Two Coelomycete genera, Ascochytula Died. and Ascochytella Tassi, were studied in order to determine their generic affinities, especially with Ascochyta. Ascochytula obiones (Jaap) Died., the type species of Ascochytula, is considered to be congeneric with Ascochyta pisi Lib., the type species of the earlier genus, Ascochyta Lib. Ascochytula is thus reduced to synonymy with Ascochyta. Of the thirty-six species and two varieties named in, or directly associated with, Ascochytula, twenty are herein described as species of Ascochyta and four are excluded from Ascochyta. The remaining species were either not examined, or are nomina dubia. The following names are proposed: Ascochyta asparagina (Petrak) comb. nov., A. deformis (P. Karsten) comb. nov., A. dorycnii (Petrak) comb. nov., A. ludwigiana (Petrak) comb. nov., A. moravica (Petrak) comb. nov., A. obiones (Jaap) comb. nov., A. phlomidicola nom. nov., and A. ulicis (Grove) comb. nov. Ascochytella Tassi, which has often been confused with Ascochytula, is also synonymised with Ascochyta. The original thirteen species in Ascochytella were examined, and A. vicina (Sacc.) Tassi chosen as the lecto-type species. Most of the thirteen species are regarded as being either misplaced in Ascochytella, or nomina dubia, and only four, including the lectotype, are accepted as species of Ascochyta. The name, Placodiplodia canthiifolia (Cooke & Massee) comb. nov. is proposed. The type species of Ascochyta, and of six related genera, Ascochytulina Petrak, Coniothyrium Corda. Diplodina Westend., Pseudodiplodia (P. Karsten) Sacc., Scolecosporiella Petrak, and Stagonospora (Sacc.) Sacc. were studied to determine the distinctions between these six genera and Ascochyta. Microdiplodia Allescher and Diplodia Fr. are also discussed, in relationt to Ascochyta. Ascochyta paspali (H. Sydow) Punith. (≡ Ascochytula paspali H. Sydow), which causes a leaf stripe disease of Paspalum dilatatum Poir., an important perennial grass of northern North Island pastures, was examined in detail. At some temperatures, under controlled climate conditions, the fungus significantly reduced the yield of P. dilatatum. A. paspali was found to grow systemically, as mycelium within the xylem vessels, and was able to infect all parts of the plant, including the roots and seeds. Green leaves sometimes became infected systemically without production of visual symptoms. Infected seed is suggested as a means for disease spread. No teleomorph for A. paspali was found, and the fungus is thought to over-winter in the dormant grass. The seasonal fluctuation in levels of P. dilatatum and of the disease was studied in two Northland pastures with paspalum as a component. One pasture was studied for fourteen months, and the other for four months. Disease levels, and paspalum levels, were determined by point quadrat analysis and by sorting of randomly cut samples. Levels of both the host and of the disease peaked in summer, while both were at low levels, or apparently absent, over the winter months.
| Identifer | oai:union.ndltd.org:ADTP/276988 |
| Date | January 1982 |
| Creators | Buchanan, Peter Kenneth |
| Publisher | ResearchSpace@Auckland |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated., http://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm, Copyright: The author |
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