Location:2010 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 FY10 report for Project 5402-21220-007-00D. Progress was made in addressing the Problem Statement 3C, Germplasm Enhancement/Release of Improved Genetic Resources and Varieties of the NP301 Action Plan. We made significant progress in ascertaining diversity in sugarbeet genetic resources and a major plant fungal pathogen causing Fusarium yellows (Objective 1a & 1b). Beta nana is a wild relative of cultivated beet and, potentially, a genetic resource for breeding cold tolerance and other traits. Both in their habitat and in a common garden, plants of B. nana looked much the same. Single sequence repeat (microsatellite or SSR) differences were used to measure genetic diversity. Of the 12 SSRs tested thus far (on 60 individuals from 8 areas), 5 have not worked well, 3 are the same in all plants, and 4 showed differences among plants. Fusarium Yellows is caused by the fungus, Fusarium oxysporum f. sp. betae. It occurs throughout sugar beet production areas of the United States and can lead to significant reduction in yield. The ability of this fungus to cause disease in other crops, and its vegetative compatibility with other strains of the same fungus have been tested. Progress also was made in characterizing the interaction of sugarbeet with major sugarbeet pathogens (Objective 2a & 2b). How F. oxysporum f. sp. betae causes Fusarium yellow is mostly unknown. The approach is to use the DNA code of known compounds produced by similar fungi to design diagnostic code to screen the DNA from the strains of fungus that cause Fusarium yellows. Some genes have been indentified and will be checked to see if they are active in causing disease. Additionally, the first year of a three year field study to examine the influence of air temperature, soil temperature, soil moisture, and air moisture to disease severity and onset of diseases has begun. Growth chamber experiments corresponding to the field experiments also have been initiated to more closely study how air temperature contributes to disease severity. Progress has been made in developing and distributing enhanced germplasm with novel stress resistance genes (Objective 3). Breeding populations with resistance to sugarbeet cyst nematode, cercospora leaf spot, fusarium yellows, and rhizoctonia root rot have been advanced. Four rhizomania and rhizoctonia resistant germplasms were released and submitted to the Journal of Plant Registration for registration. One joint release with USDA-ARS Fargo with resistance to cercospora leaf spot and sugarbeet root maggot was submitted for registration in the Journal of Plant Registrations. Four more germplasm with resistance to rhizomania and cercospora leaf spot are being prepared for ARS release and registration.
1. Rhizoctonia root or crown rot in Sugarbeet is endemic in growing areas across the United States and an increasing problem world-wide. The use of resistant germplasm, coupled with crop rotation and other cultural practices, can provide excellent management of diseases caused by Rhizoctonia solani. Four multigerm sugarbeet germplasms with resistance to rhizomania and other disease were developed by ARS scientists in Fort Collins, Colorado, and were released to the public and private researchers. FC1018, FC1019, and FC1020 show tolerance to rhizoctonia root-rot, cercospora leaf spot, beet curly top and aphanomyces root rot. They are populations from which plant breeders will select disease-resistant, multigerm pollinator hybrid parents. FC1022 showed a moderate tolerance to beet curly top, and had good sucrose yield when tested at Salinas, CA, under rhizomania conditions. Because of a large percent monogerm (45%) seedballs and O-type parentage, it should be possible to select monogerm, O-type, cytoplasmic male sterility (CMS) maintainer lines from FC1022 as well as multigerm pollinator hybrid parents. These germplasm provide the industry with many different choices of disease resistance in a rhizomania resistant background.
Panella, L.W., Fenwick, A.L., Hill, A.L., Vagher, T.O., Webb, K.M. 2010. Rhizoctonia Crown and Root Rot Resistance of Beta PI's from the USDA-ARS NPGS, 2009. Plant Disease Management Reports. 4:FC004