Termitomyces species of central and northern Kerala

Abstract

Termitophilous fungi, commonly known as termite mushrooms, are monophyletic group of gilled mushrooms which belong to the genus Termitomyces of the family, Lyophyllaceae under Basidiomycota. These mushrooms are native to tropical and subtropical regions of Africa and South-east Asia and exist exclusively in symbiosis with termites of the sub-family Macrotermitinae in their natural habitats. The warm humid tropical climate along with the diverse soil types of Kerala, support the luxuriant growth of various termite mushroom species throughout the monsoon season. Although several research on this mushroom have been conducted, many of them concentrated mainly on the morphological characters and proximate analysis of the available species. In light of this, the current study, entitled “Termitomyces species of Central and Northern Kerala” was undertaken to document the habitat, distribution, and species diversity of termite mushrooms across Central and Northern Kerala and to compare the nutritive value of different edible species. A purposive sampling survey was conducted across the Central and Northern regions of Kerala, including the districts of Thrissur (AEU 02, 06, 10), Kasaragod (AEU 07, 11), and Wayanad (AEU 20, 21), to collect the fresh basidiocarps of Termitomyces species during the North-East and South-West monsoon seasons (October 2023 - October 2024). Among the seven AEUs selected, 10 locations were surveyed, and 28 samples were collected and subjected to morphological and molecular characterization. Out of the 28 Termitomyces samples collected, 20 samples were from Thrissur district, six from Wayanad district and two samples were obtained from Kasaragod district. Of the collected samples, T. microcarpus (T1, T2, T8, T20, W5, W6, K1, K2), was the most widely distributed species which typically appeared in groups of 15 - 60 fruiting bodies under mixed vegetation. The next most prevalent species were T. srilankensis (T13, T14, T15, W4), appeared as solitary fruiting body and T. heimii (T18) observed in groups of 6 to 70 sporocarps in humus-rich soils of Thrissur district over a continuous three-week period in the month of September 2024. The sample, W6 collected from Wayanad district was found to appear periodically in the same location thrice in the surveyed period.

Based on morphological characteristics of the pileus, perforatorium, stipe, annulus and pseudorhiza, nine species were identified to species level, which include T. eurrhizus, T. srilankensis, T. fuliginosus, T. microcarpus, T. heimii, T. striatus, T. schimperi, T. clypeatus, and T. robustus. The macroscopic observations such as size of the pileus (diameter) in observed samples of Termitomyces varied from 0.7 cm (T. microcarpus) to 15.4 cm (T. srilankensis) and colour varied between white, light brown to dark brown. The perforatorium was varied in its shape from umbonate, conical to spiny form with the colour variation from light brown to dark brown. The lamellae were adnate to adnexed and freely arranged (T. microcarpus), to compact arrangement in all the other species and its colour varied from yellowish (T. microcarpus) to light brown and whitish. The stipe colour varied from whitish to greyish or brown, depending on the species and measured 1.8-3.8 cm in length and 0.2-0.3 cm in diameter in T. microcarpus, whereas larger species like T. eurrhizus, T. srilankensis, T. fuliginosus, T. heimii, T.schimperi, T. clypeatus, T. striatus, and T. robustus showed stipe size of 14.5- 15.2 cm x 2.3-10.6 cm. Annulus was present only in T. schimperi and T. heimii. Pseudorhiza was observed in all the species with varying size and nature but was absent in T.microcarpus. The micro-morphological characters like, size and shape of basidia, pleurocystidia and cheilocystidia, along with basidiospores and type of pileipellis layer were studied. Among the 28 samples, six samples had cutis form of pileipellis layer, 20 samples with ixocutis form, and two samples showed ixotrichodermium form. The shape of the basidia varied from clavate, fusiform to elongated, and measured between 17-24 μm x 4-8 μm. Basidiospores were ellipsoid, double walled of size 5-7.9 μm x 4-7.4 μm, and were hyaline in nature. The pleurocystidia showed clavate to pyriform shape, withthin wall and hyaline appearance, measuring 6.13-48.61 x 4.81-23.49 μm in size. The cheilocystidia, measured between 12.5-51.82 x 8.76-30.31 μm in size, and were clavate to elongated, thin walled and hyaline. Among the 28 samples, 10 were selected for molecular characterization based on their prevalence and prominence in distribution across the selected locations. The fungal genomic DNA was isolated, sequenced and in silico analysis with BLASTn output resulted in the identification of samples as T. eurrhizus (T12, W3), T.

srilankensis (T13, T14, T15, W4), T. fuliginosus (T17), T. heimii (T18), T. microcrpus (W5), and Termitomyces spp. BAB 5063 (W1). A study was conducted to estimate the different nutritional parameters like carbohydrate, protein, crude fibre, Vitamin C, moisture percentage and ash content by adopting standard protocols. The carbohydrate content of Termitomyces spp. ranged between 31.2 to 46.9 g/100g on dry weight basis and recorded the maximum content of 46.9 g/100g in T. microcarpus. The protein content varied between 14.4 to 19.5 g/100g on dry weight basis with the highest amount of 19.5 g/100g in T. fuliginosus. The crude fibre content showed variation between 6.6 to 16.6 per cent, where, T. eurrhizus exhibited maximum per cent of crude fibre content of 16.6 per cent. The Vitamin C content ranged between 26.40 to 36.01 mg/100g with highest quantity in T. eurrhizus (36.01 mg/100g). Estimated moisture content of Termitomyces spp. was between 87.14 to 93.15 per cent, where T. srilankensis recorded the maximum amount of 93.15 per cent. Ash content of the samples ranged between 7.78 to 15.4 per cent, with T. fuliginosus recording maximum value of 15.4 per cent. The study documented the distribution of 28 Termitomyces species across diverse habitats in Central and Northern Kerala. Among these, T. microcarpus emerged as the most abundant species, with significant collections from Thrissur, Wayanad, and Kasaragod districts. The studied edible mushroom is nutritionally rich, containing substantial amounts of carbohydrates, proteins, crude fibre, vitamin C, ash, and moisture percentage in its sporocarps.