Genetic and histological characterization of downy mildew resistance at the cotyledon stage in Raphanus sativus L.

AbstractPlasmopara viticola is the oomycete that causes downy mildew in grapevine. Varying levels of resistance to P. viticola across grape cultivars allowed quantitative trait loci to be identified. The Rpv3 locus is located at chromosome 18, in a region enriched in TIR-NBS-LRR genes, and the phenotype associated is a high hypersensitive response. In this work, we aimed to identify candidate genes associated with resistance to downy mildew on the Rpv3 locus and to evaluate their transcriptional profiles in a susceptible and a resistant grapevine cultivar after challenging with P. viticola. Candidate genes were identified by representational differential analysis and also by functional enrichment tests. Many predicted genes associated with resistance to diseases were found at the Rpv3 locus. In total, seventeen genes were evaluated by RT-qPCR. Differences in the steady-state expression of these genes were observed between the two cultivars. Four genes were found to be expressed only in Villard Blanc, suggesting their association to the hypersensitivity reaction. Concerning marker assisted-selection for downy mildew resistance, we show the efficient use of a haplotype of SSR markers. Furthermore, based on Rpv3-located SNPs between grapevine cultivars contrasting in downy mildew resistance, we developed and tested forty-one new markers for assisted selection. After genotypic and phenotypic evaluations on segregant populations, two markers, Rpv3_15 and Rpv3_33, were considered efficient for downy mildew resistance identification. This study constitutes an in-depth genomic characterization of the Rpv3 locus, confirms its involvement in resistance against P. viticola infection and presents promising biotechnological tools for the selection of young resistant individuals.

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Characterization of a TIR-NBS-LRR gene associated with downy mildew resistance in grape

Genetics and Molecular Research ◽

10.4238/2015.july.17.4 ◽

2015 ◽

Vol 14 (3) ◽

pp. 7964-7975 ◽

Cited By ~ 6

Author(s):

J.J. Fan ◽

P. Wang ◽

X. Xu ◽

K. Liu ◽

Y.Y. Ruan ◽

...

Keyword(s):

Downy Mildew ◽

Downy Mildew Resistance ◽

Mildew Resistance

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Identification and characterization of potential NBS-encoding resistance genes and induction kinetics of a putative candidate gene associated with downy mildew resistance in Cucumis

BMC Plant Biology ◽

10.1186/1471-2229-10-186 ◽

2010 ◽

Vol 10 (1) ◽

pp. 186 ◽

Cited By ~ 32

Author(s):

Hongjian Wan ◽

Zhenguo Zhao ◽

Ahmed Malik ◽

Chuntao Qian ◽

Jinfeng Chen

Keyword(s):

Candidate Gene ◽

Downy Mildew ◽

Resistance Genes ◽

Downy Mildew Resistance ◽

Mildew Resistance ◽

Induction Kinetics ◽

Putative Candidate Gene ◽

Kinetics Of ◽

Identification And Characterization

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033 Characterization of Downy Mildew Resistance in USDA Broccoli Inbreds

HortScience ◽

10.21273/hortsci.34.3.446e ◽

1999 ◽

Vol 34 (3) ◽

pp. 446E-447

Author(s):

Min Wang ◽

Mark W. Farnham

Keyword(s):

Downy Mildew ◽

Screening Tests ◽

Downy Mildew Resistance ◽

Block Designs ◽

Peronospora Parasitica ◽

Seedling Resistance ◽

Mature Plant Resistance ◽

Leaf Stage ◽

Cotyledon Stage

Downy mildew, caused by Peronospora parasitica (Pers. ex Fr.), is one of the most economically important diseases in broccoli (Brassica oleracea L. Italica group). Previous studies reported that resistance to downy mildew in broccoli depends on plant age and that seedling resistance appears to be independent of mature-plant resistance. The objectives of our studies were to evaluate resistance and susceptibility of USDA broccoli inbreds to downy mildew and to investigate the interaction between the host and pathogen at two plant stages with single or double inoculation. Multiple screening tests at both cotyledon and three-expanded leaf stages using 38 entries, including USDA inbreds and commercial hybrids, were conducted in randomized complete-block designs. In these tests, every leaf of each plant was thoroughly sprayed with P. parasitica isolate PP1 at a concentration of 10,000 sporangia per ml at both stages. Ratings for downy mildew reaction phenotype were made at 9 days postinoculation on a 0-9 scale of increasing disease severity. We found significant phenotypic variation to infection among broccoli entries. We observed three general phenotypes: 1) resistance at both stages; 2) susceptible at cotyledon stage combined with resistance at three-expanded leaf stage; and 3) susceptibility at both stages. Additionally, inoculation at the cotyledon stage had no effect on inoculation at the three-expanded leaf stage.

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Phenotypic Variation for Downy Mildew Resistance among Inbred Broccoli

HortScience ◽

10.21273/hortsci.35.5.925 ◽

2000 ◽

Vol 35 (5) ◽

pp. 925-929 ◽

Cited By ~ 10

Author(s):

Min Wang ◽

Mark W. Farnham ◽

Claude E. Thomas

Keyword(s):

Downy Mildew ◽

Plant Resistance ◽

Developmental Stages ◽

Downy Mildew Resistance ◽

Mildew Resistance ◽

Leaf Stage ◽

True Leaf ◽

Cotyledon Stage ◽

Geographic Regions ◽

Dh Lines

Downy mildew, caused by Peronospora parasitica (Pers. Fr.) Fr., is one of the most economically important diseases of broccoli (Brassica oleracea L. Italica group). Previous studies have shown that resistance to downy mildew in broccoli is dependent on plant age with seedling resistance being independent of mature-plant resistance. The objectives of this study were to: 1) determine if valid evaluations for downy mildew resistance can be conducted at both the cotyledon and the three to four true-leaf stages on the same plants of a given broccoli entry; 2) determine if doubled-haploid (DH) lines derived from the resistant hybrid `Everest' also exhibit resistance to downy mildew and if so, characterize the resistance phenotype(s) in these lines; and 3) determine if identified resistant DH lines exhibit resistance to isolates of P. parasitica acquired from different geographic regions of the United States. Twenty-three DH broccoli inbreds and two commercial hybrids were evaluated for reaction at different developmental stages to infection by P. parasitica in a controlled environment. Results showed that broccoli plants can be evaluated for downy mildew resistance in a two-stage process. Inoculation at the cotyledon stage did not offer any cross-protection or otherwise influence the expression of reaction phenotype (RP) when the same plants were subsequently inoculated at the three to four true-leaf stage. Three different RPs to infection by P. parasitica were identified in DH inbreds. These were: 1) susceptibility at both the cotyledon stage and the true-leaf stage; 2) resistance at both the cotyledon and true-leaf stage; and 3) susceptibility at the cotyledon stage but resistance at the true-leaf stage. There was no effect of two pathogenic isolates from different geographic regions on RP of DH broccoli inbreds. Selection of plant resistance to downy mildew at the cotyledon stage will effectively identify plants with high levels of resistance at subsequent developmental stages.

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SCREENING TECHNIQUES FOR DOWNY MILDEW RESISTANCE IN GHERKIN CUCUMBERS

International Journal of Geomate ◽

10.21660/2017.40.2603 ◽

2017 ◽

Vol 13 (40) ◽

Author(s):

Piyavadee Charoenwattana

Keyword(s):

Downy Mildew ◽

Downy Mildew Resistance ◽

Mildew Resistance ◽

Screening Techniques

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High resolution mapping and candidate gene identification of downy mildew race 16 resistance in spinach

BMC Genomics ◽

10.1186/s12864-021-07788-8 ◽

2021 ◽

Vol 22 (1) ◽

Author(s):

Gehendra Bhattarai ◽

Wei Yang ◽

Ainong Shi ◽

Chunda Feng ◽

Braham Dhillon ◽

...

Keyword(s):

Candidate Genes ◽

Downy Mildew ◽

Association Analysis ◽

Spinacia Oleracea ◽

Genotyping By Sequencing ◽

Significant Snps ◽

Snp Markers ◽

Resistance Locus ◽

Downy Mildew Resistance ◽

Mildew Resistance

Abstract Background Downy mildew, the most devastating disease of spinach (Spinacia oleracea L.), is caused by the oomycete Peronospora effusa [=P. farinosa f. sp. spinaciae]. The P. effusa shows race specificities to the resistant host and comprises 19 reported races and many novel isolates. Sixteen new P. effusa races were identified during the past three decades, and the new pathogen races are continually overcoming the genetic resistances used in commercial cultivars. A spinach breeding population derived from the cross between cultivars Whale and Lazio was inoculated with P. effusa race 16 in an environment-controlled facility; disease response was recorded and genotyped using genotyping by sequencing (GBS). The main objective of this study was to identify resistance-associated single nucleotide polymorphism (SNP) markers from the cultivar Whale against the P. effusa race 16. Results Association analysis conducted using GBS markers identified six significant SNPs (S3_658,306, S3_692697, S3_1050601, S3_1227787, S3_1227802, S3_1231197). The downy mildew resistance locus from cultivar Whale was mapped to a 0.57 Mb region on chromosome 3, including four disease resistance candidate genes (Spo12736, Spo12784, Spo12908, and Spo12821) within 2.69–11.28 Kb of the peak SNP. Conclusions Genomewide association analysis approach was used to map the P. effusa race 16 resistance loci and identify associated SNP markers and the candidate genes. The results from this study could be valuable in understanding the genetic basis of downy mildew resistance, and the SNP marker will be useful in spinach breeding to select resistant lines.

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