A Morphological and physiological study of the Genus Termitomyces Heim in South Africa

Abstract

Eight different species of the genus Termitomyces Heim were collected in the Republic of South Africa viz. : (i) T. umkowaani (Cooke & Mass.) Reid (ii) T. reticulatus v. d. Westh. & Eicker sp. nov. (iii) T. sagittaeformis (Kalchbr. & Cooke) Reid (iv) T. clypeatus Heim (v) T. microcarpus (Berk. & Br.) Heim (vi) T. schimperi (Pat.) Heim (vii) T. striatus (Beeli) Heim and (viii) sporodochial mycelium from the combs of Macrotermes natalensis Hav. and Odontotermes badius Hav. The basidiocarp morphology of all the species was described and cultural studies were conducted on six species. Macroscopic characters of cultures differed markedly between species but microscopic characters appear to be very similar. Microscopic characters of the pileal surface, basidiospores and cystidia coupled with the velar remains on the pileus proved to \. be reliable taxonomic criteria for the identification of species in this genus. Microscopic characters of sporodochia from the combs of M. natalensis and 0. badius displayed some small but conspicuous differences and may indicate that microscopic characters of the anamorph of Termitomyces where it grows on the comb, is not completely identical according to presently held views. With the exception of T. microcaus all the species in pure culture produced conidiophores and holoarthric conidia similar to those of comb sporodochia and indicate an intimate relation between the anamorph and teleomorph of this genus. Whether cultures are prepared from fruit body context or comb sporodochia, the anamorph will always develop in culture and microscopic characters will be very similar. Conidia from comb sporodochia or cultures germinated readily in vitro but basidiospores did not. A new species of Termitomyces, Treticu1atus, was described from South Africa. The association of this species with 0. badius and 0. transvaalensis, T. umkowaani with 0. badius and T. sagittaeformis with 0. 1atericius are new records. Micro and microscopical characters of T. mi crocarpus cultures and fruit bodies differed greatly from other species in the subgenus Eutermitomyces. It is therefore suggested that this species should be placed in the genus Podabre11a Singer. The influence of three environmental factors on mycelium growth was assessed. Optimal mycelium growth was observed in the pH range 5 to 7, in the temperature range 20 °c to 30 °c and under completely dark incubation conditions. Natural cellulose fibres supported maximal mycelium growth of all the species. Hemicellulose (xylan), starch, casein, natural and synthetic lipids and pectic substrates were degraded as well and was coupled with secretion of the relevant exoenzymes into the culture media. Mycelium growth was possible on a wide range of carbon sources with the exception of certain amino sugars, sugar alcohols, dicarboxylic acids and uronic acids. Several nitrogen sources were utilized e.g. complex amino acid mixtures and inorganic ammonium sources supported good mycelium growth. The ability of T. umkowaani mycelium to grow on natural substrates was investigated. Excellent growth was supported by a mixture of wheat, sorghum, sawdust and digestive bran. Growth remained vegetative and no fruit body formation occurred. The biological value of mycelium protein grown on a defined medium was assessed for three species and was compared with that of Agaricusbisporus. The essential amino acid contents of T. sagittaeformis and T. umkowaani compared favourably with that of A. bisporus and a standard reference protein, whereas the biological value of T. reticulatus protein appeared to be of a mediocre to poor quality. Mycelium protein of both T. sagittaeformis and T. umkowaani exceeded the essential amino acid requirements of adults.