Validation of the QTL for grain length linked to the Rht-B1 locus in two genetic backgrounds of bread wheat (Triticum aestivum L.)

Onishi, Kazumitsu and Akie, Taiga and Cao, Liangzi and Mori, Masahiko and Hattori, Maya and Hira, Kazuma and Wano, Atsushi and Oki, Wakana and Miura, Hideho (2021) Validation of the QTL for grain length linked to the Rht-B1 locus in two genetic backgrounds of bread wheat (Triticum aestivum L.). CEREAL RESEARCH COMMUNICATIONS, 49 (4). pp. 559-566. ISSN 0133-3720 (print), 1788-9170 (online)

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Abstract

Grain size is an important agronomic trait that influences the yield and end-use quality of bread wheat (Triticum aestivum L.). We conducted quantitative trait loci (QTL) analysis using recombinant inbred lines derived from a cross of a semi-dwarf modern variety with large grains (Zenkoujikomugi: Zen) and a landrace with small grains (Chinese Spring: CS). Grain size was evaluated as grain length (GL), grain width (GW), grain thickness (GT), and thousand-grain weight (TGW) under two environmental conditions. A major QTL (QGl.obu-4B) associated with GL was detected in both environments near the Rht-B1 locus for the semi-dwarf trait on chromosome 4B, despite Zen and CS having the same Rht-B1a allele. No QTL for GW was found in the QGl.obu-4B region, and QTLs for GT and TGW was detected in only one environment. To validate the effect of QGl.obu-4B, we developed two backcrossed populations in the CS and Zen genetic backgrounds. The Zen-derived allele conferred larger GL, GW, and GT, resulting in greater TGW (13.7% increase compared to the CS-derived allele) in the CS background. In contrast, the QGl.obu-4B effect was smaller in the Zen background, and the Zen-derived allele increased TGW by only 7.0%. The QTL was located within the 168-Mbp region tightly linked to the Rht-B1 locus. Further characterization and fine-mapping of QGl.obu-4B will facilitate the use of this allele by marker-assisted selection in wheat breeding programs.

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