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Postharvest decay of stone fruit : infection and latency of Botrytis cinerea
Dissertation (PhDAgric) -- University of Stellenbosch, 1992.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2012
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| _version_ | 1867613781228519424 |
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| access_status_str | Open Access |
| author | Fourie, Johannes Frederick |
| author2 | Holz, G. |
| author_browse | Fourie, Johannes Frederick Holz, G. |
| author_facet | Holz, G. Fourie, Johannes Frederick |
| author_sort | Fourie, Johannes Frederick |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Dissertation (PhDAgric) -- University of Stellenbosch, 1992. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/69743 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:41:35.993Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2012 |
| publishDateRange | 2012 |
| publishDateSort | 2012 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/69743 Postharvest decay of stone fruit : infection and latency of Botrytis cinerea Fourie, Johannes Frederick Holz, G. Stellenbosch University. Faculty of AgriSciences. Dept. of Plant Pathology. Stone fruit -- Diseases and pests Botrytis cinerea Dissertations -- Plant pathology Dissertation (PhDAgric) -- University of Stellenbosch, 1992. Grey mould, caused by Botrytis cinerea Pers.: Fr., is one of the major postharvest diseases of plums and nectarines in South Africa. Infection and colonization of these fruit by B. cinerea, and the possible role of latent infection in postharvest decay, was investigated in a number of trials over a 6-year period. No relationship was found between postharvest decay and blossom infection. This was ascribed to the fungus's inability to colonize either the ovary or the calyx base. However, under moist conditions, B. cinerea infected stamens, petals and the upper part of styles to cause blossom blight. This suggested that flower infection might contribute indirectly to fruit decay by supplying secondary inoculum for the infection of different stone fruit types as their fruit ripen. Light and electron microscope studies showed that conidia germinated readily on both immature and mature fruit. The pathogen penetrated the cuticle by means of a very thin infection peg formed from the inner appressorium wall. The marginal alteration of the cuticle around the infection peg indicated only restricted cutinase activity. This mode of penetration differed from that of B. cinerea in other fruit, where the infection peg was covered by the plasma membrane and the enzymatic degradation of the cuticle was more pronounced. Passage through the cuticle was severely hampered in green plum and nectarine fruit. During the resistant phase, the penetration peg grew for various distances into the cuticle but did not reach the epidermis. Although the pathogen also entered lenticels and the stomatal chamber of immature fruit, further growth in the fruit tissue was not observed. Histological studies indicated that hyphae confined to the stomata and lenticels of green fruit may be killed by resistant reactions. Resistance to infection diminished as the fruit ripened, and picking ripe fruit was rapidly invaded by the pathogen, causing tissue breakdown. Plums remained more resistant than nectarines, which decayed rapidly. Gas chromatographic determinations of sugars in fruit exudates showed that the shift in susceptibility coincided with an increase in sugar, especially that of sucrose, and that the structural resistance, provided by the cuticle of immature fruit, could be nullified by the addition of sugar and pollen exudates to the inoculum. The study further showed that injuries made near the picking-ripe stage or during harvesting and handling were the most important means by which this pathogen entered plum and nectarine fruit. Experiments with fruit under conditions simulating export showed that free moisture formed within minutes on fruit during loading. However, the subsequent rapid drop in temperature inhibited further germination and germ tube elongation. Conidia were not killed on the fruit surface at -0.5°C. After the rise in temperature from -0.5 to 7.5°C (after 5 days for plums and 21 days for nectarines), free moisture remained on the surface of the fruit for 65 hours, thus facilitating infection. Inoculum present on fruit during the period of ripening will therefore play an important role in postharvest decay and growers should concentrate on cultural practices which reduce or eliminate wounding, and which reduce the initial inoculum on picking-ripe fruit. Doctoral 2012-08-27T12:27:14Z 2012-08-27T12:27:14Z 1992 Thesis http://hdl.handle.net/10019.1/69743 en Stellenbosch University 75 pages : ill. application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Stone fruit -- Diseases and pests Botrytis cinerea Dissertations -- Plant pathology Fourie, Johannes Frederick Postharvest decay of stone fruit : infection and latency of Botrytis cinerea |
| title | Postharvest decay of stone fruit : infection and latency of Botrytis cinerea |
| title_full | Postharvest decay of stone fruit : infection and latency of Botrytis cinerea |
| title_fullStr | Postharvest decay of stone fruit : infection and latency of Botrytis cinerea |
| title_full_unstemmed | Postharvest decay of stone fruit : infection and latency of Botrytis cinerea |
| title_short | Postharvest decay of stone fruit : infection and latency of Botrytis cinerea |
| title_sort | postharvest decay of stone fruit infection and latency of botrytis cinerea |
| topic | Stone fruit -- Diseases and pests Botrytis cinerea Dissertations -- Plant pathology |
| url | http://hdl.handle.net/10019.1/69743 |
| work_keys_str_mv | AT fouriejohannesfrederick postharvestdecayofstonefruitinfectionandlatencyofbotrytiscinerea |