Jointed goatgrass (Aegilops cylindrica Host; 2n=4x=28; CCDD) is an
agriculturally important species both as a weed and as a genetic resource for
wheat (Triticum aestivum L.; 2n=6x=42; AABBDD) improvement. In order to
better understand the evolution of this species, the diversity of Ae. cylindrica
was evaluated along with its progenitors, Ae. markgrafii (Greuter) Hammer
(2n=2x=14; CC) and Ae. tauschii Coss. (2n=2x=14; DD), using chloroplast and
nuclear microsatellite markers. Ae. cylindrica had lower levels of plastome and
nuclear diversity than its progenitors. The plastome diversity of Ae. cylindrica
was lower than its nuclear diversity. Ae. cylindrica was found to have either C-or
D-type plastomes, derived from Ae. markgrafii or Ae. tauschii, respectively,
where the C-type plastome was found to occur at a lower frequency than the
D-type plastome. The nuclear genomes of Ae. cylindrica accessions with C-or
D-type plastome were found to be very closely related, suggesting a
monotypic origin. Furthermore, analyses suggests that Ae. tauschii ssp.
tauschii contributed its D genome and D-type plastome to Ae. cylindrica. Ae.
cylindrica accessions collected near Van Lake in southeastern Turkey, an area
where Ae. tauschii ssp. tauschii and Ae. markgrafii overlap, showed high allelic diversity and may represent the site where Ae. cylindrica formed.
Population structure analyses suggested a lack of regional genetic structure in
Ae. cylindrica and evidence of migration of Ae. cylindrica among various
regions. Finally, Ae. cylindrica accessions in the USA were found to be closely
related to accessions from at least three regions of its native range central
Anatolia, central East Turkey and western Armenia, and Caucasia.
Wheat and jointed goatgrass are closely related and both have the D-genome.
These two species can hybridize and produce backcross derivatives
under natural conditions, a situation that may allow gene flow between these
two species. In order to better understand mating patterns between these two
species, a total of 413 first-generation backcross (BC₁) seeds obtained from
127 wheat-jointed goatgrass F₁ hybrids, produced under natural conditions,
were evaluated for their parentage using chloroplast and nuclear microsatellite
markers. Of the 127 F₁ hybrids evaluated, 109 had jointed goatgrass as the
female parent, while the remaining 18 F₁ plants had wheat as the female
parent. Of the 413 BC₁ plants analyzed, 358 had wheat and 24 had jointed
goatgrass as the recurrent male parent. The male parentage of 31 BC₁ plants
could not be determined. Although the majority of hybrids were pollinated by
wheat, backcrossing of hybrids to jointed goatgrass would enable gene flow
from wheat to jointed goatgrass. Though the observed frequency of jointed
goatgrass-backcrossed hybrids (F₁ X jointed goatgrass) was low under field
conditions, their absolute number is dependent on frequency of hybrids, which
in turn, depends on the density of jointed goatgrass in wheat fields. Therefore, the recommendations to control jointed goatgrass in wheat fields and adjacent
areas and to plant jointed goatgrass free wheat seed should be followed in
order to avoid gene flow from wheat to jointed goatgrass. / Graduation date: 2006
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/28764 |
| Date | 16 June 2005 |
| Creators | Gandhi, Harish Tulshiramji |
| Contributors | Riera-Lizarazu, Oscar, Mallory-Smith, Carol A. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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