Multiple projects were conducted to investigate the potential for developing a breeding program utilizing species of <i>Catalpa</i> Scop. and <i>Chilopsis</i> D. Don. The efficacy of oryzalin was evaluated for inducing polyploidy and restoring fertility in the sterile, intergeneric hybrid ×<i>Chitalpa tashkentensis</i> Elias & Wisura [<i>Catalpa bignonioides</i>Walt. x <i>Chilopsis linearis</i> (Cav.) Sweet] 'Pink Dawn'. Submerging meristems in 150 µM oryzalin for up to 24 hours was effective at inducing tetraploids and cytochimeras. Pollen from the diploid cultivar was non-viable, but pollen from the polyploid stained and germinated as well as pollen from progenitor taxa. Polyploid ×<i>Chitalpa</i> were self-compatible yielding tetraploids when self pollinated and triploids when crossed with <i>C. bignonioides</i>, but reciprocal crosses with <i>Chilopsis</i> taxa failed. To increase recovery of triploids, we investigated germination of ovules and embryos at various harvest dates on Schenk and Hildebrandt (SH) basal salts supplemented with various medium components. Germination of triploid [(polyploid ×<i>Chitalpa</i>) x <i>C. bignonioides</i>] and tetraploid (selfed polyploid ×<i>Chitalp</i>a) embryos was greatest at 7 weeks after pollination on SH with 20 g·L<sup>-1</sup> sucrose and ≥ 1 µM gibberellic acid (GA<sub>3</sub>). Triploids [<i>Chilopsis linearis</i> x (polyploid ×<i>Chitalpa</i>)] germinated < 5%. Additional studies were conducted to screen diverse taxa for resistance to powdery mildew (PM), <i>Erysiphe elevata</i> (Burr.) U. Braun & S. Takam, and catalpa sphinx larvae (CSL), <i>Ceratomia catalpae</i> (Boisduval). Twenty-four taxa from <i>Catalpa</i> (section <i>Catalpa</i> Paclt and <i>Macrocatalpa</i> Grisebach), <i>Chilopsis</i>, and ×<i>Chitalpa</i> were screened in 2004-05 for susceptibility to PM. Disease incidence and severity were recorded to calculate area under the disease progress curves (AUDPC) for each year. North American <i>Catalpa</i> spp. in sect. <i>Catalpa</i>, <i>Chilopsis</i>, and ×<i>Chitalpa</i> taxa were all moderate to highly susceptible to PM. Chinese <i>Catalpa</i> spp. in sect. <i>Catalpa</i> and West Indian sect. <i>Macrocatalpa</i> were resistant to PM. Hybrids among North American and Chinese <i>Catalpa</i> spp. in sect. <i>Catalpa</i> varied in susceptibility, indicating inheritance of partial resistance to PM. A no-choice feeding study conducted with CSL in 2005 found no differences in survival or growth of larvae reared on taxa from both sections of <i>Catalpa</i>, <i>Chilopsis</i>, and ×<i>Chitalpa</i>. Future breeding of ×<i>Chitalpa</i> can utilize the identified sources of resistance for PM; however, a source of resistance to CSL was not found. Triploids are generally infertile and may be deployed by breeders to limit invasive potential of introduced ornamentals. However, inheritance of ornamental traits can be complex at higher ploidy levels. Inheritance of two mutant foliage types, variegated and purple, was investigated for diploid, triploid and tetraploid tutsan (<i>Hypericum androsaemum</i> L.). Fertility of progeny was evaluated with pollen viability tests, percent fruit set, and germinative capacity of seed from specific crosses. Segregation ratios were determined for diploids in reciprocal di-hybrid F<sub>1</sub>, F<sub>2</sub>, BC<sub>1P1</sub>, and BC<sub>1P2</sub> families and selfed F<sub>2</sub>s with the parental phenotypes and triploid and tetraploid F<sub>2</sub>s. Diploid di-hybrid crosses fit the expected 9:3:3:1 ratio for a single, simple recessive gene for both traits, with no evidence of linkage. A novel phenotype representing a combination of parental phenotypes was recovered. Data from backcrosses and selfing also supported the recessive model. Both traits behaved as expected at the triploid level; however, at the tetraploid level the number of variegated progeny increased, with segregation ratios between random chromosome and random chromatid assortment models. We propose the gene symbol <i>var</i> (<i>variegated</i>) and <i>pl </i> (<i>purple leaf</i>) for the variegated and purple alleles, respectively. Triploid pollen stained moderately well, but pollen germination was low. Triploid plants demonstrated extremely low male fertility and no measurable female fertility (no viable seed production). Research presented herein demonstrates the feasibility of manipulating ploidy levels for breeding desirable ornamental traits including non-invasiveness.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-04052006-131144 |
| Date | 13 April 2006 |
| Creators | Olsen, Richard Thomas |
| Contributors | G. Craig Yencho, Dennis J. Werner, Thomas G. Ranney, David A. Danehower |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-04052006-131144/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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