Puccinia xanthii is a fungal pathogen of plants in the Asteraceae, and can infect hosts from at least 42 genera within that family,Zhang, P., Lu, G., Sun, X., Zhang, W., Qu, B., & Tian, X. (2011). The infection process of puccinia xanthii f. sp.. ambrosiae-trifidae on ambrosia trifida. Botany, 89(11), 771–777. https://doi.org/10.1139/b11-067 most notably species in the Xanthium and Ambrosia genera. This pathogen was discovered growing on Xanthium strumarium in North Carolina, United States in 1822.Puccinia xanthii Schwein. Index fungorum . (2024). https://www.indexfungorum.org/names/NamesRecord.asp?RecordID=199752 Common names of P. xanthii include Summer RustPuccinia xanthii var. parthenii-hysterophorae. (2022). CABI Compendium. https://doi.org/10.1079/cabicompendium.48337333 and Cocklebur Rust.Gulya, T. J., & Charlet, L. D. (2007). First report of Puccinia xanthii on sunflower in North America. Plant Disease, 86(5), 564–564. https://doi.org/10.1094/pdis.2002.86.5.564a
Distribution Puccinia xanthii is native to the continental United States, Canada, Mexico, Hawaii, Cuba, Haiti, the Dominican Republic, Puerto Rico, and the Bahamas.Ryu, M., Ryu, H., Jeon, E. J., Park, Y. J., Kang, B., Ono, Y., Kim, O.-K., & Lee, S.-J. (2024). First report of Puccinia xanthii causing rust disease on Xanthium orientale in Korea. Plant Disease, 108(6), 1895. https://doi.org/10.1094/pdis-01-24-0143-pdn This fungus has been reported in several countries throughout Europe, Asia, Africa and Australia; often following the introduction of invasive host plants from North America or intentional release as a biocontrol agent.
Europe Researchers have detected P. xanthii in Bulgaria, southern France, Hungary, northern Italy, Romania, Spain, and the former Yugoslavia (Bosnia, Serbia, Slovenia, Montenegro, Macedonia, Herzegovina, and Croatia).Morin, L., Brown, J. F., & Auld, B. A. (1992). Teliospore germination, basidiospore formation and the infection process of Puccinia xanthii on Xanthium Occidentale. Mycological Research, 96(8), 661–669. https://doi.org/10.1016/s0953-7562(09)80494-2Dávid, I., Harcz, P., & Kövics, G. J. (2003). First report of Puccinia xanthii on Xanthium italicum in eastern Hungary. Plant Disease, 87(12), 1536–1536. https://doi.org/10.1094/pdis.2003.87.12.1536cKassai-Jáger, E., Seier, M. K., Evans, H. C., & Kiss, L. (2015). Molecular identification and pathogenicity assessment of a rust fungus infecting common ragweed (ambrosia artemisiifolia) in its native North American range. European Journal of Plant Pathology, 145(1), 81–87. https://doi.org/10.1007/s10658-015-0815-4 Puccinia xanthii was found growing on Xanthium orientale subsp. italicum in eastern Hungary in December 2002.Zhao, Y.-Z., Feng, Y.-L., Liu, M.-C., & Liu, Z.-H. (2014). First report of rust caused by Puccinia xanthii on Xanthium orientale subsp. italicum in China. Plant Disease, 98(11), 1582–1582. https://doi.org/10.1094/pdis-03-14-0277-pdn
Asia Puccinia xanthii has been detected in India, Indonesia, Japan, Pakistan, and Korea.Afshan, N. S., Riaz, M., Ahmad, M. A., & Khalid, A. N. (2023). Puccinia malvacearum and P. xanthii newly recorded from Pakistan. Mycotaxon, 137(4), 893–897. https://doi.org/10.5248/137.893 Puccinia xanthii was found growing in lesions on leaves of Xanthium orientale in Okcheon-gun, Korea in October 2021 and from Xanthium orientale subsp. italicum in the Liaoning Province of China in August 2013. Xanthium orientale subsp. italicum was first found in Beijing, China in 1991 and has been shown to decrease the biodiversity of native flora and cause human health hazards from allergenic pollen. As a result of this, the P. xanthii is considered beneficial in this area as it may decrease the vigor of this weed. Puccinia xanthii was also found on Xanthium strumarium in Parachinar, Pakistan in 2018.
Australia Puccinia xanthii was observed on Xanthium occidentale in Australia in 1975.Morin, L., Auld, B. A., & Brown, J. F. (1993). Host range of Puccinia xanthiiand postpenetration development on Xanthium occidentale. Canadian Journal of Botany, 71(7), 959–965. https://doi.org/10.1139/b93-108
Africa Puccinia xanthii was found growing on Helianthus annous in the Northwest Province of South Africa in February 2000.Pretorius, Z. A., van Wyk, P. S., & Kriel, W. M. (2000). Occurrence of Puccinia xanthii on sunflower in South Africa. Plant Disease, 84(8), 924–924. https://doi.org/10.1094/pdis.2000.84.8.924a
Taxonomy Puccinia xanthii is a rust in the phylum Basidiomycota, subphylum Pucciniomycotina, class Pucciniomycetes, order Pucciniales, and family Pucciniaceae. Its full scientific name is Puccinia xanthii Schwein., Schriften der Naturforschenden Gesellschaft zu Leipzig 1:73.Puccinia xanthii. MycoBank Database. (2024). https://www.mycobank.org/page/Name%20details%20page/field/Mycobank%20%23/199752 Using data from ITS (internal transcribed spacer) and TEF (translation elongation factor) phylogenetic analyses, the closest relative of P. xanthii is P. melampodii, and these species are a sister group to the fungus Dietelia portoricensis.Seier, M. K., Morin, L., van der merwe, M., Evans, H. C., & Romero, Á. (2009). Are the microcyclic rust species Puccinia melampodii and Puccinia xanthii conspecific? Mycological Research, 113(11), 1271–1282. https://doi.org/10.1016/j.mycres.2009.08.009 In 2005, Hennen et al. proposed that P. xanthii, P. melampodii, and 51 other microcyclic rusts from the Americas and Eurasia that infect members of the Asteraceae should be grouped under the single morphospecies name Puccinia cnici-oleracei. This complex is based on morphology and needs further proof to be considered valid, however, P. xanthii and P. melampodii could not be easily separated at the species level using phylogenetic data from the ITS and TEF regions.
This fungus has a high level of intraspecies variation, resulting in many different strains that specialize on one or a few hosts in the Asteraceae. Studies on the pathogenicity of Puccinia xanthii vary considerably based on where the isolate (which cannot be grown in culture) was taken. This high level of genetic variation is created through sexual recombination during karyogamy, somatic hybridization, mutations, and genes introduced from closely related species or other strains of P. xanthii. For example, an Australian strain of P. xanthii was able to infect Calendula offinalis and some cultivars of Helianthus annus while an American strain was able to infect only Ambrosia trifida in cross inoculation tests.Kiss, L. (2007). Is Puccinia xanthii a suitable biological control agent of Ambrosia artemisiifolia? Biocontrol Science and Technology, 17(5), 535–539. https://doi.org/10.1080/09583150701311705 Index Fungorum recognizes three classifications of P. xanthii below the species level: Puccinia xanthii var. ambrosiae-trifidae, Puccinia xanthii var. parthenii-hysterophorae, and Puccinia xanthii var. xanthii. This pathogen requires more study as the number of reported host species of Puccinia xanthii comprises more species than those infected by these subclassifications.
Puccinia xanthii var. ambrosiae-trifidae This is an obligate pathogen of Ambrosia trifida, commonly known as the giant ragweed. Studies in the Liaoning Province of China show that P. xanthii var. ambrosiae-trifidae is a suitable biocontrol for this plant, which is highly allergenic and invasive throughout Asia, Europe, and Australia. There is controversy over whether P. xanthii var. ambrosiae-trifidae is considered a forma specialis, as it was originally named in 1981, or a variety. Genetic evidence considering the degree or similarity between P. xanthii morphospecies suggests that the term variety is more accurate to distinguish between populations of P. xanthii, but literature varies in the use of f. sp. or var.
Puccinia xanthii var. parthenii-hysterophorae This variation is native to Mexico and specializes in infecting the plant Parthenium hysterophorus. Outside of its native range, this North American weed has caused issues in agriculture via allopathic chemicals, decreased biodiversity, and its pollen is a human health hazard. P. xanthii var. parthenii-hysterophorae has been intentionally introduced to north and central Queensland, Australia in 2000 as a biocontrol for this invasive plant. It was also introduced in South Africa as a biocontrol in 2010 as part of an effort to contain this weed from spreading through sub-Saharan Africa.Studies from Agricultural Research Council Add New Findings in the Area of African Entomology. (2011). Veterinary Week, 92. https://doi.org/link.gale.com/apps/doc/A275098083/PPAG?u=gain40375&sid=bookmark-PPAG&xid=c1a031bf.
Puccinia xanthii var. xanthii This variation specializes on plants in the Xanthium genus.
Synonyms Leptopuccinia xanthiiPuccinia xanthii. MycoBank Database. (2024). https://www.mycobank.org/page/Name%20details%20page/field/Mycobank%20%23/199752
Micropuccinia xanthii
Dasyspora xanthii
Disease Cycle Puccinia xanthii is a microcyclic, autoecious obligate biotroph. This means that it only produces basidiospores and teliospores (and lacks spermatia, aeciospores, and urediniospores) and completes its life cycle on a single living host plant. Due to the cyclic nature of rusts, this lifecycle doesn't have a "start" point. In this case, a basidiospore landing on a leaf is arbitrarily chosen to begin the life cycle.
Basidiospores of P. xanthii are carried to new plants via wind or through physical contact with nearby plants. These basidiospores germinate a polar, or occasionally lateral, germ tube that can be thin or thick. Thicker germ tubes often lead to the formation of a non-sequential basidiospore, or a smaller, secondary basidiospore that forms from the germ tube of the original. Thicker germ tubes can also lead to chains of basidiospores, which is most common in P. xanthii f. sp. ambrosiae-trifidae and functions as a form of asexual reproduction. Germ tubes are highly variable in length, and have a roughly equal chance of being 0.5-1.5 μm or 5-10 μm long. In 3% of cases, germ tubes are several times the length of the basidiospore.
At the end of the germ tube, an appressorium (specialized structure used to attach to and penetrate the leaf surface) is formed. Puccinia xanthii has been shown to produce its appressoria preferentially along the cellular gaps of the leaf epidermis. The appressoria is attached to the leaf with a mucilaginous exudate that helps protect it from desiccation and may also provide a reservoir of enzymes to help penetrate the host epidermis. This structure ranges in form from a swollen bump to a well defined lobing at the end of the germ tube. Underneath the appressorium, numerous wedge-shaped papillae and a penetration peg are formed. The penetration peg goes directly through the epidermis. While splitting the cuticle wall, the penetration peg is quite thin then expands when it reaches the cell membrane. The penetration peg continues growing and forms intraepidermal vesicles to contain the remaining contents of the basidiospore before putting down a septum and differentiating into primary hyphae.
The hyphae colonizes the plant tissue as it grows and branches into neighboring epidermal cells, intercellular space, and finally into the spongy parenchyma cells. During this colonization, the hyphae forms haustoria 24 to 48 hours after inoculation. The haustoria of P. xanthii look like swellings of the hyphae (lacking morphological specialization seen in haustoria with projections) that grow inside plant cells and absorb nutrients and water.