Location:2013 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 final report for Project 5402-21220-007-00D. Research continues in bridging project 5402-21220-008-00D and 5-year replacement project 5402-21220-009-00D. Objective 1: In the course of this project, we were able to analyze the data allowing us to determine the spatial scale of genetic differentiation among populations of B. nana. This has implications for the Greek government’s plans to provide in situ conservation for this threatened species. Diversity in sugarbeet genetic resources was ascertained through screening for rhizoctonia root rot and the curly top virus in field nurseries. We were able to finish experiments to further characterize genetic diversity of pathogenicity, morphology, host range, and symptoms within Fusarium oxysporum f. sp. betae (FOB). We used sequence data, greenhouse and field pathogenicity testing, and vegetative compatibility grouping. We have shown cross pathogenicity with some FOB isolates being able to attack both onion and sugar beet, which often are grown in rotation. Objective 2: Progress has been made in understanding the interaction of Fusarium yellows (FOB) and Rhizoctonia root and crown rot, fungal diseases, with sugar beet. Experiments examining the impact of air temperature on the severity of these diseases were conducted in the field, greenhouse and growth chamber. We found that resistant varieties remain effective as temperatures increase. We are completing the last 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. We performed the proteomic profiling from two susceptible sugarbeet, both infected with BNYVV, to clarify the types of proteins prevalent during compatible virus-host plant interactions. Many identified proteins previously have been associated with systemic acquired resistance and general plant defense responses, particularly those mediated by reactive oxygen species. These results expand on limited proteomic data available for sugarbeet and provide the ground work for future studies focused on understanding the interaction of BNYVV with sugarbeet. 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. Eleven germplasm have been released and registered in the Journal of Plant Registrations. They have different resistances to multiple pests and diseases of sugar beet including rhizomania, cercospora leaf spot, aphanomyces root rot, rhizoctonia root and crown rot, curly top virus, sugar beet root maggot and sugar beet root aphid. The releases and registrations were FC220, FC221, FC1018, FC 1019, FC1020, FC1022, FC1028, FC1036, FC1037, FC1038, and F1024.
1. Publication of the book "Beta maritima: the origin of beets." The USDA-ARS National Plant Germplasm System’s (NPGS) Beta PI Collection is one of the best characterized collections in the NPGS system. This has allowed public and private breeders to incorporate important genes from crop wild relatives into cultivated beet and broadened the base of the cultivated crop. In a collaborative effort, two ARS scientists and an Italian university researcher published a book focused on the most important of the crop wild relatives, Beta vulgaris subspecies maritima. This book brings together over 2,000 references on this wild progenitor of our cultivated beet crops, and discusses the domestication, taxonomy, distribution, physiology, use in breeding, and conservation of this important genetic resource. It serves as an important resource not only to students and researchers working with cultivated beet but also to the ecologists and population geneticists, for whom Beta vulgaris subspecies maritima is a model species.
2. Effect of temperature on Fusarium wilt. Environment plays a critical role in pathogen invasion of plants. The environment influences pathogen interactions with the sugar beet; it impacts pathogen effectiveness in colonizing the sugar beet, and regulates the genetic mechanisms associated with expression of sugar beet resistance to the disease the pathogen causes. Although Fusarium yellows development is believed to be extremely dependent on temperature, little information is known how much air or soil temperature(s) individually contribute(s) to Fusarium oxysporum’s successful invasion of sugar beet, and its potential impact on the effectiveness of sugar beet resistance. All that was known was that very little disease occurred at < 20C, and optimum symptom development occurred between 24-28C. Therefore, in growth chamber experiments ARS researchers at this location determined how temperatures (day time/night time) corresponded to early (16/6C), mid (26/11C) and late (32/16C) season. Also how temperature contributed to severity of disease development on both susceptible and resistant varieties, using multiple pathogenic isolates of F. oxysporum f. sp. betae and measuring the area under the disease progress curve (AUDPC) was examined. The most disease was observed when plants were grown at 26/11C and the least amount of disease occurring at the coolest temperatures (16/6C). There were differences in severity of disease as well as initial symptom development between the all of the varieties. This information will aid in the development of predictive models to alert growers when disease is likely to occur, so they can initiate protective measures.
Panella, L.W., Lewellen, R.T., McGrath, J.M. 2013. Registration of 'FC1028', 'FC1037, 'FC1038' and, 'FC1036' multigerm sugarbeet germplasm with multiple disease resistances. Journal of Plant Registrations. 7:229-237. DOI:10.3198/jpr2012.06.0002crg.