Developmental characteristics of sporogenous hyphae: a new observation between Brassica juncea var. tumida and Albugo candida

Brassica juncea var. tumida (tumorous stem mustard) is widely cultivated as a feature vegetable in Ningbo, Zhejiang Province, and is used as a raw material for pickles in China. White blister rust, caused by Albugo candida, has severe negative effects on tumorous stem mustard, resulting in significant economic losses. In this study, hypha colonization and extension, haustorial formation, and the development process of sporogenous hyphae and sporangia in A. candida-infected tissues were studied using light and transmission electron microscopy. Additionally, the complex and unique sporogenous hypha developmental process was revealed. During A. candida infection, cytological and ultrastructural characteristics were similar to those of cruciferous plants. During sporogenous hyphae development, an initially cylindrical sporogenous hypha with a thin inner wall at the apex developed from a cell with a thick inner wall. At the apical end of the sporogenous hypha, an electron-dense complex gathered, causing the disintegration of the inner and outer walls and the formation of new inner and outer walls. With the formation of a clavate sporogenous hypha, a deep constriction of the cell wall occurred at its subapex, in which a septum was produced and a primary sporangium was separated from the sporogenous hypha. Both layers of the sporogenous hypha wall took part in the formation of the sporangial wall but were not related the formation of the sporangial outer wall in a septum, providing direct evidence of the holoblastic formation of sporangia. Furthermore, ultrastructural observation demonstrated that the development of the primary sporangial walls within a septum occurred later than that of their lateral walls, including the degradation of constricted outer walls around the septum, formation of the inner wall and subsequent outer walls of a sporangium in the upper septum layers, confirming the earlier observation. Therefore, this study provided the model of sporogenous hyphae development and sporangial formation in chain.

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

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.

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

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.

TWO CASES OF MRI-INDUCED SKIN BURNS

Materials and methods: Both cases were imaged using a GE Optima™ MR450w 1.5T scanner. A combination of anterior and posterior arrays were used. In both cases, patients were placed in the headfi rst prone position. Results and discussion: In the fi rst case, there was a red area on the skin and a white blister appeared after 15 minutes. A closed conducting loop was created in the patient’s body, which caused increased local temperature at the junction of her thighs. We could prevent this by using insulation, such as foam pads, which is one of eight steps for preventing MRI-induced skin burns. In the second case, there were red spots on the skin of the left and right thighs at the contact of the scrotum where a white blister appeared after 15 minutes. This could not have been prevented, even if we considered all the steps for preventing MRI-induced skin burns. Conclusion: I reported a case of burns on a small area of skin at the junction of the patient’s thighs, which we could have prevented by using insulation pads, and a case of burns on the skin at the contact of the scrotum, which we could not have prevented, even if we considered all the steps for preventing MRI-induced skin burns. However, we could have stopped the increase in the degree of the burn by recognising early signs.

Mycological Characterization Of White Pustule Symptom On Ipomea Reptans Poir Leaves In Bogor-Indonesia

Ipomoea reptans Poir. (Convolvulaceae) is one of the favorite vegetables consumed by Indonesian citizens. However, the plant is commonly infected by white pustule symptom of particular pathogen on it’s leaves. The pustule known as white blister, is common disease in I. reptans Poir. leaves in Indonesia. Even so, till time, there was no microscopic description of this pathogen ever provided in previous reports in Indonesia. This study aimed to provide the biological information on the morphological and microscopic characteristics of the certain pathogen. The result revealed that the microorganism was Albugo ipomeae-aquaticae Sawada with brief characteristics in the following result.