Diversification of the downy mildew resistance gene pool by introgression of a new gene, Pl35, from wild Helianthus argophyllus into oilseed and confection sunflowers (Helianthus annuus L.)

Authors: Qi, Lili; MA, GUOJIA - North Dakota State University; LI, XUEHUI - North Dakota State University; Seiler, Gerald

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2019
Publication Date: 6/18/2019
Citation: Qi, L.L., Ma, G.J., Li, X., Seiler, G.J. 2019. Diversification of the downy mildew resistance gene pool by introgression of a new gene, Pl35, from wild Helianthus argophyllus into oilseed and confection sunflowers (Helianthus annuus L.). Theoretical and Applied Genetics. 132(9):2553–2565. https://doi.org/10.1007/s00122-019-03370-9.
DOI: https://doi.org/10.1007/s00122-019-03370-9

Interpretive Summary: Downy mildew (DM) is an economically important and widespread disease in sunflower worldwide. Planting of genetically resistant hybrids and the use of fungicide seed treatments have been the most common methods to manage this disease. However, use of the plant’s natural resistance is the most economical and sustainable strategy to prevent crop losses. The discovery of novel DM resistance gene is a long-term task due to the frequent changes of the DM pathogen population, which reduces the effectiveness of resistance genes in cultivated sunflower. In this study, we report the transfer of a new resistance gene, Pl35, from the wild species Helianthus argophyllus (silver-leaf sunflower) into both oilseed and confection sunflowers. Molecular mapping placed Pl35 on chromosome 1 of the sunflower genome. DNA markers diagnostic for the Pl35 gene were validated in a panel of 548 diversified sunflower lines collected worldwide. The developed oilseed and confection germplasms with DNA markers specific for Pl35 will be very useful resources for breeding DM resistance in sunflower.

Technical Abstract: Sunflower downy mildew (DM), caused by the oomycete pathogen Plasmopara halstedii, is an economically important and widespread sunflower disease worldwide. Non-race-specific resistance is not available in sunflower and breeding for DM resistance relies on race-specific resistance to control this disease. The discovery of the novel DM resistance genes is a long-term task due to the highly virulent and aggressive nature of the P. halstedii pathogen, which reduces the effectiveness of resistance genes. The objectives of this study were to: 1) transfer DM resistance from a wild sunflower species Helianthus argophyllus (PI 494576) into cultivated sunflowers; 2) map the resistance gene; and 3) develop diagnostic single nucleotide polymorphism (SNP) markers for efficient targeting of the gene in breeding programs. The H. argophyllus accession PI 494576 previously identified with resistance to the most virulent P. halstedii race 777 was crossed with oilseed and confection sunflower in 2012. Molecular mapping using the BC2F2 and BC2F3 populations derived from the cross CONFSCLB1/PI 494576 located a new resistance gene Pl35 on linkage group 1 of the sunflower genome. The new gene Pl35 was successfully transferred from PI 494576 into cultivated sunflowers. SNP markers flanking Pl35 were surveyed in a validation panel of 548 diversified sunflower lines collected globally. Eleven SNP markers were found to be diagnostic for Pl35 SNP alleles, with four co-segregating with Pl35. The developed oilseed and confection germplasms with diagnostic SNP markers for Pl35 will be very useful resources for breeding of DM resistance in sunflower.