Five clones of giant type bermudagrass, Cynodon dactylon (L.) pers. vars. aridus and afghanicus Harlan et de Wet, progenies from crosses among those five, and crossed, selfed, and open pollination progeny from selected F₁ plants were evaluated for response to simazine (2-chloro-4,6-bis(ethylamino)-s-triazine). The first two generations were also evaluated for their response to ametryn (2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine). Two techniques were used. Culm cuttings, rooted in wet vermiculite, were placed into test tubes of simazine or ametryn suspensions at various concentrations or water. Culms were rated (1 to 9, 9 normal, 1 dead) for herbicide injury. Seeds were placed into petri dishes on moist filter paper, germinated in a germinator (day 35C, night 21C) and treated with 8ppm simazine or water in a greenhouse. Seedlings were rated visually for herbicide injury (7 normal, 5 affected, 1 dead) weekly, later daily, until a final drying and weighing of seedlings after all those in simazine were dead. Tolerance of all treated materials was expressed as percentage of control. There were significant differences among plants in tolerance to simazine with significance up to .001, although there was great variance within genotypes affected. The correlation between ametryn and simazine reaction was low. Tolerance scores were affected by condition of culms (significance .05), dosage, and nutrient levels. The clone by nutrient level interaction was significant at .01. Tolerance to simazine varied widely (more than 60%) among progeny of any plant as maternal parent. Progeny of reciprocal crosses between resistant and susceptible clones had similar (45 to 46) mean tolerance scores intermediate between parental scores indicating no dominance. Plants with the same cytoplasm ranged from most resistant (88%) to most susceptible (11%). Maternal effect on tolerance appears absent. The range of response for progeny of parents of any tolerance level indicates several pairs of genes are involved. Open pollination seedlings from consistently resistant plants averaged more resistant than seedlings from consistently susceptible plants. Giant bermudagrass simazine tolerance must be quantitatively inherited, possibly additive, with penetrance varying with plant condition, dosage, and other environmental constraints.

A method was developed for rapid plant regeneration from protoplasts of birdsfoot trefoil (Lotus corniculatus cv. Leo) using in vitro cotyledons and a new enzyme formula. Protoplasts of a transgenic Nicotiana tabacum cv. Xanthi line KCR were isolated from leaves, in vitro shoots, and calli by an enzyme formula consisting of 0.5 % Cellulase R-10 and 0.05 % Pectolyase Y23 with either 0.4 M sucrose or 0.5 M mannitol as the osmoticum. Nine asymmetric fusion experiments were conducted between iodoacetate inactivated birdsfoot trefoil and irradiated transgenic tobacco protoplasts. The fusion products underwent several divisions but no visible colonies were obtained. Resistance analyses revealed the inactivation of the herbicide resistant gene in the transgenic tobacco calli. A putative chlorsulfuron resistant line has been obtained by in vitro selection from birdsfoot trefoil cotyledonous protoplasts. Their regenerants had normal ploidy, and expressed improved tolerance when sprayed with chlorsulfuron at the rate of 30 g/ha.

Bibliography: leaves 151-172. / vii, 172 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Applied and Molecular Ecology, 2000?

Bibliography: leaves 126-143. / x, 143 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Adelaide University, Dept. of Applied and Molecular Ecology, 2001

Thesis (Ph. D.)--University of Adelaide, 1993. / Includes bibliographical references (leaves 203-220).

Thesis (Ph. D.)--University of Adelaide, Dept. of Crop Protection, 1996? / Includes bibliographical references (leaves 159-184).

Thesis (Ph. D.)--Dept. of Agronomy and Farming Systems, The University of Adelaide, Roseworthy Campus, 1998. / Includes bibliographical references (leaves 128-146).

Thesis (M.Sc.) - Carleton University, 2007. / Includes bibliographical references (p. 130-139). Also available in electronic format on the Internet.

Bibliography: leaves 151-172.

Herbicide resistance is increasing in incidence among weed populations and poses a threat to food security. In Sunflower County, MS, a population of junglerice was identified with resistance to four herbicides, fenoxaprop-P-ethyl, imazamox, quinclorac, and propanil, each representing a different mechanism of action. The target site of fenoxaprop-P-ethyl, acetyl coenzyme A carboxylase (ACCase), was investigated. The ACCase contained none of the known resistance-conferring point mutations and an enzyme assay revealed no difference in response to increasing levels of fenoxaprop-P-ethyl between the resistant biotype and a sensitive biotype, indicating that the ACCase enzyme in the resistant biotype was sensitive to the herbicide. Whole-plant dose response assays in the presence and absence of cytochrome P450 and glutathione-S-transferase (GST) inhibitors did not increase efficacy of fenoxaprop-P-ethyl in the resistant biotype. However, when malathion, a cytochrome P450 inhibitor, was applied with imazamox or quinclorac, a reduction in resistance was observed in the resistant biotype, suggesting that a cytochrome P450 was important to the resistance mechanism for these two herbicides. RNA was isolated from the resistant and sensitive biotypes before and one hour after imazamox treatment for RNA-seq analysis. The reads from all samples were pooled to assemble the first E. colona leaf transcriptome. Differential gene expression analysis comparing untreated and treated samples for both biotypes revealed that several stress response genes were upregulated following herbicide exposure. A time course examining six of these genes showed that expression peaked between 4 and 12 hours and then dropped to untreated levels by 48 hours. Comparison of untreated resistant and sensitive plants revealed that a kinase and GST were significantly upregulated in the resistant biotype and an F-box protein was significantly downregulated. SNP analysis of cytochrome P450 sequences identified several nonsynonymous point mutations of interest including two transcripts that had premature stop codons in the sensitive but not the resistant biotype. These transcripts and their products should be the subject of future studies to determine if and how they are involved in resistance.