Location: Sunflower Improvement Research
Project Number: 3060-21000-047-005-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jul 1, 2020
End Date: Jun 30, 2025
Objective:
1. Identify novel QTL associated with Sclerotinia HR resistance in an F4 population (Pop1) derived from the cross of HR21 and HA 234. The HR resistance in HR21 is derived from the wild perennial species, H. maximiliani.
2. Identify novel QTL associated with Sclerotinia HR resistance in an F4 population (Pop2) derived from the cross of HR92 and HA 234. The HR resistance in HR92 is derived from the wild perennial species, H. nuttallii.
3. Investigate the phenotypic interaction among major QTL conferring partial resistance to Sclerotinia BSR in sunflower, and develop germplasms combining different BSR-resistance QTL with enhanced resistance.
Approach:
Two populations have been developed for HR resistance QTL mapping by crossing the sunflower inbred line HA 234 with two germplasm lines, HR21 and HR92. Both HR21 and HR92 are resistant to HR with resistance derived from the wild species H. maximiliani and H. nuttallii as resistance donors, respectively. The F2 progenies from each cross were advanced to the F4 generation. Each population will be assayed separately for response to Sclerotinia HR infection in replicated field trials using artificial inoculation over a 3-year period (2020-2022). Phenotypic disease reaction data from field trials will be collected across locations and years. Simultaneous discovery of single nucleotide polymorphism (SNP) markers and genotyping of individual lines of each population will be performed using genotyping-by-sequencing (GBS). A linkage map for each population will be constructed and SNP markers associated with QTL conditioning resistance to HR as measured in the field will be detected using QTL analysis software. In addition, the two publicly available highly dense sunflower genetic maps containing more than 15,000 SNP will be used to further saturate the QTL region associated with Sclerotinia HR resistance to better define the genomic position of QTL. SNP markers associated with QTL could potentially provide an aid to conventional breeding in introgressing complex traits during inbred development.
BSR resistance QTL identified previously in cultivated and wild sunflowers will be pyramided into various genetic combinations to examine QTL interactions and develop germplasm lines with enhanced BSR resistance. Six F2 populations have already been developed using BSR resistant germplasms possessing QTL from cultivated sunflower and sunflower wild species H. argophyllus, H. petiolaris, and H. praecox. The F2 populations will be screened for BSR resistance under intensive disease pressure in the greenhouse and the selected resistant F2 plants will be advanced to F4 generations. Subsequent generations will be evaluated for their resistance to BSR in the field. SNP markers linked to QTL will be used to validate the presence of QTL in the selected lines.
