Molecular mapping of the downy mildew and rust resistance genes in a sunflower germplasm line TX16R

Authors: LIU, ZHAO - North Dakota State University; LEI, ZHANG - Academy Of Agricultural Science; MA, GUOJIA - North Dakota State University; Seiler, Gerald; JAN, CHAOCHIEN - Retired ARS Employee; Qi, Lili

Submitted to: Molecular Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2018
Publication Date: 2/8/2019
Citation: Liu, Z., Zhang, L., Ma, G.J., Seiler, G.J., Jan, C.C., Qi, L.L. 2019. Molecular mapping of the downy mildew and rust resistance genes in a sunflower germplasm line TX16R. Molecular Breeding. 39:19. https://doi.org/10.1007/s11032-018-0921-z.
DOI: https://doi.org/10.1007/s11032-018-0921-z

Interpretive Summary: Downy mildew (DM) and rust are two of the most serious diseases of cultivated sunflower globally. Disease epidemics can cause serious reductions in yield and end-use quality. The most economical and effective manner to manage both DM and rust in sunflower is to plant resistant hybrids. A sunflower germplasm line TX16R released in 2005 is highly effective against all DM and rust pathogen races identified in the US. The broad-spectrum resistance to DM and rust makes TX16R an extremely valuable genetic resource for disease resistance breeding in sunflower. Developing tightly linked and informative markers is a worthwhile goal for breeding programs. In the current study, the DM and rust resistance genes Pl22 and R16 from TX16R were genetically mapped to chromosomes 4 and 13 of the sunflower genome, respectively. The identified molecular markers linked to Pl22 and R16 can be used in marker-assisted introgression of Pl22 and R16 into newly developed elite sunflower breeding lines, and for gene pyramiding. The new Pl22 and R16 genes are desirable because they provide a way to increase the complexity and diversity of disease resistance in sunflower.

Technical Abstract: The sunflower germplasm line TX16R is resistant to Plasmopara halstedii (causal agent of sunflower downy mildew) and Puccinia helianthi (causal agent of sunflower rust). This study reports the mapping of the downy mildew and rust resistance genes Pl22 and R16 from TX16R, respectively. Progeny testing of half-diallel test crosses for downy mildew resistance suggested that Pl22 localizes to linkage group (LG) 4 of the sunflower genome. Molecular mapping of Pl22 using simple sequence repeat (SSR), and single nucleotide polymorphism (SNP) markers identified Pl22 cosegregating with ORS644, ORS963, SFW04901, and SFW04052, and linking to two SNPs, NSA_006089 and NSA_008496, at a genetic distance of 0.2 cM on the proximal side. This is the third Pl gene reported on LG4. Bulked segregant analysis using SSR and EST-SSR markers from LGs previously reported for rust genes identified polymorphic SSR markers associated with rust resistance on LG13. R16 was mapped between SFW08875 and SFW04317 on LG13, with a genetic distance of 1.8 and 1.1 cM, respectively. The fifteen linked markers span a genetic distance of 27.4 cM in LG13. The cosegregating or closely linked markers to the two resistance genes will facilitate marker-assisted selection (MAS) and gene pyramiding, and will further assist in identifying genes responsible for DM and rust resistance.