U.S. Department of Agriculture, Agricultural Research Service Systematic Mycology and Microbiology Laboratory - Invasive Fungi Fact Sheets Ampelopsis rust -Phakopsora ampelopsidis The rust fungus Phakopsora ampelopsidis as currently defined is a pathogen of hosts in the genus Ampelopsis and perhaps in related genera in the family Vitaceae, but not of the cultivated grapevine species of Vitis or the ornamental species in Parthenocissus. Plants in Ampelopsis occur in Asia from Japan to Turkey as well as in North America, but the rust is not known in Europe, and has not been reported on Ampelopsis in the Americas. Only in eastern Asia, where the medicinal uses of species of Ampelopsis are being investigated is this rust a potential problem. It is most likely to be spread by aerial dispersal of urediniospores to nearer parts of Asia where species in the host genus are distributed. Phakopsora ampelopsidis Dietel & P. Syd. 1898 Spermogonia and aecia unknown. Uredinia on abaxial side of leaf, scattered or aggregated in small groups on a lesion, subepidermal, becoming erumpent, surrounded by paraphyses. The paraphyses are united at the base, strongly incurved, 21-43 µm high, thick-walled, 2.5-5.5 µm, both dorsally and ventrally. Urediniospores obovoid, obovoid-ellipsoid or oblong-ellipsoid, 16-27 x 11-17 µm. Wall evenly ca 1.5 µm thick, almost colourless, evenly echinulate. Four or six germ pores in equatorial zone of the spore wall, rarely scattered. Telia also formed on the abaxial surface, crustose, orange-brown,becoming dark brown to blackish brown, often confluent, subepidermal, applanate. Teliospores more or less randomly arranged in 3-4 layers, oblong or ellipsoid, angular and 13-28 x 6-15 µm. Wall evenly thin and colourless except in the uppermost spores whose wall is ca 2 µm thick and pale brown. Basidiospores kidney-shaped, 8.8-12.4. x 5.6-8.1 µm. Symptoms: Infection of the Ampelopsis plants causes yellowish to pale brownish spots or irregular shaped lesions. Sometimes, no symptom occurs before fungal sporulation. Yellowish masses of urediniospores are produced in uredinia formed on the abaxial surface of the lesion. Telium formation follows presence of the uredinia; the telia are formed around the uredinia or separately. The telia are crust-like and orange-brown initially, but become dark brown or almost black. Heavy infection is not rare, causing entire leaves to turn yellow or brown with dense production of uredinia and/or telia. Heavy infection causes early senescence and dropping of the leaves. For additional description and illustration, see Ono, 2000. Host range: Restricted to species of Ampelopsis (Vitaceae) Geographic distribution: China, Japan, Korea, Philippines, Taiwan NOTES ON TAXONOMY AND NOMENCLATURE At one time the species concept of Phakopsora ampelopsidis was broadened to include the pathogen of grapevine, P. euvitis, but it has now been narrowed to exclude grape leaf rust. Phakopsora ampelopsidis was described based on a specimen on Ampelopsis brevipedunculata (as A. leeoides) collected in Tokyo, Japan (Dietel, 1898). Soon after, the fungus that causes leaf rust of Boston ivy (Parthenocissus tricuspidata) was described and named as Phakopsora vitis based on a collection also made in Tokyo (Sydow, 1899). Previously, two anamorphic fungi found on Vitis vinifera in North America, Uredo vitis (Thümen, 1878) and U. vialae (Lagerheim, 1890), had been identified. These teleomorphic and anamorphic fungi were later considered to be conspecific and the oldest legitimate name for the teleomorph, P. ampelopsidis, was applied (Hiratsuka, 1900; Hiratsuka, 1935). However, Ono (2000) has shown that the fungi on the three host genera are distinct in their host ranges and life cycles and that the host-delimited fungi are also morphologically different. Three species were distinguished: P. ampelopsidis on Ampelopsis, P. vitis on Parthenocissus and the newly described P. euvitis on vitis (Ono, 2000). This taxonomy is supported by the molecular study of Chatasiri and Ono (2008), in which isolates of the three species were placed in separate phylogenetic clades within the genus, based on sequences of the D1D2 and ITS2 regions of rDNA. The name Physopella ampelopsidis (Cummins and Ramachar, 1958) has been widely used to refer to the grape rust fungus, in place of the name in Phakopsora (see Punithalingam, 1968: Hiratsuka et al., 1992). However, the genus Physopella is anamorphic (Ono et al., 1992; Ono, 2000) and its type species, P. vitis, is based on an anamorphic stage of the grape leaf rust, Phakopsora euvitis (Ono, 2000). DISTRIBUTION Under the previous broad definition of the species, a rust with this name has been reported from North and South America and the West Indies, and in Asia from India to Japan, Indonesia, and the Philippines (Punithalingam, 1968; Leu, 1988; Hiratsuka et al., 1992). By restricting the definition to the fungus on Ampelopsis (and possibly on some related genera), Ono (2000) reduces its known distribution to China, Japan, Korea, Taiwan and the Philippines. RISK OF INTRODUCTION This rust is most likely to be spread by aerial dispersal of urediniospores to nearer parts of Asia where species in the host genus are distributed than by introduction on plant material to distant parts of Asia or the Americas. Unless the host range is wider than known, its introduction would not threaten any cultivated species, but wild Ampelopsis species in the Americas might be particularly susceptible. BIOLOGY AND ECOLOGY SECTION This fungus appears to be highly host-specific, being restricted to the genus Ampelopsis with only a few possible other hosts (Ono, 2000). Thus, correct identification of the host ensures the identification of this species within the genus Phakopsora. Phakopsora ampelopsidis forms strongly incurved, evenly thick-walled (2.5-5.5 µm) paraphyses in the uredinium, subglobose to oblong teliospores randomly arranged (not in rows) and not with spores in the upper row longer, and kidney-shaped basidiospores, by which it can be distinguished from the morphologically similar P. vitis on Parthenocissus and P. euvitis on vitis. DETECTION AND INSPECTION METHODS The undersides of Ampelopsis leaves should be examined for yellowish powdery uredinia and/or crust-like orange-brown to blackish-brown telia. DIAGNOSTIC METHOD Except for characters of the uredinial paraphrases, the differences in morphology of the species on Vitaceae are subtle, and not all of the spore forms will be available for examination at one time. Sequences of the D1D2 and ITS2 regions of ribosomal DNA are available in GenBank for comparison with those of isolates (NCBI, 2009). NOTES ON CROPS/OTHER PLANTS AFFECTED Species of the host genus Ampelopsis are distributed throughout Asia as far west as Turkey, and in North America (USDA-ARS, 2009). Phakopsora rust fungi on Cayratia, Cissus and Tetrastigma collected in China (Zhuang, 1983) have been included in P. ampelopsidis; information on host specificity, life cycle and morphological features necessary for species identification is lacking for these fungi (Ono, 2000). BIOLOGY AND ECOLOGY A complete life cycle of the fungus is not known. Repeated basidiospore inoculations did not result in infection of Ampelopsis brevipedunculata or Meliosma myriantha, the most likely hosts for the spermogonial and aecial forms (Ono, 2000). This indicated that the fungus has a heteroecious life cycle and that, unlike the related species P. euvitis and P. vitis, it produces the spermogonial and -aecial stages on a plant other than M. myriantha. This species may persist in tropical and subtropical climates as uredinial mycelium in the leaves or young shoots, repeatedly producing urediniospores (Leu, 1988). Conditions for spore production, germination, infection and growth in the host may be similar to those reported for P. euvitis on grape (Leu, 1988); no apparent physiological differences between the species were reported by Ono (2000). MOVEMENT AND DISPERSAL Natural dispersal: Urediniospores and basidiospores of rust fungi are distributed by wind (Alexopoulos et al., 1996;). CONTROL Control practices developed for P. euvitis on grapvines will most likely be effective on any Ampelopsis put into cultivation or managed as a wild plant. GAPS IN KNOWLEDGE/RESEARCH NEEDS The full host range for the uredinial form is undetermined and the host for the aecial stage is unknown. Phakopsora rust on Ampelopsis has not been reported from the Americas (SMML/USDA, 2009). References

Suggested citation: Chalkley, D..Systematic Mycology and Microbiology Laboratory, ARS, USDA. . Invasive Fungi. Ampelopsis rust -Phakopsora ampelopsidis. Retrieved October 1, 2021, from /sbmlweb/fungi/index.cfm . Use this link to revisit SMML website