Survival time of Phytophthora species in peat-reduced growing media under different storage conditions
In horticulture, the ecologically urgent switch to peat-free or peat-reduced growing media is a complex and challenging issue. Substrates should not only give the optimal chemical conditions for growing plant cultures but also be safe from soil-borne pathogens. One of the most destructive group of...
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| Main Authors: | , |
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| Format: | Article |
| Language: | deu |
| Published: |
Julius Kühn-Institut
2025-08-01
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| Series: | Journal für Kulturpflanzen |
| Subjects: | |
| Online Access: | https://ojs.openagrar.de/index.php/Kulturpflanzenjournal/article/view/17802 |
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| Summary: | In horticulture, the ecologically urgent switch to peat-free or peat-reduced growing media is a complex and challenging issue. Substrates should not only give the optimal chemical conditions for growing plant cultures but also be safe from soil-borne pathogens. One of the most destructive group of pathogens is the oomycete genus of Phytophthora, which can pose significant risks to plant nurseries. Commonly, these oomycetes remain latent in substrates until the proper conditions come to infect the plants. So far, little research has been done on the survival time of this oomycete genus in potentially new culture media.
The aim of this study was to determine the survival time of Phytophthora spp. in peat-reduced substrates suitable for horticultural crops. These include combinations of coir pith, humus, compost, wood fibre, fibre nettle, digestate and peat. Four pathogenic species were selected: P. pseudocryptogea, P. lateralis, P. cactorum and P. nicotianae. These are potential pathogens of three important horticultural crops: Lawson cypress (Chamaecyparis lawsoniana), garden strawberry (Fragaria × ananassa) and Persian cyclamen (Cyclamen persicum).
The substrate mixtures were disinfected, inoculated artificially with three different isolates of one Phytophthora species and incubated under defined conditions (4 °C or 15 °C). To check the survival time, a baiting test procedure for the isolation of oomycetes with Rhododendron leaves was carried out at regular intervals in order to reisolate living and active oomycetes. Results showed a significant suppression effect from a mixture of peat and digestate (fermentation product) against P. lateralis and P. pseudocryptogea at both 4 °C and 15 °C. While different substrate mixtures had no influence on the survival time of P. nicotianae, a significantly higher survival time was exhibited at 15 °C temperature compared to 4 °C. No effects of the substrates or the temperature on P. cactorum was derived from the statistical analysis under the experiment conditions.
These results can be used to glean recommendations for the storage time of peat-reduced growing media at 4 °C or 15 °C to develop management practices on horticultural substrates at the level of nurseries or substrate manufacturers to minimize the risk of the spread of oomycetes.
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| ISSN: | 1867-0911 1867-0938 |