The agricultural use of bio-stimulants to increase crop yield is increasing as a result of the ever growing human population. Since bio-stimulants do not have the negative environmental effects usually associated with fungicides and pesticides, the identification and testing of new bio-stimulants are a priority. It was previously shown that treatment of wheat cultivar PAN 3377 with a crude Lupinus albus L. seed suspension extract increased the yield compared to an untreated control. The agricultural use of bio-stimulants to increase crop yield is increasing as a result of the ever growing human population. Since bio-stimulants do not have the negative environmental effects usually associated with fungicides and pesticides, the identification and testing of new bio-stimulants are a priority. It was previously shown that treatment of wheat cultivar PAN 3377 with a crude Lupinus albus L. seed suspension extract increased the yield compared to an untreated control. During the current study, the bio-stimulatory effect of a 60% purified extract called SS was investigated. The initial aim was to analyse the effect of the purified SS extract on yield of the wheat cultivar Thatcher+Lr34. No significant increases in yield or any of the associated parameters were obtained in response to SS treatment. This indicated that, while the crude and complex SS extract increased yield in wheat, the purified molecule was unable to do it. To validate the glass house results, proteomic analysis of SS treated wheat cultivar Thatcher+Lr34 was done. Results indicated that the purified SS extract mainly targets the photosynthetic machinery of the plant by altering three main pathways. While the levels of polypeptides active in both the Calvin cycle and electron transport chain were generally down-regulated following treatment, a few polypeptides involved in the PSII and general repair mechanisms, were up-regulated. These results were validated by qPCR analysis of three randomly selected genes from each of the mentioned pathways. When wheat cultivar Tugela was treated with the 60% pure SS extract and exposed to heat stress, a stabilising effect on chloroplast ultrastructure was observed. Thylakoid membranes were intact and no induction of the membrane stabilising gene OEE2 was observed. However, when infected with RWA, the 60% pure SS extract was unable to facilitate chloroplast membrane stabilisation. This was supported by the induced expression of both the OEE2 and HCF136 genes. This study concludes that the 60% pure SS extract, of which glycerol trilinoleate is the active ingredient, cannot be used as a bio-stimulant independently. It is proposed that during the purification of the crude SS extract, additional components responsible for increasing yield in wheat, was lost and thereby its ability to increase yield. This product could however be of value when used in combination with other compounds that is able to facilitate yield increases.

There is no abstract available for this thesis.

Venturia inaequalis (Cke.) Wint., the apple scab fungus, grows during the summer on the living leaf, producing a mycelium which develops only between the cuticle and the epidermis. But when the infected leaf dies naturally, this mycelium then grows as a saprophyte and sends its hyphae all through the tissues of the dead leaf. It is during this saprophytic part of its life cycle that the fungus passes through its sexual stage. Ascogonial hyphae arise in the mesophyll of the dead leaves and, after fertilization by antheridia from oppositely sexed thalli, initiate the perithecia. These fruiting structures then are the result of the fertilization of an ascogonium from a mycelium of one sex by an antheridium from a colony of opposite sex. The perithecia do not enlarge greatly and show little internal differentiation during the winter. As soon as snow has melted, however, the asci in the perithecia become differentiated, the perithecia enlarge rapidly and by the time the apple trees start to grow, the twocelled ascospores are formed and, if the weather is suitable, are discharged into the air, from the dead leaves on the ground. These ascospores cause primary scab infections in the orchard. The dead leaves in which apple scab is living and fruiting, are certain to harbour other saprophytic organisms. It has been a common observation that dead leaves support growth of many saprophytes. No doubt these saprophytes, in their struggle for existence, must influence [...]

Two theories have been offered to explain the wilting symptoms displayed by plants attacked with vascular invading micro-organisms. These are the bundle plugging theory and the toxin theory. According to the former the movement of water through the water conducting vessels of the stem is hindered or even prevented by the clogging of the vessels with the pathogenic bacteria or fungi and other obstruction materials such as tyloses and gums formed under the stimulation of the pathogen. The proponents of the toxin theory claim that the wilting symptoms are due to toxins formed by the invading organisms or resulting from the interaction between host and parasite. Each of these theories is supported and weakened by experimental evidences. One approach to the solution of this problem is to study the effects of the disease upon certain aspects of the physiology of the host, such as transpiration, stomatal movement and photosynthesis. Many investigators working on diseases caused by wilt organisms have measured the transpiration course of the wilting plant. The methods used for these measurements vary a great deal and are very often specially adapted to the type of plant under observation, although the weighing method seems to have been most generally adopted. Weights are recorded daily or at different intervals during the day. To obtain more accurate frequent measurements of the water uptake is not necessary.[...]

Acronecrosis, or top-necrosis, is a systemic virus disease which manifests itself in certain potato varieties following graft introduction of certain specific plant viruses. Acronecrosis is externally characterized by a necrotic spotting of the uppermost leaves followed by a dying of the plant from the top, downward, in the absence of any mottling. Necrotic areas are invariably found in the stem. These necroses, which are most severe in the distal portions of the plant, originate usually but not always, In the internal phloem and spread into the surrounding tissues. Necroses, similar in their origin and appearance to those in the stem, are found in the petioles, frequently being so severe as to lead to the death of the leaf blades. Axillary buds also become infected and are ultimately killed. In the tubers the necroses develop in the same manner as those in the stem, and spread rapidly to the storage parenchyma. Cork layers abstricting the necrotic areas are always found in affected tubers and are produced occasionally in stems grown at high temperatures. Usually the tuber necrosis spreads by way of the vascular tissues to one or more of the eyes and kills the buds, causing an irregular, sunken depression on the surface of the tuber. Often, buds of some eyes survive to produce secondary plants which soon develop necrotic spots similar to those in the parent plant. [...]

Helminthosporium sativum P.K. & B. causes a disease of barley affecting the seedlings as well as the roots, leaves and heads of mature plants. This disease results in an annual reduction in barley yield and is at least partially responsible for fluctuations in yield from year to year and for the restriction of the present barley growing area. The exact amount of loss, however, is difficult to estimate, and often is attributed to factors other than this disease. Machacek (1943) stated that the common root rot of cereals and grasses was widespread in Manitoba.

No description available.

Venturia inaequalis (Cke.) Wint., the apple s cab fungus, grows during the summer on the living leaf, producing a mycelium which develops only between the cuticle and the epidermis. But when the infected leaf dies naturally, this mycelium then grows as a saprophyte and sends its hyphae all through the tissues of the dead leaf. It is during this saprophytic part of its life cycle that the fungus passes through it s sexual stage. Ascogonial hyphae arise in the mesophyll of the dead leaves and after fertilization by antheridia from oppositely sexed thalli, initiate the perithecia.

Birdsfoot trefoil, Lotus corniculatus L., and closely related species are long-lived perennial legumes, which have a potential in agriculture for replacing clovers and alfalfas in locations which have proven to be generally unsuitable for the growth of most other legumes. However, the life of birdsfoot trefoil has been only two or three years in Quebec, instead of at least ten which is expected in the southeastern area of the United States (Drake 1958). The reduction in the life span of this plant in Quebec is generally attributed to "winter killing," but the cause of winter killing could be due to a number of factors such as: frost; Sclerotinia trifoliorum Erikss. (crown and root rot or red clover); or other factors.

In the summer of 1951, an outbreak of cabbage yellows due to Fusarium oxysporum f. conglutinans (Wr.) Snyder and Hansen) was discovered generally distributed in a large field of cabbage at St-Vincent de Paul, a few miles north-east of Montreal. So far as is known this is the first and only occurence of this disease in this region. It is a very well established disease in many parts of the United States, and in a few areas in Canada where it often causes very heavy losses.