This thesis describes the investigation of the bioactivity of triterpenoids, limonoids and spiro-triterpenoids, isolated from the order of the Rutales. The focus of this research has been towards the development of botanical insecticides with non-neurotoxic modes of action in insects. It follows the recent development of Neem (Azadirachta indica, Meliaceae) as a botanical insecticide containing a limonoid azadirachtin as its main active compound. Because so few Meliaceae members have been examined for insecticidal activity the project was initiated by the screening of over sixty ethanol extracts of various parts of twenty species (collected from Costa Rica and the Tropical Museum in Miami, Florida) for bioactivity against the European corn borer (Ostrinia nubilalis) and the Variegated cutworm (Peridroma saucia). The data suggest that a majority of the extracts studied inhibited growth significantly; some are more active than neem leaf extracts. Swietenia mahogani bark, Trichilia glabra bark, T. hirta leaves, T. americana bark, T. trifolia wood, T. pleana and Azadirachta indica wood showed potent activity against the cutworm. Ruptiliocarpon caracolito bark, Cedrela odorata leaves, Aphanamixis polystachys wood, T. glabra wood and T. pleana bark showed good activity against the corn borer larvae. Bioassay guided fractionation of the most active crude extract, the bark of Ruptiliocarpon caracolito, has resulted in the isolation of six very novel spiro-CD-triterpenoids, the spirocaracolitones. The spirocaracolitones, at 100 ppm, were screened for antifungal activity against Fusarium using a hyphal growth bioassay. After 48 h a high degree of inhibition of growth (59-79%) was observed. These novel triterpenoids exhibited no antimalarial activity when screened against Plasmodium falciparum. A study of the effects of these compounds, incorporated into artificial diet, on the neonate life cycle of the European corn borer was conducted. All the spirocaracolitones effected the growth and the development of the insects but spirocaracolitone B and spirocaracolitone C were substancially more active than the other spirocaracolitones. Two postulates dealing with the biosynthesis of these unique spiro-compounds are also presented. Both commence with a friedelin derivative because canophyllol was isolated in large quantities from the hexane extract. They envisage generation of a carbocation at C12 followed by migration of the C23 methyl group this results in the formation of a carbocation at C13. The spirosystem results from migration of the C8-C14 bond. An investigation of the structure/activity relationships of gedunin was conducted to determine the moieties responsible for its antimalarial and/or antifeedant properties. Ten derivatives of gedunin were prepared (1,2-dihydrogedunin, 1,2-epoxygedunin, 1,2-dihydro-3$\beta$-gedunol, 3$\beta$-acetoxy-1,2-dihydrogedunin, 7-deacetylgedunin, 7-ketogdunin, hexahydrogedunin, tetrahydrogedunin, 21-acetylgedunin, 23-acetylgedunin) along with five other limonoids (limonin, epilimonol, nomilin, obacunone, hirtin) closely related to gedunin were evaluated for antifeedant activity (Ostrinia nubilalis) and antimalarial activity (Plasmodium falciparum). Evaluation of these compounds for antimalarial activity presented no increase in activity however it was clearly determined that alterations to the enone in ring A and at C7 of gedunin resulted in large losses of activity. Evaluation of the effects of these limonoids on the neonate life cycle of the European corn borer at 5 and 50 ppm incorporation into the artificial diet did lot produced dramatic effects on the growth and development of the larvae. At these concentrations structure/activity relationships could not be proposed.$\sp*$ ftn$\sp*$Please refer to the dissertation for diagrams.

The purpose of this research is to describe and analyze the present and potential role of non-governmental organizations (NGO's) in the management of agricultural soil erosion and associated water quality decline (ASEWQ), in Ontario. A series of five tasks are associated with this research purpose. These tasks include: the cataloguing of all agricultural NGO's in Ontario; the assessment of this NGO population's vertical interaction; the assessment of the NGO population's horizontal spread; analysis of NGO mobilization potential in the area of ASEWQ management; and finally the characterization of degree of NGO favourability towards, and involvement in, ASEWQ management. Research has led to the discovery of a very large and complex population of agricultural organizations in Ontario. The horizontal distribution of this population closely reflects the geographic configuration of agricultural activity in the province. The vertical distribution reveals a high degree of organizational affiliation and networking which gives the grassroots indirect access to provincial policy influence. Despite the size, complexity and general favourability of this population towards soil conservation, few NGO's have suitable potential to mobilize on the ASEWQ issue. As a result, only a few strategically placed and organized NGO's have any involvement in controlling agricultural soil erosion. In conclusion, this research offers a series of recommendations to provincial government agricultural policy makers and future research avenues. (Abstract shortened by UMI.)

The effect of vernalization on seedling growth of spring wheat, Triticum vulgare (var. Rideau) has been studied by observing morphological and biochemical changes in the first three leaves. Leaf length, dry weight and total protein measurements indicated that vernalization accelerated all stages of leaf development although the maximum leaf size was unaffected. The composition of the alcohol amino acid pool varied with leaf ontogeny in both untreated and vernalized plants. The most pronounced effect of vernalization was to depress the relative content of arginine which was one of the major pool constituents in untreated leaves. The concentrations of other important amino acids, gamma-aminobutyric acid and glutamic acid varied with the physiological age of the leaf, and vernalization did not alter this relationship. The activity of the enzyme glutamic decarboxylase was also mainly dependent on the physiological leaf age. Vernalization caused a great increase in meristematic activity of the root tip.

Changes in protein content, amino acid, fatty acid and phosphate metabolism were followed in the morphologically distinct parts and whole grains of Marquis (spring) and Rideau (winter) wheats during imbibition'and vernalisation. Vernalisation had a negligible effect on the protein content of the grains of either wheats. However, large increases in the total alcohol soluble amino acid and amide fractions were observed in the grain parts (embryo-scutellum and endosperm) of vernalised wheats. The percentage distribution varied both between grain parts and between spring and winter wheats. The duration of the imbibition period prior to vernalisation was another important variant. Despite these variations, the embryo fractions of both wheats consistently contained larger amounts of nine amino acids following vernalisation. After vernalisation the ratio of acidic to total basic amino acids decreased in the grain parts. Three methods of computing the amino acid data were used in all cases; namely, per protein content, dry weight or grain part. Whereas the general trends outlined were consistent throughout, differences in the magnitude of change were observed to be dependent upon the base from which the data were calculated. With regard to fatty acid composition, it was observed that vernalisation increased the degree of unsaturation in the plumule, radicle and scutellum of Marquis grains (largely as a result of the increased proportions of oleic and linoleic acids), while under the same conditions the degree of unsaturation in these three grain parts of Rideau grains were decreased (largely as a result of a decrease in the proportion of linoleic acid). The major fatty acid components of the Marquis endosperm and all the grain parts of Rideau wheat were oleic and linoleic acids. The proportions of these acids did not change with vernalisation in the endosperm of either variety. Only traces of linoleic acid were noted before and after vernalisation in all the grain parts of both varieties except in the plumules of the partially and fully vernalised Marquis wheat. 32P-orthophosphate taken up by both varieites during imbibition was incorporated largely into water-soluble organic phosphates and this incorporation continued during vernalisation. Chilling accelerated the uptake of 32P into the total nucleic acids of the grain parts and whole grains of Rideau wheat, relative to the uptake of 32P into the nucleic acids of the controls. Incorporation of 32P into the total nucleic acids of Marquis whole grains was low and varied only slightly during vernalisation. The 32P incorporated into the phospholipids of the various Rideau and Marquis grain parts was concentrated in the "lysophos - phatidic acid" and lecithin components. In all the Rideau grain parts, the uptake of 32P into lecithin increased with vernalisation; simultaneously, the incorporation of 32P into the "lysophosphatidic acid" component decreased. The 32P incorporation data suggest that the scutellum of both varieties act as a "sink" for the phosphate metabolites from the other grain parts. From the results obtained in these studies, a hypothesis has been suggested to account for the mode of action of vernalisation in winter wheat grains.

Sequential changes in the alcohol soluble amino acid and carbohydrate fractions of vernalized and control root tips of Triticum aestivum var. Marquis (spring) and Rideau (winter) wheats have been followed. Substantial changes in these fractions could be related to developmental changes in the root tip. Vernalization superimposed additional, consistent changes mainly in the content of the amino acids asparagine, glutamine, glycine, and glutamic acid, and of the sugars fructose and sucrose. Incorporation studies using 14C glutamic acid and aspartic acid served to emphasize the distinct metabolic differences between the mitotic and elongating regions of the root tips. In the mitotic region, the highest incorporation of label was in the protein fraction, whereas in the elongating region, the highest activity was recovered in the free amino acid pool. Two enzyme systems, namely amylase and glutamic acid-alanine transaminase were also studied. The possibility of using the uptake of 51Cr as an indicator of metabolic change in wheat root tips, as it is in animal tissues, was also examined. A consistent Patttern of 51Cr incorporation was observed in the serial Sections of both wheat varieties. The changed metabolic state attendant on vernalization was reflected by a higher level of 51Cr incorporation. Histochemical studies of sulphtydryl group distribution along the wheat root tip were also carried out in order to determine whether there exists a relationship between sulphydryl groups and the pattern of 51Cr uptake. No such correlation could be established. The effect of the water content of the grain during vernalization which is known to affect the subsequent root growth, was also examined. Incomplete imbibition led to a lessened metabolic response to the cold treatment.

Abstract not available. *This research was aided by a grant from the National Research Council of Canada (A-735).

Development of maize, Zea mays L., germplasm resistant to the European corn borer, Ostrinia nubilalis (Hubner) and Fusarium fungal pests has been in progress for more than three decades as a worldwide cooperative effort. Some of the host plant resistance to the European corn borer and Fusarium has been attributed to the phytochemical product 6-methoxybenzoxazolinone. However, it has been shown that seasonal weather impacts concurrently on maize development, corn borer and Fusarium phenology. It was hypothesized that some of the maize resistance to both pests depended directly on climatological conditions. In the United States, genotype selection for first generation borer resistance is achieved during June infestations using leaf feeding assessment. In Canada, first selection began at the silk stage of plant development in July. The second genotype selection is conducted at grain harvest in October by plant dissections. The larval population, number of tunnels and tunnel length in the first 30 cm of the stalk above the soil surface were used to differentiate genotype susceptibility to corn borers. Grain moisture was directly correlated with genotype resistance to corn borer. Fungi encountered comprised Fusarium moniliforme, F. graminearum, F. sporotrichioides, F. oxysporum, F. avenaceum, and F. equiseti. Two species, F. moniliforme and F. equiseti, were recovered throughout the season. These fungi were first recovered from pollen caught in the leaf collar sheath. As the leaf sheath of maize is relaxed with plant development, the Fusarium contaminated soil and the pollen run down past the ligule by wind, rain splash, and insect movement to settle within the sheath cavity. Undamage pith samples (by the borer) taken at grain harvest showed sporadic tissue contamination by Fusarium. Oppositely, as the corn borer larvae migrated downward on the plant, they drilled the collar sheath, the stalk rind and dug galleries in the stalk to feed on the pith tissue to complete their development. Consequently, the larvae and borer tunnels were repeatedly contaminated with Fusarium. It was shown that pith tissues were initially colonized by primary fungi such as F. equiseti which initiate pith breakdown; then these fungi were overgrown by more competitive species such as F. moniliforme or F. sporotrichioides. Correlation of the stalk rot incidence to genotype maturity and the stalk rot incidence to grain moisture were both negative and significant; indicating that physiological activity during October protected the stalk against fungi infection. It was hypothesized that genotype maturity based on the heat unit rating (given by companies) or grain moisture at harvest (indicator of genotype maturity) were the two common factors related to Fusarium stalk rot resistance. (Abstract shortened by UMI.)

The purpose of this thesis was to study the potential factors involved in mycorrhizae-assisted drought tolerance in maize (Zea mays L.). We hypothesized that the AM colonization promotes drought tolerance of the host plant. This may be as a consequence of altered water relations, metabolism or nutritional status of the host plant. These changes enable the host plant to sustain water deficit conditions and recover more rapidly when irrigation is restored. To test these hypotheses, the five objectives were: (i) To measure the physiological responses in maize plants in the absence or presence of AM colonization; (ii) To examine the metabolic changes in these plants; (iii) To determine the host plant nutritional status in order to assess the ability of AM plants to support kernel development; (iv) To evaluate the drought recovery of maize and (v) To examine the effects of AM colonization on nitrogen assimilation in maize as a potential factor in drought tolerance. The AM colonization in maize had a beneficial effect on the water relations and leaf enlargement under water deficit conditions. In comparison to non-AM plants, the AM colonized plants maintained higher (less negative) leaf water potential (LWP) and lower stomatal resistance even after 3 wks of withholding water at the tasselling stage. Mycorrhizal colonization improved the nutritional status of maize through the enhanced uptake of N, P and other micronutrients. This indirectly helps the AM plants to utilize the soil available moisture more effectively. Our data indicated that the total N content in drought-stressed maize plants were nearly doubled in the presence of AM association. The overall results support the hypothesis that the AM colonization assists the two tropical maize cultivars to withstand under moderate drought conditions. The drought tolerance was achieved due to the physiological, metabolic and nutritional modifications in the host plant. These changes can be primarily related to the improved host plant water relations and the nutritional status, especially N and P. This thesis has provided new insights into the changes in N acquisition and assimilation of mycorrhizal plants under drought conditions. The findings of this thesis support the idea that AM fungi are one of the major biological components in the rhizosphere needed to accomplish the goal of sustainable agriculture in arid and semiarid areas. (Abstract shortened by UMI.)

Four subspecies of Fragaria chiloensis defined on a geographic basis have been proposed, but never supported with quantitative data; ssp. lucida and ssp. pacifica from North America, ssp. chiloensis from South America and ssp. sandwicensis from the Hawaiian Islands. The objective of the present research was to develop a classification that was both operational and an accurate portrayal of genetic relationships in order to achieve efficient protection and utilization of germplasm in crop improvement. Discriminant analysis based on 14 measurements in 95 herbaruim specimens revealed a distinct separation of ssp. sandwicensis: longer leaflets, longer hairs on the undersurface of the leaflets and more numerous leaflet veins. The South and North American plants were significantly different but overlapped to a degree, the former having 6-10 petals, instead of 5-6 (rarely 7). The two North American subspecies overlapped extensively with the only morphological distinction being hair type. DNA was removed from fresh leaf tissue of 54 plants and analysed using random amplified polymorphic DNA (RAPDs). From 100 primers screened, 12 were selected providing 68 scorable polymorphic bands. The phenogram (corphenetic correlation, $r = 0.97)$ based on UPGMA clustering of Jaccard's coefficients revealed a clear division between North and South American plants but only partial separation between the two North American subspecies. It is proposed that the two North American subspecies be reduced to the rank of forma. The resulting taxonomic change creates Fragaria chiloensis (L.) Duchesne ssp. lucida (E. Vilm) f. lucida and f. pacifica (Staudt) Catling & Porebski. Ssp. lucida and ssp. sandwicensis provide a valuable source of novel genes for incorporation into the crop. (Abstract shortened by UMI.)

No description available.