New host range and distribution of Ceratocystis pirilliformis in South Africa

Abstract

Ceratocystis pirilliformis was first described from wounds on Eucalyptus trees in Australia and subsequently found as a common wound inhabitant on these trees in South Africa. During a recent disease survey carried out to identify Ceratocystis species infecting tree wounds in South Africa, C. pirilliformis was isolated from various tree species, including a native Rapanea species and two non-native hosts, Acacia mearnsii and E. grandis growing in the Western Cape Province. These new collections from the Western Cape Province, together with isolates of C. pirilliformis previously collected from Eucalyptus species in the eastern part of the country, provided the opportunity to investigate the possible movement of the pathogen since it was first recorded in South Africa. The identity of newly collected isolates of C. pirilliformis was confirmed using DNA sequence comparisons using partial β-tubulin and TEF-1α gene regions. Microsatellite markers were screened on a collection of C. pirilliformis isolates from the Western Cape Province. Results showed that this population has higher levels of population genetic estimates such as private allele frequency, allelic richness, and gene diversity. Inoculation tests were performed to determine whether C. pirilliformis is a pathogen of A. mearnsii, which is planted as an important plantation forestry tree in the country. All isolates were shown to be highly virulent. Results of the study consequently revealed that C. pirilliformis has a wider host range and geographic distribution in South Africa than previously recognized and that it is a potentially important pathogen of A. mearnsii.