Location: Sugarbeet and Bean Research2011 Annual Report
1a. Objectives (from AD-416)
1) Enhance and release sugarbeet germplasm that represents substantially improved populations enriched for novel genetic combinations for the unique Eastern U.S. growing regions; 2) Develop and exploit sugarbeet and other species nucleotide sequence information for marker-assisted gene discovery, including development and release of simple sequence repeats (SSR) and single nucleotide polymorphism (SNP) markers; and 3) Develop simplified phenotyping assays for priority biotic and abiotic stress resistance and early season development suitable for molecular analyses.
1b. Approach (from AD-416)
Traditional sugarbeet population improvement approaches will be deployed for open pollinated, self-incompatible germplasm for release to industry. Production of improved populations will follow from mother root selection under field, greenhouse, or laboratory conditions of one or more germplasm sources, followed by random inter-mating, and harvest of seed from either individual plants, genetically related individuals, or as an entire population. Selfed families will be created from self-fertile materials generated to dissect the genetic control of high priority disease resistances. A program of phenotypic selection is followed by selecting mother roots from field nurseries, selfing these hybrids in the greenhouse, and applying molecular markers. Molecular markers will be developed from sugar beet nucleotide sequences, located to one of the nine beet chromosomes, and compared with segregation of disease and agronomic traits to identify genetic control. Mapped molecular markers will also be used to integrate sugar beet Bacterial Artificial Clones on the genetic linkage map for eventual isolation of specific genes that control agronomic and disease traits. Transcript profiling will be employed for gene discovery, however these tools are new for germplasm enhancement and their use has not been well explored. Examining transcript of profiles during sugar beet development, and during abiotic and biotic stress will allow deduction of important physiological and biochemical clues to the plant responses to stress and development that can be used towards more rigorous application in germplasm enhancement. The prevalence of different sugar beet pathogens in the Michigan agro-ecosystem will be ascertained, and used to develop high priority targets for transcript profiling. Differential disease reaction to Fusarium oxysporum, for instance, as an example of a newly discovered pathogen for Michigan, will form the basis for transcript profiling experiments that will better characterize the disease infection process and assist in identifying targets of opportunity for breeding intervention. Populations and their progeny showing good agronomic and disease performance will be folded into the general agronomic and disease nursery evaluations, and released to industry as enhanced germplasm.
3. Progress Report
Germplasm enhancement activities continue with individual field trials and greenhouse seed increases in Michigan encompassing agronomic evaluation, selection for resistance to Cercospora leaf spot, Fusarium yellows, and Rhizoctonia seedling and root diseases, selection for sugar beet cyst nematode resistance and salt tolerance during germination, and assessment of stand establishment potential. Over 1,000 distinct entries, not including those submitted for the official leaf spot nursery, are being evaluated. From these trials, individuals with superior characteristics will be selected after evaluation of their performance during the current growing season. From FY10, over 4,000 roots were selected, vernalized, and selfed in the greenhouse for inbred seed production, and an equal number selected for greenhouse and field seed production for open-pollinated population enhancement. Multiple wild and unadapted germplasms have been incorporated into these population improvement schemes. Marker discovery and genetic analyses activities were productive with using second-generation sequence acquisition technologies for marker development using single nucleotide polymorphism technologies. A coalition of ARS researchers, and university and industry scientists has been formed to obtain a full-length sugar beet genome sequence in conjunction with industry partners. Bioinformatic capacity was acquired that should ease the computational load from the high volume of data generated by these new genomic technologies. Simplifying phenotypic selection through development of new methods yielded very positive results. Synergistic interactions between root pathogens including Fusarium, Rhizoctonia, and Rhizopus were demonstrated. The fourth year of a comprehensive survey of sugarbeet disease-causing fungal pathogens present in the Great Lakes growing areas is continuing - the first survey in over 25 years. Results confirm presence of known pathogens and suggest involvement of others whose precise roles are being ascertained, and unlike previous years, Fusarium seedling disease is a major issue for Michigan growers in 2011. Experiments to determine the role of pathology and genetics in long-term storage were initiated, with good results in that different germplasm showed delayed susceptibility to storage rot pathogens, with the caveat that storage at low temperatures induces the flowering response and concomitantly roots from all tested germplasm become increasingly susceptible by this 12 -16 week period after harvest with germplasm varying in the rate of both flowering response and increased disease susceptibility. Correlation was found between the rate of change in the two physiological processes, which opens up new areas for research.
1. Construction of the first Recombinant Inbred Line (RIL) population in beet. Sugar beet is an open-pollinated crop with wind-blown pollen that makes precise genetic analyses of agronomic and other traits very difficult. ARS researchers at East Lansing, MI initiated a program 12 years ago to inbreed populations of beets to assist with general genetic analyses, mapping of single gene traits, and dissection of traits important for the production, profitability, and expansion of beet products to new markets. Progeny from a single hybrid individual from a cross between a sugar beet and a red table beet were propagated by single seed descent for six generations, resulting in an inbred RIL population of >900 individual lines in FY11, most (>70%) producing sufficient seed for field trials. This population will be used to determine the genetics of morphological characters that define differences between sugar beet and red table beet as well as define the minimum number of genes that contribute to the economic sucrose production of sugar beet. This is the first RIL population of beet and demonstrates that deeply inbred sugar beet germplasm can be created, and thus allow precise and repeatable molecular determinations of agronomic traits to be accomplished by scientists interested in sugar beet biology and breeding.
2. Development of enhanced sugar beet germplasm with resistance to seedling Rhizoctonia disease. Rhizoctonia diseases of sugar beet affect all phases of sugar beet production, from emergence to adult plants to storage beets. Rhizoctonia diseases of different crop stages, although named differently, are caused by the same organism. Disease incidence and severity is increasing worldwide to the extent that the seed industry now places major emphasis on genetic control of Rhizoctonia diseases and agrochemical companies are actively screening new compounds for Rhizoctonia control. ARS scientists at East Lansing, MI have developed an enhanced genetic source of resistance to the seedling phase of the disease, having previously discovered seedling resistance in 2006. Further, these scientists have shown that this resistance is effective against the adult plant phase of the disease (crown and root rot) and likely delays susceptibility to some storage rot(s). It is expected the new germplasm and knowledge gained through its development will be widely deployed to combat these pernicious rots of sugar beet and related crop types.
Gachango, E., Kirk, W.W., Hanson, L.E., Rojas, A., Tumbalam, P., Shetty, K. 2011. First report of in-vitro fludioxonil-resistant isolates of Fusarium spp. causing potato dry rot in Michigan. Plant Disease. 95:228.