Phytophthora verrucosa in Association With Toe Rot of Tomatoes

Munro, Mary C. D (1944) Phytophthora verrucosa in Association With Toe Rot of Tomatoes. PhD thesis, University of Glasgow.

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1. The symptoms of Toe Rot of Tomato roots have been detailed and a description of P. verrucosa given. 2. Reproductive structures, on which the identify of the fungus depends, were produced very irregularly . 3. Repeated attempts to derive a pure culture of the fungus from roots plated on a variety of media met with no success. Other Phycomy-cetous fungi of a vegetative nature were present in sufficient quantity to confuse the issue. 4. An attempt was made to isolate P. verrucosa from oospores which had been subjected to various pretreatments before germination. Initial vegetative hyphae were produced on a few occasions, but subsequent growth could not be sustained. 5. Information was obtained regarding the mode of germination of oospores of this species. Germination may take place in a "direct" method, producing branching hyphae, or "indirectly" with the formation of vesicles and the release of zoospores from these. 6. Toe Rot symptoms have been produced by plant- ing in diseased soil, but oogonia to confirm the presence of P. verrucosa were frequently lacking. P. verrucosa was induced artificially, however, by immersing the roots of seedlings for 6 days in water in which oogonia had borne vesicles and these had become evacuated. Oogonia were found on these seedlings 16 days after immersion. 7. As oogonia of P. verrucosa were not invariably present as evidence of infection by that fungus, a record was made of other fungal flora recurring on Toe Rot plants. None of these appear in themselves to be sufficiently actively parasitic to act as Pathogen. P. verrucosa is therefore still regarded as the primary cause. The Toe Rot symptoms may be produced by the fungus in a vegetative state, unidentifiable, in the absence of oogonia, as P. verrucosa. 8. Control experiments were set up. Owing to the sporadic nature of the infection in untreated sections, no true basis for comparison was available. A fuller understanding of the conditions favouring attack is necessary before satisfactory control measures can be planned.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Plant sciences, Plant pathology
Date of Award: 1944
Depositing User: Enlighten Team
Unique ID: glathesis:1944-79609
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 04 Mar 2020 16:39
Last Modified: 04 Mar 2020 16:39

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