Browsing by Subject "Rosa"
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Item Analysis of Genetic Diversity and Relationships in the China Rose Group(2011-02-22) Soules, Valerie AnnThe wild origin, early breeding history, and diversity of the China Rose group, including R. chinensis and its varieties, cultivars, and hybrids, are largely unknown. The aims of this study were to investigate the genetic diversity and relationships of the China Roses with related species and hybrids, including information in support of, or refuting, the hypothesis that these roses are the hybrid result of the wild R. chinensis var. spontanea and R. odorata var. gigantea. Ninety Rosa accessions, including China Roses, a Miscellaneous Old Garden Rose, Noisettes, early Polyanthas, Bourbons, Teas, and species from Sections Indicae and Synstylae were surveyed using 23 microsatellite primer pairs. The trnH-psbA chloroplast intergenic spacer was also sequenced for the China Roses, Misc. Old Garden Rose, and the species to look specifically at maternal relationships. A total of 291 alleles were scored for the 23 microsatellites, with alleles per locus ranging from 6-22 and averaging 12.65. A dendrogram based on Dice similarity and a three-dimensional Principle Coordinate Analysis (PCoorA) graph were plotted with the data. In the cluster analysis, the similarity coefficients ranged from ~0.15-0.99, with the cultivated roses forming well-defined groups at about 0.45 similarity. These groups generally reflected the American Rose Society horticultural classifications. A large number of sports and synonyms in the China Rose group were identified through this analysis as well. The PCoorA gave a better graphical representation of the relationships of the species and cultivars, and with the inclusion of the chloroplast sequence haplotypes, some maternal relationships could also be identified. This study shows that the cultivated China Roses are a closely related group and identified which accessions were likely Hybrid China Roses. The results also suggest that the China Roses were maternally derived from R. chinensis var. spontanea. Based on the microsatellites and chloroplast sequence haplotypes, the identity of the R. odorata var. gigantea accessions in this study are suspect, but the China Roses may also have this species in their background as the result of natural or artificial hybridization.Item Characterization of Resistance to Black Spot Disease of Rosa Spp.(2014-12-01) Dong, QianniBlack spot disease (BSD), caused by the fungus Diplocarpon rosae Wolf, is one of the most serious diseases of garden roses. Both complete (vertical) resistance conditioned by dominant Rdr genes and partial (horizontal) resistance (PR) conditioned by multiple genes have been described. The use of resistant rose cultivars would reduce the demand of agrochemical application. The characterization of 16 genotypes using two laboratory assays, the detached leaf assay (DLA) and the whole plant inoculation (WPI) approach, indicated that these were well correlated. Thus either method could be used to assess the resistance of the plants to the BSD. Fifteen diploid hybrid populations from 10 parents segregating for black spot partial (horizontal) resistance were assessed for black spot resistance by quantifying by the percentage of the leaf area with symptoms (LAS) and lesion length (LL) measured by the diameter of the largest lesion in detached leaf assays. Nine of these populations were also evaluated in field trials by rating the incidence of damage due to the fungal infection. The narrow sense heritability of partial resistance to black spot as measured by LAS and LL data of DLA was estimated from 0.3 to 0.4 when calculated with a genetic variance analysis and from 0.7 to 0.9 when generated from mid-parent offspring regression. In the field assessments, the second year assessments were better than the assessments done the first year due to higher and more uniform inoculum levels which minimized problems with escapes. In general there was no or just low correlations between field and DLA assessments of black spot indicating that perhaps these two assessments are measuring different aspects of resistance. The narrow and broad sense heritability estimates from the combined analysis of field assessments is 0.3 and 0.4 respectively. An examination of the assessment data from the laboratory and the field showed that some seedlings were rated as resistant using both approaches. Two microsatellite markers linked with Rdr1 locus and one SCAR marker linked to Rdr3 locus were found to be germplasm specific. The hybrid population ?Golden Gardens? x ?Homerun? that segregates for race 8 resistance was phenotyped for resistance to race 8 and genotyped for 38 SSR markers to assess if any of these SSR markers were associated with Rdr3. This resistance trait from the triploid source segregated non randomly and differentially in haploid and diploid gametes. None of the SSR markers examined were associated with Rdr3.Item Construction of the Diploid, Tetraploid and Integrated Diploid-tetraploid Genetic Linkage Maps in Roses Using Simple Sequence Repeat (SSR) Markers(2014-01-03) Tsai, Ching-JungThis study uses polymorphic microsatellites (SSR) to elucidate the similarities among the diploid and tetraploid rose genomes by comparing their maps and clarifying the predominant inheritance patterns (disomic versus tetrasomic) seen in the tetraploid population. One hundred and eight out of 175 SSRs were polymorphic in both the OBxWOB26 (Old Blush x (?Basye?s Thornless? x ?Old Blush?) diploid backcross population and the GGFC (?Golden Gate? x ?Fragrant Cloud?) tetraploid full-sib population. Of these 69 fluorescently labeled SSRs and 5 morphological traits were used which generated 107 loci and 5 trait loci with 99 diploid population progeny. The tetraploid map was constructed with SSRs and AFLPs with 131 tetraploid progeny using the single dose restriction fragment (SDRF) analysis. The degree of preferential chromosome pairing in the tetraploid population was examined by looking at the segregation ratios among the double-dose markers (DDMs) as well as the ratio of loci in repulsion vs coupling phase using single-dose markers (SDMs). These approaches showed that there was a combination of disomic and tetrasomic inheritance. A diploid, a tetraploid and an integrated diploid-tetraploid genetic linkage map were developed from two populations using JoinMap 4 with the cross pollination option. In the diploid map, 7 integrated linkage groups covered a length of 352.3 cM with an average chromosome size of 50.3 cM. The morphological traits, prickles on stem (prickles), recurrent bloom (RB)) and flower type (Blfo) were mapped on the Chr LG3 which matched with the ICM (Integrated consensus map) published by Spillers et al., (2010). Moreover, 5 out of the 69 SSR markers (RhJ404, H9_B01, RW11E5, RW8B8 and RhE3) were mapped to two or more loci each on different chromosomes of the diploid map. In the tetraploid map, 174 out of 346 (50%) loci of single-dose markers (SDMs) and double-dose markers (DDMs) were mapped on a length of 883.4 cM with 9 linkage groups. Sixty anchor SSR markers were used to join the diploid and tetraploid maps which included 215 loci with a map length of 632 cM. Synteny of common SSRs and morphological traits, prickles, RB, Blfo, powdery mildew resistance (PM) and petal number (PN) on the integrated diploid-tetraploid map with the ICM, the GGFC and the K5 map demonstrated the collinear alignment among these maps.