Cultivation techniques of edible tropical mushroom,Macrocybe sp.

Abstract

The genus Macrocybe, belonging to the family Callistosporiaceae within the phylum Basidiomycota, represents a distinct group of large agaric mushrooms characterized by their exceptionally massive fruiting bodies, which commonly occur in clusters on decaying organic substrates. The name Macrocybe is derived from two Greek words “makros” (long) and “kube” (head), which denotes the remarkable size of its sporophores. To date, eight species have been reported within this genus, among which Macrocybe gigantea is the most extensively studied. It is also the most widely distributed species, particularly across the tropical and subtropical regions. Members of Macrocybe are well known for their edibility, fleshy texture, and appealing flavour, which emphasize their potential for commercial cultivation and nutritional utilisation. Hence, the present study was undertaken to standardise the techniques for in vitro culturing, spawn production, and cultivation of Macrocybe species under Kerala conditions. Mushroom samples morphologically resembling Macrocybe, were collected during the summer showers of 2024 from three distinct locations across Kerala viz., Malappuram (MAL-1), Thrissur (MEL-1), and Kottayam (KTM-1) districts. Tissue isolation was carried out on potato dextrose agar medium under aseptic conditions. A white, cottony mycelial growth was observed around the inoculated tissue after 14 days of incubation from the sample MAL-1, whereas white, fluffy growth appeared within 8 days from the sample MEL-1. However, the sample collected from Kottayam (KTM-1) failed to establish under in vitro. Molecular characterisation was performed to confirm the identity of the isolates, revealing that sample MAL-1 corresponded to Calocybe indica, while sample MEL-1 was identified as Macrocybe gigantea. The confirmed M. gigantea isolate (MEL-1) was subsequently maintained on potato sorghum dextrose agar slants at 4 ± 1°C and utilized for further experimental studies. In vitro experiments were conducted to standardise the culture medium and its components for optimizing the mycelial growth of M. gigantea under both solid and liquid conditions. Among the different media tested, potato sorghum dextrose medium supported the most vigorous mycelial growth, and sucrose was identified as the most effective carbon source. The experiments on standardisation of pH and temperature revealed pH of 5 and temperature 30 ± 2 °C to be optimum for in vitro culturing of M. gigantea. Upon standardisation of light conditions, incubation under blue light and complete darkness were found to produce maximum growth with dense mycelia. In vivo experiment was conducted to standardise suitable substrate for spawning, bedding and casing material for the cultivation of M. gigantea under Kerala conditions. Sorghum was proved to be the most effective spawn substrate among the different grains tested, showing mycelial initiation within six days and completing the spawn run in 9.67 days with thick and fluffy growth. Paddy straw was identified as the best bedding substrate, supporting the fastest crop cycle with 10.67 days for spawn run, 10 days for pinhead initiation, and 13 days for the first harvest after pinhead formation, completing a full crop cycle in 33.66 days. The sporophores produced on paddy straw were healthy and well-developed, with an average stipe length of 11.33 cm and a pileus diameter of 9.89 cm. Paddy straw also recorded the highest biological efficiency (51.95%) and the maximum benefit–cost ratio (4.08). Among the casing materials tested, vermicompost applied at 5 cm thickness proved to be the most suitable, requiring only 8.3 days for case run, 19.33 days for pinhead initiation, and 30 days for the first harvest after casing. It produced well-developed sporophores with an average stipe length of 10.7 cm and a pileus diameter of 9.7 cm, achieving the highest biological efficiency (58.86%). The proximate composition analysis of M. gigantea revealed 27.30 per cent protein, 4.15 per cent fat, 6.5 per cent carbohydrate, 2.66 per cent crude fibre, and 7.95 per cent ash on a dry weight basis, with a moisture content of 87.50 per cent on a wet weight basis. The post-harvest shelf life of fresh mushroom sporophores was found to be greatly influenced by the type of packaging material and storage conditions. At room temperature, sporophores stored in non-perforated polypropylene covers remained free from spoilage for 6.3 days, whereas those stored under refrigerated conditions in perforated polypropylene covers exhibited an extended shelf life up to 16 days. Organoleptic evaluation conducted in comparison with Agaricus sp. revealed that M. gigantea possessed superior sensory qualities in terms of colour, taste, flavour, appearance, and texture. Overall, M. gigantea emerges as a high-yielding and highly palatable species, destined to be a valuable new addition to the basket of cultivated mushrooms.