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The feasibility of using diploid by tetraploid crosses to obtain triploid hops (Humulus lupulus L.)

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dc.contributor.advisor Haunold, Alfred
dc.creator DeNoma, Jeanine Streeter
dc.date.accessioned 2012-11-16T17:38:13Z
dc.date.available 2012-11-16T17:38:13Z
dc.date.copyright 1994-11-04
dc.date.issued 1994-11-04
dc.identifier.uri http://hdl.handle.net/1957/35084
dc.description Graduation date: 1995 en_US
dc.description.abstract The hop (Humulus lupulus L.) is a dioecious, diploid (2n=2x=20) species. Triploid hops (2n=3x=30) are easily obtained from tetraploid by diploid crosses and are preferred because of their natural seedlessness and increased vigor. The female inflorescence is used for flavoring beer. Because brewers require product consistency, the brewing characteristics of a new aroma-type hop must closely match the variety it is intended to replace while showing improved adaptation and agronomic traits. Since triploid offspring should more closely resemble the tetraploid parent from which they receive two-thirds of their genetic material, breeders have traditionally selected known varieties to be the tetraploid parent with the expectation this will increase the likelihood of obtaining progeny with similar brewing chemistry. Tetraploid female parents are obtained through colchicine treatment of desirable diploid varieties. Naturally occurring tetraploid seedlings, sometimes found among the offspring of tetraploid by diploid crosses, if suitable for breeding, could eliminate the tedious colchicine treatment process now used to obtain tetraploids. Two such tetraploid males were obtained from an Oregon cross in 1983. Since these two tetraploid males had attractive quality traits similar to other males in the USDA germplasm collection with a proven history of producing aroma-type progeny, they were thought to be suitable for use in a polyploid breeding program for aroma hops. The objective of this study was to determine the feasibility of using males as tetraploid parents in diploid by tetraploid crosses to obtain triploid aroma hops. Tettnanger, a prized German aroma hop, was used as the diploid female parent for these crosses. Meiotic cells of the two tetraploid males showed some abnormalities at anaphase I and the quartet stage; however, fertility, as determined from seed production and germination, was adequate for breeding. Of 185 seedlings obtained, 57 were triploid females. The diploid by tetraploid seedling population had a higher percentage of males than previously reported for tetraploid by diploid crosses. One tetraploid male produced no triploid female offspring. Seed content of the female triploid seedlings when subjected to a heavy pollen load averaged 2.4% compared to 20.1% for diploid seedlings from Tettnanger crosses. Triploid progeny produced higher average yield than the Tettnanger parent. The two tetraploid males and Tettnanger were very similar in chemical quality traits comparable in male and female hops. Comparison among triploid and diploid progeny from diploid by tetraploid crosses and diploid open-pollinated Tettnanger seedlings demonstrated that the male parent influenced the a ratio, cohumulone content, and humulene to caryophyllene ratio of the offspring. Many of the female triploid offspring genotypes showed chemical quality traits similar to those of Tettnanger. en_US
dc.language.iso en_US en_US
dc.subject.lcsh Hops -- Breeding en_US
dc.subject.lcsh Hops -- Genetics en_US
dc.title The feasibility of using diploid by tetraploid crosses to obtain triploid hops (Humulus lupulus L.) en_US
dc.type Thesis/Dissertation en_US
dc.degree.name Master of Science (M.S.) in Crop Science en_US
dc.degree.level Master's en_US
dc.degree.discipline Agricultural Sciences en_US
dc.degree.grantor Oregon State University en_US
dc.contributor.committeemember Mosley, Alvin
dc.contributor.committeemember Mok, Machteld
dc.contributor.committeemember Doescher, Paul
dc.description.digitization File scanned at 300 ppi (Monochrome) using ScandAll PRO 1.8.1 on a Fi-6770A in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR. en_US
dc.description.peerreview no en_us


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