Comparison of Sphaeropsis sapinea and Sphaeropsis sapinea f. sp. cupressi

Abstract

Seven isolates of Sphaeropsis sapinea , and three of a fungus reported to represent a physiological form of S. sapinea , i.e. S. sapinea f. sp. cupressi , were compared on the basis of various morphological and cultural criteria. All isolates lacked conidiophores and conidia were generally produced through holoblastic ontogeny and percurrent proliferation. Conidial lengths of S. sapinea were significantly ( P = 0·001) longer than those of S. sapinea f. sp. cupressi but widths did not differ significantly. All isolates of S. sapinea grew significantly faster ( P = 0·01) than any single isolate of S. sapinea f. sp. cupressi on 5 of 6 culture media and at 10, 20, 25 and 30°C. Sphaeropsis sapinea, S. sapinea f. sp. cupressi and three closely related taxa, namely Lasiodiplodia theobromae, Diplodia mutila , and Botryosphaeria dothidea were compared using isozyme analysis. Of the 16 alleles that occurred in S. sapinea f. sp. cupressi , 3 were unique to this taxon. With the exception of Amy (160) and Gpi (107), which occurred only in S. sapinea and S. sapinea f. sp. cupressi , 11 other alleles common to these two taxa were also common with 1, or more, of the remaining 3 taxa. Cluster analysis of the genetic distances between the five taxa revealed that S. sapinea was more closely related to D. mutila than to S. sapinea f. sp. cupressi . The results of this study, therefore, provide substantial evidence for the lack of a close relationship between S. sapinea f. sp. cupressi and S. sapinea .