Construction of a genome-wide genetic linkage map and identification of quantitative trait loci for powdery mildew resistance in Gerbera daisy

Abstract

Powdery mildew (PM) is a common fungal disease in many important crops. The PM caused by Podosphaera xanthii has been the most challenging problem in commercial Gerbera (Gerbera hybrida) production globally, often leading to severe losses of crop yield and quality. A small number of PM-resistant breeding lines and cultivars have been reported in Gerbera, but the underlying genetics for PM resistance in Gerbera is largely unknown. Scarcity of genomic resources such as genetic linkage maps and molecular markers has severely hindered the effort to understand the genetic basis and locate loci controlling PM resistance in Gerbera. This study aimed to construct a genome-wide genetic linkage map, identify quantitative trait loci (QTL), and molecular markers for PM resistance in Gerbera. A segregating mapping population was developed by crossing PM-resistant and -susceptible Gerbera breeding lines, genotyped by sequencing, and phenotyped for PM resistance. A genome-wide genetic linkage map constructed with 791 single polymorphic site (SNP) markers spans 1912.30 cM across 27 linkage groups (LG) and reaches a density of 1 marker per 2.42 cM. One major consistent QTL was discovered in LG16, explaining more than 16.6% of the phenotypic variance for PM resistance. The QTL was tagged with two flanking SNP markers. The availability of this genetic linkage map will be very useful for locating and tagging QTLs for other important traits in Gerbera, and the newly discovered QTL and SNP markers will enable development of molecular markers for improving Gerbera for resistance to PM.

Phenotypic Variation in Flower Color and Morphology in the Gerbera (Gerbera hybrida) F1 Hybrid Population and Their Association with EST-SSR Markers

“…Previous studies have shown that R 2 is often low in association with the analysis of complex quantitative traits, especially in heterozygous plants such [ 44 , 45 ], and gerbera is a typical heterozygous plant. SNP markers have been developed in recent years, but only a small fraction can be mapped to linkage groups, possibly because of the high heterozygosity of gerbera [ 23 , 24 ]. The lack of a genome further limits the molecular marker-assisted breeding of gerbera.…”

“…In our previous work, we developed new EST-SSR markers based on transcriptomes and identified several molecular markers linked to flower color through association analysis, laying the foundation for the molecular marker breeding of gerbera [ 21 ]. Fu et al [ 23 ] and Bhattarai et al [ 24 ] also developed SNP markers and constructed a genetic map of gerbera. However, the high heterozygosity of gerbera limited the mapping of SNPs to linkage groups.…”