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Comparative mapping of the Oregon Wolfe Barley using doubled haploid lines derived from female and male gametes L. Cistue, A. Cuesta-Marcos, S. Chao, B. Echavarri, Y. Chutimanitsakun, A. Corey, T. Filichkina, N. Garchia-Marino, I. Romagosa, P. M. Hayes Rationale/Goals • Aimed to increase the Oregon Wolfe Barley population size to create a more useful linkage map • Great resource, particularly for Barley research • Barley is an economically important plant • Aimed to study differences in creating linkage maps from doubled haploid populations with different sources (female vs male gametes) • Increased population size better for QTL mapping Introduction • Previous population doubled haploids from female gametes (H.b.) – 82 unique individuals • A number of different types of molecular data were used on linkage map for this population • RFLP, AFLP, SSR, DArTs, SNPS, RADs • Created population of doubled haploids from male gametes (A.C.) – 93 individuals • Combined population – 82+93 = 175 Doubled Haploids Parent 1 Parent 2 OWB Dominant Parent OWB Recessive Parent F1 Gametes Materials and Methods • Create linkage map using molecular markers • SNP markers (total of 1,328 polymorphic markers) • Created linkage maps for the A.C. population, the H.b. population, and the combined data set • Phenotypes • Grew plants in greenhouse and measured a number of characters important to barley growers • QTL Mapping • QTL = quantitative trait locus • Links phenotype with genotype • Finding the locus (or loci) that control a phenotypic trait Results • All the loci are in the same order! Results • Why would we see different numbers of crossovers between these two populations? Because male and female gametes may have different rates of recombination (one reason that this study was done with male gametes – to see if this was true) Because the two populations were derived from different meiotic events, and one would expect some level of variability Recombination rate is 1.78 in A.C., 1.72 for H.b. So, pretty darn close Results • What is the expected dominant allele frequency in this population? Female Gamete Male Gamete 0.5 – same for recessive • What are the different dashed lines? Different confidence levels Way to avoid calling false positives • What does it mean if the peak is over the dashed lines? Segregation distortion – genotype frequencies NOT what expected Combined Results • Main takeaway: • Segregation distortion was higher in the A.C. population • Regions on 3H and 5H correspond with areas found to control phenotypes that could have affected a plant’s ability to survive the A.C. process • Region on 2H corresponds with ZEO-1, a dominant dwarfing allele. • Perhaps when ZEO-1 was dominant, the plants did not survive, so the study did not see their alleles in the population. QTL mapping = connecting phenotype to genotype Shows positions on the chromosome (in cM) where QTLs, or the region controlling traits, are found. The peaks also map to the same place as known genes VRS1 and ZEO1 The peaks are not straight lines at a single position because of linkage These genes are pleiotropic – seen in multiple peaks aligned with each gene Conclusions • Some differences between populations from male and female gametes, but both would be suitable for linkage map studies • Recombination rate slightly higher in A.C. population • Higher segregation distortion in A.C. population, but not due to production method • Gained further insight into relationships between genotype and phenotype and what loci control which phenotypes • Successfully created a larger population of OWB doubled haploids for future studies Generate F1 progeny B B b Bb Bb b Bb Bb Make doubled haploids from pollen of progeny BB or bb genotype Plant grows and produces seed Plant two seeds per individual to phenotype in greenhouse