Mycoscience VOL.62 (2021) 239-243 Short communication A new desert-dwelling oomycete, Pustula persica sp. nov., on Gymnarrhena micrantha (Asteraceae) from Iran Mohammad Reza Mirzaee1, Sebastian Ploch2, Marco Thines2,3,* 1 Plant Protection Research Department, South Khorasan Agricultural and Natural Resources Research and Education Center, AREEO, Birjand, Iran 2 Senckenberg Biodiversity and Climate Research Centre, Senckenberganlage 25, 60325 Frankfurt am Main, Germany 3 Goethe University, Department of Biological Sciences, Institute of Ecology, Evolution and Diversity, Max-von-Laue-Str. 13, 60483 Frankfurt am Main, Germany ABSTRACT The obligate biotrophic oomycete genus Pustula is one of the four major linages of white blister rusts (Albuginaceae) identified so far. Species of the genus Pustula cause white blister rust on numerous genera in the asterids, represented by several phylogenetically distinct genus-specific lineages, most of which still await formal description. Thus, the observation of the species of Pustula on the Asteraceae subfamily Gymnorhenoideae pointed out to the existence of a hitherto undescribed species. By the morphological and molecular phylo- genetic investigation conducted in this study it is concluded that the pathogen on Gymnarrhena micrantha from Iran indeed represents a hitherto unknown species and is described as P. persica. This species has apparently adapted to desert condition and is, after Albugo arenosa, the second species of white blister rust from Iranian deserts, highlighting the adaptability of white blister rusts to hot and dry habitats. Keywords: Albuginales, cox2, one new species, phylogeny Article history: Received 13 January 2021, Revised 16 March 2021, Accepted 16 March 2021, Available online 20 July 2021. Despite similarities, such as filamentous growth and osmo- asitizes mostly Brassicales, but a few lineages are present on other trophic nutrient uptake, the phylum Oomycota is unrelated to fungi orders (Choi, Shin, Ploch, & Thines, 2011b; Ploch, Choi, & Thines, of the kingdom Mycota, but instead belongs to the kingdom Stra- 2018). Albugo s.l. parasitizes members of the Convolvulaceae and is minipila, which also contains diatoms and brown seaweeds distinguishable from Albugo s.str. by a pronounced oogonium or- (Beakes & Thines, 2017). Organisms in the Oomycota have adapted namentation (Voglmayr & Riethmüller, 2006; Thines & Voglmayr, to a wide range of climate conditions and lifestyles (Thines, 2014) 2009). Wilsoniana is parasitic to caryophyllids and features broadly and can be found in both arctic habitats (Hassett, Thines, Buaya, pear-shaped sporangia and densely ridged or reticulate oospores Ploch, & Gradinger, 2019) and hot deserts (Mirzaee et al., 2013). (Thines & Spring, 2005; Thines & Voglmayr, 2009). Pustula parasit- The highest diversity has so far been found among the two inde- izes various asterids, in particular Asteraceae, and is characterised pendently-evolved, obligate biotrophic lineages parasitizing angio- by usually densely reticulate oospores and sporangia with an equa- sperm plants, the downy mildews and white blister rusts (Thines, torial wall thickening (Thines & Spring, 2005; Choi, Thines, Tek, & 2014; Wijayawardene et al., 2020). The white blister rusts have Shin, 2012). Traditionally, it has been assumed that species causing evolved to sporulate below the epidermis of their hosts and to liber- white blister rust disease are specific mostly on the host family ate their spores by enzymatic digestion of the epidermal layer cov- level (Wilson, 1907; Biga, 1955; Choi & Priest, 1995). However, phy- ering the pustules (Heller & Thines, 2009). The family Albuginace- logenetic investigations have revealed that in Albugo, besides the ae contains the three genera that cause white blister disease of generalist species, A. candida (Pers.) Roussel, several distinct, host- angiosperms, Albugo, Pustula, and Wilsoniana. The latter two have specific species exist, which seem to be specific below the host ge- been segregated from Albugo based on their largely different cytol- nus level (Choi, Shin, Hong, & Thines, 2007; Choi, Shin, Ploch, & ogy, differences in sporangia and oospore morphology, as well as Thines, 2008; Choi, Shin, & Thines, 2009; Thines et al., 2009; Ploch deep phylogenetic divide (Thines & Spring, 2005). In total, there et al., 2010; Choi & Thines, 2011). Also in the genus Pustula, species are four major lineages in the Albuginaceae (Voglmayr & Ri- seem to be specific on at least the host genus level (Ploch et al., ethmüller, 2006), each with a specific host range. Albugo s.str. par- 2011), leading to the description of P. helianthicola C. Rost & Thines affecting sunflower (Rost & Thines, 2011), and the re-ap- * Corresponding author. praisal of several species previously thought to be synonyms of P. Senckenberg Biodiversity and Climate Research Centre, Senckenberg Gesellschaft für Naturforschung, Mertonstr. 17-21, 60325 Frankfurt am Main, Germany obtusata (Link) C. Rost (syn. P. tragopogonis (Pers.) Thines) (Choi E-Mail address: [email protected] (M.Thines) et al., 2012). In line with this, three new species of Pustula were This is an open-access paper distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivative 4.0 international license (CC BY-NC-ND 4.0: https://creativecommons.org/licenses/by-nc-nd/4.0/). doi: org/10.47371/mycosci.2021.03.006 ― 239 ― M.R. Mirzaee et al. / Mycoscience VOL.62 (2021) 239-243 recently introduced from the Junggar Basin in China (Xu, Song, Xi, The partial cox2 sequences from the specimens were edited us- & Jiang, 2016; Xu et al., 2018). ing the DNASTAR computer package version 8 (Lasergene, Madi- During field trips in Iran, the occurrence of Pustula on Gymnar- son, WI, USA), and Geneious version 5.3.4 (Biomatters Ltd., Auck- rhena micrantha Desf. was noticed. Gymnarrhena micrantha is a land, New Zealand). Subsequently, they were added to the dataset hardy member of Asteraceae growing in dry, mostly bare and sandy of Ploch et al. (2011). In addition, the sequences of two Pustula areas in the deserts of Iran. It is an ephemeric, amphicarpic, dwarf species recently described were added (Xu et al., 2016, 2018). Se- desert annual herb which is mainly distributed in the drier parts of quences were aligned on the Mafft webserver (Katoh, Rozewicki, & the Mediterranean biome of North Africa and the Middle East. Al- Yamada, 2019) using default settings. Phylogenetic analyses were though some variation across the distribution range has been no- done on the TrEase webserver (http://thines-lab.senckenberg.de/ ticed in collections, there is only one species recognized in the ge- trease/) using FastTree2 (Price, Dehal, & Arkin, 2010) for Mini- nus. In a study of the tribe Inuleae using the cpDNA gene ndhF, it mum Evolution inference, RAxML (Stamatakis, 2014) for Maxi- was found that Gymnarrhena did not belonging to Asteroideae as mum Likelihood inference, both with 1,000 bootstrap replicates, previously thought, but rather to the paraphyletic Cichorioideae and Bayesian inference using MrBayes, version 3.2 (Ronquist et al., complex or sister to the entire Asteroideae,. Thus, it was, proposed 2012) with 5 Million generations, while other parameters were set as the sole member of the subfamily Gymnarrhenoideae (Ander- to default. berg, Eldenäs, Bayer, & Englund, 2005; Funk & Fragman-Sapir, In the phylogenetic reconstructions (Fig. 1), Pustula sp. from 2009). infecting Gymnarrhena micrantha is occupying an isolated posi- Given the host specificity previously observed for the genus tion, with no clear affinities to any other lineage. The two speci- Pustula (Ploch et al., 2011; Xu et al., 2016, 2018), it seemed plausi- mens from G. micrantha were identical in sequence and clustered ble that the Pustula species occurring on Gymnarrhena does not together with maximum support in all analyses. The specimens belong to any Pustula species described so far. Therefore, it was the from P. obtusata s.lat. infecting Tragopogon graminifolius DC. clus- aim of this study to clarify the phylogenetic relationships of the tered with P. obtusata from other species of Tragopogon with high potential new species and to investigate its morphology. to maximum support. However, some genetic divergence between Specimens sequenced in this study have been deposited in the the two groups was observed. Apart from a sister-group relation- Herbarium Senckenbergianum in Frankfurt (international herbar- ship of P. obtusata and P. junggarensis B. Xu & Z. D. Jiang, which ium code FR). The collection details are given in Table 1. Thin cross received strong to maximum support, no other subdivisions in sections using a razor blade were done on wetted herbarium speci- Pustula received strong support in all analyses. mens with white blister symptoms. Sections were transferred to Pustula is a cosmopolitan genus of white blister rusts, reported 60% lactic acid or 5% aqueous chloral hydrate solution on a slide. from all continents except for Antarctica, and affecting a wide The preparations for microscopy were warmed up, covered with range of members of the Asterales (Ploch et al., 2011). Most species coverslips and screened in bright-field using a compound light mi- of Pustula have been observed in the Asteraceae subfamilies Lactu- croscope (VWR TR 500 PH, VWR International, Darmstadt, Ger- coideae, Carduoideae and Asteroideae. So far, there has been no many). Subsequently, suitable preparations were investigated in occurrence reported in the subfamily