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Title: Heading date QTL in winter wheat (Triticum aestivum L.) coincide with major developmental genes Vernalization-1 and Photoperiod-1

Author
item GUEDIRA, MOHAMMED - North Carolina State University
item XIONG, MAI - North Carolina State University
item HAO, YUAN - University Of Georgia
item JOHNSON, JERRY - University Of Georgia
item HARRISON, STEVE - Louisana State University
item Marshall, David
item Brown-Guedira, Gina

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2016
Publication Date: 5/10/2016
Citation: Guedira, M., Xiong, M., Hao, Y.F., Johnson, J., Harrison, S., Marshall, D.S., Brown Guedira, G.L. 2016. Heading date QTL in winter wheat (Triticum aestivum L.) coincide with major developmental genes Vernalization-1 and Photoperiod-1. PLoS One. 11(5):e0154242.

Interpretive Summary: In wheat, time from planting to spike emergence is influenced by genes controlling response to cold treatment, referred to as vernalization requirement, and day length, referred to as photoperiod response. Characterizing the available genetic diversity of known and novel alleles of major flowering time genes Vernalization-1 (Vrn-1) and Photoperiod-1 (Ppd-1) in winter wheat can inform approaches for breeding climate resilient varieties. This study identified effects on heading date associated with multiple Vrn-1 and Ppd-1 genes in a population developed from a cross between two early flowering soft red winter wheat cultivars. When the population was grown in the greenhouse after partial vernalization treatment, major heading date effects co-located with the Vrn-A1 and Vrn-B1 loci. The number of copies of the Vrn-A1 gene influenced HD such that lines having three copies required longer cold exposure to transition to flowering than lines having two Vrn-A1 copies. Sequencing of the vrn-B1 winter allele of the parents revealed multiple differences at the DNA level associated with a major HD effect. A 36 bp deletion in the first intron of Vrn-B1 was associated with earlier HD after partial vernalization in lines having either two or three gene copies of Vrn-A1. The Vrn-1 loci interacted significantly and influenced time to heading in field experiments in Louisiana, Georgia and North Carolina. The Ppd-1 loci were significant determinants of heading date in the fully vernalized treatment in the greenhouse and in all field environments. Heading date effects were associated with the Ppd-A1, Ppd-B1 and Ppd-D1 genes. The Ppd-D1 gene was determined to have the largest genetic effect, followed by Ppd-A1 and Ppd-B1. Our results demonstrate that Vrn-1 and Ppd-1 alleles of varying strength allow fine tuning of flowering time in diverse winter wheat growing environments.

Technical Abstract: In wheat (Triticum aestivum L.), time from planting to spike emergence is influenced by genes controlling vernalization requirement and photoperiod response. Characterizing the available genetic diversity of known and novel alleles of Vernalization-1 (Vrn-1) and Photoperiod-1 (Ppd-1) in winter wheat can inform approaches for breeding climate resilient cultivars. This study identified QTL for heading date (HD) associated with multiple Vrn-1 and Ppd-1 loci in a population developed from a cross between two early flowering winter wheat cultivars. When the population was grown in the greenhouse after partial vernalization treatment, major heading date QTLs co-located with the Vrn-A1 and Vrn-B1 loci. Copy number variation at Vrn-A1 locus influenced HD such that RIL having three copies required longer cold exposure to transition to flowering than RIL having two Vrn-A1 copies. Sequencing of the vrn-B1 winter allele of the parents revealed multiple polymorphisms in the first intron that were the basis of mapping a major HD QTL coinciding with Vrn-B1. A 36 bp deletion in the first intron of Vrn-B1 was associated with earlier HD after partial vernalization in lines having either two or three haploid copies of Vrn-A1. The Vrn-1 loci interacted significantly and influenced time to heading in field experiments in Louisiana, Georgia and North Carolina. The Ppd-1 loci were significant determinants of heading date in the fully vernalized treatment in the greenhouse and in all field environments. Heading date QTL were associated with alleles having large deletions in the upstream regions of Ppd-A1 and Ppd-D1 and with copy number variants at the Ppd-B1 locus. The Ppd-D1 locus was determined to have the largest genetic effect, followed by Ppd-A1 and Ppd-B1. Our results demonstrate that Vrn-1 and Ppd-1 alleles of varying strength allow fine tuning of flowering time in diverse winter wheat growing environments.