A rare SNP mutation in Brachytic2 moderately reduces plant height and increases yield potential in maize.

Anqi Xing,Xiaohong Yang,Yufeng Gao,Lichun Cai,Lingfeng Ye,Jiansheng Li,Jianbing Yan,Lin Liu,Weiping Zhang,Victor Llaca,Blaine Johnson,Ada Ching,Dingming Kang

doi:10.1093/jxb/erv182

Abstract

Plant height has long been an important agronomic trait in maize breeding. Many plant height QTLs have been reported, but few of these have been cloned. In this study, a major plant height QTL, qph1, was mapped to a 1.6kb interval in Brachytic2 (Br2) coding sequence on maize chromosome 1. A naturally occurring rare SNP in qph1, which resulted in an amino acid substitution, was validated as the causative mutation. QPH1 protein is located in the plasma membrane and polar auxin transport is impaired in the short near-isogenic line RIL88(qph1). Allelism testing showed that the SNP variant in qph1 reduces longitudinal cell number and decreases plant height by 20% in RIL88(qph1) compared to RIL88(QPH1), and is milder than known br2 mutant alleles. The effect of qph1 on plant height is significant and has no or a slight influence on yield in four F2 backgrounds and in six pairs of single-cross hybrids. Moreover, qph1 could reduce plant height when heterozygous, allowing it to be easily employed in maize breeding. Thus, a less-severe allele of a known dwarf mutant explains part of the quantitative variation for plant height and has great potential in maize improvement.

Highlights

Short stature, erect leaf angle, disease resistance, and high yield are traits that have been pursued by breeders for decades
We previously identified a major QTL affecting multiple traits in bin7 on chromosome 1 using F2:3, immortalized F2, and recombinant inbred line (RIL) populations derived from Zong3 and 87-1, a hybrid known as ‘Yuyu22’ that has been widely planted in China for the past two decades
We report a rare SNP mutation in the maize Brachyric2 gene underlying the major plant height QTL qph1

Summary

Introduction

Erect leaf angle, disease resistance, and high yield are traits that have been pursued by breeders for decades. Maize (Zea mays) production improved dramatically due to the adoption of hybrids and use of moderately short varieties that are more resistant to lodging and compatible with higher planting density (Duvick, 2005). Many of the Green Revolution genes, such as sd-1 in rice (Sasaki et al, 2002) and rht in wheat (Peng et al, 1999), have been identified and utilized in crop improvement. These genes encode proteins that either regulate the synthesis of plant hormones or modulate their signalling pathways.

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