scholarly journals The Role of Primary and Secondary Infection in Host Response to Plasmodiophora brassicae

2014 ◽  
Vol 104 (10) ◽  
pp. 1078-1087 ◽  
Author(s):  
Mary Ruth McDonald ◽  
Kalpana Sharma ◽  
Bruce D. Gossen ◽  
Abhinandan Deora ◽  
Jie Feng ◽  
...  
Keyword(s):  
Plasmodiophora Brassicae ◽  
Secondary Infection ◽  
Root Hairs ◽  
Secondary Phase ◽  
Primary Phase ◽  
Root Cortex ◽  
Resting Spores ◽  
Cortical Infection ◽  
Root Hair Infection

The disease cycle of Plasmodiophora brassicae consists of a primary phase in root hairs followed by a secondary phase in the root cortex and adjacent tissues. However, the role of root hair infection in subsequent cortical infection and development of P. brassicae is not well understood. To examine the role of the primary and secondary stages separately, inoculation studies with resting spores (source of primary zoospores) and secondary zoospores of a virulent and avirulent pathotype were conducted on canola (Brassica napus). The size of secondary zoospores and number of nuclei were also examined. The zoospores were larger (≈9.6 to 14.4 μm) than in previous reports and all were uninucleate. Inoculation with secondary zoospores alone produced both primary and secondary infection, even with the avirulent pathotype. No symptoms developed from inoculation with avirulent primary zoospores but tiny, bead-shaped clubs developed from inoculation with avirulent secondary zoospores. Inoculation with virulent secondary zoospores alone resulted in lower disease severity than inoculation with virulent resting spores alone. The results indicate that recognition of infection by the host and initiation of a response (induction or suppression of resistance) occurs during primary infection, although recognition can also occur during cortical infection and development.

The life history of Plasmodiophora brassicae Woron

1972 ◽  
Vol 180 (1058) ◽  
pp. 103-112 ◽  
Keyword(s):  
Life History ◽  
Root Hair ◽  
Plasmodiophora Brassicae ◽  
Root Hairs ◽  
Secondary Phase ◽  
Tissue Cultures ◽  
Resting Spore ◽  
Resting Spores ◽  
Seedling Roots ◽  
History Of

Resting spore germination and the root hair stages of the life history of Plasmodiophora brassicae were studied in stained preparations of infected Brassica rapa seedling roots. Naked protoplasts, usually possessing two unequal flagella, were released from resting spores through a small circular pore. They penetrated the root hairs of B. rapa and there developed into plasmodia which, after becoming multinucleate, cleaved to form zoosporangia con­taining incipient zoospores. Biflagellate zoospores were released from root hair zoosporangia and fused in pairs, although karyogamy did not occur. The resulting binucleate zoospores infected the cortical dells of B. rapa to form binucleate plasmodia, the earliest stages of the secondary phase of the life history. These findings are discussed in relation to previous studies on the life history of P. brassicae in Brassica plants and in Brassica tissue cultures, and a new complete life history, including nuclear fusion in the secondary plasmodium, is suggested for the organism.

scholarly journals Effect of Temperature on Cortical Infection by Plasmodiophora brassicae and Clubroot Severity

2011 ◽  
Vol 101 (12) ◽  
pp. 1424-1432 ◽  
Author(s):  
Kalpana Sharma ◽  
Bruce D. Gossen ◽  
Mary Ruth McDonald
Keyword(s):  
Life Cycle ◽  
Brassica Rapa ◽  
Plasmodiophora Brassicae ◽  
Consistent Pattern ◽  
Effect Of Temperature ◽  
Symptom Development ◽  
Root Cortex ◽  
Brassica Crops ◽  
Resting Spores ◽  
Cortical Infection

A study was conducted to assess the effect of temperature on infection and development of Plasmodiophora brassicae in the root cortex of Shanghai pak choy (Brassica rapa subsp. chinensis) and on subsequent clubroot severity. Ten-day-old seedlings were grown individually, inoculated with resting spores, and maintained in growth cabinets at 10, 15, 20, 25, and 30°C. Seedlings were harvested at 2-day intervals, starting 8 days after inoculation (DAI) and continuing until 42 DAI. Roots were assessed at 4-day intervals for the incidence of cortical infection and stage of infection (young plasmodia, mature plasmodia, and resting spores), at 2-day intervals for symptom development and clubroot severity, and at 8-day intervals for the number of spores per gram of gall. Temperature affected every stage of clubroot development. Cortical infection was highest and symptoms were observed earliest at 25°C, intermediate at 20 and 30°C, and lowest and latest at 15°C. No cortical infection or symptoms were observed at 42 DAI in plants grown at 10°C. A substantial delay in the development of the pathogen was observed at 15°C. Resting spores were first observed at 38 DAI in plants at 15°C, 26 DAI at 20 and 30°C, and 22 DAI at 25°C. The yield of resting spores from galls was higher in galls that developed at 20 to 30°C than those that developed at 15°C over 42 days of assessment. These results support the observation in companion studies that cool temperatures result in slower development of clubroot symptoms in brassica crops, and demonstrate that the temperature has a consistent pattern of effect throughout the life cycle of the pathogen.

scholarly journals Histopathology of the Plasmodiophora brassicae-Chinese Cabbage Interaction in Hosts Carrying Different Sources of Resistance

2022 ◽  
Vol 12 ◽  
Author(s):  
Xitong Liu ◽  
Stephen E. Strelkov ◽  
Rifei Sun ◽  
Sheau-Fang Hwang ◽  
Rudolph Fredua-Agyeman ◽  
...  
Keyword(s):  
Chinese Cabbage ◽  
Vascular System ◽  
Plasmodiophora Brassicae ◽  
Secondary Infection ◽  
Root Hairs ◽  
Recessive Gene ◽  
Post Inoculation ◽  
Sources Of Resistance ◽  
Cortical Infection ◽  
Different Sources

Clubroot is a serious soil-borne disease of crucifers caused by the obligate parasite Plasmodiophora brassicae. The genetic basis and histopathology of clubroot resistance in two Chinese cabbage (Brassica rapa ssp. pekinensis) inbred lines Bap055 and Bap246, challenged with pathotype 4 of P. brassicae, was evaluated. The Chinese cabbage cultivar “Juxin” served as a susceptible check. The resistance in Bap055 was found to be controlled by the CRa gene, while resistance in Bap246 fit a model of control by unknown recessive gene. Infection of the roots by P. brassicae was examined by inverted microscopy. Despite their resistance, primary and secondary infection were observed to occur in Bap055 and Bap246. Primary infection was detected at 2 days post-inoculation (DPI) in “Juxin,” at 4 DPI in Bap055, and at 6 DPI in Bap246. Infection occurred most quickly on “Juxin,” with 60% of the root hairs infected at 10 DPI, followed by Bap055 (31% of the root hairs infected at 12 DPI) and Bap246 (20% of the root hairs infected at 14 DPI). Secondary infection of “Juxin” was first observed at 8 DPI, while in Bap055 and Bap246, secondary infection was first observed at 10 DPI. At 14 DPI, the percentage of cortical infection in “Juxin,” Bap055 and Bap246 was 93.3, 20.0, and 11.1%, respectively. Although cortical infection was more widespread in Bap055 than in Bap246, secondary infection in both of these hosts was restricted relative to the susceptible check, and the vascular system remained intact. A large number of binucleate secondary plasmodia were observed in “Juxin” and the vascular system was disrupted at 16 DPI; in Bap055 and Bap246, only a few secondary plasmodia were visible, with no binucleate secondary plasmodia. The defense mechanisms and expression of resistance appears to differ between Chinese cabbage cultivars carrying different sources of resistance.

scholarly journals Transcriptome and Coexpression Network Analyses Reveal Hub Genes in Chinese Cabbage (Brassica rapa L. ssp. pekinensis) During Different Stages of Plasmodiophora brassicae Infection

2021 ◽  
Vol 12 ◽  
Author(s):  
Yuxiang Yuan ◽  
Liuyue Qin ◽  
Henan Su ◽  
Shuangjuan Yang ◽  
Xiaochun Wei ◽  
...  
Keyword(s):  
Chinese Cabbage ◽  
Plasmodiophora Brassicae ◽  
Primary Root ◽  
Resistance Mechanisms ◽  
Coexpression Network ◽  
Hub Genes ◽  
Clubroot Resistance ◽  
Network Analyses ◽  
Cortical Infection ◽  
Root Hair Infection

Clubroot, caused by the soil-borne protist Plasmodiophora brassicae, is one of the most destructive diseases of Chinese cabbage worldwide. However, the clubroot resistance mechanisms remain unclear. In this study, in both clubroot-resistant (DH40R) and clubroot-susceptible (DH199S) Chinese cabbage lines, the primary (root hair infection) and secondary (cortical infection) infection stages started 2 and 5 days after inoculation (dai), respectively. With the extension of the infection time, cortical infection was blocked and complete P. brassica resistance was observed in DH40R, while disease scales of 1, 2, and 3 were observed at 8, 13, and 22 dai in DH199S. Transcriptome analysis at 0, 2, 5, 8, 13, and 22 dai identified 5,750 relative DEGs (rDEGs) between DH40R and DH199S. The results indicated that genes associated with auxin, PR, disease resistance proteins, oxidative stress, and WRKY and MYB transcription factors were involved in clubroot resistance regulation. In addition, weighted gene coexpression network analysis (WGCNA) identified three of the modules whose functions were highly associated with clubroot-resistant, including ten hub genes related to clubroot resistance (ARF2, EDR1, LOX4, NHL3, NHL13, NAC29, two AOP1, EARLI 1, and POD56). These results provide valuable information for better understanding the molecular regulatory mechanism of Chinese cabbage clubroot resistance.

scholarly journals First Report of Club Root Caused by Plasmodiophora brassicae on Canola in Australia

Plant Disease ◽  
2012 ◽  
Vol 96 (7) ◽  
pp. 1075-1075 ◽  
Author(s):  
R. K. Khangura ◽  
D. W. Wright
Keyword(s):  
Western Australia ◽  
Plasmodiophora Brassicae ◽  
Root Hairs ◽  
The United States ◽  
Brassica Napus L ◽  
Cortical Cells ◽  
First Report ◽  
Modified Method ◽  
Resting Spores ◽  
Species Specific

In 2009, a disease survey was conducted in 97 commercial canola (Brassica napus L.) fields in Western Australia by the Department of Agriculture and Food, Western Australia (DAFWA). In about 20% of the fields from the northern agricultural region of Western Australia, small patches were observed where canola plants showed symptoms of stunting and wilting. These plants were collected and roots of affected plants were washed thoroughly and examined for the presence of root disease. Small galls and clublike structures were observed on the secondary roots and sometimes on the main root of the affected plants. Examination of thin free hand sections from the root galls revealed that several cortical cells were enlarged and full of resting spores. The diameter of resting spores ranged between 2.5 and 3.0 μm. Plasmodia and zoosporangia were also observed in the root hairs. The identity of Plasmodiophora brassicae Woronin was confirmed by PCR using a modified method of Cao et al. 2007 (1). DNA from spores and slices of the galls of 14 different samples were extracted using DNeasy plant mini kit (QIAGEN Australia) as per manufacturer's instructions. Samples were disrupted by placing them into MPBIO tube A and placed in the Fast Prep machine at speed of 6 ms–1 for 40 s. This was repeated twice. The species-specific primers TC1F (5′-GTGGTCGAACTTCATTAAATTTGGGCTCTT-3′)/TC1R (5′-TTCACCTACGGAACGTATATGTGCATGTGA-3′) and TC2F (5′-AAACAACGAGTCAGCTTGAATGCTAGTGTG-3′)/TC2R (5′-CTTTAGTTGTGTTTCGGCTAGGATGGTTCG-3′) were used (1). The primers TC1F and TC1R failed to produce a PCR product of 548-bp size but using the primers TC2F and TC2R the PCR reaction resulted in a 519- bp fragment. Seven out of 14 samples gave positive results for P. brassicae with primers TC2F and TC2R. This indicates that the P. brassicae pathotype from Western Australia may be different than the one found in Alberta, Canada. However, pathotypes of P. brassicae from brassica vegetables from Australia have been found similar to the populations of P. brassicae present in the United States (2). Pathogenicity of P. brassicae was tested by dipping roots of five 10-day-old canola plants var. Cobbler in a spore suspension (1 × 106 resting spores/ml). Roots of five control plants were dipped in sterile water. Five weeks after inoculation, small galls were observed on the roots of three inoculated plants and the control plants remained symptomless. Resting spores were recovered from the galls developed on the roots of affected plants. Presence of P. brassicae in the affected roots was further confirmed by PCR using the method described above. To our knowledge, this is the first report of club root of canola in Australia. Club root is reported from vegetable brassicas and white mustard (Sinapis alba L.) in Australia. Club root has become a serious disease of canola in Canada since its detection in Alberta in 2006 (3). The resting spores of the fungus can survive for several years in soil, and therefore, this disease could pose a significant threat to canola production in Western Australia. References: (1) Cao et al. Plant Dis. 91:80, 2007. (2) Donald et al. Ann. App. Biol. 148:239, 2006. (3) S. Streklov et al. Can. J. Plant Pathol. 28:467, 2006.

THE ROLE OF OXYGEN IN RETROLENTAL FIBROPLASIA

PEDIATRICS ◽  
1957 ◽  
Vol 19 (3) ◽  
pp. 504-524 ◽  
Author(s):  
Arnall Patz
Keyword(s):  
Secondary Phase ◽  
Primary Phase ◽  
Principal Factor ◽  
Single Factor ◽  
Toxic Agent ◽  
Retrolental Fibroplasia ◽  
Oxygen Administration ◽  
Vascular Proliferation ◽  
Early Human

The results of a controlled nursery study, supported by observations of others in both uncontrolled and controlled studies, clearly established the overuse of oxygen in the premature nursery as an important and probably the principal factor in the development of retrolental fibroplasia. The clinical data is supported by observations in the newborn or young mouse, rat, kitten, and puppy where retinal lesions, identical to those seen in early human retrolental fibroplasia are produced following exposure to an enriched oxygen environment. Fundamental to all these experiments, and apparently to the pathogenesis of human retrolental fibroplasia, is the uniform ocular susceptibility to oxygen when the retinas are immaturely vascularized, and a resistance to oxygen damage where vascularization is complete. The animal lesions produced by oxygen are proportional to the concentration of oxygen administered and the duration of exposure, and inversely proportional to the degree of vascularization of the retina. Duration of exposure to oxygen proved to be the most important single factor in these experiments. The ocular effects of oxygen on the immature retina can be divided into a primary phase of vasoconstriction and obliteration and a secondary phase of vascular proliferation. These clinical and experimental data justify recommendations for a rigid supervision of oxygen administration to the premature infant to avoid any unnecessary overuse of this potentially toxic agent.

scholarly journals Infection and Gene Expression of the Clubroot Pathogen Plasmodiophora brassicae in Resistant and Susceptible Canola Cultivars

Plant Disease ◽  
2016 ◽  
Vol 100 (4) ◽  
pp. 824-828 ◽  
Author(s):  
Weixin Fei ◽  
Jie Feng ◽  
Songbai Rong ◽  
Stephen E. Strelkov ◽  
Zhimou Gao ◽  
...  
Keyword(s):  
Primary Infection ◽  
Plasmodiophora Brassicae ◽  
Secondary Infection ◽  
Quantitative Polymerase Chain Reaction ◽  
Expression Patterns ◽  
Root Hairs ◽  
Resistant Cultivar ◽  
In Planta ◽  
Secondary Infections ◽  
Polymerase Chain

Infection by the clubroot pathogen Plasmodiophora brassicae on resistant and susceptible canola cultivars was investigated at various times following inoculation. Primary infection occurred on more than 90% of root hairs in both cultivars at 7 days after inoculation (dai), and thereafter declined to less than 20% at 14 to 35 dai. The amount of primary infection on the two cultivars was similar at each time point. Secondary infections were rare in both cultivars at 5 and 7 dai but became common after 14 dai. At 14 to 28 dai, the level of secondary infection was greater in the resistant cultivar than in the susceptible one. The in planta expression of 12 selected P. brassicae genes was investigated by reverse-transcription quantitative polymerase chain reaction. All genes were upregulated at 5 or 7 dai in the resistant cultivar. In the susceptible cultivar, the 12 genes could be classified into three groups according to their expression patterns: 2 genes showed an expression peak at 14 dai, 3 showed two expression peaks at 14 and 35 dai, and the others showed an expression peak at 35 dai. Results from this study will be useful in breeding for resistance and in selecting candidate pathogenicity genes for further studies.

Opposite Effect of Lysine on Platelet Aggregation Induced by Arachidonate and by Other Aggregants

1982 ◽  
Vol 48 (01) ◽  
pp. 078-083 ◽  
Author(s):  
C Ts'ao ◽  
S J Hart ◽  
D V Krajewski ◽  
P G Sorensen
Keyword(s):  
Platelet Aggregation ◽  
Secondary Phase ◽  
Aminocaproic Acid ◽  
Adenosine Diphosphate ◽  
Inhibitory Effect ◽  
Human Platelets ◽  
Primary Phase ◽  
High Doses ◽  
The Many ◽  
Induced Aggregation

SummaryEarlier, we found that ε-aminocaproic acid (EACA) inhibited human platelet aggregation induced by adenosine diphosphate (ADP) and collagen, but not aggregation by arachidonic acid (AA). Since EACA is structurally similar to lysine, yet these two agents exhibit vast difference in their antifibrinolytic activities, we chose to study the effect of lysine on platelet aggregation. We used L-lysine-HCl in these studies because of its high solubility in aqueous solutions while causing no change in pH when added to human plasma. With lysine, we repeatedly found inhibition of ADP-, collagen- and ristocetin-induced aggregation, but potentiation of AA-induced aggregation. Both the inhibitory and potentiation effects were dose-dependent. Low doses of lysine inhibited the secondary phase of aggregation; high doses of it also inhibited the primary phase of aggregation. Potentiation of AA-induced aggregation was accompanied by increased release of serotonin and formation of malondialdehyde. These effects were not confined to human platelets; rat platelets were similarly affected. Platelets, exposed to lysine and then washed and resuspended in an artificial medium not containing lysine, remained hypersensitive to AA, but no longer showed decreased aggregation by collagen. Comparing the effects of lysine with equimolar concentrations of sucrose, EACA, and α-amino-n-butyric acid, we attribute the potent inhibitory effect of lysine to either the excess positive charge or H+ and C1− ions. The -NH2 group on the α-carbon on lysine appears to be the determining factor for the potentiation effect; the effect seems to be exerted on the cyclooxygenase level of AA metabolism. Lysine and other chemicals with platelet-affecting properties similar to lysine may be used as a tool for the study of the many aspects of a platelet aggregation reaction.

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