Thesis (Ph. D.)--University of Wyoming, 2006. / Title from PDF title page (viewed on June 30, 2008). Includes bibliographical references (p. 51-57).

Winter wheat stubble and dried plant residue in Conservation Reserve Program (CRP) fields were burned in the fall and spring to evaluate effects on jointed goatgrass (Aegilops cylindrica Host.) seed survival and germination. Laboratory studies were also conducted to determine minimum temperatures and heat duration needed to reduce jointed goatgrass seed viability. Maximum air temperatures attained during various field burns reached from 74 C to over 700 C. Temperatures 2.5 em above the soil surface remained above 400 C for over 10 seconds and above 600 C for 2 to 8 seconds in burning CRP stubble. Results for the winter wheat stubble location were similar with temperatures sustained above 400 C for over 30 seconds. Seed exposure in the lab to 400 and 600 C flames for 1 second reduced germination to 20 and 15 percent, respectively. Germination was reduced to zero with exposures of 10 seconds or more. Oven temperatures of 150 C reduced germination to 85, 57.5, 17.5, 0 and 0 percent for exposures of 20, 30, 60, 120 and 300 seconds, respectively. At 275 C oven temperature germinability dropped to 50% after a 10 second exposure and 0% after a 20 second exposure. Jointed goatgrass plant populations were reduced 54 to 92% after field burning in the spring or fall. Fall burning provided 70 to 85% control of goatgrass the following spring. In non-burned non-disked plots over 90% of emerging plants germinated from seeds on the soil surface. In burned non-disked plots few seeds germinated from on the surface, with 80 to 90 percent of surviving plants having germinated from buried seed. Herbicides provided limited control of jointed goatgrass. None of the herbicides provided greater than 50% control.

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

Thesis (Ph. D.)--University of Idaho, 2005. / Also available online in PDF format. Abstract. "December 2005." Includes bibliographical references.

Jointed goatgrass (Aegilops cylindrica Host) infestations in winter wheat (Triticum aestivum L.) production regions of the central and western USA result in severe economic losses in the wheat market. Field and greenhouse studies were conducted to determine the vernalization requirements of winter wheat, spring wheat, jointed goatgrass, and wheat by jointed goatgrass reciprocal hybrid plants. In field studies, jointed goatgrass plants required more vernalization to produce spikelets and germinable seed than 'Madsen' winter wheat plants. In greenhouse studies, plants of jointed goatgrass populations collected from Oregon and Washington wheat fields required fewer vernalization days to reach the joint stage than Madsen plants. Detailed observations in the greenhouse revealed a longer period between jointing and anthesis for most jointed goatgrass populations that was overlooked in field studies. Vernalization for 6-wk represents the minimum treatment for synchronous reproductive development among jointed goatgrass populations, Madsen winter wheat, and Madsen by jointed goatgrass hybrids, yet the risk of gene transfer might be greater after 7-wk vernalization. In the jointed goatgrass populations tested, there was not selection for a vernalization insensitive growth habit. Because jointed goatgrass spikelets often contain two seed, germination was recorded for primary and secondary positioned seed. Germination of freshly harvested jointed goatgrass seed was promoted by 25/15 C day/night temperatures. However, light and 30/20 C incubation was necessary for maximum germination of non-dormant, primary positioned seed. Both primary and secondary positioned seed within jointed goatgrass spikelets were non-dormant after 16-wk after-ripening at 22 ± 2 C. Under optimum growing conditions, no planting depth selectively allowed wheat germination and emergence while preventing jointed goatgrass germination and emergence. Glume removal did not alleviate dormancy completely in jointed goatgrass seed. Research confirmed jointed goatgrass population polymorphism for vernalization requirements and seed dormancy. Jointed goatgrass reproductive variability might be part of a general purpose genotype strategy to germinate and colonize a wide range of environments. Wheat by jointed goatgrass hybrid plants should be removed from winter and spring wheat fields. Despite a short dormancy period, three or more years of rotation outside of winter annual crops may be necessary to reduce populations of jointed goatgrass. / Graduation date: 2006