Thesis (M. Phil.)--University of Hong Kong, 1987.

Thesis (Ph. D.)--University of Wisconsin-Madison, 1974. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 135-140).

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Attempts were made to explore the possibility of haploid plant production in oats (Avena sativa L.) through in vitro techniques. For anther culture, among 89 entries, only four cultivars, namely, Cayuse, Manod, Stout and Tarpan, produced calluses. Serial sections of the callusing anthers revealed the pollen origin of these calluses. Genotypic differences in anther response in oats were confirmed. Aborted multicellular structures were observed in the pollen sacs of 12 cultivars/strains. Further improvement of the medium is necessary to ensure the continual development of initiated pollen grains to plantlet formation. Cultivar differences in the frequency of non-stained (NS) grains were observed. Cold pre-treatment did not increase the frequency of NS or abnormal bi-nucleate grains. The possible effect of cold pre-treatment is to delay anther deterioration, which ensures the survival of more grains to switch into embryogenesis. / For ovary and panicle culture, no callus formation was obtained. The potential of the latter approach is discussed.

Agronomic, genetic and environmental influences on oat grain quality were investigated. Nitrogen application at the boot stage of crop development did not generally affect physical characteristics of oat grain. Groat protein content increased with the application of nitrogen at the boot stage of crop development but oil content tended to decrease while $ beta$-glucan content was generally not affected. Delayed seeding usually reduced oat grain quality and usually increased protein and $ beta$-glucan contents. Heritability of $ beta$-glucan content, groat percentage and rust resistance were all low; hence, breeding to improve these traits may be difficult. Results of experiments on the inheritance of $ beta$-glucan were not conclusive but it appears that $ beta$-glucan content is under the influence of the endosperm genome. Genotype by environment interactions were significant for grain yield and for protein, oil and $ beta$-glucan contents. The cultivars Ultima and Sylva were superior in mean grain yield across environments compared to other cultivars. The cultivars Laurent and Nova were superior for mean protein content across environments and the cultivar Marion QC was superior for mean oil and $ beta$-glucan contents. AMMI (Additive main effects and multiplicative interaction) analysis would be favoured over the other genotype by environment analyses used in this study because AMMI afforded more information about the genotype by environment interactions.

Effects of environmental conditions and the fatuoid character on the naked trait in oat were investigated. Each of three genotypes responded differently to 2,4-D and 2,4-D increased hull content in some genotypes. In field experiments, there was usually a higher hull content in samples grown in a cool year than in a warmer year, but in growth cabinets, there was no consistent response to temperature treatments. Groats of hulled grains were smaller than groats of naked grains. Among field grown samples there was an association between the proportion by weight of hull tissue in grain and the frequency of hulled grains. With gentle threshing in one of two crosses, the naked versus hulled character fit a 3:1 ratio, i.e., 3 plants with naked grain or both hulled and naked grain:1 plant with only hulled grain. With vigorous threshing the 3:1 ratio did not fit in either cross. The awned character of the fatuoid condition displayed monogenic inheritance according to a codominant-gene model where the expression of the heterozygote was variable. Expression of the fatuoid character was more variable for F2:3 families derived from naked F2 plants than for F2:3 families derived from hulled F2 plants. F2 and F2:3 plants with two or more awns per spikelet produced higher proportions of naked grain than F2 plants with fewer than two awns per spikelet. In most immature florets of fatuoid plants a row of small cells at the articulation zone was observed. This row of small cells acts as an abscission layer in grains of hulled-grained fatuoid plants but not in grains of naked-grained fatuoid plants.