Taxonomy, phylogeny and identification of Botryosphaeriaceae associated with pome and stone fruit trees in South Africa and other regions of the world

Abstract

Species of Botryosphaeria are well-recognized pathogens of pome and stone fruit trees. The taxonomy of these fungi, however, has been confused in the past. Recent taxonomic changes to the Botryosphaeriaceae further influence the literature pertaining to these fungi. This study reviews the taxonomic status of Botryosphaeriaceae associated with fruit tree diseases, identifies them in South Africa and elsewhere, and develops a reliable identification technique for them. Comparisons were made using DNA sequence data from the nuclear ITS rRNA operon and anamorph morphology. These analyses distinguished six clades amongst isolates associated with fruit tree diseases, corresponding to Neofusicoccum ribis (= B. ribis), N. parvum (= B. parva), N. australe (= B. australis), B. dothidea, Diplodia mutila (= B. stevensii) and ‘Botryosphaeria’ obtusa (the genus Botryosphaeria is no longer available for the fungus known as B. obtusa, but a new name has not been proposed yet). Isolates from fruit trees in South Africa were grouped in the N. australe and ‘Botryosphaeria’ obtusa clades. This is the first report of N. australe from fruit trees. PCR-RFLP analysis using the restriction endonucleases CfoI and HaeIII distinguished the major clades. However, two groups of closely related species, N. ribis and N. parvum, and N. australe and N. luteum (= B. lutea), had identical RFLP profiles. Using RFLP, it was shown that ‘Botryosphaeria’ obtusa is the dominant species on fruit trees in the Western Cape Province of South Africa. These results and methods will be useful in future epidemiological studies and disease management of Botryosphaeriaceae from fruit trees.