New host associations and a novel species for the gall-inducing acacia rust genus Ravenelia in South Africa

Abstract

Trees in the genusVachellia(previouslyAcacia) are commonly infected by the gall-inducing rustsRaveneliamacowanianaandR.evansii. Rust galls bearing aecial infections and relating uredinial and telial infections on the leaves of nineVachelliaspecies not previously recorded to be infected byRaveneliaspp. have recently been collected in South Africa. The rust fungi causing these infections were characterised using molecular phylogenetic analyses of DNA sequence data of the LSU and ITS rDNA regions as well as morphological examinations. The host range ofR.macowanianaandR.evansiiwas thus re-assessed and extended from four to nine species and from one to three species, respectively. Application of Principal Component Analyses (PCA) of telial morphological characters provided evidence of an effect of the host species on the teliospore morphology inR.evansii, but only minor effects inR.macowaniana. A novel gall-inducingRaveneliasp. closely related toR.macowaniana, was found onVachelliaxanthophloeaand it is described here asR.xanthophloeae.