scholarly journals Elaboração e validação de diagramas de área padrão (DAP) para avaliação da severidade do míldio (Peronospora variabilis Gäum) em quinoa (Chenopodium quinoa Willd)

2021 ◽  
Vol 4 (4) ◽  
pp. 43-54
Author(s):  
Pablo Israel Álvarez-Romero ◽  
◽  
Virginia Mariño-Frías ◽  
Carlos Francisco Carpio-Coba ◽  
Ana Francisca Ferreira-Ferreira ◽  
...  
Keyword(s):  
Downy Mildew ◽  
Chenopodium Quinoa ◽  
Epidemiological Studies ◽  
Accuracy And Precision ◽  
Severity Levels

The quinoa downy mildew is one of the major diseases affecting quinoa in Ecuador. Considering the lack of standardized methods to quantify this disease on leaves, the aim of this study was to develop a standard area diagram to quantify the severity of the quinoa downy mildew. To standardize the assessment, we developed two sets of standard area diagrams. To validate the diagram, twelve raters estimated the severity of 50 scanned leaf images at different severity levels. The proposed diagram with linear increments provided good levels of accuracy and precision, constituting thus a useful tool in epidemiological studies and for the development of strategies to control the quinoa downy mildew.

scholarly journals Diagrammatic scale to assess downy mildew severity in melon

2009 ◽  
Vol 27 (1) ◽  
pp. 76-79 ◽  
Author(s):  
Sami J Michereff ◽  
Marissônia A Noronha ◽  
Gaus SA Lima ◽  
Ígor CL Albert ◽  
Edilaine A Melo ◽  
...  
Keyword(s):  
Linear Regression ◽  
Leaf Area ◽  
Downy Mildew ◽  
Pseudoperonospora Cubensis ◽  
Northeast Brazil ◽  
Simple Linear Regression ◽  
Standard Methods ◽  
Accuracy And Precision ◽  
Severity Levels ◽  
Diagrammatic Scale

The downy mildew, caused by Pseudoperonospora cubensis, is an important melon disease in Northeast Brazil. Considering the lack of standard methods for its assessment, a diagrammatic scale was developed with 2, 4, 8, 16, 32, 64, 82, and 96% of affected leaf area. The scale was then checked for its accuracy, precision, and reproducibility in estimating downy mildew severity. The diagrammatic scale was validated by eight disease raters; using 50 leaves with different severity levels, previously measured using the software Assess®. Two evaluations were performed on the same set of leaves, but in a different sequence order, by the same raters, within a 15-day interval. The accuracy and precision of each rater was determined by simple linear regression between the actual and the estimated severity. The scale provided good levels of accuracy (means of 87.5%) and excellent levels of precision (means of 94%), with absolute errors concentrated around 10%. Raters showed great repeatability (means of 94%) and reproducibility (>90% in 90.3% of cases) of estimates. Therefore, we could conclude that the diagrammatic scale presented here was suitable for evaluating downy mildew severity in melon.

scholarly journals Phylogenetic Analysis of Downy Mildew Pathogens of Opium Poppy and PCR-Based In Planta and Seed Detection of Peronospora arborescens

2007 ◽  
Vol 97 (11) ◽  
pp. 1380-1390 ◽  
Author(s):  
Blanca B. Landa ◽  
Miguel Montes-Borrego ◽  
Francisco J. Muñoz-Ledesma ◽  
Rafael M. Jiménez-Díaz
Keyword(s):  
Downy Mildew ◽  
Field Experiments ◽  
Phylogenetic Analyses ◽  
Its Region ◽  
Epidemiological Studies ◽  
Papaver Somniferum ◽  
Opium Poppy ◽  
Recent Common Ancestor ◽  
In Planta ◽  
Commercial Seed

Severe downy mildew diseases of opium poppy (Papaver somniferum) can be caused by Peronospora arborescens and P. cristata, but differentiating between the two pathogens is difficult because they share morphological features and a similar host range. In Spain, where severe epidemics of downy mildew of opium poppy have occurred recently, the pathogen was identified as P. arborescens on the basis of morphological traits. In this current study, sequence homology and phylogenetic analyses of the internal transcribed spacer regions (ITS) of the ribosomal DNA (rDNA) were carried out with DNA from P. arborescens and P. cristata from diverse geographic origins, which suggested that only P. arborescens occurs in cultivated Papaver somniferum in Spain. Moreover, analyses of the rDNA ITS region from 27 samples of downy-mildew-affected tissues from all opium-poppy-growing regions in Spain showed that genetic diversity exists within P. arborescens populations in Spain and that these are phylogenetically distinct from P. cristata. P. cristata instead shares a more recent, common ancestor with a range of Peronospora species that includes those found on host plants that are not members of the Papaveraceae. Species-specific primers and a PCR assay protocol were developed that differentiated P. arborescens and P. cristata and proved useful for the detection of P. arborescens in symptomatic and asymptomatic opium poppy plant parts. Use of these primers demonstrated that P. arborescens can be transmitted in seeds and that commercial seed stocks collected from crops with high incidence of the disease were frequently infected. Field experiments conducted in microplots free from P. arborescens using seed stocks harvested from infected capsules further demonstrated that transmission from seedborne P. arborescens to opium poppy plants can occur. Therefore, the specific-PCR detection protocol developed in this study can be of use for epidemiological studies and diagnosing the pathogen in commercial seed stocks; thus facilitating the sanitary control of the disease and avoidance of the pathogen distribution in seeds.

Morphological and Molecular Characterization of the Causal Agent of Downy Mildew on Quinoa (Chenopodium quinoa)

2010 ◽  
Vol 169 (5) ◽  
pp. 403-412 ◽  
Author(s):  
Young-Joon Choi ◽  
Solveig Danielsen ◽  
Mette Lübeck ◽  
Seung-Beom Hong ◽  
Rolf Delhey ◽  
...  
Keyword(s):  
Downy Mildew ◽  
Molecular Characterization ◽  
Chenopodium Quinoa ◽  
Causal Agent ◽  
Morphological And Molecular Characterization

Mutation induction to improve quinoa (Chenopodium quinoa) resistance to downy mildew (Peronospora variabilis).

2021 ◽  
pp. 194-202
Author(s):  
Luz Gomez-Pando ◽  
Jesus Bernardo-Rojas ◽  
Denisse Deza-Montoya ◽  
Martha Ibañez-Tremolada ◽  
Enrique Aguilar-Castellanos
Keyword(s):  
Downy Mildew ◽  
Quantitative Resistance ◽  
Natural Infection ◽  
Chenopodium Quinoa ◽  
Yield Potential ◽  
High Yield ◽  
Small Scale ◽  
Mutation Induction ◽  
Leaf Infection ◽  
Mutant Lines

Abstract Quinoa is an important crop due to its nutritional characteristics (better than cereals) and its tolerance to abiotic stresses. However, various factors such as high susceptibility to diseases, especially downy mildew caused by Peronospora variabilis, limit its agricultural performance. Genetic improvement of quinoa could reduce the need to use fungicides for this crop and maintain the organic quality of Peruvian production in small-scale farms. Seeds of var. 'Amarilla Marangani', irradiated with 150 and 250 Gy of gamma-rays (60Co), were evaluated in two experimental locations in Peru: coastland at La Molina and highland at Huancayo. Resistance to downy mildew and other agricultural traits in the M3 and M4 generations was studied. In both locations, downy mildew was observed in susceptible plants under natural infection, from the seedling stage to plant maturity. At the coastland site, six mutants with 30% leaf infection were obtained in the progeny of plants exposed to 150 Gy. Five additional mutants with 40% leaf infection were found in the progeny of plants exposed to 250 Gy. In the highland trial, only seven lines were identified with 30% severity (foliar area with symptoms) among the plants from the 150 Gy experiment. The parent materials showed 70-80% disease severity. Mutant lines with quantitative resistance and tolerance to downy mildew, high yield potential, reduced duration, shorter plant height, altered inflorescence shape and grain colour mutations were selected from both doses. This study showed that quantitative resistance and tolerance to downy mildew could be obtained in quinoa and this resulted in increased grain yields.

scholarly journals Molecular Detection of Peronospora variabilis in Quinoa Seed and Phylogeny of the Quinoa Downy Mildew Pathogen in South America and the United States

2014 ◽  
Vol 104 (4) ◽  
pp. 379-386 ◽  
Author(s):  
Anna L. Testen ◽  
María del Mar Jiménez-Gasco ◽  
José B. Ochoa ◽  
Paul A. Backman
Keyword(s):  
United States ◽  
South America ◽  
Downy Mildew ◽  
Detection Method ◽  
Chenopodium Quinoa ◽  
The United States ◽  
Human Consumption ◽  
South American ◽  
Geographical Differences ◽  
Polymerase Chain

Quinoa (Chenopodium quinoa) is an important export of the Andean region, and its key disease is quinoa downy mildew, caused by Peronospora variabilis. P. variabilis oospores can be seedborne and rapid methods to detect seedborne P. variabilis have not been developed. In this research, a polymerase chain reaction (PCR)-based detection method was developed to detect seedborne P. variabilis and a sequencing-based method was used to validate the PCR-based method. P. variabilis was detected in 31 of 33 quinoa seed lots using the PCR-based method and in 32 of 33 quinoa seed lots using the sequencing-based method. Thirty-one of the quinoa seed lots tested in this study were sold for human consumption, with seed originating from six different countries. Internal transcribed spacer (ITS) and cytochrome c oxidase subunit 2 (COX2) phylogenies were examined to determine whether geographical differences occurred in P. variabilis populations originating from Ecuador, Bolivia, and the United States. No geographical differences were observed in the ITS-derived phylogeny but the COX2 phylogeny indicated that geographical differences existed between U.S. and South American samples. Both ITS and COX2 phylogenies supported the existence of a Peronospora sp., distinct from P. variabilis, that causes systemic-like downy mildew symptoms on quinoa in Ecuador. The results of these studies allow for a better understanding of P. variabilis populations in South America and identified a new causal agent for quinoa downy mildew. The PCR-based seed detection method allows for the development of P. variabilis-free quinoa seed, which may prove important for management of quinoa downy mildew.

scholarly journals Genetic variation for tolerance to the downy mildew pathogen Peronospora variabilis in genetic resources of quinoa (Chenopodium quinoa)

2020 ◽  
Author(s):  
Carla Colque-Little ◽  
Miguel Correa Abondano ◽  
Ole Søgard Lund ◽  
Daniel Buchvaldt Amby ◽  
Hans-Peter Piepho ◽  
...  
Keyword(s):  
Genetic Resources ◽  
Downy Mildew ◽  
Mixed Models ◽  
Genetic Basis ◽  
Chenopodium Quinoa ◽  
South American ◽  
Sources Of Resistance ◽  
Saponin Content ◽  
Genome Wide ◽  
Grain Crop

AbstractBackgroundQuinoa (Chenopodium quinoa Willd.) is an ancient grain crop that is tolerant to abiotic stress and has favorable nutritional properties. Downy mildew is the main disease of quinoa and is caused by infections of the biotrophic oomycete Peronospora variabilis Gaüm. Since the disease causes major yield losses, identifying sources of downy mildew tolerance in genetic resources and understanding its genetic basis are important goals in quinoa breeding.ResultsWe infected 132 South American genotypes, three Danish cultivars and the weedy relative C. album with a single isolate of P. variabilis under greenhouse conditions and observed a large variation in disease traits like severity of infection, which ranged from 5% to 83%. Linear mixed models revealed a significant effect of genotypes on disease traits with high heritabilities (0.72 to 0.81). Factors like altitude at site of origin or seed saponin content did not correlate with mildew tolerance, but stomatal width was weakly correlated with severity of infection. Despite the strong genotypic effects on mildew tolerance, genome-wide association mapping with 88 genotypes failed to identify significant marker-trait associations indicating a polygenic architecture of mildew tolerance.ConclusionsThe strong genetic effects on mildew tolerance allow to identify genetic resources, which are valuable sources of resistance in future quinoa breeding.

scholarly journals Genetic variation for tolerance to the downy mildew pathogen Peronospora variabilis in genetic resources of quinoa (Chenopodium quinoa)

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Carla Colque-Little ◽  
Miguel Correa Abondano ◽  
Ole Søgaard Lund ◽  
Daniel Buchvaldt Amby ◽  
Hans-Peter Piepho ◽  
...  
Keyword(s):  
Genetic Resources ◽  
Downy Mildew ◽  
Mixed Models ◽  
Genetic Basis ◽  
Chenopodium Quinoa ◽  
South American ◽  
Sources Of Resistance ◽  
Saponin Content ◽  
Genome Wide ◽  
Grain Crop

Abstract Background Quinoa (Chenopodium quinoa Willd.) is an ancient grain crop that is tolerant to abiotic stress and has favorable nutritional properties. Downy mildew is the main disease of quinoa and is caused by infections of the biotrophic oomycete Peronospora variabilis Gaüm. Since the disease causes major yield losses, identifying sources of downy mildew tolerance in genetic resources and understanding its genetic basis are important goals in quinoa breeding. Results We infected 132 South American genotypes, three Danish cultivars and the weedy relative C. album with a single isolate of P. variabilis under greenhouse conditions and observed a large variation in disease traits like severity of infection, which ranged from 5 to 83%. Linear mixed models revealed a significant effect of genotypes on disease traits with high heritabilities (0.72 to 0.81). Factors like altitude at site of origin or seed saponin content did not correlate with mildew tolerance, but stomatal width was weakly correlated with severity of infection. Despite the strong genotypic effects on mildew tolerance, genome-wide association mapping with 88 genotypes failed to identify significant marker-trait associations indicating a polygenic architecture of mildew tolerance. Conclusions The strong genetic effects on mildew tolerance allow to identify genetic resources, which are valuable sources of resistance in future quinoa breeding.

scholarly journals First Report of Quinoa Downy Mildew Caused by Peronospora variabilis in Republic of Korea

Plant Disease ◽  
2014 ◽  
Vol 98 (7) ◽  
pp. 1003-1003 ◽  
Author(s):  
Y. J. Choi ◽  
I. Y. Choi ◽  
J. S. Kim ◽  
H. D. Shin
Keyword(s):  
Downy Mildew ◽  
Chenopodium Quinoa ◽  
Its Region ◽  
The United States ◽  
Field Trials ◽  
Republic Of Korea ◽  
Soil Conditions ◽  
Width Ratio ◽  
Morphological Identification ◽  
First Report

Quinoa (Chenopodium quinoa Willd.) has become increasingly popular due to its high nutritional value and adaptability to harsh environments. Several field trials have recently been conducted to determine the ability of quinoa cultivars to grow under climate and soil conditions of Republic of Korea. During July 2013, which is the rainy season, plants showing typical symptoms of downy mildew were first observed in an experimental plot in Iksan City, Korea. Infection resulted in small to large, irregular chlorotic areas on the upper leaf surface with a gray mildew developing on the abaxial surface, and often leading to early defoliation. The same symptoms of downy mildew were also found in Pyeongchang County and Imsil County, Korea. A sample from Iksan City was deposited in the Korea University Herbarium (Accession No. KUS-F27388) and used for microscopy and molecular studies. Microscopic examination revealed colorless conidiophores emerging from stomata, straight to slightly curved, 350 to 550 × 10 to 18 μm, and sub-dichotomously branched in 5 to 7 orders. Ultimate branchlets were mostly in pairs, flexuous to curved, 10 to 30 μm long, and had obtuse tips. Conidia were pale brown to olivaceous, broadly ellipsoidal to ellipsoidal, and 25 to 32 × 22 to 25 μm with a length/width ratio of 1.20 to 1.35. These characteristics fit well with Peronospora variabilis, which was previously recorded to be parasitic to C. quinoa and C. album, although P. farinosa f. sp. chenopodii has often been considered a causal agent of downy mildew on quinoa (1). To confirm this morphological identification, amplification and sequencing of the internal transcribed spacer (ITS) region of the rDNA of the Korean specimen were performed using procedures outlined by Choi et al. (1) with oomycete-specific primers DC6 and LR0. The resulting 796-bp sequence was deposited in GenBank (Accession No. KF887493). A comparison with the ITS sequences available in GenBank revealed that it is identical to P. variabilis found on C. album (EF614959, EF614961), and shows only one base pair substitution with another isolates from C. quinoa (EU113305, EU113306). Therefore, the pathogen found in Korea was confirmed to be P. variabilis. Downy mildew is the most damaging disease of quinoa in Argentina, Bolivia, Colombia, Ecuador, and Peru (1). Increasing reports of this disease from India, Canada, the United States, Portugal, and Denmark (2,3,4) have revealed its worldwide occurrence and spread. To our knowledge, this is the first report of a downy mildew on quinoa in Korea (3). It suggests that quinoa downy mildew poses a new and serious threat to production of this crop in Korea. References: (1) Y. J. Choi et al. Mycopathologia 169:403, 2010. (2) S. Danielson et al. Seed Sci. Technol. 32:91, 2004. (3) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., Online publication, ARS, USDA, Retrieved November 5, 2013. (4) A. L. Testen et al. Plant Dis. 96:146, 2012.

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