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Stott, K. and A. Broderick. 1996. Response of Australian strains of the mushroom Lepista nuda to temperature and substrate. p. 476-479. In: J. Janick (ed.), Progress in new crops. ASHS Press, Arlington, VA.

Response of Australian Strains of the Mushroom Lepista nuda to Temperature and Substrate

Karen Stott* and Andrew Broderick

  1. METHODOLOGY
    1. Isolates
    2. Temperature
    3. Substrate and Cold Shock
  2. RESULTS
    1. Isolates
    2. Temperature
    3. Substrate and Cold Shock
  3. CONCLUSION
  4. REFERENCES
  5. Table 1
  6. Table 2
Taxonomic classification of macrofungi is constantly changing as new species are discovered in North America, South Africa, and Australia. In Australia there are probably 3000 to 5000 species, most of which have not been properly described (Wood 1992). Improved techniques have enabled microscopic details to be better researched and this has resulted in changes in taxonomic classification.

The recent increase in consumption of wild mushrooms in many countries has provided the impetus to explore new sources of edible mushrooms. In addition, the wild harvesting of edible mushrooms must be curbed to ensure that the environment and ecosystems where these mushrooms grow are not destroyed. Mycologists need to explore new mushroom sources (Purkayastha and Chandra 1985) and develop cultivation techniques.

Worldwide there are 200 edible fungi of which only 25 species are widely accepted as human food and are cultivated (Hashioka and Arita 1978; Chang 1981; Pathak 1986). Fungi other than Agaricus bisporus represent about 30% of world production (Olivier 1991). The influx of migrants with a European heritage into Australia has created a demand for edible mushrooms produced locally. Amongst the gilled fungi, there are a number of edible species in the Agaricaceae, Bolbitiaceae, Lepiotaceae, and Tricholomataceae.

The fungus Lepista nuda, Tricholomataceae (syn: Tricholoma nudum, Rhodopaxillus nudus, Clitocybe nuda) is found in Europe, the Americas, and Australia. It has an international reputation as an excellent edible species and the combination of its lilac color, solid fleshy structure, good shelf life, flavor, and aroma makes the development of commercial cultivation techniques highly desirable. Developing techniques for commercial cultivation requires a detailed understanding of environmental and nutritional parameters which optimise vegetative growth and induce fruiting bodies.

The development of an appropriate substrate requires the chemical, physical, and biological conditioning of composted matter. This creates an environment selective for a particular species that is critical for fruit body production. Factors to be considered in the substrate are microbial activity, physical characteristics, pH, chemical components, aeration, water content, substrate composition, and extent of composting undergone by the substrate. Some species require the application of a casing layer of peat or soil to enhance yield and quality. Casing assists the induction of fruit bodies, but how this occurs is largely unknown. It is thought that casing provides a high water holding layer for hyphae, entraps volatiles released by compost, has a different mycoflora to the substrate, and physically supports the growing fruit body. The physical and chemical characteristics, optimal depth and number of applications for a given casing material can be different for each species. Temperature, light, O2 , CO2 , watering and care must be managed to encourage fruit body formation. Previous studies on substrate requirements of European Lepista (Vaandrager and Visscher 1981) indicate that fruit body production is enhanced by the addition of 10% uncomposted straw to commercial Agaricus compost. Guinberteau et al. (1989) and Brian et al. (1979) reported that a cold shock is essential for the formation of fruit bodies of L. nuda and temperatures of 8° to 15°C have been found to be effective. However Australian isolates (Young 1994) have been found under more variable environmental and substrate conditions than European isolates (Moser 1978, Breitenbach and Kranzlin 1991).

The objective of the present study was to provide the Australian mushroom industry with viable commercial cultivation techniques for Australian species of Lepista. This paper describes Australian forms of L. nuda isolated from the wild and examines the effect of temperature and substrate on hyphal growth and fructification.

METHODOLOGY

Isolates

Under Australian conditions Lepista appears in the wild from April to July. Isolates of Lepista were collected from various sites and voucher documentation, identification, and isolation of strains was carried out. Most isolates were confirmed as L. nuda and comparisons were undertaken with French isolates of Lepista, provided by Dr. Guinberteau of Station de Recherches sur les Champignons at Institut National de la Recherche Agronomique, France (Table 1).

Temperature

Optimum temperature for hyphal growth is a critical factor in obtaining rapid colonisation of substrate and casing. Isolates were selected from locations with different temperature and environmental characteristics to enable comparison with French isolates. Growth response of four Australian (A1, A2, A3, A4) and four French (F1, F2, F7, F8) isolates of L. nuda from warm (A1, A2, F1, F2) and cool (A2, A3, F7, F8) climates were compared at different temperatures to determine maximum and minimum temperatures for hyphal growth.

Isolates were grown on malt extract agar plus 2% yeast (MEAY) at 5°, 12°, 15°, 20°, 25° and 30°C. Radial growth of hyphae was measured on day 8 in two directions and the average taken. Data was analysed by analysis of variance.

Substrate and Cold Shock

Agaricus compost alone or suplemented with 10% uncomposted cereal straw (w/w) was inoculated with Lepista at 2%-3% w/w. Trays were sealed and placed at 25°C in a cabinet with temperature and light control. After 12 days substrate was cased with a 75% moisture content 50/50 mix of blond/dark peat. After hyphae had grown through casing, lids were loosened to allow air movement over substrate and cold shock of 12° or 15°C was applied to replicates of both substrates.

RESULTS

Isolates

The location and environment of selected isolates are shown in Table 1. Cool climate isolates (4° to 25°C during growing season) were found in leaf litter under Rhododendron, Cedrus deodara, Quercus suber or grass (Poa pratensis). Basidiocarp very robust and fleshy, lilac to lilaceous brown; pileus 75-132mm, lilaceous brown, shiny, convex to shallow convex with age; stipe 50-78 mm x 25-33 mm.

Warm climate isolates (8° to 35°C during growing season) were found in Kikuyu (Pennisetum) and Couch (Cynodon dactylon) grass in groups or rings. Basidiocarp strong lilac to lilaceous brown; pileus 30-75 mm, strong lilac, shallow convex with umbo at all stages; stipe 65 mm, bright lilac to deep lilac or lilaceous brown.

Temperature

The optimum temperature for Australian isolates was found to be higher than for French isolates as was the minimum growth temperature. The growth rate of Australian isolates is more than double the rate of French isolates at all temperatures except 5°C (Table 2).

Substrate and Cold Shock

The addition of 10% uncomposted cereal straw encouraged hyphal growth, but discouraged the initiation of fruiting bodies and was not beneficial to Australian isolates. A cold shock of 12°C encouraged more hyphal aggregations than 15°C. No fruit bodies were produced.

CONCLUSION

Australian isolates differ from overseas isolates morphologically in shape, form, and size. They are found at different temperatures and in different environments than European species. Whether they are new species or varieties resulting from the Australian environment and habitat has yet to be determined.

The response of Australian isolates to temperature indicates that these isolates have the capacity to colonise substrate more rapidly than French isolates. This would be advantageous to commercial growers as cropping time could be reduced.

The addition of 10% uncomposted straw to Agaricus compost had no beneficial effect on the initiation of fruit bodies. Whether it would effect quality or yield is unknown and further research into this area is recommended.

Information from this study can provide the basis for the development of viable commercial cultivation techniques for the exotic mushroom industry in Australia. The differences in cultivation requirements and growth rates of Australian and French strains indicates that a shorter production cycle than is currently achieved with French isolates will be possible.

REFERENCES

*Thanks to the Rural Industries Research and Development Corporation for scholarship funding; INRA-Bordeaux for cultures; N.G. Nair and R. Tolson for supervision.
Table 1. Location and environment of Lepista isolates at time of fruiting.

Country Strain Location Environment
Australia A1, A4 New South Wales Warmz
A2, A3 New South Wales Cooly
France F1 Landes Warmx
F2 Gironde Warmx
F7 Pyrenees Coolw
F8 Haute Alps Coolw
zMaximum temperature 24°C, minimum temperature 8°C
yMaximum temperature 20°C, minimum temperature 4°C
xAverage day temperature 14°C
wAverage day temperature 11°C

Table 2. Response of Australian and French Lepista isolates temperature.

Isolate Maximum radial
growth (mm2)z		 Optimal
temperature (°C)
A1 32.6 25-30
A2 25.7 25
A3 24.7 30
A4 24.7 25
F1 12.7 22-25
F2 14.0 24
F7 13.0 22-24
F8 12.0 24-25
zAustralian isolates almost double hyphal growth of French isolates.

Last update June 24, 1997 aw