G.C.A. van der Westhuizen

Morphology and taxonomy of South African isolates of Colletotrichum.

South African isolates of Colletotrichum Corda were examined in culture and on host material. The following eleven species are recognized: C. acutatum, C. coccodes, C. crassipes, C. dematium, C. destructivum, C. gloeosporioides, C. graminicola, C. lindemuthianum, C. musae, C. orbiculare and C. trifolii. A key for their identification is supplied. The taxonomic and nomenclatorial history of these species is discussed and their culture characteristics and morphology are fully described and illustrated. Culture characteristics are regarded as good taxonomic criteria while conidiophore structure and conidium development together with seta development and structure are regarded as less useful discriminatory characters. Appressorium dimensions and shape could be used to characterize only one species. Percurrent proliferation of some conidiogenous cells was observed in several species.

Species of Termitomyces occurring in South Africa

Seven species of Termitomyces were identified — T. clypeatus, T. microcarpus, T. sagittiformis, T. schimperi, T. striatus, T. umkowaani and T. reticulatus sp. nov. The wood-destroying termite Odontotermes badius was found to be the most commonly associated termite species. Termitomyces sagittiformis was associated with Odontotermes latericius, a new record. The morphologies of the Termitomyces spp. are described and illustrated and their occurrence, distribution and termite associations are discussed.

Some Fungal Symbionts of Ectotrophic Mycorrhizae of Pines in South Africa

SYNOPSIS Earlier research of mycorrhiza of pines in South Africa is reviewed. Twenty-one species of Basidiomycetes which are considered to be obligate symbionts of mycorrhizae of pines, were found in four major pine-growing areas of South Africa. These include 10 Agaricales, seven Boletaceae, three Gasteromycetes and Thelephora terrestris. The largest number of symbionts were found in the south-western Cape Province and the largest number of Amanita spp. were seen in the eastern Transvaal where no Russula spp. occurred. Two species, Amanita excelsa and Russula caerulea, are recorded from South Africa for the first time. Five more species, known to be mycorrhizal symbionts and previously recorded in South Africa, were not found during this survey. An important mycorrhizal symbiont, Pisolithus tinctorius, was never found under pines. The species recorded are well-known in the mycoflora of south-western Europe. The implications of their association with the pines of North and Central American origin which ar...

A DISEASE OF YOUNG EUCALYPTUS SALIGNA IN NORTHERN TRANSVAAL

SUMMARY A DISEASE of the bark of young E. saligna trees in plantations in the north-eastern Transvaal is described. A list of fungi isolated from affected parts is included. Cytospora eucalypticola van der West, was most frequently isolated from die diseased bark. It is concluded that severe drought conditions predisposed the young trees to attack by this fungus.

CYSTOSPORA EUCALYPTICOLA SP. NOV. ON EUCALYPTUS SALIGNA FROM NORTHERN TRANSVAAL

SUMMARY Cytospora eucalypticola sp. nov., a fungus associated with a disease of Eucalyptus saligna, is described. Its relationship to other species of Cytospora on Eucalyptus is discussed.

SOME ASPECTS OF THE BIOLOGY OF DIPLODIA PINEA IN RELATION TO ITS CONTROL BY FUNGICIDES

SUMMARY Studies of the rates of mycelial growth and spore germination at different temperatures as well as the sensitivity to fungicides of Diplodia pinea were undertaken to investigate the possibility of controlling its invasion of haildamaged pine trees by aerial spraying or dusting with fungicides. Pycnospores were found to be capable of rapid germination and mycelium of rapid growth over a wide range of temperatures. Maneb and cycloheximide were found to inhibit mycelial growth on potato-dextrose agar at one-eighth of the concentration, or less, of copper-based fungicides. Weather conditions and other considerations may, however, result in postponement of application of the fungicides so that cycloheximide may prove to be the only fungicide of any practical value. Further investigation of the use of cycloheximide against D. pinea is, however, required.

A new section and two new species of Podaxis (Gasteromycetes) from South Africa

Podaxis africana De Villiers, Eicker & van der Westhuizen and P. rugospora De Villiers, Eicker & van der Westhuizen, two new species from Transvaal are described and illustrated. A new section, Umbricorticalis De Villiers, Eicker & van der Westhuizen is proposed in the genus Podaxis to accommodate P. africana. Morphologically P. africana resembles P. microporus McKnight but it is distinguished by its large globose, subglobose to broadly ovoid spores, the absence of a ‘pin prick’ pore structure, the black gleba, and the deep orange to strong brown inner cortex of the stipe. P. rugospora is allied to P. pistillaris (L. ex Pers.) Fr. emend. Morse from which it differs by reason of the hyaline, narrow, flattened, occasionally septate capillitium threads and the grayish-olive, light olive or light to moderate yellowish-brown gleba. The most remarkable character of these new species is the rugose spores.

The morphology and cultural characters of Pisolithus tinctorius (Gasteromycetes) in South Africa

Sporocarp morphology as well as surface ornamentation of the basidiospores of South African collections of Pisolithus tinctorius agree in respect of those of specimens from Australia. Cultural characters and micromorphology of isolates made from certain of these collections correspond with those of P. tinctorius cultures obtained from sporocarps of strains forming mycorrhizal associations with pines in France and the U.S.A. It is concluded that only strains of the fungus which are unable to form mycorrhizas with pines occur in South Africa.

A synoptic key to South African isolates of Colletotrichum

A synoptic key to the following species of Colletotrichum is presented: C. acutatum Simmonds, C. coccodes (Wallr.) Hughes, C. crassipes (Speg.) Arx, C. dematium (Pers. ex Fr.) Grove, C. destructivum O’Gara, C. gloeosporioides (Penz.) Penz. & Sacc., C. graminicola (Ces.) Wilson. C. lindemuthianum (Sacc. & Magn.) Br. & Cav., C. musae (Berk. & Curt.) Arx, C. orbiculare (Berk. & Mont.) Arx and C. trifolii Bain & Essary. The key is based on morphology and culture characteristics of South African isolates. Descriptions and illustrations of the species together with a dichotomous key have already been published.

The ‘Omajowa’ or ‘Termitenpilz’, Termitomyces sp. (Agaricales) of Namibia

The ‘Omajowa’ or ‘Termitenpilz’ which grows in groups around the bases of tall termite mounds, is illustrated and described. It is identified as Termitomyces schimperi (Pat.) Heim. Available evidence indicates that Macrotermes michaelseni (Sjostedt) is the associated termite, an association previously unrecorded. The biology and distribution of T. schimperiin Namibia are discussed.