Detached leaf inoculation assay for evaluating resistance to the spinach downy mildew pathogen

2020 ◽  
Vol 158 (2) ◽  
pp. 511-520
Author(s):  
Gehendra Bhattarai ◽  
Chunda Feng ◽  
Braham Dhillon ◽  
Ainong Shi ◽  
Maria Villarroel-Zeballos ◽  
...  
Keyword(s):  
Downy Mildew ◽  
Detached Leaf ◽  
Spinach Downy Mildew ◽  
Inoculation Assay

scholarly journals Identification and Cultivar Reaction to Three New Races of the Spinach Downy Mildew Pathogen from the United States and Europe

Plant Disease ◽  
2003 ◽  
Vol 87 (5) ◽  
pp. 567-572 ◽  
Author(s):  
B. M. Irish ◽  
J. C. Correll ◽  
S. T. Koike ◽  
J. Schafer ◽  
T. E. Morelock
Keyword(s):  
United States ◽  
The Netherlands ◽  
Downy Mildew ◽  
Quantitative Resistance ◽  
The United States ◽  
True Leaf ◽  
Differential Cultivars ◽  
Spinach Downy Mildew ◽  
New Races ◽  
Inoculation Assay

Since 1996, commercial spinach cultivars with resistance to four previously described races of Peronospora farinosa f. sp. spinaciae (races 1, 2, 3, and 4) were observed with high incidences of downy mildew both in California and Europe. Isolates of P. farinosa f. sp. spinaciae collected in California between 1997 and 2001, Arizona in 1999, and a single isolate collected in the Netherlands in 1996 were examined for their disease reaction on differential spinach cultivars and a set of commercial spinach cultivars. Disease reactions on the differential cultivars indicated the occurrence of three new races of P. farinosa f. sp. spinaciae. Two newly identified races, designated race 5 (isolate CA1) and race 6 (isolate SP1), were detected in the United States. The isolate from the Netherlands also was distinct and designated race 7 (isolate JVN7). Some cultivars with resistance to races 1, 2, 3, and 4 were susceptible to race 5, whereas others were resistant, indicating that resistance to a given race may be governed by different genes (or alleles) depending on the source of resistance. A survey of races in California indicated that races 5 and 6 predominated. Although the majority of the cultivars examined were susceptible to race 6 based on the traditional qualitative cotyledon inoculation assay, significant quantitative differences in resistance to race 6 were observed using a true-leaf greenhouse screening procedure. Although more work is needed to confirm the results of the true-leaf assays, the quantitative resistance observed using this procedure appears to be race specific.

scholarly journals Genome reconstruction of the non-culturable spinach downy mildew Peronospora effusa by metagenome filtering

2019 ◽  
Author(s):  
Joël Klein ◽  
Manon Neilen ◽  
Marcel van Verk ◽  
Guido Van den Ackerveken ◽  
Bas E. Dutilh
Keyword(s):  
Downy Mildew ◽  
Dna Isolation ◽  
Spinacia Oleracea ◽  
Gene Repertoire ◽  
Phylogenetic Distance ◽  
Annotate Orfs ◽  
A Genome ◽  
Spinach Downy Mildew ◽  
Insight Into ◽  
Spinach Leaves

Peronospora effusa (previously known as  P. farinosa f. sp. spinaciae, and here referred to as Pfs) is an obligate biotrophic oomycete that causes downy mildew on spinach (Spinacia oleracea). To combat this destructive disease resistant cultivars are continually bred. However, new Pfs races rapidly break the employed resistance genes. To get insight into the gene repertoire of Pfs and identify infection-related genes, the genome of the first reference race, Pfs1, was sequenced, assembled, and annotated. Due to the obligate biotrophic nature of this pathogen, material for DNA isolation can only be collected from infected spinach leaves that, however, also contain many other microorganisms. The obtained sequences are, therefore, considered a metagenome. To filter and obtain Pfs sequences we utilized the CAT tool to taxonomically annotate ORFs residing on long sequences of a genome pre-assembly. This study is the first to show that CAT filtering performs well on eukaryotic contigs. Based on the taxonomy, determined on multiple ORFs, contaminating long sequences and corresponding reads were removed. Filtered reads were re-assembled to provide a clean and improved Pfs genome sequence of 32.40 Mbp consisting of 8,635 scaffolds. Transcript sequencing of a range of infection time points aided the prediction of a total of 13,277 gene models, including 99 RXLR(-like) effector, and 14 putative Crinkler genes. Comparative analysis identified common features in the secretomes of different obligate biotrophic oomycetes, regardless of their phylogenetic distance. Their secretomes are generally smaller, compared to hemibiotrophic and necrotrophic oomycete species. We observe a reduction in proteins involved cell wall degradation, in Nep1-like proteins (NLPs), proteins with PAN/apple domains, and host translocated effectors. The genome of Pfs1 will be instrumental in studying downy mildew virulence and for understanding the molecular adaptations by which new isolates break spinach resistance.

scholarly journals Characterization of a Resistance Locus (Pfs-1) to the Spinach Downy Mildew Pathogen (Peronospora farinosa f. sp. spinaciae) and Development of a Molecular Marker Linked to Pfs-1

2008 ◽  
Vol 98 (8) ◽  
pp. 894-900 ◽  
Author(s):  
B. M. Irish ◽  
J. C. Correll ◽  
C. Feng ◽  
T. Bentley ◽  
B. G. de los Reyes
Keyword(s):  
Disease Resistance ◽  
Downy Mildew ◽  
Scar Marker ◽  
Mapping Population ◽  
Dominant Gene ◽  
Resistance Locus ◽  
Sequence Characterized Amplified Region ◽  
Wide Range ◽  
Spinach Downy Mildew ◽  
Homozygous Resistant

Downy mildew is a destructive disease of spinach worldwide. There have been 10 races described since 1824, six of which have been identified in the past 10 years. Race identification is based on qualitative disease reactions on a set of diverse host differentials which include open-pollinated cultivars, contemporary hybrid cultivars, and older hybrid cultivars that are no longer produced. The development of a set of near-isogenic open-pollinated spinach lines (NILs), having different resistance loci in a susceptible and otherwise common genetic background, would facilitate identification of races of the downy mildew pathogen, provide a tool to better understand the genetics of resistance, and expedite the development of molecular markers linked to these disease resistance loci. To achieve this objective, the spinach cv. Viroflay, susceptible to race 6 of Peronospora farinosa f. sp. spinaciae, was used as the recurrent susceptible parent in crosses with the hybrid spinach cv. Lion, resistant to race 6. Resistant F1 progeny were subsequently backcrossed to Viroflay four times with selection for race 6 resistance each time. Analysis of the segregation data showed that resistance was controlled by a single dominant gene, and the resistance locus was designated Pfs-1. By bulk segregant analysis, an amplified fragment length polymorphism (AFLP) marker (E-ACT/M-CTG) linked to Pfs-1 was identified and used to develop a co-dominant Sequence characterized amplified region (SCAR) marker. This SCAR marker, designated Dm-1, was closely linked (≈1.7 cM) to the Pfs-1 locus and could discriminate among spinach genotypes that were homozygous resistant (Pfs-1Pfs-1), heterozygous resistant (Pfs-1pfs-1), or homozygous susceptible (pfs-1pfs-1) to race 6 within the original mapping population. Evaluation of a wide range of commercial spinach lines outside of the mapping population indicated that Dm-1 could effectively identify Pfs-1 resistant genotypes; the Dm-1 marker correctly predicted the disease resistance phenotype in 120 out of 123 lines tested. In addition, the NIL containing the Pfs-1 locus (Pfs-1Pfs-1) was resistant to multiple races of the downy mildew pathogen indicating Pfs-1 locus may contain a cluster of resistance genes.

Recent races of spinach downy mildew pathogen Peronospora farinosa f. sp. spinaciae in Japan

2017 ◽  
Vol 83 (2) ◽  
pp. 117-120 ◽  
Author(s):  
Masaharu Kubota ◽  
Osamu Tamura ◽  
Yasuhiro Nomura ◽  
Noriko Orihara ◽  
Norihito Yamauchi ◽  
...  
Keyword(s):  
Downy Mildew ◽  
Spinach Downy Mildew

A New Race of Spinach Downy Mildew in Japan

2002 ◽  
Vol 68 (1) ◽  
pp. 49-51 ◽  
Author(s):  
Mamoru SATOU ◽  
Takuma SUGIURA ◽  
Ryuki OHSAKI ◽  
Noriyuki HONDA ◽  
Seizo HORIUCHI ◽  
...  
Keyword(s):  
Downy Mildew ◽  
New Race ◽  
Spinach Downy Mildew

scholarly journals Extracts of Inula viscosa Control Downy Mildew of Grapes Caused by Plasmopara viticola

2006 ◽  
Vol 96 (4) ◽  
pp. 417-424 ◽  
Author(s):  
Yigal Cohen ◽  
Wenqiao Wang ◽  
Bat-Hen Ben-Daniel ◽  
Yigal Ben-Daniel
Keyword(s):  
Downy Mildew ◽  
Plasmopara Viticola ◽  
Seasonal Fluctuations ◽  
Control Efficacy ◽  
Detached Leaf ◽  
Inhibitory Compounds ◽  
Excellent Activity ◽  
Dose Concentration ◽  
Leaf Tissues ◽  
Layer Chromatography

The oily paste extracts of Inula viscosa leaves made with organic solvents were effective in controlling downy mildew caused by Plasmopara viticola in detached leaf tissues of grapes in growth chambers. Thin-layer chromatography of such extracts revealed the presence of 11 Rf regions of which four contained highly effective compounds against the disease. Two major inhibitory compounds, each comprising 10.6% of the total paste weight, were identified as tomentosin and costic acid. An emulsified concentrate formulation of the oily paste extracts provided excellent activity against the disease in the field. The effective dose (concentration) required for 90% control of the disease in treated shoots in the field was below 0.125% (paste in water). No seasonal fluctuations were observed in the control efficacy of six extracts made from I. viscosa leaves harvested during the period of May to July. In whole vines, treated and artificially inoculated, the paste concentration required for 90% control of the disease ranged between 0.30 to 0.37%, whereas in naturally infected vines it was 0.58%. It appears that I. viscosa is a valuable source for fungicidal preparations against downy mildew of grapes. This is the first report on the control of a disease with I. viscosa extracts under field conditions.

scholarly journals New Races and Novel Strains of the Spinach Downy Mildew Pathogen Peronospora effusa

Plant Disease ◽  
2018 ◽  
Vol 102 (3) ◽  
pp. 613-618 ◽  
Author(s):  
Chunda Feng ◽  
Katsunori Saito ◽  
Bo Liu ◽  
Aurora Manley ◽  
Katherine Kammeijer ◽  
...  
Keyword(s):  
Downy Mildew ◽  
Disease Development ◽  
Fresh Market ◽  
Department Of Agriculture ◽  
Disease Management Strategy ◽  
Spinach Downy Mildew ◽  
New Races ◽  
Production Areas ◽  
Race 4 ◽  
Virulence Diversity

Downy mildew disease, caused by Peronospora effusa (=P. farinosa f. sp. spinaciae [Pfs]), is the most economically important disease of spinach. Current high-density fresh-market spinach production provides conducive conditions for disease development, and downy mildew frequently forces growers to harvest early owing to disease development, to cull symptomatic leaves prior to harvest, or to abandon the field if the disease is too severe. The use of resistant cultivars to manage downy mildew, particularly on increasing acreages of organic spinach production, applies strong selection pressure on the pathogen, and many new races of Pfs have been identified in recent years in spinach production areas worldwide. To monitor the virulence diversity in the Pfs population, downy mildew samples were collected from spinach production areas and tested for race identification based on the disease reactions of a standard set of international spinach differentials. Two new races (designated races 15 and 16) and eight novel strains were identified between 2013 and 2017. The disease reaction of Pfs 15 was similar to race 4, except race 4 could not overcome the resistance imparted by the RPF9 locus. Several resistance loci (RPF1, 2, 4, and 6) were effective in preventing disease caused by Pfs 15. The race Pfs 16 could overcome several resistance loci (RPF2, 4, 5, 9, and 10) but not others (RPF1, 3, 6, and 7). One novel strain (UA1014) could overcome the resistance of spinach resistant loci RPF1 to RPF7 but only infected the cotyledons and not the true leaves of certain cultivars. A new set of near-isogenic lines has been developed and evaluated for disease reactions to the new races and novel strains as differentials. None of the 360 U.S. Department of Agriculture spinach germplasm accessions tested were resistant to Pfs 16 or UA1014. A survey of isolates over several years highlighted the dynamic nature of the virulence diversity of the Pfs population. Identification of virulence diversity and evaluation of the genetics of resistance to Pfs will continue to allow for a more effective disease management strategy through resistance gene deployment.

First report of spinach downy mildew caused by race Pfs:8 of Peronospora farinosa f. sp. spinaciae in Japan

2011 ◽  
Vol 77 (4) ◽  
pp. 260-262 ◽  
Author(s):  
Norihito Yamauchi ◽  
Hayato Horinouchi ◽  
Kazuhiko Sakai ◽  
Kengo Yonemoto ◽  
Mamoru Satou ◽  
...  
Keyword(s):  
Downy Mildew ◽  
First Report ◽  
Spinach Downy Mildew

scholarly journals Three New Races of the Spinach Downy Mildew Pathogen Identified by a Modified Set of Spinach Differentials

Plant Disease ◽  
2007 ◽  
Vol 91 (11) ◽  
pp. 1392-1396 ◽  
Author(s):  
B. M. Irish ◽  
J. C. Correll ◽  
S. T. Koike ◽  
T. E. Morelock
Keyword(s):  
United States ◽  
European Union ◽  
Downy Mildew ◽  
The United States ◽  
The European Union ◽  
The Past ◽  
Differential Cultivars ◽  
Spinach Downy Mildew ◽  
New Races ◽  
Important Disease

Spinach downy mildew, caused by Peronospora farinosa f. sp. spinaciae, is the most economically important disease of spinach worldwide. During the past few years, spinach cultivars resistant to the seven previously described races of P. farinosa f. sp. spinaciae were observed to be severely affected by downy mildew in both the United States and the European Union. Four new isolates of P. farinosa f. sp. spinaciae were collected from California and The Netherlands and characterized based on disease reactions on two modified sets of spinach differentials. The results led to the description of three new races of the downy mildew pathogen, designated races 8, 9, and 10. Four differential cultivars with resistance to races 1 to 7 were used to distinguish the three new races. Dolphin was susceptible to races 8 and 10 but resistant to race 9; Lion was susceptible to race 10 but resistant to races 8 and 9; Lazio was resistant to races 1 to 7 as well as races 8, 9, and 10; and Tarpy was susceptible to all three new races. The three new races also were used to evaluate the disease reactions on 43 contemporary commercial spinach cultivars in greenhouse trials. A survey of 58 isolates of P. farinosa f. sp. spinaciae collected in California and Arizona between 2004 and 2006 revealed that race 10 predominated in the areas sampled.

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