Characterization of White Rust of Perennial Pepperweed Caused by Albugo candida in California

In California, perennial pepperweed (Lepidium latifolium) is an introduced Brassicaceae plant that is invasive, highly competitive, and listed as a noxious weed that grows in areas such as marshes, meadows, roadsides, and irrigation ditches. From 2008 through 2010, perennial pepperweed growing near farms in Monterey and Santa Clara counties was infected with white rust. Symptoms were light green-to-chlorotic spots on adaxial leaf surfaces and corresponding white, blister-like sori growing underneath the raised leaf epidermis on the abaxial surface. Sporangia were collected from lesions and used for DNA extraction. The internal transcribed spacer (ITS) region was amplified with primers ITS1/ITS4 and sequenced. The sequence matched with Albugo candida by BLAST against GenBank. On the basis of morphological and molecular data, the pathogen was confirmed to be A. candida. Pathogenicity was tested by scraping sporangia from infected leaves and spraying a suspension (1 × 105 sporangia/ml) onto pepperweed seedlings grown in pots. Plants were placed in an incubator at 100% relative humidity and 12°C for 48 h to induce zoospore release. Plants were subsequently maintained in a greenhouse. After 15 to 17 days, inoculated plants developed white rust symptoms and signs. Control plants sprayed with water did not become diseased. The experiment was completed two times with the same results. To determine the race of A. candida from perennial pepperweed, 4- to 5-week-old plants and 1- to 2-week-old seedlings of differential hosts (1–4) were inoculated in a similar fashion. The differential hosts were the following: Raphanus sativus (race 1), Brassica juncea cv. Burgonde (race 2A), B. juncea cv. Cutlass (race 2V), Armoracia rusticana (race 3), Capsella bursa-pastoris (race 4), Sisymbrium officinale (race 5), Rorippa islandica (race 6), B. rapa (B. campestris) cv. Torch (race 7A), B. rapa cvs. Reward, Cutlass, and AC Parkland (race 7V), B. nigra (race 8), B. oleracea (race 9), Sinapis alba (race 10), B. carinata (race 11), and perennial pepperweed as a control. White rust developed on pepperweed 10 to 14 days later but was not found on any of the differential hosts, indicating that this pathogen is not one of the currently described 11 races. The following commercial crop species were inoculated using the same method: arugula (Eruca sativa), Japanese mustard (B. campestris subsp. nipposinica), red mustard (B. juncea subsp. rugosa), tah tsai (B. campestris subsp. narinosa), cauliflower (B. oleracea subsp. botrytis), Chinese cabbage (B. campestris subsp. pekinensis), bok choy (B. rapa Chinensis group), broccoli raab (B. rapa subsp. rapa), and perennial pepperweed as a control. Only the perennial pepperweed developed white rust. To our knowledge, this is the first characterization of A. candida infecting perennial pepperweed in California. The disease has been documented on this plant in Colorado and also in Bulgaria, Portugal, and Spain. The host range information is important to growers because it indicates that the race currently infecting perennial pepperweed will not infect commercial crucifers. References: (1) P. A. Delwich and P. H. Williams. Cruciferae Newsl. 2:39, 1977. (2) C. B. Hill et al. Cruciferae Newsl. 13:112, 1988. (3) S. R. Rimmer et al. Can. J. Plant Pathol. 22:229, 2000. (4) P. R. Verma et al. Can. J. Bot. 53:1016, 1975.

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First Report of Albugo candida Causing White Rust on Lunaria annua in Italy

Plant Disease ◽

10.1094/pdis-07-10-0513 ◽

2011 ◽

Vol 95 (1) ◽

pp. 72-72

Author(s):

I. Camele ◽

S. M. Mang ◽

G. L. Rana

Keyword(s):

Direct Sequencing ◽

Morphological Characteristics ◽

Its Region ◽

First Report ◽

Albugo Candida ◽

White Rust ◽

Landscape Plant ◽

Average Maximum ◽

Mother Plants ◽

Health Progress

Money plant or annual honesty (Lunaria annua L.) is an ornamental landscape plant used in flower beds and borders and also in flower arrangements. It is a biennial plant with large, pointed, oval leaves. Plants of L. annua showing white-to-cream, blister-like lesions on leaves and siliques (2) were found in private gardens where approximately 800 plants of 1,000 (approximately 80 to 90%) that were observed showed symptoms. The disease was also found in two ornamental nurseries, although it was limited to a few mother plants because of extensive fungicide treatments. The gardens and ornamental nurseries were located in Potenza Province (Basilicata Region, southern Italy). Sporangiophores were mostly straight or arched and almost cylindrical with attenuated base and flat or rounded apex and measured 29.2 to 33.4 × 12.8 to 13.4 μm. Sporangia, produced in chains and joined by short connectives, exhibited a spherical or angular shape, were subhyaline, contained vacuoles, and had average maximum and minimum diameters ranging from 15.8 to 18.8 and 14 to 16 μm, respectively. The morphological characteristics closely resembled those reported for Albugo candida (Pers.) Kuntze (3). Sori were collected from naturally and artificially inoculated tissues of L. annua, with the aid of a stereomicroscope, and used to extract genomic DNA via a DNeasy Plant Mini DNA extraction kit (Qiagen, Hilden, Germany) according to the manufacturer's directions. The extracted DNA was used as a template for amplification of the internal transcribed spacer (ITS) region of rDNA with primer pair ITS4/DC6 (1,4) and sequenced. One sequence, GenBank Accession No. GQ328846, matched several sequences of A. candida (Pers). Kuntze (e.g., GenBank Accession Nos. GQ328837, GQ328836, GQ328835, GQ328834, and AF271231), showing 98% identity. Pathogenicity tests were performed and repeated twice. Leaves of 10 healthy seedlings of L. annua were surface cleaned during several washings with distilled water and then spray inoculated with a suspension of 103 sporangia/ml of A. candida. Five healthy seedlings were spray inoculated with the same volume of sterile water and served as controls. Inoculated seedlings were maintained in a moist chamber for 48 h at 20°C before being moved to a shaded glasshouse at 16 to 24°C and 90% relative humidity. White rust symptoms, similar to those observed in natural conditions, appeared on leaves of inoculated seedlings 10 to 14 days later, demonstrating that A. candida was the causal agent of the disease. Control plants remained symptomless. White rust has been reported on L. annua in Europe (Czech Republic, Germany, Poland, and the United Kingdom) and in the northwestern United States (3). To our knowledge, this is the first report of A. candida infecting annual honesty plant in Italy. References: (1) P. Bonants et al. Eur. J. Plant Pathol. 103:345, 1997. (2) D. Choi et al. Mycotaxon 53:261, 1995. (3) D. A. Glawe et al. Online publication. doi:10.1094/PHP-2004-0317-01-HN. Plant Health Progress, 2004. (4) T. J. White et al. Amplification and direct sequencing of fungal ribosomal RNA genes for phylogenetics. In: PCR Protocols. A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990.

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Albugo candida. [Descriptions of Fungi and Bacteria].

IMI Descriptions of Fungi and Bacteria ◽

10.1079/dfb/20056400460 ◽

1975 ◽

Author(s):

K. G. Mukerji

Keyword(s):

Geographical Distribution ◽

Primary Infection ◽

World Wide ◽

Plant Debris ◽

Albugo Candida ◽

White Rust ◽

Previous Crop ◽

White Blister

Abstract A description is provided for Albugo candida. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On members of Cruciferae and Capparidaceae and also on leaves of Reseda alba (Jorstad, 1964). DISEASE: White blister or white rust of crucifers. Infection occurs mostly in young plants. White chalky pustules present all over the plant except the roots. Often causes damage to cabbage and its varieties and other crucifers (25, 416; 32, 100; 39, 334; 51, 813). The attacked parts often show marked hypertrophy, especially of the inflorescence. In rare instances galls have been found on roots of radish, contining oospores and globular haustoria (30, 194; 32, 81, 192; 33, 459). GEOGRAPHICAL DISTRIBUTION: World wide where hosts are present. TRANSMISSION: Primary infection is by zoospores from germinating zoospores left in the soil or plant debris from a previous crop (Butler & Jones, 1949; 34, 69, 336; 38, 582; 39, 753). Wind-borne sporangia also germinate by formation of zoospores.

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First Report of White Rust Disease Caused by Albugo koreana on Camelina sativa in China

Plant Disease ◽

10.1094/pdis-11-20-2332-pdn ◽

2021 ◽

Author(s):

Hui Yang ◽

Zhen Xi Zhao ◽

Ya Xu Guo ◽

Biao Xu

Keyword(s):

Morphological Characteristics ◽

Lower Surface ◽

Camelina Sativa ◽

Its Rdna ◽

Bootstrap Support ◽

Oilseed Crop ◽

Rust Disease ◽

White Rust ◽

Zoospore Release ◽

White Blister

Camelina sativa, an herbaceous annual plant in the family Brassicaceae, is especially well known for its oilseed crop that produce camelina oil (Hovsepyan et al. 2008). In April 2016, white blister rust disease on C. sativa were observed in a cultivated farmland with an incidence of about 60% in Xinyuan County (43°33'39.17"N, 83°14'54.04"E), Xinjiang, China. Symptoms appeared as light-yellow chlorotic spots on the upper surface of the leaves and white blister on the corresponding lower surface. Blister sori were white, oval to ellipsoidal, scattered or coalesce, and 1.8 to 4 mm in diameter. Two representative voucher specimens were deposited in the Mycological Herbarium of Tarim University (HMUT 2527 and HMUT 2528), Aral, China. Sporangiophores hyaline, clavate or cylindrical, straight to slightly curved, (23.7 to) 27.9 to 37.9 (to 42.1) (av. 31) × (7.9 to) 9.6 to 13.7 (to 15.1) (av. 11.4) μm (n = 30), thick-walled on their lower parts, bearing sporangia in chains. Primary sporangia were globose to subglobose, wall equal thickness, and (9.5 to) 10.6 to 13.2 (to 14.3) (av. 11.9) μm in diameter (n = 50). Secondary sporangia were mostly subglobose to ovoid, with a subtruncated base, and (12.1 to) 13.2 to 16.9 (to 18) (av. 15.1) μm × (11 to) 12.1 to 15 (to 16.1) (av. 13.4) μm in size (n = 50). Oogonia were globose to subglobose, (39.7 to) 42.7 to 51.7 (to 54.1) (av. 48.3) μm in diameter (n = 30), irregular. Oospores were globose to subglobose, brown, (34.5 to) 37 to 42.7 (to 45.2) (av. 41.1) μm in diameter (n = 30), 3 to 5 μm wall in thickness, with single warts, 1.5 to 4 × 2 to 3.5 μm (n = 30). The morphological characteristics of specimens were consistent with those of Albugo koreana (Choi et al. 2007). To confirm the identification, genomic DNA were extracted directly from sori on diseased leaves from isolates HMUT 2527 and HMUT 2528, respectively. The internal transcribed spacer (ITS) rDNA and cytochrome oxidase II (cox2) mtDNA were amplified with primers DC6/LR-0 described by Choi et al. (2006) and cox2-F/cox2-R described by Hudspeth et al. (2000), respectively. A BLASTn search revealed that the ITS rDNA sequences (GenBank accession Nos. MW135444 and MW135445) were 99% (838/844 nucleotides)identical to that of A. koreana from Capsella bursa-pastoris (AY929829), and the cox2 sequences (GenBank accession Nos. MW147150 and MW147151) were 100% (567/567 nucleotides) identical to that of A. koreana from C. bursa-pastoris (AY927048). Based on the concatenated ITS and cox2 sequences, Maximum Likelihood and Bayesian analysis showed that pathogen from C. sativa with the reference isolate of A. koreana (ex C. bursa-pastoris) with high bootstrap support values and maximum posterior probability (100 ML BS and 1.00 BPP, respectively). For pathogenicity, sporangia collected from the infected leaves were suspended in sterile water at 4°C for 2 hours to improve zoospore release, and the zoospore suspension obtained from sporangial suspension (1×105 sporangia/ml) was inoculated to the lower surface of six healthy potted plants. Three non-inoculated plants were served as controls. Each plant was kept in a separate plastic humid chamber in a greenhouse with 25°C and 80% humidity for 15 days. Typical symptoms of white rust pustules developed on the inoculated plants were identical to that observed on the originally infected leaves. Control plants remained symptomless.. Based on morphological characteristics, molecular data, as well as pathogenicity tests, the pathogen on C. sativa was identified as Albugo koreana. A. koreana aslo is reported only on C. bursa-pastoris in Korea (Choi et al. 2007; Farr and Rossman 2020). To our knowledge, this is the first record of white rust disease caused by A. koreana on C. sativa, and the species is new to China. This report represents a new host plant association and a new geographical expansion for this species, presenting a potential threat to camelina production in northwest China.

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The Arabidopsis WRR4A and WRR4B paralogous NLR proteins both confer recognition of multiple Albugo candida effectors

10.1101/2021.03.29.436918 ◽

2021 ◽

Author(s):

Amey Redkar ◽

Volkan Cevik ◽

Kate Bailey ◽

Oliver J. Furzer ◽

Sebastian Fairhead ◽

...

Keyword(s):

Resistance Proteins ◽

Albugo Candida ◽

Secretion Signal ◽

White Rust ◽

Brassica Crops ◽

Broad Spectrum Resistance ◽

White Blister ◽

White Blister Rust ◽

Race 4 ◽

Important Disease

The oomycete Albugo candida causes white blister rust, an important disease of Brassica crops. Distinct races of A. candida are defined by their specificity for infecting different host species. The White Rust Resistance 4 (WRR4) locus in Col-0 accession of Arabidopsis thaliana contains three genes that encode TIR-NLR resistance proteins. The Col-0 alleles of WRR4A and WRR4B confer resistance to at least four A. candida races (2, 7 and 9 from B. juncea, B. rapa and B. oleracea, respectively, and Race 4 from Capsella bursa-pastoris). Resistance mediated by both paralogs can be overcome by Col-0-virulent isolates of Race 4. After comparing repertoires of candidate effectors in resisted and resistance-breaking strains, we used transient co-expression in tobacco or Arabidopsis to identify effectors recognized by WRR4A and WRR4B. A library of CCG effectors from four A. candida races was screened for WRR4A- or WRR4B- dependent elicitation of hypersensitive response (HR). These CCG genes were validated for WRR-dependent HR by bombardment assays in wild type Col-0, wrr4A or wrr4B mutants. Our analysis revealed eight WRR4A-recognized CCGs and four WRR4B-recognized CCGs. Remarkably, the N-terminal region of 100 amino acids after the secretion signal is sufficient for WRR4A recognition of these eight recognized effectors. This multiple recognition capacity potentially explains the broad-spectrum resistance to many A. candida races conferred by WRR4 paralogs.

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Transgressive segregation reveals mechanisms of Arabidopsis immunity to Brassica-infecting races of white rust (Albugo candida)

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1812911116 ◽

2019 ◽

Vol 116 (7) ◽

pp. 2767-2773 ◽

Cited By ~ 17

Author(s):

Volkan Cevik ◽

Freddy Boutrot ◽

Wiebke Apel ◽

Alexandre Robert-Seilaniantz ◽

Oliver J. Furzer ◽

...

Keyword(s):

Positional Cloning ◽

Recombinant Inbred Lines ◽

Inbred Lines ◽

Transgressive Segregation ◽

Crop Species ◽

Albugo Candida ◽

White Rust ◽

Adult Leaf ◽

Genes Encoding ◽

Race 2

Arabidopsis thaliana accessions are universally resistant at the adult leaf stage to white rust (Albugo candida) races that infect the crop species Brassica juncea and Brassica oleracea. We used transgressive segregation in recombinant inbred lines to test if this apparent species-wide (nonhost) resistance in A. thaliana is due to natural pyramiding of multiple Resistance (R) genes. We screened 593 inbred lines from an Arabidopsis multiparent advanced generation intercross (MAGIC) mapping population, derived from 19 resistant parental accessions, and identified two transgressive segregants that are susceptible to the pathogen. These were crossed to each MAGIC parent, and analysis of resulting F2 progeny followed by positional cloning showed that resistance to an isolate of A. candida race 2 (Ac2V) can be explained in each accession by at least one of four genes encoding nucleotide-binding, leucine-rich repeat (NLR) immune receptors. An additional gene was identified that confers resistance to an isolate of A. candida race 9 (AcBoT) that infects B. oleracea. Thus, effector-triggered immunity conferred by distinct NLR-encoding genes in multiple A. thaliana accessions provides species-wide resistance to these crop pathogens.

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Cryptococcus rajasthanensis sp. nov., an anamorphic yeast species related to Cryptococcus laurentii, isolated from Rajasthan, India

INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY ◽

10.1099/ijs.0.64543-0 ◽

2007 ◽

Vol 57 (2) ◽

pp. 414-418 ◽

Cited By ~ 11

Author(s):

Puja Saluja ◽

G. S. Prasad

Keyword(s):

Large Subunit ◽

Its Region ◽

Molecular Data ◽

Lsu Rdna ◽

Cryptococcus Laurentii ◽

The Novel ◽

D2 Domain ◽

Its Regions ◽

Anamorphic Yeast ◽

Physiological Tests

Two novel anamorphic yeast strains (S-15LT and 3-C1) were isolated from the inflorescences of plants collected in two different towns in Rajasthan State, India. Sequencing of the D1/D2 domains of the large-subunit (LSU) rDNA and the internal transcribed spacer (ITS) regions suggested they are strains of the same species. Phenotypic characteristics such as the absence of fermentation, the absence of sexual structures and ballistoconidia, the assimilation of myo-inositol and d-glucuronate, and positive Diazonium blue B and urease reactions indicated that these strains belong to the genus Cryptococcus. The novel strains differed from Cryptococcus laurentii in six physiological tests and differed from other related species in more than six tests. A phylogenetic analysis of the sequences of the D1/D2 domains of the LSU rDNA and the ITS regions placed these strains in the Bulleromyces clade within the order Tremellales, with C. laurentii as their closest described relative. The novel strains showed 1.6 and 7.5 % divergence in the D1/D2 domain of the LSU rDNA and ITS regions, respectively, with respect to C. laurentii. The divergence from other species was more than 3 % for the D1/D2 domain and more than 9 % for the ITS region. On the basis of the phenotypic and molecular data, strains S-15LT and 3-C1 represent a novel species within the genus Cryptococcus, for which the name Cryptococcus rajasthanensis sp. nov. is proposed. The type strain is S-15LT (=MTCC 7075T=CBS 10406T).

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Higher-level relationships among the eucalypts are resolved by ITS-sequence data

Australian Systematic Botany ◽

10.1071/sb00039 ◽

2002 ◽

Vol 15 (1) ◽

pp. 49 ◽

Cited By ~ 82

Author(s):

Dorothy A. Steane ◽

Dean Nicolle ◽

Gay E. McKinnon ◽

René E. Vaillancourt ◽

Brad M. Potts

Keyword(s):

Internal Transcribed Spacer ◽

Sequence Data ◽

Its Region ◽

Molecular Data ◽

Nuclear Ribosomal Dna ◽

Its Sequence ◽

Phylogenetic Groups ◽

Single Section ◽

Western Australian ◽

Genus Eucalyptus

This expanded survey of ITS sequences represents the largest analysis of molecular data ever attempted on Eucalyptus. Sequences of the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA were included in an analysis of 90 species of Eucalyptus s.s. and 28 species representing eight other genera (Allosyncarpia, Angophora, Arillastrum, Corymbia, Eucalyptopsis, Stockwellia, Lophostemon and Metrosideros). The results of the study indicate that Angophora and Corymbia form a well-supported clade that is highly differentiated from Eucalyptus s.s. Corymbia species are divided between two clades, one of which may be the sister to Angophora. Allosyncarpia, Arillastrum, Eucalyptopsis and ‘Stockwellia’ are also highly differentiated from Eucalyptus s.s. If the genus Eucalyptus is to be expanded to include Angophora and Corymbia(sensu Brooker 2000), ITS data suggest that Allosyncarpia, Eucalyptopsis, ‘Stockwellia’ and potentially Arillastrum should also be included in Eucalyptus s.l. The ITS data suggest that subg. Symphyomyrtus is paraphyletic and that subg. Minutifructus should be included within it. Within subg.Symphyomyrtus, only sect. Maidenaria appears to be monophyletic. Sections Adnataria and Dumaria are probably monophyletic; sections Exsertaria and Latoangulatae are very close and probably should be combined in a single section. Section Bisectae is polyphyletic and is divided into two distinct lineages. The phylogenetic groups depicted by ITS data are consistent with the frequency of natural inter-specific hybridisations as well as data from controlled crosses within subgenus Symphyomyrtus. The ITS data illustrate that subg. Idiogenes and western Australian monocalypts are early evolutionary lines relative to E. diversifolia, E. rubiginosa (monotypic subg. Primitiva) and the eastern monocalypts and that subg. Primitiva should be sunk into subg. Eucalyptus. Subgenus Eudesmia may be monophyletic, grouping with subgenera Idiogenes and Eucalyptus. Further work is required to confirm the phylogenetic positions of the monotypic subgenera Alveolata, Cruciformes, Acerosae and Cuboidea.

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Systematic discovery and characterization of stress-related microRNA genes in Oryza sativa

Biologia ◽

10.1515/biolog-2015-0001 ◽

2015 ◽

Vol 70 (1) ◽

Cited By ~ 1

Author(s):

Kai Bin Xie ◽

Xue Zhou ◽

Tian Hai Zhang ◽

Bao Long Zhang ◽

Li Ming Chen ◽

...

Keyword(s):

Abiotic Stress ◽

Stress Responses ◽

Systematic Investigation ◽

Chemical Toxicity ◽

Promoter Regions ◽

Crop Species ◽

Translation Inhibition ◽

Microrna Genes ◽

Insight Into

AbstractAbiotic stresses including drought, salinity, extreme temperatures, chemical toxicity and oxidative are the natural status of the environment to exert serious threats to agriculture. Abiotic stress-related microRNAs (ASmiRNAs) are a group of microRNAs (miRNAs) regulating stress responses in plants. However, the systematic investigation of ASmiRNAs is limited in Rice (O. sativa), a typical abiotic stress-resistant crop species. In the present work, we systematically investigated ASmiRNAs in silico. First, we identified 177 putative ASmiRNAs in O.sativa. Second, we found most ASmiRNAs were driven by TATA-promoter and most stress-related miRNA promoter regions contained the stress-related elements. Third, we found many ASmiRNAs families were species/family specific and a set of miRNAs might derive from genomic repeat-sequences in O. sativa. Finally, we found the ASmiRNAs in O. sativa target 289 genes with 1050 predicted target sites in which 98% sites have cleavage activity and 2% sites have translation inhibition activity. In conclusion, our findings provide an insight into both the function and evolution of ASmiRNAs and improve our understanding on the mechanism of abiotic stress resistance in O. sativa.

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