disease-resistant, multigerm pollinator parents and monogerm, O-type, CMS maintainer lines from these lines.
McGrath, J.M., Panella, L.W., Frese, L. 2011. Beta. In: Kole, Chittaranjan, editor. Wild Crop Relatives: Genomic and Breeding Resources Industrial Crops. Heidelberg, Germany: Springer. p. 1-28.