Location: Crop Improvement and Protection Research2010 Annual Report
1a. Objectives (from AD-416)
The long-term objective of this project is to develop sugarbeet (Beta vulgaris L. subsp. vulgaris) breeding lines and populations with resistance to specific diseases and pests. Genes and gene pools from wild beet relatives will be evaluated, characterized, and introgressed into adapted germplasm. Progeny lines and specific breeding materials will be genotyped and phenotyped to determine inheritance patterns and to search for molecular genetic markers. Markers will be validated for usefulness in marker-assisted selection. The efficacy of resistance genes will be evaluated in biological evaluations and replicated trials. The breeding and population improvement program will be continued to accumulate numerous favorable alleles and combine broadly based host plant resistance and high productivity. Over the next 40 months the program will focus on the following objectives: Objective 1: Analyze the inheritance of disease resistance mechanisms to pathogens common in the United States, especially in the Western growing regions, through mapping sources of disease resistance and identifying phenotypic variation for disease resistance. Objective 2: Identify novel sources of disease resistance within sugarbeet and its wild relatives to broaden the sugarbeet germplasm base. Objective 3: Improve sugarbeet germplasm and develop genetic resources through utilization of traditional and molecular breeding tools for release to international sugarbeet seed companies for improved agronomic, quality, disease resistance, and tolerance to abiotic stresses.
1b. Approach (from AD-416)
Develop populations and genetic stocks for mapping qualitative and quantitative sources of disease resistance in sugarbeet. Identify regions of the Beta vulgaris genome associated with phenotypic variation for disease resistance and select advantageous alleles to facilitate marker-assisted selection. Evaluate wild and ancestral relatives of sugarbeet both phenotypically and genotypically for novel sources of disease resistance. Characterize and introgress genetically diverse resistance alleles into enhanced sugarbeet germplasm. Continue a sugarbeet pre-breeding, population, and breeding line improvement program. Integrate genomic tools to develop new germplasm with improved agronomic and quality characteristics and resistance to biotic and abiotic stresses.
3. Progress Report
Progress was made on all three objectives, which fall under National Program 301, Component 2, Crop Informatics, Genomics, and Genetic Analyses, and Component 3, Genetic Improvement of Crops. Under Objective 1A, 14 crosses were made to develop genetic stocks and mapping populations. Of these, nine crosses were to study the inheritance of rhizomania resistance, two for powdery mildew resistance, and one for sugarbeet cyst nematode (SBCN) resistance. Under Objective 1B, significant progress was made towards identifying regions of the Beta vulgaris genome associated with SBCN resistance. We used a resistant x susceptible mapping population, developed in collaboration with ARS, Fort Collins, CO, and performed greenhouse disease screening for SBCN resistance under inoculated soil conditions on 3,680 individuals from 88 mapping population lines and four check varieties to test the segregation of resistance. Of these lines, we selected 127 individuals from 58 lines to transplant and vernalize for crossing next year and for potential germplasm improvement and release. Under Objective 2A, we progressed with the evaluation of wild sugarbeet relatives for unique sources of disease resistance. In collaboration with ARS, Pullman, WA, we extracted DNA from four individuals per Beta vulgaris subsp. maritima (Bvm) accession in the National Genetic Resources Program (NPGS) collection. There are 424 accessions in the NPGS collection and we have DNA for 1,696 Bvm individuals. We have developed three pools of individuals: 1. a pool of all four individuals for a single accession, 2. a pool of 12 individuals from different accessions, and 3. a single individual from one accession. We are running 162 SSR molecular markers on these pools to identify polymorphisms. Under Objective 2B, crosses were made between recurrent parent, 8747, and 11 C79 rhizomania resistant-lines released by ARS, Salinas, CA in 1994. Each line has a different Bvm accession donor parent. Literature and field trials have confirmed that these lines are resistant to the wild type-rhizomania virus strain and research is underway to determine which of the lines confer resistance to the resistance breaking-rhizomania virus strain. Under Objective 3A, continued progress was made on the sugarbeet pre-breeding, population, and breeding line improvement program. At our Salinas locations, we evaluated 532 plots comprising 295 lines for traits including stand count, powdery mildew resistance, rhizomania resistance, cercospora leaf spot resistance, tons roots harvested per acre, and percent soluble solids. We evaluated 736 plots of 424 lines in our Brawley location for stand count and sugarbeet cyst nematode resistance. In addition, progress continues on purifying isolates of Polymyxa betae from different regions to establish a culture collection we can work with. We are also collaborating with ARS, East Lansing, MI and University of Minnesota on looking at the population structure of Rhizoctonia solani on sugarbeet.
1. Identification of a potentially unique source of resistance to sugarbeet cyst nematode. While qualitative sources of resistance confer a more complete resistance, they are often less durable in terms of long-term stability and utility than quantitative type resistance. Offspring of quantitatively resistant x susceptible crosses show a range, often continuous, of phenotypes. ARS researchers at Salinas, CA tested 3,680 individuals from a sugarbeet cyst nematode resistant by susceptible cross. We identified five lines that consistently show sugarbeet cyst nematode resistance in field and greenhouse experiments. Further testing on these lines will be conducted to determine usefulness for future germplasm improvement and ultimate release to growers.
5. Significant Activities that Support Special Target Populations
Visited the fifth grade classes at Los Padres School, an elementary school in Salinas serving primarily Hispanic students, and presented lessons and experiments related to general plant and animal biology. Hired two Hispanic summer internship students from Hartnell College, a Hispanic-Serving Institution and local community college.
Kongprakhon, P., Cuesta-Marcos, A., Hayes, P.M., Richardson, K.L., Sirithunya, P., Sato, K., Steffenson, B., and Toojinda, T. 2009. Validation of rice blast resistance genes in barley using a QTL mapping population and near-isolines. Breeding Science. 59: 341-349.