Detection and integration of gene mapping of downy mildew resistance in maize inbred lines though linkage and association

Downy mildew caused by Plasmopara halstedii is one of the most economically important fungal diseases on sunflower (Helianthus annuus). To date, several downy mildew resistance genes called Pl genes have been reported on sunflower genetic map. Previous findings have confirmed that Iranian sunflower germplasms are harbouring Pl resistance genes that may be used to control downy mildew. In the current study, there were investigated the Pl5 and Pl16 downy mildew resistance genes in 51 inbred lines of Iranian sunflower, using PCR-based method. Fifteen differential lines carrying Pl5 and Pl16 downy mildew resistance genes were used as positive control. DNAs from 51 sunflower inbred lines were used in PCR reactions using primer pair RS1008 and Hap3 previously reported to serve as tightly linked to Pl16 and P5 loci, respectively. The PCR results confirmed the presence of two Pl16 and Pl5 bands with the size of about 280 and 1,580 bp, respectively, in differential lines. The results indicated that 1 inbred line out of 51 was found to carry Pl5 gene and 10 lines were found to carry Pl16 gene across the studied Iranian sunflower genotypes. These findings may be used to assist breeders for conservation and selection of downy mildew resistant sunflower genotypes.

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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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Mutants of downy mildew resistance in Lactuca sativa (lettuce).

Genetics ◽

10.1093/genetics/137.3.867 ◽

1994 ◽

Vol 137 (3) ◽

pp. 867-874

Author(s):

P A Okubara ◽

P A Anderson ◽

O E Ochoa ◽

R W Michelmore

Keyword(s):

Molecular Marker ◽

Downy Mildew ◽

Genomic Dna ◽

Spontaneous Mutation ◽

Multigene Families ◽

Downy Mildew Resistance ◽

Bremia Lactucae ◽

Wild Type ◽

Mildew Resistance ◽

Recessive Mutations

Abstract As part of our investigation of disease resistance in lettuce, we generated mutants that have lost resistance to Bremia lactucae, the casual fungus of downy mildew. Using a rapid and reliable screen, we identified 16 distinct mutants of Latuca sativa that have lost activity of one of four different downy mildew resistance genes (Dm). In all mutants, only a single Dm specificity was affected. Genetic analysis indicated that the lesions segregated as single, recessive mutations at the Dm loci. Dm3 was inactivated in nine of the mutants. One of five Dm 1 mutants was selected from a population of untreated seeds and therefore carried a spontaneous mutation. All other Dm1, Dm3, Dm5/8 and Dm7 mutants were derived from gamma- or fast neutron-irradiated seed. In two separate Dm 1 mutants and in each of the eight Dm3 mutants analyzed, at least one closely linked molecular marker was absent. Also, high molecular weight genomic DNA fragments that hybridized to a tightly linked molecular marker in wild type were either missing entirely or were truncated in two of the Dm3 mutants, providing additional evidence that deletions had occurred in these mutants. Absence of mutations at loci epistatic to the Dm genes suggested that such loci were either members of multigene families, were critical for plant survival, or encoded components of duplicated pathways for resistance; alternatively, the genes determining downy mildew resistance might be limited to the Dm loci.

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