An expanded concept of Ceratocystis manginecans and five new species in the Latin American clade of Ceratocystis.

The genus Ceratocystis contains a number of emerging plant pathogens, mostly members of the Latin American Clade (LAC), in which there are several unresolved taxonomic controversies. Among the most important are Brazilian pathogens in the C. fimbriata complex, C. manginecans and C. eucalypticola. Representatives of C. manginecans and C. eucalypticola from India and China, respectively, were shown to be fully interfertile in laboratory matings, and hybrids between the putative species were identified on Punica in India. An Indian tester strain was sexually compatible with representatives of what has been considered C. fimbriata on numerous hosts across Brazil. In this revision of the LAC, the name C. fimbriata is restricted to the widely dispersed Ipomoea strain, and C. manginecans is recognized as a Brazilian species that is important on Mangifera, Eucalyptus, and many other crops. C. mangivora and C. mangicola are also considered synonyms of C. manginecans. Based on phylogenetics and mating studies, two other Brazilian species are recognized: C. atlantica, sp. nov., and C. alfenasii, sp. nov., each with wide host ranges. Three new Caribbean species are recognized based on phylogenetics and earlier inoculation studies: C. costaricensis, sp. nov., on Coffea, C. cubensis, sp. nov., on Spathodea, and C. xanthosomatis, sp. nov., on the vegetatively propagated aroids Xanthosoma and Syngonium. Some of the other Ceratocystis species were based primarily on unique internal transcribed spacer (ITS) rDNA sequences, but the unreliability of rDNA sequences was demonstrated when intraspecific crossing of isolates with differing ITS sequences generated single-ascospore progeny with intragenomic variation in ITS sequences and others with new ITS sequences. Species recognition in Ceratocystis should use phenotype, including intersterility tests, to help identify which lineages are species. Although some species remain under-studied, we recognize 16 species in the LAC, all believed to be native to Latin America, the Caribbean region, or eastern USA.

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.

New Record of Ceratocystis fimbriata Causing Wilt of Pomegranate in India.

Wilt of pomegranate (Punica granatum L.) was first noticed in two areas of the Bijapur district (16°49'N; 75°43'E) of India in 1990. Around 1993, rapid spread of this disease was observed in the entire Bijapur district. The cause was not identified until 1995. Initial symptoms were yellowing and wilting of leaves on one to several branches leading to death of affected plants in a few weeks. Cross sections of diseased plants revealed brown discoloration in the outer xylem from roots to the main trunk. A survey of 44 locations from 1995 to 1998 showed an approximate loss of Rs. 30 lakhs (ca. US$69,770) and 7.5% (3,474 of 47,096 plants wilted) of the crop. At 13 locations, plants also were severely infested with shot hole borer (Xyleborus spp.). In 1996, the fungus, a Ceratocystis sp., was isolated from discolored stem, root, and branch tissues on wilted plants collected from various locations, e.g., A. Sangapur, Bagalkot, Bijapur, Bilagi, Kanamadi, Tajpur, and Tikota. The fungus isolated from Bagalkot was confirmed by the International Mycological Institute (UK) as C. fimbriata Ellis & Halst. (Specimen No. W 5496, PBUR) in 1997; the strain of this fungus, i.e., Latin American group, was identified in 1998 by T. C. Harrington (Iowa State University). Morphological characteristics of mycelium, conidia, conidiophore, chlamydospores, perithecia, and ascospores were similar to those described previously (1). Pathogenicity of this fungus was confirmed by inoculating wounded roots. This is the first report of C. fimbriata causing wilt on pomegranate. Reference: (1) Anonymous. C.M.I. Descriptions of Pathogenic Fungi and Bacteria. No. 141. CAB, Surrey, England.