Xudong Zhou

Calonectria species associated with cutting rot of Eucalyptus

Decline in the productivity of Eucalyptus hybrid cutting production in the Guangdong Province of China is linked to cutting rot associated with several Calonectria spp. The aim of this study was to identify these fungi using morphological and DNA sequence comparisons. Two previously undescribed Calonectria spp., Ca. pseudoreteaudii sp. nov. and Ca. cerciana sp. nov. were identified together with Ca. pauciramosa. Calonectria pseudoreteaudii resides in the Ca. reteaudii complex and Ca. cerciana is closely related to Ca. morganii. Connected to the discovery of Ca. pseudoreteaudii, species in the Ca. reteaudii complex were re-considered and the group is shown to accommodate two cryptic species. These originate from Australia and are described as Ca. queenslandica sp. nov. and Ca. terrae-reginae sp. nov.

Characterisation of Ophiostoma species associated with pine bark beetles from Mexico, including O. pulvinisporum sp. nov.

Bark beetles (Coleoptera: Scolytidae) are common vectors of Ophiostoma species. These fungi include primary tree pathogens and important sapstain agents. In Mexico, Ips calligraphus and Dendroctonus mexicanus occur on many species of pine. Pinus maximinoi and P. pseudostrobus are the hosts of both species of insects. Little research has been done on ophiostomatoid fungi associated with pine bark beetles in Mexico. We recently obtained specimens of these bark beetles and their galleries from Mexico. The aim of the study was to isolate and identify Ophiostoma species associated with the two beetle species. In total, six ophiostomatoid species were found to be associated with them. These included Ceratocystiopsis minuta, Ophiostoma pluriannulatum, an O. galeiformis-like species, two unidentified Sporothrix spp., as well as a new species similar to O. adjuncti, O. ips, and O. montium, that we name as O. pulvinisporum sp. nov.

Novel species of Calonectria associated with Eucalyptus leaf blight in Southeast China

Leaf blight caused by Calonectria spp. is an important disease occurring on Eucalyptus trees grown in plantations of Southeast Asia. Symptoms of leaf blight caused by Calonectria spp. have recently been observed in commercial Eucalyptus plantations in FuJian Province in Southeast China. The aim of this study was to identify these Calonectria spp. employing morphological characteristics, DNA sequence comparisons for the β-tubulin, histone H3 and translation elongation factor-1α gene regions and sexual compatibility. Four Calonectria spp. were identified, including Ca. pauciramosa and three novel taxa described here as Ca. crousiana, Ca. fujianensis and Ca. pseudocolhounii. Inoculation tests showed that all four Calonectria spp. found in this study were pathogenic on two different E. urophylla × E. grandis hybrid clones, commercially utilised in eucalypt plantations in China.

Novel species of Celoporthe from Eucalyptus and Syzygium trees in China and Indonesia

Many species in the Cryphonectriaceae cause diseases of trees, including those in the genera Eucalyptus and Syzygium. During disease surveys on these trees in southern China, fruiting structures typical of fungi in the Cryphonectriaceae and associated with dying branches and stems were observed. Morphological comparisons suggested that these fungi were distinct from the well known Chrysoporthe deuterocubensis, also found on these trees in China. The aim of this study was to identify these fungi and evaluate their pathogenicity to Eucalyptus clones/species as well as Syzygium cumini. Three morphologically similar fungal isolates collected previously from Indonesia also were included in the study. Isolates were characterized based on comparisons of morphology and DNA sequence data for the partial LSU and ITS nuclear ribosomal DNA, β-tubulin and TEF-1α gene regions. After glasshouse trials to select virulent isolates field inoculations were undertaken to screen different commercial Eucalyptus clones/species and S. cumini trees for susceptibility to infection. Phylogenetic analyses showed that the Chinese isolates and those from Indonesia reside in a clade close to previously identified South African Celoporthe isolates. Based on morphology and DNA sequence comparisons, four new Celoporthe spp. were identified and they are described as C. syzygii, C. eucalypti, C. guangdongensis and C. indonesiensis. Field inoculations indicated that the three Chinese Celoporthe spp., C. syzygii, C. eucalypti and C. guangdongensis, are pathogenic to all tested Eucalyptus and S. cumini trees. Significant differences in the susceptibility of the inoculated Eucalyptus clones/species suggest that it will be possible to select disease-tolerant planting stock for forestry operations in the future.

Eucalypt diseases and their management in China

Eucalypts were first introduced into China in 1890 and the first commercial eucalypt plantation was established in ZhanJiang, GuangDong province in 1954. Because natural ecosystems have been strictly protected from logging since 2000, eucalypt plantations in South China have been substantially expanded to meet the needs of a rapidly growing local economy. Approximately 3.6 million ha of eucalypt plantations have now been established and half of these represent clones of Eucalyptus urophylla x E. grandis, and E. camaldulensis x E. grandis hybrids. However, the sustainable development of the eucalypt plantations is under increasing threat due to pathogens and pests. The fact that there has been very limited work on eucalypt pathology in China compounds this fact. During the course of past five years, a programme known as the CFEPP (http://www.fabinet.up.ac.za/cfepp/index) focusing on eucalypt health problems in China has been developed, and a large number of eucalypt disease surveys have been conducted in areas such as GuangXi, GuangDong, HaiNan, FuJian and Yunnan. This work has resulted in the collection of over 2000 fungal strains many of which are well-known eucalypt pathogens. A total of 30 fungal species (eight of them new to science) residing in 11genera such as Calonectria, Celoporthe, Chrysorporthe, Quambalaria and Teratosphaeria, have been characterized based on comparisons of morphology and DNA sequence data. Both glass-house and field trials have been conducted to test the pathogenicity of the most important of these fungi on commercially used eucalypt clones. Results have shown that there are significant differences in the susceptibility of these clones to fungal isolates/species, indicating that selection of resistant material for commercial planting in the future can be achieved.

Characterisation of synnematous bark beetle-associated fungi from China, including Graphium carbonarium sp. nov.

Ophiostomatoid fungi on trees are typically bark beetle associates that cause sapstain in timber and some are pathogens. Very little is known regarding the ophiostomatoid fungi associated with bark beetles in China and the aim of this study was to identify a collection of these fungi with synnematous anamorphs. Micromorphology and DNA sequences of the internal transcribed spacer regions (ITS) of the ribosomal DNA and the partial β-tubulin gene were used for identifications. The isolates could be divided in six morphological groups. DNA sequence comparisons with published data confirmed that these groups represented six species, four in the Ophiostomatales (Sordariomycetidae) and two in the Microascales (Hypocreomycetidae). The majority of these were isolated from conifer hosts. Ophiostoma quercus, O. setosum, Pesotum fragrans (Ophiostomatales) and Graphium pseudormiticum (Microascales) were found on Tsuga dumosa infested by a Pissodes sp. In addition, O. quercus and P. fragrans were found associated with Tomicus yunnanensis on Pinus yunnanensis, P. fragrans with a Pissodes sp. on P. armandi, and O. piceae with Ips subelongatus on Larix olgensis. Only two species, O. quercus and a new species in the Graphium penicilliodes complex, described here as Graphium carbonarium sp. nov., were isolated from Pissodes galleries on Salix babylonica. These results include several new fungus-host and fungus-insect associations, and G. pseudormiticum is reported here for the first time from China.

Taxonomy and phylogeny of the Leptographium procerum complex, including Leptographium sinense sp. nov. and Leptographium longiconidiophorum sp. nov.

Leptographium procerum (Ophiostomatales, Ascomycota) is a well-known fungal associate of pine root-infesting bark beetles and weevils, occurring in several countries of the world. The fungus is not a primary pathogen but has been associated with white pine root decline in the USA and with serious damage caused by the introduced red turpentine beetle (RTB) Dendroctonus valens in China. Several species closely related to L. procerum have been described during the past decade. The aim of this study was to reevaluate species boundaries in the L. procerum complex using multigene phylogenetic analyses and morphological comparisons. Phylogenetic analyses of seven gene regions (ITS2-LSU, actin, β-tubulin, calmodulin, translation elongation factor 1-α, and the mating type genes MAT1-1-3 and MAT1-2-1) distinguished between nine species in the complex. These included L. procerum, L. bhutanense, L. gracile, L. profanum, L. pini-densiflorae, L. sibiricum, L. sinoprocerum, as well as two new species described here as Leptographium sinense sp. nov. from Hylobitelus xiaoi on Pinus elliottii in China, and Leptographium longiconidiophorum sp. nov. from Pinus densiflora in Japan. Leptographium latens is reduced to synonymy with L. gracile, and an epitype is designated for L. procerum, because a living culture associated with the holotype of L. procerum did not exist. Amplification patterns of the mating type genes suggest that all known species in the L. procerum complex are heterothallic, although sexual states have not been observed for any of the species. The results also suggest that Eastern Asia is most probably the centre of species diversity for the L. procerum complex.

Multigene phylogenies of Ophiostomataceae associated with Monterey pine bark beetles in Spain reveal three new fungal species

Ophiostoma species, some of which cause sapstain in timber and/or are mild pathogens, are common fungal associates of bark beetles (Coleoptera: Scolytinae). Three new Ophiostomataceae from Spain are recognized in the present study based on comparisons of sequence data for three gene regions as well as morphological characteristics. The new taxa are described as Ophiostoma nebulare sp. nov., Ophiostoma euskadiense sp. nov. and Graphilbum crescericum sp. nov.

Epitypification of Ophiostoma galeiforme and phylogeny of species in the O. galeiforme complex

Ophiostoma galeiforme was described first in 1951 from Larix kaempferi in Scotland, where it was found to be associated with the bark beetles Hy-lurgops palliatus, Dryocoetes autographus, and the ambrosia beetle Trypodendron lineatum. The taxonomy of this fungus has been uncertain because of a lack of sexual structures on the type specimen and contamination of a preserved ex-type culture. The aim of this study was to clarify application of the species name, O. galeiforme, by designating an epitype and to consider phylogenetic relationships of the species. Nineteen isolates resembling O. galeiforme from different parts of the world were used, including collections from Pinus sylvestris infested with Tomicus pi-niperda in Scotland and the contaminated ex-type culture. Morphological characteristics of isolates from Sweden, South Africa, Scotland, Chile and Aus-tria corresponded well with those originally described for O. galeiforme, and an isolate from Scotland is designated as the epitype. A detailed description is provided. Results of interfertility tests showed that O. galeiforme is heterothallic. Analysis of ITS rDNA sequences showed that the isolates representing O. galeiforme were distinct from three morphologically similar isolates from the USA and Mexico, which probably represent an undescribed taxon.

Identification and Pathogenicity of Chrysoporthe cubensis on Eucalyptus and Syzygium spp. in South China

The genus Chrysoporthe includes important pathogens of plantation-grown Eucalyptus spp. and has been reported from several tree genera in the order Myrtales in tropical and subtropical areas of the world. During disease surveys in South China, fruiting structures typical of Chrysoporthe spp. were observed on cankers on Eucalyptus spp. and Syzygium cumini trees. The aim of this study was to confirm the identity of the Chrysoporthe cubensis infecting the Eucalyptus spp. and S. cumini and to test the pathogenicity of the fungus. Following glasshouse trials to select virulent isolates, field inoculations were undertaken to screen different commercial Eucalyptus genotypes for their susceptibility to the fungus. Isolates were characterized based on their morphology and DNA sequence data for the β-tubulin and internal transcribed spacer regions of the ribosomal DNA. Results showed that the putative pathogen represented the Asian form of C. cubensis, which occurred on numerous different Eucalyptus spp. and hybrid clones as well as S. cumini. Field inoculations showed that all six of the Eucalyptus genotypes tested are susceptible to infection by C. cubensis. Significant differences were observed between them, providing prospects to select disease-tolerant planting stock in the future.