Mapping and Characterization of QTLs for Awn Morphology Using Crosses between "Double-Awn" Wheat 4045 and Awnless Wheat Zhiluowumai.

Tianxiang Liu,Jun Wang,Yong Wang,Xue Shi,Jiawang Song,Zhonghua Wang,Enshi Xiao,Xin Gao,Wenzhi Nan

doi:10.3390/plants10122588

Tianxiang Liu, Jun Wang + Show 7 more

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https://doi.org/10.3390/plants10122588

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Abstract

Awns play important roles in seed dispersal, protection against predators, and photosynthesis. The characterization of genes related to the formation of awns helps understand the regulation mechanisms of awn development. In the present study, the “double-awn” wheat 4045, which features super-long lemma awns and long glume awns, and an awnless wheat line, Zhiluowumai, were used to investigate QTLs or genes involved in awn development. QTL analysis identified three loci—Qawn-1D, Qawn-5A, and Qawn-7B—using a population of 101 4045 × ZLWM F2 plants. Fine mapping with a total of 9018 progenies narrowed the mapping interval of Qawn-5A to an 809-kb region, which was consistent with the B1 locus, containing five genes on chromosome 5AL. Gene structure and expression analysis indicated that TraesCS5A02G542800 was the causal gene, which was subsequently verified by overexpression of TraesCS5A02G542800 in a “double-awn” wheat, Yangmai20. The retained “double-awn” phenotype of transgenic plants suggested that B1 represses the elongation but does not influence the emergence of the awns. Moreover, 4045 harbors a new allele of B1 with a 261-bp insertion in the promoter region and a lack of the EAR2 motif in the encoding region, which influences several important agronomic traits. In this study, we identify two novel QTLs and a novel allele of B1, providing new resources for exploration of awn development.

Highlights

Awns are needle-like structures that emerge from the tips of the lemma in Poaceae grasses such as wheat (Triticum aestivum L.), rice (Oryza sativa L.), barley (Hordeum vulgare L.), and rye (Secale cereale L.)
The awns consist of sclerenchyma, two chlorenchyma zones, and three well-developed vascular bundles inside, with rows of stomata on the epidermis of the abaxial terminal [2]
The zonal distribution of the sclerenchyma tissue and three vascular bundles supports the solid awn structure [2], which helps to protect the seeds from being ingested by animals or birds [3]

Summary

Introduction

Awns are needle-like structures that emerge from the tips of the lemma in Poaceae grasses such as wheat (Triticum aestivum L.), rice (Oryza sativa L.), barley (Hordeum vulgare L.), and rye (Secale cereale L.). The awns consist of sclerenchyma, two chlorenchyma zones, and three well-developed vascular bundles inside, with rows of stomata on the epidermis of the abaxial terminal [2]. The zonal distribution of the sclerenchyma tissue and three vascular bundles supports the solid awn structure [2], which helps to protect the seeds from being ingested by animals or birds [3]. By enhancing the carbon exchange rate and water use efficiency, awns facilitate photosynthesis and increase the grain filling efficiency [6–8]. Under extreme conditions, such as drought and heat stress, the awns contribute up to 16% of the total grain production [6,8–10]

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