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Published on: March 9, 2021
Haplotype characterization and markers at the barley Mlo powdery mildew resistance locus as tools for marker-assisted
G Tacconi1, V Baldassarre, N C Collins
1Istituto Sperimentale per la Cerealicoltura, Consiglio per Ricerca e Sperimentazione in Agricoltura, Fiorenzuola d'Arda, PC, Italy.
Abstract:
Recessive mlo alleles of the barley Mlo gene confer resistance to almost all known isolates of the powdery mildew fungal pathogen targeting barley (Hordeum vulgare). To characterize haplotypes present in the Mlo chromosomal region of cultivated Mlo and mlo barley genotypes, we conducted a polymorphism search in 3 predicted low-copy sequence regions adjacent to the Mlo gene by examining a sample of 4 Mlo and 3 mlo cultivars. Eight single-nucleotide polymorphisms (SNPs) and 1 insertion-deletion (indel) were detected, and easy to use PCR-based markers were developed for typing the SNPs. The PCR markers were used to characterize a collection of 46 Mlo and 25 mlo barley cultivars, identifying 3 distinct mlo-11 haplotypes, 1 mlo-9 haplotype, and 4 Mlo haplotypes. We summarized the haplotype and marker information obtained here and in a previous study to help breeders identify strategies for mlo marker-assisted selection. The ability of the markers to identify mlo-resistant genotypes in segregating populations was demonstrated using 2 resistance-characterized F2 populations derived by 3-way crosses.
Insights
Barley powdery mildew resistance is conferred by recessive Mlo alleles. New PCR markers efficiently identify Mlo haplotypes in barley cultivars, aiding marker-assisted selection for disease resistance breeding.
Area of Science:
- Plant genetics
- Agricultural science
- Molecular biology
Background:
- Powdery mildew (caused by fungal pathogens) is a significant disease in barley (Hordeum vulgare).
- Recessive alleles of the barley Mlo gene provide broad-spectrum resistance against most powdery mildew isolates.
- Understanding Mlo haplotypes is crucial for breeding resistant barley varieties.
Purpose of the Study:
- To characterize Mlo haplotypes in cultivated barley genotypes.
- To develop and validate PCR-based markers for Mlo haplotype typing.
- To facilitate marker-assisted selection for powdery mildew resistance in barley breeding programs.
Main Methods:
- Polymorphism search in low-copy sequence regions adjacent to the Mlo gene.
- Identification of single-nucleotide polymorphisms (SNPs) and insertion-deletions (indels).
- Development of PCR-based markers for SNP typing and characterization of barley cultivars.
Main Results:
- Eight SNPs and one indel were detected in the Mlo chromosomal region.
- Developed PCR markers successfully typed a collection of barley cultivars.
- Identified three distinct mlo-11 haplotypes, one mlo-9 haplotype, and four Mlo haplotypes.
- Demonstrated marker utility in identifying mlo-resistant genotypes in segregating F2 populations.
Conclusions:
- The developed PCR markers are effective for Mlo haplotype discrimination in barley.
- This haplotype information aids breeders in developing marker-assisted selection strategies for powdery mildew resistance.
- The study provides valuable tools for enhancing disease resistance in barley breeding.
