Search

Eucalyptus spp. in plantations are negatively affected by canker and wilt diseases caused by several species of Ceratocystis , particularly those in the Latin American Clade (LAC). Ceratocystis eucalypticola and Ceratocystis manginecans are of particular concern where disease epidemics are reported globally, with recent outbreaks emerging in South African and Indonesian Eucalyptus plantations. Consequently, a rapid screening protocol is required for these pathogens. In this study, a high-resolution melting curve analysis (HRMA) was developed to detect C. eucalypticola and C. manginecans that bypasses time-consuming isolation and post-PCR procedures. Primers targeting a 172 bp region of the cerato-platanin (CP) gene were designed. Using these primers, the accuracy of HRMA to detect and distinguish between these two LAC species was assessed using pure fungal DNA, and DNA extracted directly from Eucalyptus samples naturally infected with C. eucalypticola. The assay accurately detected the presence of C. eucalypticola and C. manginecans and quantifies their DNA, both from cultures, and directly from wood samples. HRMA further differentiated these two species from all other tested LAC individuals. This assay was also able to detect the presence of all the tested LAC species and distinguish seven of these, including C. fimbriata, to species level. Ceratocystis polyconidia was the only non-LAC off-target species detected. Based on these results, the developed assay can be used to rapidly identify C. eucalypticola and C. manginecans directly from infected plant material or fungal cultures, with the potential to also screen for several other LAC species. • Rapid diagnostic assay to detect and differentiate C. eucalypticola and C. manginecans in the form of a qPCR-HRMA assay. • The assay can identify C. eucalypticola and C. manginecans from fungal cultures or directly from infected plant material. • The assay shows the potential to be used for other species in the LAC. [ABSTRACT FROM AUTHOR]

The African fungal tree pathogen, Ceratocystis albifundus, undergoes uni-directional mating type switching, giving rise to either self-fertile or self-sterile progeny. Self-sterile isolates lack the MAT1-2-1 gene and have reduced fitness such as slower growth and reduced pathogenicity, relative to self-fertile isolates. While it has been hypothesized that there is a 1:1 ratio of self-fertile to self-sterile ascospore progeny in relatives of C. albifundus , some studies have reported a significant bias in this ratio. This could be due to the fact that either fewer self-sterile ascospores are produced or that self-sterile ascospores have low viability. We quantified the percentage of self-sterile and self-fertile ascospores from ascospore masses in C. albifundus using real-time PCR. Primers were designed to distinguish between spores that contained the MAT1-2-1 gene and those where this gene had been deleted. A significant bias towards the self-fertile mating type was observed in all single ascospore masses taken from sexual structures produced in haploid-selfed cultures. The same result was observed from a disease outbreak situation in an intensively managed field of cultivated native trees, and this was coupled with very low population diversity in the pathogen. This was in contrast to the results obtained from ascospore masses taken from the crosses performed under laboratory conditions or ascomata on native trees in a non-disease situation, where either self-fertile or self-sterile ascospores were dominant. The results suggest that reproductive strategies play a significant role in the infection biology and genetic structure of C. albifundus populations. [ABSTRACT FROM AUTHOR]

Ceratocystis tsitsikammensis was first isolated from bark harvesting wounds on two indigenous tree species in the Afromontane forests of the Western Cape Province of South Africa. Inoculation studies indicated that it is a potential pathogen of native Rapanea melanophloeos trees. In this study, we investigated the distribution, ecology and biology of C. tsitsikammensis in the Garden Route National Park of South Africa. Isolates were obtained from wounds on R. melanophloeos, three non-native hosts as well as from nitidulid and staphylinid beetles visiting wounds on these trees. The genetic diversity and population biology of the fungus was examined using microsatellite markers. Its mating strategy was also determined by amplifying its mating type genes and the fungus was shown to be homothallic. Despite the homothallic nature of the fungus, high levels of random mating and absence of genetic structure was found in the investigated population, suggesting a strong effect of gene flow, probably linked to insect dispersal. The gene diversity of C. tsitsikammensis was similar to that of a related fungus, Ceratocystis albifundus , that is known to be native in Africa. This, together with the fact that C. tsitiskamensis is not known elsewhere, within or outside South Africa, suggests that it is native and endemic to the Cape Afromontane region. [ABSTRACT FROM AUTHOR]

Little is known about the biology of the monotypic genus Cornuvesica ( Microascales ), apart from that isolates are notoriously difficult to culture on artificial media. A recent collection of material resembling this genus from freshly made wounds on Gmelina arborea in Indonesia, provided an opportunity to reconsider all available material of Cornuvesica falcata , type species of the genus. In addition to morphological comparisons, multigene phylogenetic analyses were made using sequences of the SSU, ITS, LSU and TEF-1α genes. Our results showed that the holotype of Cor. falcata from pine in Canada differed from all other material previously considered to represent this species and also from the new Indonesian collections. The collections considered represented three additional species that we describe here as new. Three New Zealand isolates and an isolate from UK were respectively described as Cor. acuminata and Cor. crypta , while the Indonesian isolates were described as Cor. magnispora . Phylogenies based on the SSU and LSU data sets showed that Cornuvesica spp. do not belong in the Ceratocystidaceae as previously suggested, but represent a distinct lineage in the Microascales that has yet to be named. Results showed that culture filtrates from other fungi or ferric chloride markedly stimulated the growth of Cor. magnispora . [ABSTRACT FROM AUTHOR]