A Synoptic Key and Evaluation of Species in theAspergillus FlavusGroup

Abstract

Listen

Translate article

SUMMARY A synoptic key for identification of 16 taxa in the Aspergillus flavus group is presented. The key uses definitive and readily observable features: vesicle size, color of conidial heads, conidiophore and conidium features, growth at 37 C, and form and size of sclerotia. Brief descriptions are included as an aid to identification. The author's interpretation of relatedness among species, based upon morphological and cultural data and involving an ordination using coefficients of similarity, is compared to results from chemotaxonomic studies by other workers. A distributional and ecological analysis has been based upon examination of species lists in nearly 100 surveys. Aspergillus leporis, A. avenaceus, A. sojae, A. subolivaceus, and A. zonatus, in particular, are interpreted as morphologically and ecologically distinct species. Aspergillus flavus, A. oryzae, and A. parasiticus are in part domesticated species with broad and overlapping morphologies. Aspergillus toxicarius appears to be a biseriate form of A. parasiticus, and A. kambarensis probably belongs with A. oryzae. Additional isolates of Aspergillus leporis States & Christensen (65) from cool desert soils in Wyoming, southern Utah and northern Arizona, and isolation of a closely related taxon, also tightly columnar but with elongate, cream to russet sclerotia, stimulated a comparative study of species in the A. flavus group. The distinctive strain, 0 168, is a variant of A. leporis and is mentioned again in the brief description of that species. Aspergillus leporis is distinguished from A. flavus Link in the key and in the descriptions; it is not a synonym of A. flavus as has been suggested (59). The key was written with the intention of providing a practical guide to identification of species in the A. flavus group. Evaluations of synoptic keys and suggestions regarding their use can be found elsewhere (18, 39). The A. flavus group as described by Raper and Fennell (54) contained nine species. Since 1965, five species and four varieties have been newly described (6, 41, 48, 59, 65, 67), A. sojae Sakaguchi & Yamada, listed as a probable synonym of A. parasiticus Speare by Raper and Fennell, has been elevated to species status again (48), and A. corolligenus (Massee) Subram. and A. insecticola Subram., originally described in 1910 and 1879, respectively, have been transferred to Aspergillus, A. flavus group, from Sterigmatocystis Cramer (66). 1056