U.S. Department of Agriculture, Agricultural Research Service Systematic Mycology and Microbiology Laboratory - Invasive Fungi Fact Sheets Blue stain of Mongolian -Ophiostoma longicollum Ophiostoma longicollum is a perithecial ascomycete that was isolated from the wood of dying Mongolian oak trees attacked by the wood-boring quercivorus on the west coast of Japan. Neither the pathogenicity of the nor any definite association with the beetle as a vector has been established. The beetle is ranked first as a Prioritized Pest for the USA (USDA/APHIS, 2010) and another fungus, shown to be vectored by the beetle, has been associated with the tree mortality. Ophiostoma longicollum Masuya 1998 (Ascomycetes, Ophiostomatales) Anamorph: Sporothrix-like Perithecia produced on 1% pablum agar or on oak wood blocks. Basal part globose to subglobose, black, 100-370 µm diam, ornamented with unbranched, brown hyphal appendages up to 280 µm long. Neck cylindrical or tapered, straight or bent, black, 1-10 mm long, 30-60 µm wide at base, 15-50 µm and pale brown at apex. Apex truncate to obtuse, covered by a hyaline gelatinous cap. Asci evanescent, not described. Ascospores hyaline, aseptate, broadly lunate in side view, globose in end view, ellipsoid in top view, 1.9-3.3 x 0.8-1.6 µm, collecting in a yellow-orange mass at ostiole. Conidiophores arising from surface or aerial mycelium, hyaline, septate, bearing terminal conidiogenous cells. Cells 0.3-2.0 x 0.5-5.5 µm, proliferating sympodially, slightly denticulate. Conidia holoblastic, hyaline, aseptate, ellipsoidal, slightly curved, sometimes Y-shaped, 2.0-6.0 x 0.6-2.5µm, aggregating in slimy masses at cell tip. Colony white to pale brown on 2% MEA, growing 2.4-3.1 mm/day at 20C (optimum). Growth is reduced 60% by 2.5 g/L cycloheximide at 25° C. No growth at 4° C. For additional details, see Masuya et al. (1998) Distribution: Asia (Japan). Host: Quercus mongolica () Notes: Ophiostoma longicollum was described by Masuya et al. (1998) from dying oak trees on the west coast of Japan. The new fungus differed from other species of "ophiostomatoid" fungi reported on the same host by its perithecium and spore sizes, long neck, and other neck morphology. The species has a Sporothrix anamorph and, like other members of the genus, tolerates cycloheximide (Masuya et al., 1998). Recent molecular phylogenetic studies of Ophiostoma and Sporothrix (Aghayeva et al., 2005; Zipfel et al., 2006; Grobbelaar et al, 2009; Alamouti et al., 2009) have not considered O. longicollum. DISTRIBUTION The fungus is known so far only from Japan, but the host species (Quercus mongolica) is also native to other parts of Asia, including Korea, China, Mongolia, Siberia and Far Eastern Russia (USDA-ARS, 2009). RISK OF INTRODUCTION The risk of introduction is unknown. The pathogenicity of the species, and even whether or not its growth can stain wood, is not established. Although there was a simultaneous observation of galleries of a wood-boring beetle and ophiostomatoid fungi are generally vectored by including such , no clear association of the fungus with the beetle was demonstrated. Fungi can have either a specific association with a certain species of vector or be more generally distributed by . If the association is specific, and the fungus were introduced in wood or unprocessed wood products from Asia, then the beetle, P. quercivorus, might have to be introduced as well in order for the fungus to pose a possible threat to American trees. On other hand, species of the beetle genus Platypus do occur in North America and Europe (Davis et al., 2005). SIMILARITIES TO OTHER SPECIES Masuya et al. (1998) noted that seventeen species of Ophiostoma were reported from oak at that time and none closely resembled O. longicollum except O. grandicarpum (Kowalski & Butin) Rulamort. The Japanese species differs from that European species, known from Quercus robur, in having a smaller ascomata and smaller ascospores and in producing a gelatinous cap on the ostiole (Masuya et al.,1998). It differs from a more recently described European species on oak, O. dentifundum Aghayeva & M.J. Wingf., in that the newer fungus has conidia that are longer and of a different shape, and also bears ostiolar hairs on the perithecium (Aghayeva et al., 2005). The ascospores are quite similar. The neck of the ascomata of O. dentifundum is long, but is not reported to reach 10 mm. Three species of related fungi were previously reported from the same variety of Q. mongolica in Japan (Masuya et al., 1998). Both Ophiostoma piceae and O. pluriannulatum occur worldwide on both conifers and broad-leaved trees, including . The former species has a Pesotum anamorph (Zipfel et al., 2006; Grobbelaar et al., 2009); the latter resembles O. longicollum is having a Sporothrix anamorph (Upadhyay, 1981; Benade et al., 1998). Perithecia of both are reported to bear ostiolar hairs, which are lacking in the Japanese species. The third species, Ceratocystis moniliformis, is also of worldwide distribution, but has a Chalara-like anamorph and, despite the convergent morphology of the sexual form, is placed in a different order, the Microascales (Paulin and Harrington, 2000; Alamoutui et al., 2006). In any case, the identifications made in 1961 of these species occurring in Japan are currently considered uncertain (Masuya et al., 2008). DETECTION AND INSPECTION METHODS The fungus was detected originally by its growth on wood blocks from -infested oak trees. The symptoms of the declining oaks were not described. Mass mortality of oaks on the western coast of Japan is reported to be preceded by wilting and has been associated with the presence of the ambrosia beetle, Platypus quercivorus (Kinuura, 2002; Ito et al., 2003). DIAGNOSTIC METHOD A simple and rapid PCR protocol for the identification of other Ophiostoma species in wood, which might be adapted for O. longicollum, was developed by Kim et al. (1999). There are no sequences of any DNA region for this species deposited in GenBank (as of January, 2010), but sequences for other species in the genus are available for comparison (NCBI, 2010). NOTES ON PLANTS AFFECTED Only Quercus mongolica Fisch ex Ledeb. was identified as a host in Japan (Masuya et al., 1998). In current , this species includes both Q. mongolica var. grosseserrata (Blume) Rehder & E. H. Wilson and Q. mongolica subsp. crispula (Blume) Menitsky (USDA-ARS, 2010). SYMPTOMS - DESCRIPTION The symptoms of the declining oaks from which the fungus was isolated were not described. Mass mortality of oaks on the western coast of Japan has been reported to be preceded by wilting in early summer, followed by reddening of the leaves (Kinuura, 1994; Ito et al., 2003), but this has been associated with the fungus Raffalaea quercivora. (Ito et al., 2003). BIOLOGY AND ECOLOGY Life cycle: Ophiostoma longicollum may be expected to have a biology similar to that of other ophiostomatoid fungi. Carried by arthropods to trees, the fungus would grow in beetle galleries, producing conidia that may serve for local dispersal or as spermatia in mating between strains. Ascomata then develop in the galleries and the ascospores collecting in a sticky mass at the apex of the neck become attached to the bodies of arthropods and are carried to new trees (Malloch and Blackwell, 1993). Associations: The fungus was isolated from sapwood containing the galleries of the beetle Platypus quercivorus (Masuya et al., 1998), but no definite interaction with the beetle was established. The ambrosia fungus Raffalaea quercivora has a close association with the same beetle. It has been isolated from the beetle's body surfaces and mycangia and appears to be vectored by it (Kinuura, 2002; Kubono and Ito, 2002). MOVEMENT AND DISPERSAL Natural dispersal: In related fungi, conidia are considered likely to serve the function of local dispersal in the tree (Malloch and Blackwell, 1993). If they were produced in functioning xylem, they could be carried to the roots and through them to other trees in natural root grafting as occurs for O. ulmi (Sinclair and Lyon, 2005). Vector transmission: The fungus is likely to have one or more vectors. Malloch and Blackwell (1993) report that all species in the Ophiostomatoid groups are disseminated by arthropods. Association with galleries of the beetle P. quercivorus was observed by Masuya et al. (1998). Other Ophiostoma species occurring in Abies (Yamaoka et al., 2004) and Pinus densiflora (Masuya et al., 2009) appear to have associations with one or more species of bark beetles. Accidental introduction: Logs, unprocessed wood or wood bearing bark imported from eastern Asia could carry the fungus and/or an infested insect vector. IMPACTS No impact of this species has been reported, but the possible beetle vector, Platypus quercivorus, is already a Prioritized Pest for USDA/APHIS (2010) based on its potential economic and environmental damage (Davis et al., 2005). Separation of damage due to O. longicollum from that which is associated with the fungus Raffalaea quercivora (Ito et al., 1998, 2003; Kubono and Ito, 2002) which is known to be vectored by the beetle (Kinuura, 2002), may be difficult. MANAGEMENT SPS measures Existing measures that prohibit logs, lumber, wood products or other materials that could carry fungi or insects (Davis et al., 2005; CFIA, 2009) should be maintained against importations of Quercus mongolica. Control Not enough is known of the biology of O. longicollum to require or permit the design of suitable control measures. If an arthropod vector is in fact involved in its transmission outside of the tree, the strategy of controlling the vector is likely to be most feasible. GAPS IN KNOWLEDGE/RESEARCH NEEDS DNA sequences from this species are needed for comparison with those of other Ophiostoma species. Tests of pathogenicity and virulence to Quercus mongolica and some assessment of the potential host range of O. longicollum should determine whether the fungus is a threat as an introduced species. If the fungus does appear likely to be invasive, its distribution in the known host across Asia should be surveyed. The nature of the association, if any, with Platypus quercivorus or other wood-boring beetles infesting Japanese oaks should be clarified. Although the primary control against this type of fungus, as for any tree pathogen or insect pest of trees, must be control of entry of trees and wood materials from the infested areas. Development of a PCR protocol or other rapid test for the species in wood is desirable. References

Suggested citation: Chalkley, D..Systematic Mycology and Microbiology Laboratory, ARS, USDA. . Invasive Fungi. Blue stain of Mongolian oak-Ophiostoma longicollum. Retrieved September 27, 2021, from /sbmlweb/fungi/index.cfm . Use this link to revisit SMML website Conidiophore and conidia, 1000x. CBS 109233: from Conidiophore and conidia, 1000x. CBS 109233: from potato-dextrose agar. potato-dextrose agar.

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