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Using molecular phylogenetic analyses (ITS) and morphological data obtained from light and electron microscopy, some European and North American species and genera placed or formerly placed in the genus Pucciniastrum in the Coleosporiaceae and Pucciniastraceae (Pucciniales) were taxonomically revised. The ITS analyses confirmed recent familiar concepts based on less variable markers except for the genus Hyalopsora. The family Pucciniastraceae is characterized by Abietoideae (Abies, Tsuga) aecial hosts. Pucciniastrum is described as a genus that consists of host-alternating species forming aecia on needles of Abies hosts, with special features of aeciospore morphology, and Onagraceae telial hosts. Other genera in the Pucciniastraceae are Calyptospora, Melampsorella, and additional taxa, which are currently provisionally placed in Pucciniastrum, but must be revised in future studies. Pucciniastrum epilobii (s. lat.), the type species of Pucciniastraceae, represents at least two species with different life cycles and urediniospore characteristics and is lecto- and epitypified. The family Coleosporiaceae, characterized by Pinoideae (Pinus) and Piceoideae (Picea) aecial hosts, contains Rosaceae rusts from three well-supported clades represented by three genera, Thekopsora, Quasipucciniastrum, and Aculeastrum gen. nov. Aculeastrum is characterized by coarsely arcuate ostiolar peridial cells and infects Rubus spp. telial hosts. The following new taxonomic combinations are proposed: Calyptospora ornamentalis comb. nov., Quasipucciniastrum ochraceum comb. nov., Q. potentillae comb. nov, Aculeastrum americanum comb. nov., and A. arcticum comb. nov. The results are discussed with emphasis on future studies in Pucciniastrum and the P. epilobii complex and on nomenclatural changes necessary for rust fungi due to the Shenzhen Code.
Using molecular phylogenetic analyses (ITS) and morphological data obtained from light and electron microscopy, some European and North American species and genera placed or formerly placed in the genus Pucciniastrum in the Coleosporiaceae and Pucciniastraceae (Pucciniales) were taxonomically revised. The ITS analyses confirmed recent familiar concepts based on less variable markers except for the genus Hyalopsora. The family Pucciniastraceae is characterized by Abietoideae (Abies, Tsuga) aecial hosts. Pucciniastrum is described as a genus that consists of host-alternating species forming aecia on needles of Abies hosts, with special features of aeciospore morphology, and Onagraceae telial hosts. Other genera in the Pucciniastraceae are Calyptospora, Melampsorella, and additional taxa, which are currently provisionally placed in Pucciniastrum, but must be revised in future studies. Pucciniastrum epilobii (s. lat.), the type species of Pucciniastraceae, represents at least two species with different life cycles and urediniospore characteristics and is lecto- and epitypified. The family Coleosporiaceae, characterized by Pinoideae (Pinus) and Piceoideae (Picea) aecial hosts, contains Rosaceae rusts from three well-supported clades represented by three genera, Thekopsora, Quasipucciniastrum, and Aculeastrum gen. nov. Aculeastrum is characterized by coarsely arcuate ostiolar peridial cells and infects Rubus spp. telial hosts. The following new taxonomic combinations are proposed: Calyptospora ornamentalis comb. nov., Quasipucciniastrum ochraceum comb. nov., Q. potentillae comb. nov, Aculeastrum americanum comb. nov., and A. arcticum comb. nov. The results are discussed with emphasis on future studies in Pucciniastrum and the P. epilobii complex and on nomenclatural changes necessary for rust fungi due to the Shenzhen Code.
False shamrock (Oxalis triangularis), native to South America, is an ornamental and popular plant bulb, commercialized for their attractive shape and color (purple triangular leaves) (Taha et al., 2013). In Chile, a rust was detected in O. triangularis plants growing from April to June in several gardens (n=10) in the city of Valdivia, estimating a disease incidence between 80 and 100%. The symptoms appeared as diffuse chlorotic spots from the upperside of leaves, where infected tissues eventually become completely necrotic, and yellow rust pustules were observed on the underside of leaves. Severe symptoms on infected leaves were consistently observed, showing necrosis on entire leaves. Symptomatic plants (n=50) were collected, and three representative isolates from different localities (OX1, OX2, and OX3) were used for morphological and genetic identification. Uredinia (n=20) were hypophyllous, erumpent, yellow, and irregularly distributed, with sizes from 340 to 850 μm in diameter. Urediniospores (n=150) were yellow, subglobose to globose, equinulate, with measures of 14.2 - 17.7 x 14.7 - 17.2 µm. Teliospores were absent. Based on morphological characters, this rust was identified as a Puccinia sp. These morphological characteristics coincided with those indicated by Šafránková (2014), Abbasi et al. (2018), and Khouader et al. (2018). To classify this rust genetically, sequences analyses were performed using the ITS region of the rDNA (ITS4/ITS5) (White et al., 1990). The DNA was extracted using a commercial kit. The results indicated 99% similarity with two reference sequences of P. oxalidis (MH325473 and MH325474) available at GenBank (NCBI http://www.ncbi.nlm.nih.gov/BLAST/). The sequences obtained were deposited in GenBank (ON259085 to ON259087). Based on the maximum parsimony phylogenetic tree, the sequences of Chilean isolates were clustered with those of P. oxalidis references. Pathogenicity tests were conducted using three isolates (OX1 to OX3). Surface disinfection of leaves of O. triangularis (n=36 plants), were performed by spraying 1% NaOCl solution for 1 min. Subsequently, 2 mL of urediniospores suspensions of each isolate (OX1 to OX3) at a concentration of 106 urediniospores/mL, were sprayed with an atomizer on the underside of the leaves of all plants. Urediniospores were obtained following the methodology proposed by Ferrada et al. (2020). Control leaves were disinfested and inoculated with sterile distilled water. Plants of O. triangularis of 90-day-old were incubated in a humid chamber (24°C, 80% HR), with a photoperiod of 12 light /12 dark. At 11 days post-inoculation, all leaves inoculated developed chlorosis spots and pulverulent pustules (averaged 10.9 to 25.4 pustules per leaf), and then at 26 days post-inoculation, affected leaves showed necrotic tissues. The identity of these isolates was confirmed morphologically. The symptoms in the control leaves were negative. To our knowledge, this is the first report of multiple occurrences of the leaf rust disease on gardens of false shamrock caused by P. oxalidis in Valdivia, south of Chile. Previously, P. oxalidis has been reported to cause leaf rust disease in O. triangularis in the Czech Republic (Šafránková, 2014) and O. debilis in Korea (Lee et al., 2018). The leaf rust disease could represent a threat to the ornamental gardens of O. triangularis in Valdivia. Currently, epidemiological studies of leaf rust disease are necessary to develop management strategies in gardens of O. triangularis.
Bedding plants are a major group of ornamentals produced in greenhouses or nurseries worldwide and planted outdoors. Their economic importance has increased continuously in the last four decades in both the United States and the European Union. These plants are subject to many diseases that can negatively impact their production and cultivation. The initial steps of production strongly influence the health status of these plants and, consequently, their aesthetic appeal, which is a strong requisite for consumers. Seeds, cuttings, other forms of propagative material, along with production systems and growing media can influence the phytosanitary status of the final product. In this paper, case studies of soil-borne and foliar diseases are presented together with preventive measures to achieve innovative disease management strategies. Quarantine restrictions and eradication measures are also discussed, in consideration of the high likelihood for ornamental plants to be long-distance vectors of new pathogens and pests.
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