Abstract
Preharvest sprouting (PHS) significantly reduces grain yield and quality. Identification of genetic loci for PHS resistance will facilitate breeding sprouting-resistant wheat cultivars. In this study, we constructed a genetic map comprising 1,702 non-redundant markers in a recombinant inbred line (RIL) population derived from cross Yangxiaomai/Zhongyou9507 using the wheat 15K single-nucleotide polymorphism (SNP) assay. Four quantitative trait loci (QTL) for germination index (GI), a major indicator of PHS, were identified, explaining 4.6–18.5% of the phenotypic variances. Resistance alleles of Qphs.caas-3AL, Qphs.caas-3DL, and Qphs.caas-7BL were from Yangxiaomai, and Zhongyou9507 contributed a resistance allele in Qphs.caas-4AL. No epistatic effects were detected among the QTL, and combined resistance alleles significantly increased PHS resistance. Sequencing and linkage mapping showed that Qphs.caas-3AL and Qphs.caas-3DL corresponded to grain color genes Tamyb10-A and Tamyb10-D, respectively, whereas Qphs.caas-4AL and Qphs.caas-7BL were probably new QTL for PHS. We further developed cost-effective, high-throughput kompetitive allele-specific PCR (KASP) markers tightly linked to Qphs.caas-4AL and Qphs.caas-7BL and validated their association with GI in a test panel of cultivars. The resistance alleles at the Qphs.caas-4AL and Qphs.caas-7BL loci were present in 72.2 and 16.5% cultivars, respectively, suggesting that the former might be subjected to positive selection in wheat breeding. The findings provide not only genetic resources for PHS resistance but also breeding tools for marker-assisted selection.
Highlights
Preharvest sprouting (PHS) refers to the germination of physiologically mature grains in spikes before harvest under rainy weather or humid environment (Groos et al, 2002)
The objectives of this study are to mine quantitative trait loci (QTL) for PHS resistance in a recombinant inbred line (RIL) population derived from a Yangxiaomai/Zhongyou9507 cross and to develop breedingfriendly markers for selection of PHS-resistant varieties
We confirmed that Qphs.caas-3AL and Qphs.caas-3DL co-localized with Tamyb10-A1 and Tamyb10-D1, respectively, at the R loci for grain color (Himi et al, 2011; Lang et al, 2021; Mares and Himi, 2021)
Summary
Preharvest sprouting (PHS) refers to the germination of physiologically mature grains in spikes before harvest under rainy weather or humid environment (Groos et al, 2002). PHS is a major problem in cereal production and causes losses in seed vitality, yield, and quality (Xu et al, 2019). The average annual loss of wheat caused by PHS exceeds $1 billion worldwide (Shao et al, 2018). Preharvest sprouting is a complex trait influenced by genetic and environmental factors (Barrero et al, 2015; Wang et al, 2019). An adaptive trait that prevents seeds from germinating, even under favorable conditions, is a major genetic factor for PHS (Née et al, 2017). Germination index (GI) is a common parameter to quantify genetic mechanisms underlying seed dormancy and PHS (Barrero et al, 2015). Some non-dormancy factors, such as spike erectness, spike and awn structure, and openness of florets, are associated with PHS (Zhu et al, 2019)
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