Basipetal Chains Research Articles

<p><strong><em>Periconia citlaltepetlensis sp. nov</em></strong><strong>. (Periconiaceae, Pleosporales): a psychrotolerant fungus from high elevation volcanic glacier (Mexico)</strong></p>

Periconia citlaltepetlensis sp. nov. is the first record of a fungus identified to species level from high elevation volcanic glacier in Mexico. It is a novel dothideomycete species supported by morphological, cultural characters and phylogenetic analysis (nucleotide sequences data rDNA analysis). The new species is characterized by conidiophores often with 2–4 enteroblastic, percurrent proliferations, large, globose, golden brown or reddish brown conidia that are borne singly or in basipetal chains, verrucose to irregular lobate crests, born singly or in basipetal chains of two conidia; acropetally proliferating; conidiogenesis holoblastic. The morphology of P. citlaltepetlensis is compared to other Periconia species and a detailed description and morphological illustrations are provided.

First Report of White Blister Rust Disease Caused by Albugo occidentalis on Spinach in Turkey

Spinach (Spinacia oleracea L.) is an increasingly important vegetable crop in Turkey as is the case for many parts of the world. In March 2017, detailed field surveys were conducted to investigate the occurrence of leaf diseases in major spinach fields in Hatay Province of Turkey. White blister rust disease was sporadically present in many production fields. The disease incidence on affected crops ranged from 21 to 45% across all the areas surveyed. Initial symptoms were small chlorotic spots on the upper leaf surface. As the disease developed, white pustules (sori) or blisters were frequently produced as irregularly oval, elongated concentric rings, 3 to 4 mm in diameter, mostly on the lower leaf surface but also often on the upper surface. In the advanced stages of the disease, the white pustules often coalesced, and lesions appeared grainy due to the production of numerous oospores, rendering infected leaves unmarketable. A representative specimen (SAL2) was deposited in the Korea University Herbarium (KUS-F30037). Microscopic examination revealed that sporangia were born in basipetal chains, globose to oval, with a smooth wall surface and measured 12.5 to 15.0 × 17.5 to 20.0 μm (n = 100). The small stalked spherical haustoria, which were produced within mesophyll cells, were connected to the intercellular coenocytic hyphae, and measured 5.0 μm in diameter (n = 50). Dark-colored oospores were produced in subepidermal tissue, finely reticulated, 45 to 60 µm in diameter, with a wall thickness of 5 μm (n = 50). The morphological characteristics closely resembled those reported for Albugo occidentalis by Choi and Priest (1995). To confirm the morphological identification, both the internal transcribed spacer (ITS) rDNA and the cytochrome oxidase II (cox2) mtDNA were amplified with ITS1-O and LR0 for ITS and cox2-F and cox2-RC4 and directly sequenced (Choi et al. 2015). The resulting sequences were deposited in GenBank (accession nos. MF991148 for ITS, MF991149 for cox2). A BLASTn search revealed that the Turkish isolate is identical to the ITS and the cox2 sequences (KC676794, KC676795) of A. occidentalis in GenBank. A pathogenicity test was conducted by spraying a sporangial suspension (10⁵ sporangia/ml) onto 10 healthy leaves of 3-week-old spinach plants (cv. Matador). Inoculated plants were incubated in a dew chamber for 72 h at 18°C and then maintained in a greenhouse at 20°C with a 10-h photoperiod. Ten control plants were sprayed with distilled water and maintained under the same conditions as the inoculated plants. After 10 to 12 days, white rust pustules similar to the original symptoms observed in the field developed on inoculated plants, whereas the control plants remained symptomless. The pathogen present on the inoculated plants was morphologically identical to the original one observed on the diseased plants, fulfilling Koch’s postulates. Based on morphological characteristics, molecular sequencing data, and pathogenicity test, it was concluded that the pathogen on spinach in Turkey is A. occidentalis. The causal agent has been reported as an economically important pathogen of spinach in the United States, Mexico, Greece (Farr and Rossman 2017), and Iran (Ebrahimi and Afzali 2000). To our knowledge, this is the first report of A. occidentalis in Turkey. Although prevalence and host range of the causal disease agent is limited, major spinach production areas may be vulnerable to the introduction of this disease due to an increasing demand for this crop.

Bicoloromyces kyffinensis: a new genus and species of lichen-inhabiting conidial fungi from 83°46'S

AbstractThe new genus and species Bicoloromyces kyffinensis is described as new to science from a sterile crustose lichen, perhaps Lecanora fuscobrunnea or Lecidella sp. from Ebony Ridge of Mount Kyffin, Antarctica. The fungus recalls superficially the lichenicolous species referred to Taeniolella, but differs in having semi-macronematous conidiophores, tissues encrusted with calcium oxalate, aeruginose to blue-black colouration under the microscope, and conidia which are distoseptate and formed in basipetal chains. Energy dispersive spectroscopy established that the encrustations were of calcium oxalate. Differences from genera of rock-inhabiting fungi described from the Antarctic are discussed. This appears to be the furthest south any lichen-inhabiting fungus has been reported.

First Report of White Rust of Rocket (Eruca sativa) Caused by Albugo candida in South Africa.

Garden rocket (Eruca sativa syn.: E. vesicaria subsp. sativa (Mill) Thell.) is an annual plant of the Brassicaceae grown for fresh consumption as a salad vegetable. During winter (May to July) of 2013 and 2014 in South Africa, typical symptoms of white rust were observed in two commercial crops (each ~0.5 ha) of the garden rocket cv. Rucola coltivata in Centurion, Gauteng Province, at 33 and 80% incidence, respectively. Symptomatic leaves were deposited in the National Collection of Fungi, Plant Protection Research Institute, Agricultural Research Council, Pretoria, South Africa (PREM 61073). Early infections appeared as white to cream, blister-like sori on the lower leaf surfaces, and pale yellow lesions on the corresponding upper leaf surfaces. Later stages of infection were characterized by coalescing of lesions into large, irregular, necrotic blotches and development of additional sori on the petioles and stems. Sporangiophores were hyaline, clavate or cylindrical, and measured 24 to 30 × 11 to 14 μm (n = 50). Sporangia developed in basipetal chains and were hyaline, globose or polyangular, and 15 to 20 μm (n = 100). Based on these morphological characters and the host plant, the pathogen was identified as Albugo candida (Pers.) Kunze (2). Genomic DNA was extracted using the DNeasy Plant Mini DNA extraction kit (Qiagen) from sori containing sporangia collected from naturally infected leaves, according to the manufacturer's specifications. The internal transcribed spacer (ITS) region of ribosomonal DNA (rDNA) and the cytochrome c oxidase subunit II (COX2) region were amplified and sequenced (1). The ITS (GenBank Accession No. KM588081) and COX2 (KM588082) sequences confirmed identity of the pathogen as A. candida with 100% homology to the corresponding sequences of several A. candida isolates, including DQ418503 for the ITS sequence and DQ418514 for the COX2 sequence, of a voucher specimen of A. candida on E. sativa (BPI 184870) from Pakistan. Inoculum was prepared by scraping sporangia from infected leaves of the cv. Rucola coltivata collected from the 2014 field and placing the material in sterilized, distilled water (SDW) for 12 h at 5°C to induce zoospore formation. Pathogenicity tests were performed by spraying a suspension of 1 × 105 sporangia/ml onto each of 10 5-week-old rocket seedlings of the cv. Rucola coltivata. Ten additional seedlings were inoculated similarly with SDW to serve as a control treatment. The plants were maintained at 12 to 15°C and 95% RH for 72 h (3) before being moved to a shaded greenhouse at 20 to 24°C and 90% RH. Control plants remained symptomless, whereas white rust symptoms similar to those observed in the original fields developed on leaves of inoculated seedlings 10 to 14 days later, demonstrating that A. candida was the causal agent of the disease on E. sativa. To our knowledge, this is the first report of A. candida infecting garden rocket in South Africa.

First Report of White Blister Rust Caused by Albugo candida on Wasabi in Korea.

Wasabi (Wasabia japonica (Miq.) Matsum.), a member of the Brassicaceae family, is a commercially important crop in East Asian countries such as China, Japan, Korea, and Taiwan. In Korea, wasabi is under commercial development since it has become popular as a condiment due to its strong pungent constituents. In May 2013, wasabi plants showing typical symptoms of white blister rust disease were first observed in plastic greenhouses in Taebaek City, Korea. Leaves of infected plants had whitish sori on the lower surfaces and chlorotic blotches on the corresponding upper leaf surfaces. Later, sori changed to creamy to light tan with necrosis of leaf lesion. New infections might occur anytime during the growing season. A representative sample was deposited in the Korea University Herbarium (KUS-F27596). Microscopic examination of fresh materials was performed under a light microscope. The grouped sporangiophores were hyaline, clavate or cylindric, and measured 20 to 35 × 10 to 14 μm. The sporangia were arranged in basipetal chains, hyaline, globose to subglobose, with uniform wall thickness and measured 16 to 21 × 13 to 18 μm. The primary sporangia were morphologically similar to the secondary sporangia, although the former exhibited a slightly thicker wall than the latter. No resting organs were observed. Previously, the white blister rust pathogen on wasabi has been considered either Albugo candida or A. wasabiae, although the latter name is often considered a synonym of A. candida. Based on the morphological characteristics and the specific host plant, the causal agent of this disease was identified as A. candida (2). To confirm this morphological identification, genomic DNA was extracted from infected plant tissue, and the amplification and sequencing of the internal transcribed spacer (ITS) region of rDNA of the Korean specimen were performed using procedures outlined by Choi et al. (1), with oomycete-specific primer set, DC6 and LR0. The resulting 835-bp sequence of the region was deposited in GenBank (Accession No. KF887494). Since this was the first ITS sequence submitted for A. candida on wasabi, comparable data were not available. A comparison with the ITS sequences available in the GenBank database revealed that it is identical to A. candida found on Capsella bursa-pastoris (AF271231), and shows a high similarity of 99% with many A. candida sequences originating from other brassicaceous plants. Therefore, the pathogen found in Korea was confirmed to be A. candida. In Korea, it has been reported that A. candida attacks Brassica juncea, B. campestris subsp. penikensis, and B. napus (3), but to our knowledge this is the first record of A. candida on wasabi (4). The white blister rust caused by A. candida is one of the most devastating diseases of wasabi in Japan and Taiwan where the crop is widely cultivated. On the other hand, in the United States, Canada, and New Zealand, where wasabi is a new crop on a commercial scale, there is no record of this disease. These facts taken together suggest that wasabi white blister rust be not only currently spreading in East Asia, but it also poses a new and serious threat to production of this crop in countries in which it is currently absent.

First Record of White Rust, Caused by Albugo occidentalis, on Spinach in Greece.

In early December 2012 and February 2013, severe symptoms of white rust were observed on several commercial crops of the spinach (Spinacia oleracea L.) cvs. Tahiti and Rembrandt in the Aghia Pelaghia and Elia areas, respectively, of Heraklio, Crete, Greece. Initially, small, chlorotic lesions developed on the upper side of the leaves. As disease progressed, small, glassy white pustules developed on the underside of each leaf, frequently in concentric rings. The pustules were blister-like and oval, irregularly oval, or elongated, ranging from 0.5 to 2.0 mm in diameter and up to 3 mm in length. Lesions often coalesced, and the pustules could cover the entire lower leaf surface, rendering them unmarketable. The dome-like epidermis of host tissue covering the white rust pustules ruptured and exposed a white, chalky 'dust' of numerous powdery spores in small, circular to elongate sori. The sporangia were arranged in basipetal chains, were globose to oval, with a smooth wall that was uniformly thick and measured 19.1 ± 1.93 (14.1 to 23.5) μm × 15.3 ± 1.49 (12.9 to 20.0) μm when hydrated. Oospores were absent from the leaves. The morphological characteristics closely resembled those reported for the white rust pathogen, Albugo occidentalis Wilson (4), as well as those of A. occidentalis measured from dried leaves of Chenopodium spp. and Monolepis nuttalliana (Schult.) Greene (Herb. IMI96980, IMI351202, and IMI26345, respectively), kindly loaned by the Royal Botanic Gardens, Kew, United Kingdom. Pathogenicity was confirmed by spraying a suspension of 105 sporangia/ml on 10 healthy 20-day-old potted spinach plants of cv. Tahiti. Inoculated plants were covered with polyethylene bags for 3 days and incubated in a growth chamber at 16 to 20°C with a 10-h photoperiod. White rust symptoms were observed on the lower surface of the leaves 10 days after inoculation. Ten control plants sprayed similarly with distilled water and maintained under the same conditions as inoculated plants showed no symptoms. The fungus present on the inoculated plants was morphologically identical to that originally observed on diseased plants, fulfilling Koch's postulates. Genomic DNA from spinach leaf sori was extracted, and the internal transcribed spacer (ITS) region of ribosomal DNA (rDNA), ITS1-5,8S-ITS2, as well as the cytochrome oxidase subunit II (COX2) mitochondrial gene, were amplified. PCR products were sequenced and deposited in GenBank (KC676794 and KC676795, respectively). In a BLAST search, the ITS1-5,8S-ITS2 and COX2 sequences showed 99% similarities to 684 bp (AJ553900.1) and 599 bp (AY286220.1) sequences of the corresponding A. occidentalis genes in GenBank, respectively. Based on morphological characteristics, pathogenicity tests, and molecular sequencing data, it was concluded that the pathogen on spinach in Crete is A. occidentalis. This is an economically important pathogen of spinach in the United States, that has also has been recorded in Iran (2) and India on a Chenopodium sp. (IMI351202), and in Canada on M. nuttalliana (IMI26345). To our knowledge, this is the first report of this pathogen in Greece, and the first record on spinach in Europe. A voucher specimen has been deposited at the Royal Botanic Gardens, Kew, United Kingdom (Accession No. K(M) 181610).

A Tomato Fruit Rot Caused by Trichothecium roseum in Brazil.

Fruit rots caused by distinct fungal pathogens are commonly observed on tomatoes (Solanum lycopersicum L.) throughout all major production areas in Brazil. Samples of fruits displaying white mycelial growth associated with a profuse salmon-color sporulation were collected in greenhouse-grown tomatoes in Brasília-DF in February 2011. The isolated fungus displayed pink-to-white colonies containing several conidiophores with conidia. Mycelia displayed hyaline hyphae as much as 4 μm in diameter; conidiophores were simple or branched, 112 to 300 (360) μm long, and 2 to 4 μm wide. Conidia were produced in basipetal chains (frequently clustered), were ellipsoidal to pyriform with oblique and prominent truncate basal scars, two-celled, hyaline, and (14-) 16 to 26 (-28) × (6-) 7 to 10 (-12) μm. These characteristics allocated the specimen to Trichothecium roseum (Pers.). Koch's postulates were fulfilled for one fungal isolate by either spraying 10 intact fruits or by placing a drop of a spore suspension (adjusted to 105 conidia/ml) into three to five wounds created on 10 mature fruits of each of two tomato cultivars (Santa Clara and Dominador) by puncturing each fruit with a sterile needle. Five fruits of each cultivar were treated with sterile water as the mock-inoculated control treatment. Identical symptoms to those of the original fruit were observed only in the T. roseum-inoculated samples 5 to 7 days after using both inoculation procedures. Total DNA was extracted from a pure colony of the fungus growing on potato dextrose agar medium and used as template in PCR assays with the internal transcribed spacer (ITS)-4 (5'-TCCTCCGCTTATTGATATGC-3') and ITS-5 (5'-GGAAGTAAAAGTCGTAACAAGG-3') primer pair (2). A single amplicon of approximately 630 bp was observed and directly sequenced. Sequence analysis of the Brazilian isolate (GenBank No. JN081877) indicated identity levels of 99% with T. roseum isolates reported on Leucadendron xanthoconus in South Africa (GenBank No. EU552162) and isolates from strawberry fruits in South Korea (GenBank No. HM355750). However, phylogenetic analysis was unable to discriminate isolates of T. roseum from Passalora (GenBank No. EF432764) and Fusarium (GenBank No. GU183369) isolates, confirming the low genetic variability of the ITS region in Hypocreales (3). T. roseum has been reported to be infecting greenhouse tomatoes in the United States (4) and causing postharvest disease of tomatoes in Argentina (1). To our knowledge, this is the first report of T. roseum infecting greenhouse tomatoes in Brazil.

White Blister Rust Caused by Albugo candida on Oilseed Rape in Korea

Oilseed rape, Brassica napus ssp. oleifera (DC.) Metzger, is grownworldwide for the production of vegetable oil for human consump-tion, animal feed, and biodiesel. In Korea, this crop has also beenused as an important vegetable by harvesting the leaves nilat e winteror early spring or by picking the main flowering shoots just beforethe first flowers open. Since May 2004, typical symptoms of whiteblister rust disease on oilseed rape have been continuously found inseveral localities of Korea. Leavesof infected plants had whitishs orimostly on the lower surfaces and reddish violet blotches on thecorresponding upper leaf surfaces (Fig. 1A-C). Representativesamples were deposited in the herbarium (KUS-F20204, F22717,F24893). Microscopic examination of the sori from fresh materials wasperformed under a DIC-light microscope (Zeiss AX10). Thegrouped sporangiophores were hyaline, clavate or cylindric, andmeasured 20−40×12−15 µm (Fig. 1D & E). The sporangia werearranged in basipetal chains, hyaline, globose to subglobose, withuniform wall thickness and measured 15 −22×12−19 µm (Fig. 1F).The primary sporangia were similar to the secondary sporangia,although the former exhibit a slightly thicker wall than the latter. Noresting organs were observed. Up to now, the white blister rustpathogen on oilseed rape has been considered Albugo candida or A.cruciferarum (cf. Farr and Rossman, 2010). Albugo cruciferarum isregarded as a synonym of A candida . (cf. Choiet al ., 2007). Based onthe morphological characteristics and the specific host plant, thecausal agent of this disease was identified as A. candida (Pers.)Kuntze (Choi et al., 2007).The amplification and sequencing of cox2 mtDNA and ITSrDNA were performed according to a method of Choi et al. (2006),and the resulting sequences were deposited in GenBank (Acc. No.DQ409817 and DQ409816, respectively). In cox2 mtDNA-basedphylogenetic analysis with Albugo s.str. sequences from GenBank(Fig. 2), the present causal agent formed a well-supported group withA. candida from Brassica juncea (AY927046) as well as variousbrassicaceous plants am, ong which no sequence difference was found.The sequence of ITS region was also identical to those of A. candidafrom B. oleracea (AF241767) and B. juncea (AY929828). Therefore,the sequence analysis verified the pathogen to be A. candida .In Korea, it has been reported that A. candida attacks B. junceaand B. campestris subsp. pekinensis (Korean Society of PlantPathology, 2009), but to our knowledge this is the first record of A.candida on oilseed rape. As the white blister rust caused by A.candida is one of the most devastating diseases of oilseed rape inmany countries where the crop is cultivated, the occurrence of thisdisease poses a significant threat for the commercial large-scalecultivation of oilseed rape in Korea.

The new hyphomycete genera Brachyalara and Infundichalara, the similar Exochalara and species of ‘Phialophora sect. Catenulatae’ (Leotiomycetes)

The phylogenetic relationships of five morphologically similar strains labeled Exochalara longissima were studied with sequences of Internal Transcribed Spacer (ITS1-nc5.8S-ITS2) and the small and large subunits of nuclear ribosomal DNA (nc18S and nc28S rDNA) in three different molecular data sets. The phylogenetic analyses, maximum likelihood, maximum parsimony heuristic search and Bayesian approach, revealed that these strains belong to three different genera. Based on the two-gene phylogeny of nc18S-nc28S rDNA, the true relationship of the anamorphic genus Exochalara, typified with E. longissima (strains CBS 393.82 and CBS 980.73), lies within the Helotiales of the Leotiomycetes. Exochalara is characterized by upright, pigmented conidiophores with terminally integrated cylindrical monophialides and hyaline fusiform to drop-shaped conidia, cohering end-to-end in basipetal chains. The holomorph genera Hyphodiscus (anamorph Catenulifera) and Chlorociboria (anamorph Dothiorina) are shown as closest relatives of Exochalara. The strains CBS 622.82 and CBS 114633, which differ from Exochalara in shorter, decumbent conidiophores, ampulliform monophialides, ellipsoidal to obovoidal, 1-celled hyaline conidia straw-yellow in mass and sympodial ramification/branching of conidiophores in vitro also grouped in the Leotiomycetes but on a separate position from Exochalara. The new genus Brachyalara is introduced for them. Subsequently four strains of the morphologically similar Chalara microchona were analysed. Three strains, including the ex-type strain, which formed a strongly supported clade distinct from more typical species of Chalara, Brachyalara and Exochalara, are introduced as a new monotypic genus Infundichalara. Exochalara and the two newly recognized genera are compared with Chalara, Herreromyces and Phialophora. The strain MUCL 40959, according to the ITS (ITS1-ITS2) and three-gene phylogeny (nc18S-nc5.8S-nc28S rDNA) is found to belong to Monilochaetes, which is the anamorph of the holomorph genus Australiasca in the Glomerellales, Sordariomycetes. The fungus is described as a new anamorphic species and compared with the other four species in the genus.

On the taxonomy of Monilia roreri, an important pathogen of Theobroma cacao in South America

Monilia roreri Cif., the causal agent of an important pod rot of cocoa in South America, is redescribed and illustrated. The presence of dolipore septa in the vegetative mycelium indicating basidiomycetous affinities and the development of the conidia in basipetal chains necessitate the transfer of the fungus to another genus. The new genus Moniliophthora is proposed. Conidium ontogeny shows similarities with the genera Basipetospora and the anamorph of Blumeria (=Erysiphe).

Parenthesome Fine Structure in Pleurotus Cystidiosus and Schizophyllum Commune

Aerial basidia were produced after 3 wk on malt extract or sporulation agar but were more prominent on the latter medium. Aerial basidia produced basipetal chains consisting of up to 15 spores per chain. Single-basidiospore isolates obtained by micromanipulation produced yeast cells typical of C. neoformans in vitro as well as in vivo and were pathogenic for mice. The assimilation pattern of the single-basidiospore isolates was also that of C. neoformans. I am indebted to Dr. Lindsay S. Olive, University of North Carolina, Chapel Hill, North Carolina, for his critical reading of the descriptions and Miss Edith Cash, Nineveh, New York, for preparation of the Latin diagnoses.