Gymnosporangium mori comb. nov. (Pucciniales) for Caeoma mori (≡ Aecidium mori) inferred from phylogenetic evidence

Abstract

Caeoma mori (≡ Aecidium mori), known as the mulberry rust which is an anamorphic rust fungus forming only aecidioid uredinia, were found on Morus alba in Ibaraki and Saitama Prefectures, Japan. Molecular phylogenetic analyses using the combined dataset of sequences from 28S and 18S of the nuclear ribosomal RNA gene and Cytochrome-c-oxidase subunit 3 of the mitochondrial DNA revealed that this anamorphic rust fungus was a member of the clade composed of the genus Gymnosporangium. Therefore, a new combination, Gymnosporangium mori is proposed for this species. Additionally, a new combination, G. brucense for Roestelia brucensis is proposed by phylogenetic evidence.

Mulberry (Morus, Moraceae) is shrubs or trees consisting of about 10 species, and mainly distributed in temperate regions of Asia and North America (Nepal & Ferguson, 2012). The leaves of these plants are used as foods for silkworm larvae. Some species are also cultivated for productions of edible fruits. Specimens of a rust fungus occurred on shoots and leaves of Morus alba L. (common mulberry or silkworm mulberry) were collected in the fields of Ibaraki and Saitama Prefectures, Japan in early summer of 2021 and 2023 (Fig. 1A). Morphological observations were made for the identification of this rust fungus using light microscopy and scanning electron microscopy by the same methods reported by Uzuhashi et al. (2022). Spermogonia were not found on specimens. Sori surrounded with fragile and short peridia (Fig. 1B, D, E) were amphigenous, densely formed, rounded to elliptical and cupulate. Peridial cells were loosely conjunct and their inner walls were verrucose. Spores (Fig. 1C, F) were catenulate, angularly globose to ellipsoid and 11.5-20 × 8-15.5 μm (avg. 16 × 12 µm; n = 50) in size. Their walls were hyaline, verrucose and 1-1.5 μm thick.

Fig. 1 - Gymnosporangium mori on Morus alba (TNS-F-99251). A: Sori on upper leaf surface. B: Vertical section of sorus. Peridium at margin of sori (P). C: Spores with hyaline walls. D: Sorus on leaf surface observed by scanning electron microscopy (SEM). Peridium at margin of sori (P). E: Vertical section of sorus observed by SEM. Peridium at margin of sori (P). F: Spores with verrucae on the surface observed by SEM. Bars: B, E 20 µm; C 10 µm; D 30 µm; F 2.5 µm.

Five species of rust fungi, Phakopsora fici-erectae S. Ito & Y. Otani ex S. Ito & Muray., Cerotelium fici (Castagne) Arthur, Aecidium mori (Barclay) Barclay (≡ Caeoma mori Barclay), Uredo moricola Henn. and U. morifolia Sawada have been reported on species of Morus in Japan (Hiratsuka et al., 1992; Ito, 1950). Among them sorus structures of P. fici-erectae, C. fici, U. moricola and U. morifolia are different from the rust fungus collected on M. alba in Ibaraki and Saitama Prefectures. Namely, P. fici-erectae and C. fici has peripheral paraphyses in sori and two Uredo species have no peridium in their sori. Sorus structures of this rust fungus having fragile peridia is identical with descriptions of A. mori (Hiratsuka et al., 1992; Ito, 1950; Mordue, 1991). The morphology and size of spores are also similar to those of its descriptions. Therefore, the present rust fungus on M. alba is identified as A. mori. Specimens used in this observation were deposited in the Mycological Herbarium of the Department of Botany, National Museum of Nature and Science, Tsukuba, Japan (TNS).

Caeoma mori was originally described as a rust fungus on mulberry in 1890 by Barclay. Although this species was recorded as Uredo mori (Barclay) Sacc. in 1891 by Saccardo, Barclay (1891) treated this species as same species as A. mori, described by himself, because of the presence of peridia in the sori. Aecidium mori has been widely recorded on many species of Morus and Broussonetia (Moraceae) in Asia (Hiratsuka et al., 1992; Ito, 1950; Mordue, 1991; Tai, 1979). Sori and spores of this species are morphologically as same as Aecidium-type by Cummins and Hiratsuka (1983) because of catenulate spores and presence of peridia. Therefore, spores are morphologically categorized as aeciospores which are usually produced after spermogonial formation and produce uredinia after their infections to plants. However, no spermogonium is formed and same type of sori (Aecidium-type) is produced repeatedly after infections with these spores (Kaneko, 1973). This type of sori is called as aecidioid uredinia or uredinial aecia (Kaneko, 1973; Kasuya et al., 2020; Sato & Sato, 1981). Therefore, spores of this species are functionally as same as urediniospores of rust fungi.

Sathe (1969) described a new anamorphic genus, Peridiopsora Kamat & Sathe for rust fungi producing urediniospores in Aecidium-type sori, and A. mori was transferred to this genus as P. mori (Barclay) K.V. Prasad, B.R.D. Yadav & Sullia by Prasad et al. (1993). However, A. mori has been commonly used as species name of mulberry rust in the world. Because only anamorphic stage of this rust fungus has been known, its taxonomic position among rust fungi has been unknown for long time. Recently, Aime and McTaggart (2021) suggested that this species was phylogenetically close to Gymnotelium Syd. described for group of the genus Gymnosporangium R. Hedw. ex DC. having Aecidium-type of aecia, but their analyses was insufficient.

In the present study, to clarify the taxonomic position of A. mori, the phylogenetic analyses reported by Aime and McTaggart (2021) was applied. We obtained sequence data of the large subunit (28S) and the small subunit (18S) of the nuclear ribosomal RNA gene and Cytochrome-c-oxidase subunit 3 (CO3) of the mitochondrial DNA from specimens of A. mori which were collected from Ibaraki and Saitama Prefectures and used for morphological observations. Procedures of DNA extraction, PCR and sequencing followed the method reported by Virtudazo et al. (2001), Kasuya et al. (2012) and Aime and McTaggart (2021). 28S ribosomal RNA was amplified with Rust2INV (Aime, 2006)/LR6 or LR7 (Vilgalys & Hester, 1990) and, for weak products, nested with Rust28SF (Aime et al., 2018)/LR5 or LR6 (Vilgalys & Hester, 1990). 18S ribosomal RNA was amplified with NS1 (White et al., 1990)/Rust 18S-R (Aime, 2006) and nested with RustNS2-F (Aime et al., 2018)/NS6 (White et al., 1990). The mitochondrial CO3 was amplified with CO3_F1/CO3_R1 (Vialle et al., 2009). DNA extraction, PCR and sequencing were mainly performed by TechnoSuruga Laboratory Co. Ltd. (Shizuoka, Japan).

A total of eight 28S, seven 18S and six CO3 sequences from eight specimens of A. mori were newly generated and used for the phylogenetic analyses. These sequences were deposited to the International Nucleotide Sequence Databases (INSD; Table 1). Phylogenetic analyses were conducted for the combined dataset of 28S, 18S and CO3 sequences under maximum likelihood (ML) and Bayesian inference (BI). The combined dataset of the three loci (Table 1) included 57 taxa with Puccinia boroniae Henn. used as the outgroup according to the result of phylogenetic analyses of Uredinineae Engl. by Aime and McTaggart (2021) since Pucciniaceae Chevall. has phylogenetically close relationship to Gymnosporangiaceae Chevall. A total of 48 28S, 40 18S and 10 CO3 sequences of ingroups obtained from the NCBI GenBank databases (https://www.ncbi.nlm.nih.gov/) were chosen from Gymnosporangiaceae and Sphaerophragmiaceae Cummins & Y. Hirats. based on the analyses by Zhao et al. (2020) and Aime and McTaggart (2021). The combined dataset was aligned using Muscle v.3.6 (Edgar, 2004a, 2004b), followed by manual alignment in the data editor of BioEdit ver. 7.0.1 (Hall, 1999). Hypervariable, indel-rich and ambiguously aligned regions were removed from the analyses, and gaps were scored as missing data. The final alignments were deposited in TreeBASE (https://treebase.org) under the accession number S30671.

Table 1. Specimen data used for the present phylogenetic analyses.

Species a	Voucher specimen numbers	Locality	INSD accession numbers b
			28S	18S	CO3
Austropuccinia psidii	BRIP 57793	Australia, Queensland, Brisbane	KF318449	KF318457	KT199419
Dasyspora guianensis	ZT Myc 3413	French Guiana	JF263479	JF263503	JF263519
D. nitidae	ZT Myc 3409	French Guiana	JF263484	JF263505	JF263521
D. segregaria	PMA MP4941	Panama	JF263488	JF263507	JF263523
Gymnosporangium asiaticum	IBAR 5704	Japan	KJ720161	KJ720161	n/a c
G. asiaticum	TNM F0027942	Taiwan, Taichung, Dongshi	KP308393	KP308393	n/a
G. brucense	DAOM 127906	Canada, Ontario, Ottawa	KJ720188	KJ720188	n/a
G. brucense	RSP 74-313	Mexico	KJ720189	n/a	n/a
G. clavariiforme	RSP 05-32	USA, New Mexico	KJ720164	KJ720164	n/a
G. clavariiforme	BRIP 59471	Australia	MW049261	MW049296	MW036499
G. clavipes	BPI 871102	USA	DQ354545	DQ354546	n/a
G. clavipes	NYBG 461394	USA	MN605691	MN604977	n/a
G. clavipes	CUP A-18207	USA, New York	MN605692	MN604978	n/a
G. confusum	DAOM 220748	Canada	KJ720165	KJ720165	n/a
G. cupressi	RSP 99-98	USA, Arizona	KJ720169	KJ720169	n/a
G. ellisii	YPM RN23	USA, North Carolina	KJ720156	KJ720156	n/a
G. exiguum	RSP 04-86	USA, California	KJ720170	KJ720170	n/a
G. globosum	CUP 1553	USA, New York	MN605698	MN604983	n/a
G. globosum	NYBG 237038	USA,	KU342738	MN604982	n/a
G. juniperi-virginianae	RSP 98-137	USA, Oklahoma	KJ720176	KJ720176	n/a
G. juniperi-virginianae	MCA 3585	USA	MG907217	MG917687	MG907268
G. kernianum	RSP 05-37	USA, Texas	KJ720177	KJ720177	n/a
G. libocedri	TDB 1519	USA	AF522168	AY123290	n/a
G. libocedri	PUR N10018	USA	MG907218	MG907206	MG907269
G. libocedri	HMAS 49246	USA, California	MN605717	MN605009	n/a
G. libocedri	HMAS 45643	USA	MN605718	MN605010	n/a
G. libocedri	GL3_3	Canada	OR567878	n/a	n/a
G. libocedri	GL4_6	Canada	OR568568	n/a	n/a
G. libocedri	GL2_1	Canada	OR654105	n/a	n/a
G. mori	PUR N11676	Taiwan, Taipei	MW147025	n/a	MW166323
G. mori	TNS-F-99251 (Epitype)	Japan, Ibaraki, Joso, Tategeta	OR415605	OR415613	OR423360
G. mori	TNS-F-99252	Japan, Ibaraki, Joso, Moto-toyoda	OR415606	n/a	n/a
G. mori	TNS-F-108304	Japan, Ibaraki, Tsukuba	OR415607	OR415614	n/a
G. mori	TNS-F-99265	Japan, Ibaraki, Joso, Tategata	OR415608	OR415615	OR423361
G. mori	TNS-F-99266	Japan, Ibaraki, Shimotsuma	OR415609	OR415616	OR423362
G. mori	TNS-F-99267	Japan, Saitama, Kitamoto	OR415610	OR415617	OR423363
G. mori	TNS-F-99268	Japan, Saitama, Kawajima, Demaru-nakago	OR415611	OR415618	OR423364
G. mori	TNS-F-99269	Japan, Saitama, Kawajima, Demaru-shimogo	OR415612	OR415619	OR423365
G. multiporum	RSP 05-31	USA, New Mexico	KJ720179	KJ720179	n/a
G. nidus-avis	RSP 05-29	USA, New Mexico	KJ720181	KJ720181	n/a
G. nidus-avis	NYBG 237080	USA	KU342757	MN605019	n/a
G. nidus-avis	NYBG 461234	USA	KU342758	MN605015	n/a
G. niitakayamense	TNM F0027945	Taiwan, Nantou, Ren’ai	KP308396	KP308396	n/a
G. niitakayamense	TNM F0027946	Taiwan, Hualien, Sioulin	KP308397	KP308397	n/a
G. nootkatense	PUR 63656	Canada	KJ720159	KJ720159	n/a
G. raphiolepidis	TNS-F-79706	Japan, Chiba, Choshi	MT419964	n/a	n/a
G. raphiolepidis	TNS-F-70764	Japan, Chiba, Choshi	MT419965	n/a	n/a
G. raphiolepidis	TNS-F-70765	Japan, Ibaraki, Kamisu	MT419966	n/a	n/a
G. sabinae	TUB RB2066	Germany	AY512845	n/a	n/a
G. sabinae	TNM F0030477	Bulgaria, Sofia	KY964764	KY964764	n/a
G. sabinae	CUP 0477	USA	MN605721	MN605022	n/a
G. speciosum	RSP 99-96	USA, Arizona	KJ720160	KJ720160	n/a
G. tsingchenense	HMAS 133735	China	n/a	MN605032	n/a
G. vauqueliniae	RSP 05-87	USA, Arizona	KJ720186	KJ720186	n/a
Puccinia boroniae	BPI 57810	Australia	MW147045	MW147074	MW139655
Puccorchidium polyalthiae	ZT HeRB 251	n/a	JF263493	JF263509	JF263525
Sphaerophragmium acaciae	BRIP 56910	Australia, Western Australia, Kununurra	KJ862350	KJ862429	KJ862462
S. longicorne	PUR N16513	Nigeria, Abor, Enugu	MW147053	MW147077	n/a

^a Sequences newly generated in the present study are shown in bold.

^b The International Nucleotide Sequence Databases (INSD) accession numbers for the large subunit (28S) and the small subunit (18S) of the nuclear ribosomal RNA gene and Cytochrome-c-oxidase subunit 3 (CO3) of the mitochondrial DNA sequences. Identical accession numbers for 28S and 18S indicate a single rDNA sequence containing both regions.

^c “n/a” means unavailable information.

ML analysis was performed using IQ-TREE v.1.6.12 (Nguyen et al., 2015). According to determine the lowest Bayesian information criterion scores (25315.04) by IQ-TREE, the GTR+F+I+G4 model was chosen as the best-fit evolutional model for the analysis of the combined 28S, 18S and CO3 dataset. For the ML analysis, clade robustness was assessed using the Shimodaira-Hasegawa-like approximate likelihood ratio test (SH-aLRT; Guindon et al., 2010) and ultrafast bootstraps (UFBoot; Hoang et al., 2018) with 10000 replicates, respectively. BI analysis was performed using MrBayes version 3.2.7 (Ronquist et al., 2012) based on the same method of Kasuya and Ono (2018). The GTR+I+G model was selected as the best evolutionary model for the combined dataset by the hierarchical likelihood-ratio test using MrModeltest2 (Nylander, 2004). The support of nodes was tested by posterior probabilities (BPP), obtained from a 50% majority rule consensus after deleting the trees in the burn-in period.

The combined dataset of 283, 18S and CO3 had an aligned in length of 3371 characters including gaps, of which 2090 constant and phylogenetically uninformative, and 1281 phylogenetically informative. The highest log likelihood of the resulting ML tree of the combined dataset of the three loci was -12124.92. By BI, after 850,000 generations of Markov chain Monte Carlo runs, the analysis reached stationarity: the average standard deviation of split frequencies dropped below 0.01 after 405,000 generations. After discarding the burn-in phase, the trees had a likelihood score (harmonic mean) of -12304.44 with the potential scale reduction factor of 1.000 for all parameters, indicating that the analyses were run for a sufficient number of generations. The ML and BI analyses resulted in trees that were almost identical in topology. Hence, only the ML tree topology of the combined 28S, 18S and CO3 dataset is shown in Fig. 2.

Fig. 2 - A phylogenetic tree generated from maximum likelihood (ML) analysis based on the combined dataset of sequences from the large subunit and the small subunit of the nuclear ribosomal RNA gene and Cytochrome-c-oxidase subunit 3 of the mitochondrial DNA of selected rust species. Taxon indicated by bold are newly generated sequences from the present study. “AE” and “RO” indicate that taxon produce Aecidium-type or Roestelia-type of aecia, respectively. “Unknown” means species which is not known the aecial stage. Numbers along branches are nodal supports by the Shimodaira-Hasegawa-like approximate likelihood ratio test (SH-aLRT; left), ultrafast bootstraps (UFBoot; middle) and Bayesian posterior probabilities (BPP; right). SH-aLRT, UFBoot and BPP less than 80%, 95% or 0.70 are indicated by an asterisk (*), respectively. Scale bar indicates the number of substitutions per site.

By ML and BI analyses, 28S, 18S and CO3 sequences generated from specimens of A. mori were placed within a strongly supported clade [SH-aLRT(%)/UFBoot (%)/BPP = 100/100/1.00]. It was included into the major clade comprising Gymnosporangium, but clearly distinct from the other species (Fig. 2). This clade was phylogenetically close to G. libocedri (Henn.) F. Kern [= Gymnotelium blasdaleanum (Dietel & Holw.) Arthur] and G. ellisii (Berk.) Berk. [= Gymnotelium myricatum (Schwein.) Arthur] (Fig. 2). These two species have Aecidium-type of aecia, and species of Gymnosporangium producing this type of aecia were taxonomically separated as Gymnotelium because aecial structures were different from the other species of Gymnosporangium (Roestelia-type of Cummins & Hiratsuka, 1983) (Aime & McTaggart, 2021). Although Cummins and Hiratsuka (1983) treated Gymnotelium as a synonym of Gymnosporangium, Aime and McTaggart (2021) suggested Gymnotelium as an independent genus from Gymnosporangium based on its morphology, phylogeny and host plants. They also indicated that morphological similarities of A. mori (≡ P. mori) with Gymnotelium. However, species of Gymnosporangium having Aecidium-type and Roestelia-type of aecia are scattered in our phylogenetic trees and species having each type do not make monophyletic group (Fig. 2). Results of the present analyses are also supported by phylograms of Gymnosoprangium on Malus reported by Zhao et al. (2020). Moreover, results of our phylogenetic analyses (Fig. 2) strongly support the monophyly of Gymnosporangium including G. sabinae (Dicks.) G. Winter (= G. fuscum DC.), the type species of the genus [SH-aLRT(%)/UFBoot (%)/BPP = 87/95/1.00]. Simultaneously the present phylogram shows species hitherto recognized as Gymnotelium [G. nootkatense (Trel.) Arthur (≡ Gymnotelium nootkatense (Trel.) Syd., the type species of Gymontelium), G. speciosum Peck (≡ Gymnotelium speciosum (Peck) Aime & McTaggart), G. libocedri and G. ellisii] are paraphyletic and do not form independent clade (Fig. 2). Therefore, we consider that Gymnotelium is included into Gymnosporangium.

From above phylogenetic analyses it is concluded that A. mori should be treated as a new member of Gymnosporangium although it produces only one stage of life cycle (aecidioid uredinia or uredinoid aecia). It is suspected that this species may be differentiated from aecial stage of Gymnosporangium having heteroecious life cycles and has changed function of its aeciospores to urediniospores for its survival (Cummins & Hiratsuka, 1983; Leppik, 1972), similar to G. raphiolepidis reported by Kasuya et al. (2020).

Caeoma mori is a legitimate earliest name for A. mori under ICN Shenzhen Code (Art. F.8, Turland et al., 2018). However, the application of an anamorphic genus name, Caeoma Link or Aecidium Pers. to a teleomorphic genus name, Gymnosporangium which is morphologically and taxonomically different from Caeoma or Aecidium, causes great confusion in the taxonomy of rust fungi because these anamorphic genera are connected with many teleomorphic genera (Ji et al., 2017, 2019; Kakishima et al., 2018; Kasuya et al., 2020; Ono, 2016). Therefore, we propose a new combination in Gymnosporangium for C. mori (≡ A. mori). Uredinial anamorphic name, P. mori is also treated as its obligate synonym. In addition, the present phylogenetic analyses strongly suggest that Roestelia brucensis Parmelee as a member of the genus Gymnosporangium (Fig. 2). Two sequences of R. brucensis (KJ720189 is deposited as Uredo apacheca R.S. Peterson in the NCBI GenBank databases but it was reassessed as R. brucensis by Zhao et al., 2020) were placed within a strongly supported clade [SH-aLRT(%)/UFBoot (%)/BPP = 98/100/1.00] in the major clade comprising Gymnosporangium species. Although Gymnosporangium has been conserved against the older name Roestelia Rebent. (Aime & McTaggart, 2021), R. brucensis has not been transferred to Gymnosporangium. Therefore, we here propose a new combination of R. brucensis in the genus Gymnosporangium.

Taxonomy

Gymnosporangium mori (Barclay) T. Kasuya, K. Hosaka, Jing X. Ji & Kakish., comb. nov.

MycoBank no.: MB 849771.

Basionym: Caeoma mori Barclay, J. Asiat. Soc. Bengal, Pt. 2, Nat. Sci. 59: 97, 1890.

Obligate synonyms: Aecidium mori (Barclay) Barclay, J. Asiat. Soc. Bengal, Pt. 2, Nat. Sci. 60: 225, 1891; Uredo mori (Barclay) Sacc., Syll. Fung. (Abellini) 9: 334, 1891; Peridiopsora mori (Barclay) K.V. Prasad, B.R.D. Yadav & Sullia, Curr. Sci. 65: 426, 1993.

Typus: Pl. IV, Fig. 6 in Barclay (1890) (Holotype, cited from Index Fungorum); JAPAN, Ibaraki Prefecture, Joso, Tategata (approx. 36º7’56.17 N, 139º59’51.59 E, alt. 15.8 m), on Morus alba L., 16 Jun 2021, T. Kasuya, TNS-F-99251 (Epitype, designated here). Because a figure by Barclay (1890) is designated as the type of this species (Index Fungorum) we have selected an epitype specimen to specify the morphological characteristics and phylogenetic position of this species.

DNA sequence ex-Epitype: INSD accession no. OR415605 for 28S, OR415613 for 18S and OR423360 for CO3.

Additional specimens examined: JAPAN, Ibaraki Prefecture: Joso, Tategata, on Morus alba, 30 May 2023, M. Kakishima, TNS-F-99265; Joso, Moto-toyoda, on M. alba, 16 Jun 2021, T. Kasuya, TNS-F-99252; Tsukuba, Amakubo, Tsukuba Botanical Garden, on M. alba, 24 May 2023, M. Kakishima, TNS-F-108304; Shimotsuma, Shimoda, on M. alba, 19 Jun 2023, T. Kasuya, TNS-F-99266. JAPAN, Saitama Prefecture: Kitamoto, Ishitoshuku, on M. alba, 1 Jun 2023, T. Kasuya, TNS-F-99267; Kawajima, Demaru-nakago, on M. alba, 1 Jun 2023, T. Kasuya, TNS-F-99268; Kawajima, Demaru-shimogo, on M. alba, 1 Jun 2023, TNS-F-99269.

Distribution and host plants hitherto recorded: Asia (Afghanistan, Burma, China, India, Indonesia, Japan, Korea, Pakistan, Philippines, Taiwan and Thailand). On Moraceae: Broussonetia kazinoki Sieb., B. papyrifera (L.) L’Hér. ex Vent., Morus acidosa Griff., M. alba L. [= M. atropurpurea Roxb., M. chinensis Lodd. ex Loudon, M. intermedia Perr., M. latifolia Poir., M. multicaulis (Perr.) Perr., M. tatarica L.], M. australis Poir. (= M. bombycis Koidz.), M. cathayana Hemsl., M. indica L., M. kagayamae Koidz., M. mongolica (Bureau) C.K. Schneid., M. serrata Roxb. (Ahmad et al., 1997; Boedijn, 1959; Cho & Shin, 2004; Dizon & Kakishima, 1995; Giatgong, 1980; Hiratsuka & Chen, 1991; Hiratsuka et al., 1992; Iqbal & Khalid, 1996; Ito, 1950; Kobayashi, 2007; Mordue, 1991; Prasad et al., 1993; Spaulding, 1961; Tai, 1979; Teng, 1996).

Gymnosporangium brucense (Parmelee) T. Kasuya, K. Hosaka, Jing X. Ji & Kakish., comb. nov.

MycoBank no.: MB 849772.

Basionym: Roestelia brucensis Parmelee, Can. J. Bot. 43: 259, 1965.

Distribution and host plants hitherto recorded: North America (Canada, Mexico and USA). On Juniperaceae: Juniperus horizontalis Moench. (Parmelee, 1965; Parmelee & Corlett, 1973).

Disclosure

The authors declare no conflict of interest. All the experiments undertaken in this study comply with the current laws of Japan.

Acknowledgments

We are very much obliged to Dr. Kohei Yamamoto, Mr. Ikuo Asai and Ms. Kayoko Kasuya for their helps to facilitate the fieldwork. Special thanks also go to Dr. Emi Miwa, TechnoSuruga Laboratory Co. Ltd., Japan, for her technical support to molecular experiments. We are grateful to Dr. Konstanze Bensch, Mycobank Curator at Botanische Staatsammlung München, Germany, for her valuable suggestions to the nomenclature of the rust fungus. This work was supported in part by JSPS KAKENHI Grant Numbers JP20H03006, JP20K06805 and JP23K05895.

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