Cuphea is an herbaceous genus having species whose seed
storage lipids are predominantly medium-chain triglycerides (MCTs).
Cuphea lanceolate Ait, and Cuphea viscosissima Jacq. are central to
the breeding of Cuphea as a new commercial source of MCTs. The
objectives of this thesis were to develop a reliable method to
extract DNA from Cuphea, to construct a molecular-marker linkage
map of C. lanceolate, and to evaluate quantitative-trait loci (QTL)
affecting seed capric acid content, seed oil content, and embryo
development in C. lanceolate. We used allozyme and restriction-fragment-
length-polymorphism (RFLP) markers to study Cuphea because
molecular markers are the best method available to investigate the
Mendelian genetics underlying quantitative traits, and are useful
in breeding. Adequate yield of clean DNA is essential for RFLP
mapping. We tried numerous DNA extraction methods that failed to
remove contaminants that interfere with restriction digests of
Cuphea DNA. The method described here was developed to remove
those contaminants and maintain relatively high DNA yields. In
this method, the critical step in purification consists of washing
the DNA with phenol while it is complexed with CTAB and dissolved
in 1 M NaCl. An RFLP and allozyme linkage map of C. lanceolate was
constructed having 37 markers in six linkage groups with a total
distance of 288 cM. Levels of polymorphism were estimated for
three lines of C. lanceolate and one line of C. viscosissima using
84 random genomic clones and two restriction enzymes, EcoRI and
HindIII. Twenty-nine percent of the probes detected RFLPs between
C. lanceolate lines, whereas 63% of the probes detected RFLPs
between C. lanceolate and C. viscosissima lines. Thirty RFLP and
four allozyme markers were used to locate on the C. lanceolata
linkage map QTL affecting seed capric acid content, seed oil
content, and embryo development. Three unlinked QTL explained
19.4% of the phenotypic variation in capric acid content in F₂
seed. Seed oil content and seed weight were measured on seed from
field-grown F₂ plants. Seed weight was indicative of embryo size
(development). Four unlinked QTL explained 33.9% of the phenotypic
variation in embryo size. One of these QTL, which explained 20.3%
of the variation, may have been a chromosomal deletion detected by
a marker having a null allele. Three QTL pleiotropically affected
seed oil by affecting embryo size. The one QTL that only affected
seed oil accounted for 2.8% of the phenotypic variation. / Graduation date: 1991
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/37474 |
| Date | 13 November 1990 |
| Creators | Webb, David M. (David Morton), 1954- |
| Contributors | Knapp, Steven J. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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