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United States Department of Agriculture

Agricultural Research Service

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Research Project: Molecular Mapping of Resistance Genes Effective Against Newly Emerged, Virulent Races of Downy Mildew in Sunflower

Location: Sunflower Research

Project Number: 3060-21000-039-17
Project Type: Trust

Start Date: Apr 01, 2012
End Date: Mar 31, 2015

Objective:
The objectives of this proposed project are 1) to fine map the gene PlARG in the line RHA 464 using SNP markers, 2) elucidate the inheritance of downy mildew resistance in three inbred lines, HA 458, RHA 428 and 803-1, and in a new cross with the resistance gene derived from H. argophyllus, 3) to identify the chromosome location of the underlying genes, and 4) to use SNP markers to saturate the region in which the new resistance genes reside.

Approach:
Objective 1: Twenty to thirty seeds from each F3 family, a total of 140 F3 families (~3,000-4,000 individuals), will be evaluated for downy mildew resistance in greenhouse trials in 2012. Phenotypic data will be integrated with SNP data to identify SNP markers linked to PlArg. Objective 2: We will advance F2 generations of four crosses, HA 234 × RHA 428, HA 234 × HA 458, HA 89 × 803-1, and HA 89 × H. argophyllus PI 494573, to the F3 generations. Subsequent phenotypic resistance evaluation will be conducted in F2:3 families. Twenty to thirty seedlings of each F3 family (estimated to total 4,500 to 6,000 seedlings for each population) will be inoculated with virulent race 734 for resistance screening. The phenotypic data will be used to analyze the gene model of the DM resistance in RHA 428, HA 458, 803-1, and H. argophyllus PI 494573. Objective 3: Bulked segregant analysis (BSA) will be performed to identify the genomic region harboring the new DM resistance genes. We will screen the polymorphism between each pair of parents, susceptible and resistant, with 860 selected SSR markers. Bulked segregant analysis will be performed with those SSRs showing polymorphism between resistant and susceptible parents. SSR markers showing associations with the resistance bulk in bulked segregant analysis will be genotyped on an F2 population of 150 to 200 individuals to confirm the marker-trait association. Objective 4: Depending on the availability of the funding, an oligo pool assay (OPA) for a specific linkage group of sunflower can be designed for fine mapping of DM disease association regions. Integrating our DM phenotype and SSR genotype data with SNP OPA data will allow the identification of the closest SNP markers linked to DM resistance genes.

Last Modified: 12/19/2014
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