Relocation of a rust resistance gene R 2 and its marker-assisted gene pyramiding in confection sunflower (Helianthus annuus L.)

Abstract

The rust resistance gene R 2 was reassigned to linkage group 14 of the sunflower genome. DNA markers linked to R 2 were identified and used for marker-assisted gene pyramiding in a confection type genetic background. Due to the frequent evolution of new pathogen races, sunflower rust is a recurring threat to sunflower production worldwide. The inbred line Morden Cross 29 (MC29) carries the rust resistance gene, R 2 , conferring resistance to numerous races of rust fungus in the US, Canada, and Australia, and can be used as a broad-spectrum resistance resource. Based on phenotypic assessments and SSR marker analyses on the 117 F2 individuals derived from a cross of HA 89 with MC29 (USDA), R 2 was mapped to linkage group (LG) 14 of the sunflower, and not to the previously reported location on LG9. The closest SSR marker HT567 was located at 4.3 cM distal to R 2 . Furthermore, 36 selected SNP markers from LG14 were used to saturate the R 2 region. Two SNP markers, NSA_002316 and SFW01272, flanked R 2 at a genetic distance of 2.8 and 1.8 cM, respectively. Of the three closely linked markers, SFW00211 amplified an allele specific for the presence of R 2 in a marker validation set of 46 breeding lines, and SFW01272 was also shown to be diagnostic for R 2 . These newly developed markers, together with the previously identified markers linked to the gene R 13a , were used to screen 524 F2 individuals from a cross of a confection R 2 line and HA-R6 carrying R 13a . Eleven homozygous double-resistant F2 plants with the gene combination of R 2 and R 13a were obtained. This double-resistant line will be extremely useful in confection sunflower, where few rust R genes are available, risking evolution of new virulence phenotypes and further disease epidemics.

Pl 17 is a novel gene independent of known downy mildew resistance genes in the cultivated sunflower (Helianthus annuus L.)

“…Genotyping of the SFW SNPs was performed using a strategy of converting the SNPs into length polymorphism markers. The conditions of the SNP PCR reactions have been described by Qi et al (2015). An additional 5-base oligonucleotide (5′-ATGAC-3′) was inserted between the tail and the allele-specific sequences in the AS-primer F2 to produce a length difference between the two alleles after amplification (Table 1).…”

Gene Classification and Mining of Molecular Markers Useful in Red Clover (Trifolium pratense) Breeding

“…They are used in QTL mapping (Zhao et al, 2013), evolution relationship studies (Ghamkhar et al, 2012; Isobe et al, 2012), variability assessment and genotyping of breeding material (Younas et al, 2012; Cidade et al, 2013), marker-assisted selection, and even gene pyramiding (Qi et al, 2015). Based on NGS technology, we are capable of discovering thousands of SSR and many millions of SNP markers (Zalapa et al, 2012).…”

Registration of Two Double Rust Resistant Germplasms, HA‐R12 and HA‐R13 for Confection Sunflower

“…DNA concentration was quantified on a NanoDrop 2000 Spectrophotometer (Thermo Fisher Scientific). The SSR and SNP markers linked to the genes R 2 , R 5 , and R 13a were used to confirm the homozygosity of HA‐R12 and HA‐R13 (Tables 2 and 3; Gong et al, 2013; Qi et al, 2015a,b). We performed SSR marker analysis according to the procedure described by Qi et al (2012).…”