The morphology, physiology and pathology of two isolates are described. The first in Part I is called 'India' having come from a banana plant in Madras, and E is compared with V.theobromae isolates and V.dahliae. The second isolate described in Part II is called 4655. It was thought to be a V.albo-atrum with peculiar brown spores measuring 15P in diameter - these were discovered to be Acanthamoebae polyphaga cysts. This isolate is investigated with and without its contaminant and compared with V.albo-atrum. 'India' and the V.theobromae isolates were all seen to produce microsclerotia, resting hyphae and colourless chlamydospores. Large hyphal cells were also seen. 'Melanised' excrescences on the resting hyphae and conidiophores of 'India' were an outstanding feature on Dox's agar, and all the V.theobromae isolates produced them to a lesser extent. 'India's' optimum temperature for growth was 25°C but it and V.th.8 still grew at 35° C. Its optimum pit was c7.3. 'India' was the only isolate to change Amended Dox's Agar from more acid to alkaline. Plate coverage was maximal on 5% maltose, but all additions of maltose gave the best results. Additions of sucrose, maltose and glycerine were only slightly inferior in their results. With different nitrogen sources plate coverage was best on media containing 0.1% asparagine, 0.1% peptone and 1% sodium nitrate plus 0.1% calcium carbonate. Little growth took place with 1% sodium nitrate plus 1% calcium carbonate and in general poor results were obtained with ammonium nitrate. 'India' was pathogenic to tomato and sunflower plants being reisolated from both hosts. It was decided from all the results obtained that 'India' was an isolate of V.theobromae which was confirmed by the C.M.I.4E5 was morphologically very similar to V.albo-atrum except that it produced more colourless chlamydospores and more excrescences on resting hyphae and conidiophores. It also produced a small collarette when a conidium was abstricted. Large hyphal cells were again seen, and in all cultures narrow colourless hyphae with 'melanin' spots inside occurred. In cultures with altered nitrogen content conidia with 'melanin' spots were found. Both physiologically and pathologically 4E5 behaved very much like V.albo-atrum_ except that it was a more virulent fungus so is accepted as a V.a-a isolate. Appendix 1 is included in order to suggest a means of eradicating mites. Appendix 2 deals with the extremely common presence of aerial resting structures - seen on every isolate examined.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:636147 |
| Date | January 1981 |
| Creators | Bremner, E. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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