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 [...]
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.123815 |
| Date | January 1949 |
| Creators | Cinq-Mars, Lionel, 1919-1973. |
| Contributors | Coulson, G. (Supervisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science. (Department of Plant Pathology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 000592966, Theses scanned by McGill Library. |
Page generated in 0.002 seconds