|Cruz, Von Mark|
|Brummer, E. Charles|
Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2006
Publication Date: 12/5/2006
Citation: Cruz, V.V., Luhman, R., Rife, C.L., Shoemaker, R.C., Marek, L.F., Brummer, E., Gardner, C.A. 2007. Characterization of flowering time and SSR marker analysis of spring and winter type Brassica napus L. germplasm. Euphytica. 153:43-57. Interpretive Summary: Brassica germplasm can have different reproductive life forms, annual or biennial. Biennial forms typically need to over winter, or be exposed to a long period of cold (vernalization), in order to flower and reproduce the following spring. In order to increase the seed of a variety, or accession, and maintain its original genetic profile, both types have to reproduce and their progeny be represented. It is difficult to know if a mixed reproductive life form is involved if it isn't observed. Use of genetic markers can help inform us if a variety contains a mixture. The flowering genes of Brassica have been thoroughly studied; specific genes called 'FLC' and 'CO' are known to be associated with early or delayed flowering. Accessions which were known to flower early, late, or not in a single season were tested using SSR (simple sequence repeats) markers. Presence or absence of a marker 'band' indicates whether the plant and the marker have some DNA sequence similarity. Associations of SSR marker fragments with Brassica napus reproductive life forms were determined. Analysis of molecular variation by using cluster analysis and ordination resulted in recognizable, distinct groups of annual and biennial life-form types. This information can be used to test accessions prior to planting in order to detect reproductive life form type. This research impacts the quality of the National Plant Germplasm System's collections, by providing guidance for management of future seed regenerations in order to maintain the integrity of the genetic profile of B. napus plant genetic resources. This impacts researchers and breeders directly, and the public indirectly.
Technical Abstract: Flowering dates and life forms of all available Brassica napus accessions conserved at the North Central Regional Plant Introduction Station (NCRPIS) were characterized, and a survey of molecular variation was conducted by using simple sequence repeats (SSR). To characterize flowering phenology, 598 B. napus accessions from the NCRPIS collection were planted in Iowa and Kansas field sites together with a current commercial cultivar and observed for days to flowering (first, 50% and 100% flowering). Days from planting to 50% flowering ranged from 34 to 83 in Iowa and from 53 to 89 in Kansas. Flowering time was significantly related to field location, although differences in flowering-time rank were observed for several accessions. Accessions that failed to flower in Iowa in a single growing season comprised 28.5% of the accessions; of the flowering accessions, 100% plant flowering was not always achieved. Accessions were grouped according to flowering time. A stratified sample of 50 accessions was selected from these groups, including 10 non-flowering and 40 flowering accessions of diverse geographic origins and phenological variation. Thirty SSR markers, selected across 18 Brassica linkage groups from BrassicaDB, and three derived from Brassica expressed sequence tags (ESTs) were scored in the stratified sample. An average of three alleles per locus was observed. Associations of SSR marker fragments with the life forms were determined. Analysis of molecular variation by using cluster analysis and ordination resulted in recognizable, distinct groups of annual and biennial life-form types, which may have direct applications for planning and management of future seed regenerations.