First Report of Wilt of Eucalyptus Caused by Ceratocystis fimbriata in China

Diseases Severity, Genetic Variation, and Pathogenicity of Ceratocystis Wilt on Lansium domesticum in South Sumatra, Indonesia

Ceratocystis wilt disease has caused significant mortality in duku (Lansium domesticum) since 2014 and has now spread to all districts in South Sumatra, Indonesia. Recently, 16 isolates from duku representing populations from various districts in South Sumatra were isolated. Analysis for the morphological characteristic of the isolate showed that the population has a uniform morphology. Genetic analysis based on internal transcribed spacer (ITS) and β-tubulin sequences verified that the population has being dominated by the ITS5 haplotype of Ceratocystis fimbriata and a new ITS group, the ITS7b haplotype that was localized in Musi Banyuasin. Both haplotypes were highly pathogenic to duku. Inoculation tests on various forest and agroforestry plant hosts showed that both haplotypes were highly pathogenic to Acacia mangium, moderately pathogenic to Acacia carsicarpa, Eucalyptus urophylla, and Melaleuca cajuputi, but weakly pathogenic to Dyera costulata, Hevea brasiliensis, and Alstonia scholaris. Therefore, this pathogen becomes a serious threat to Indonesia's biodiversity due to its ability to infect forest and agroforestry plants, especially the indigenous ones.

Genetic Bottlenecks for Two Populations of Ceratocystis fimbriata on Sweet Potato and Pomegranate in China

Chinese isolates of Ceratocystis fimbriata from sweet potato (Ipomoea batatas) and pomegranate (Punica granatum) were genetically compared with a worldwide collection of isolates from a variety of hosts. Isolates from black-rotted storage roots of sweet potato in China, Japan, Australasia, and the United States had identical internal transcribed spacer (ITS) ribosomal DNA (rDNA) sequences and only minor variation in microsatellite alleles. Sequences of their mating type genes were most similar to those of isolates from various hosts in Ecuador, a center of diversity for sweet potato. Isolates from Colocasia esculenta (taro) and pomegranate from Yunnan and Sichuan had only one ITS rDNA sequence (haplotype ITS5). This haplotype, sequences of mating type genes, and microsatellite alleles linked these isolates to isolates from Eucalyptus stumps in South China and diseased Eucalyptus trees in Brazil, supporting the hypothesis that the pomegranate population originated from Brazil via cuttings of Eucalyptus. Isolates from sweet potato and pomegranate in China were interfertile with tester strains of C. fimbriata, confirming that the causes of the two epidemics in China belong to a single biological species. However, other isolates from Eucalyptus stumps were intersterile with the tester strains and had ITS rDNA sequences typical of the Asian species, C. cercfabiensis.