Abstract:The Ceratocystis paradoxa complex accommodates a group of fungal pathogens that have become specialized to infect mostly monocotyledonous plants. Four species currently are recognized in this group, including C. paradoxa, which has a widespread distribution and broad host range. In this study, multigene phylogenetic analyses involving sequences of the ITS, b-tubulin and TEF-1a gene loci, in combination with phenotypic and mating studies, were used to characterize purported C. paradoxa isolates from Cameroon and to compare them with isolates from elsewhere, including protologs and type specimens of known species. We show that the C. paradoxa complex comprises substantially greater species diversity than previously recognized. One new species in this group is described from Cameroon as Ceratocystis cerberus, while C. paradoxa sensu stricto (s. str.) and four other species are redefined. Lectotypes are designated for C. ethacetica and Endoconidium fragrans (synonym of C. ethacetica), while epitypes are designated for C. paradoxa s. str., C. ethacetica and C. musarum. A neotype is designated for Catenularia echinata (synonym of C. ethacetica) and two species, previously treated in Thielaviopsis, are transferred to Ceratocystis.

Cacao trees are affected by diseases that attack either their vegetative parts, their fruits or both. In cacao pod diseases, several factors are involved in disease susceptibility, such as the fruiting cycle, fruit size, age, position on the tree and cacao genotype. To gain a clearer understanding of how these characteristics influence cacao pod diseases, four models describing pod growth in several cacao genotypes were evaluated. Three models used to estimate pod volume or surface area were also compared. Observed pod growth was of a sigmoid form and fitted best to the Richards model, well to the Logistic and Beta growth models, and least to the Gompertz model. Pod volume and probably pod surface area were best estimated using a prolate spheroid model. Pod growth models can help improve pod disease management and thereby cacao production. They can help to predict yield, as well as provide information for the timing and frequency of control operations. Information on pod size, surface area and susceptibility will help to improve dose transfer and spray deposit studies intended to optimise control efficiency. (Résumé d'auteur

The emergence of wattle wilt disease on non-native Acacia mearnsii trees in Africa, caused by the indigenous fungus Ceratocystis albifundus, has highlighted a need to better understand the diversity, ecology and distribution of Ceratocystis species in natural African environments. In this study we applied phylogenetic inference to identify and characterize isolates of Ceratocystis collected in a natural savanna ecosystem in South Africa. Three new species were recognized and are described as C. cryptoformis sp.nov. in the C. moniliformis complex, as well as C. thulamelensis sp. nov. and C. zambeziensis sp. nov., both residing in the C. fimbriata complex. Incorporating the new species into global phylogenies of Ceratocystis provided insights into the patterns of evolution and biogeography of this group of fungi. Notably, the African continent was identified as an important centre of diversification of Ceratocystis spp., from which several lineages of these fungi were shown to have radiated.

No abstract

Caution should thus be exercised when using the ITS gene region as a barcoding marker for Ceratocystis species in this clade. This study also represents the first record of a species of Ceratocystis from Cunninghamia.