Globose Conidia Research Articles

Basidiocarp Formation by Laccaria laccata in Agar Culture

Many Basidiomycetes have been known to be inhabitants of both fields and woodland soils, but the direct isolation from soils of these fungi that fruit on common mycological media has been infrequently reported. Goos (1960) reported the formation of fruiting bodies in culture by four Basidiomycetes that were isolated from soil. They were Pholiota marginata (Fr.) Quel., Irpex lacteus (Fr.) Fr., Schizophyllum commune Fr. and Pellicularia sp. In exploring the microflora of Maryland soils, we obtained a single isolate which produces well-formed fertile basidiocarps in agar culture. It was identified as Laccaria laccata (Scop. ex Fr.) Berk. & Broome according to Singer (1967) and Singer and Moser ( 1965). Since the production of fruiting bodies on agar media is a significant contribution toward study of the nutritional requirements, morphogenesis and genetics of this fungus, it is reported herein. A garden soil sample was collected in College Park, Maryland, in August 1972. The sample was taken to the laboratory and heat-treated for 30 min at 65 C. A dilution plate series was set up using lactose-peptone agar and the plates were incubated at 24 C. After several weeks a stromalike structure was formed in one plate and it was transferred to a rabbit food agar plate. Mature basidiocarps were later observed on inoculation blocks transferred from the rabbit food agar plate to the same medium in flasks and incubated in diurnal alternation of darkness and light at room temperature. The isolate is able to grow on a variety of common mycological media. Mycelial growth took place over a range of 10-45 C with the optimum of 26-37 C. An unidentified conidial state was found in the cultures grown on all the agar media tested. This imperfect state appears to be holoblastic, with hyaline unicellular conidia borne singly or in clusters on multiple random to multiple synchronous conidiogenous cells (FIG. 1). The globose conidia were formed and germinated at 20-45 C. They measured 8-11 im in diam. A clamp connection was observed at the first septum of the germ tube emerging from germinating conidia, and subsequently at most septa of the mycelium ( FIG. 2). Basidiospores of L. laccata have never germinated on laboratory media (Fries, 1966; Stack et al., 1975). Our 211

Culture studies on Hypocrea and Trichoderma I. Comparison of perfect and imperfect states of H. gelatinosa, H. rufa and Hypocrea sp. 1

Perithecial stromata of three species of Hypocrea are described and illustrated. H. gelatinosa and H. rufa are distinguishable on stromal characters and in type of conidiophore. H. gelatinosa forms conidiophores of the Gliocladium type, whilst H. rufa forms rough globose conidia which have been matched with type material of Trichoderma viride . A third species of Hypocrea is described with large pink stromata having conidia which are ellipsoidal and smooth and smaller than those of H. rufa .

Tabulation of Alternaria and Macrosporium

Incomplete descriptions, mutations, secondary development of spores, dwarfing of spores in culture, and facultative parasitism resulting in large host ranges have caused great confusion. in the classification of the species of Alternaria and Macrosporium. This tabulation was compiled to make possible the classifica? tion of the species of these fungi used in inoculations (Young, 33). The species in the table are arranged on the basis of minimum spore lengths. The columns of family names and translated generic names serve as a convenient index to the plants bearing these fungi. Monographic work of sufficient completeness, including pathological and physiological studies, will probably reduce to synon? ymy many specific names of Alternaria and Macrosporium. Alternaria tenuis Nees and Macrosporium commune Rabh. are difficult to separate. Elliott (10) placed the species of Alternaria in seven main morphological groups, and said that echinulation is not a constant character. He and Young (33) demonstrated the wide host ranges of these fungi in the laboratory and the greenhouse. Elliott clearly showed that the generic name Macrosporium should be abandoned because all the species of Macrosporium belong in Alternaria or Stemphylium because they have catenulate, sarcinaeform, or globose conidia. There is a laudable tendency to follow his emended description of Alternaria. Macrosporium is used here only because so many species were described under this name.