Sclerotinia sclerotiorum is a widespread plant pathogen that produces structures known as sclerotia. When sclerotia germinate they give rise to infective hyphae, myceliogenic germination, or they produce ascocarps, carpogenic germination. Biological control has usually targeted sclerotia or ascospores. The main objectives of the research presented herein were to observe the effect of a mycoparasite and fungus gnats (Bradysia coprophila) on the survival of sclerotia in vitro and in field conditions, and to study the enzymatic activity of the mycoparasite when in contact with sclerotia damaged by fungus gnats. / In this research several mycoparasites were evaluated for their efficacy to degrade sclerotia in soil. From these tests, an isolate of Trichoderma hamatum, TMCS 3 proved to be the most effective. Larvae of fungus gnats have also been reported to feed on sclerotia. When both organisms were combined in laboratory tests, fewer sclerotia survived than when the organisms acted alone. Sclerotia recovered from this treatment contained fewer viable cells when compared to sclerotia recovered from treatments with TMCS 3 or fungus gnats alone. The results obtained from field trials showed that TMCS 3 was effective at degrading sclerotia. Unfortunately environmental conditions were not always optimal for the establishment of high populations of fungus gnats. Few larvae were observed feeding on sclerotia and no significant differences were found among treatments. / Growth of TMCS 3 was studied using different carbon sources as substrates, including sclerotia of S. sclerotiorum. Biomass obtained from this latter treatment was significantly larger than on the other carbon sources tested. Enzymatic activity was also induced by the presence of sclerotia. In many cases, sclerotial exudates from mechanically damaged sclerotia or sclerotia damaged by larval feeding showed that the concentration of amino acids, carbohydrates, and electrolytes was increased as damage to the sclerotia has increased. Exudation of protein was not different when damaged and undamaged sclerotia were compared. Exudates from sclerotia with the melanized rind completely removed by fungus gnats feeding accelerated the germination of conidia of TMCS 3. These heavily damaged sclerotia also enhanced the growth of TMCS 3 when both organisms were grown together. However enzymatic (i.e. glucanase and chitinase) activity of TMCS 3 was not increased by the damage to the sclerotia. When damaged sclerotia were buried in soil infested with TMCS 3 they were degraded faster when the medulla of sclerotia was completely uncovered by larval feeding.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.28762 |
| Date | January 1994 |
| Creators | Gracia, Javier |
| Contributors | Paulitz, T. C. (advisor) |
| 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 | Doctor of Philosophy (Department of Plant Science.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001462976, proquestno: NN05713, Theses scanned by UMI/ProQuest. |
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