TaAPO-A1, an ortholog of rice ABERRANT PANICLE ORGANIZATION 1, is associated with total spikelet number per spike in elite European hexaploid winter wheat (Triticum aestivum L.) varieties

Quddoos H Muqaddasi,Marion S Röder,Martin W Ganal,Ravi Koppolu,Jonathan Brassac,Jörg Plieske

doi:10.1038/s41598-019-50331-9

Quddoos H Muqaddasi, Marion S Röder + Show 4 more

Open Access

https://doi.org/10.1038/s41598-019-50331-9

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Abstract

We dissected the genetic basis of total spikelet number (TSN) along with other traits, viz. spike length (SL) and flowering time (FT) in a panel of 518 elite European winter wheat varieties. Genome-wide association studies (GWAS) based on 39,908 SNP markers revealed highly significant quantitative trait loci (QTL) for TSN on chromosomes 2D, 7A, and 7B, for SL on 5A, and FT on 2D, with 2D-QTL being the functional marker for the gene Ppd-D1. The physical region of the 7A-QTL for TSN revealed the presence of a wheat ortholog (TaAPO-A1) to APO1–a rice gene that positively controls the spikelet number on the panicles. Interspecific analyses of the TaAPO-A1 orthologs showed that it is a highly conserved gene important for floral development and present in a wide range of terrestrial plants. Intraspecific studies of the TaAPO-A1 across wheat genotypes revealed a polymorphism in the conserved F-box domain, defining two haplotypes. A KASP marker developed on the polymorphic site showed a highly significant association of TaAPO-A1 with TSN, explaining 23.2% of the total genotypic variance. Also, the TaAPO-A1 alleles showed weak but significant differences for SL and grain yield. Our results demonstrate the importance of wheat sequence resources to identify candidate genes for important traits based on genetic analyses.

Highlights

A few cloned genes for the trait number of spikelet pairs in wheat are available; among them is the Q-gene which played a major role in wheat domestication and encodes an AP2 transcription factor[10]
We investigated the inheritance and genetic basis of total spikelet number (TSN) per spike, spike length and flowering time as component traits of grain yield in an elite European winter wheat panel
Our findings show the complex genetic architecture of the investigated traits, and that TaAPO-A1–an ortholog of rice ABERRANT PANICLE ORGANIZATION 1 (APO1), which is vital for inflorescence development–is associated with the TSN determination in wheat

Summary

Introduction

A few cloned genes for the trait number of spikelet pairs in wheat are available; among them is the Q-gene which played a major role in wheat domestication and encodes an AP2 transcription factor[10]. Ppd-1 and FT were reported as regulators of paired spikelet formation resulting in an increased number of grain-producing spikelets[15]. Mutants of the MADS-box genes, e.g., VRN1 or FUL2 showed an increased number of spikelets per spike, likely due to a delayed formation of the terminal spikelet[16] and a putative ortholog to rice MOC1 regulating axillary meristem initiation and outgrowth was associated with spikelet number per spike in wheat[17]. We investigated the inheritance and genetic basis of total spikelet number (TSN) per spike, spike length and flowering time as component traits of grain yield in an elite European winter wheat panel. Our findings show the complex genetic architecture of the investigated traits, and that TaAPO-A1–an ortholog of rice APO1, which is vital for inflorescence development–is associated with the TSN determination in wheat. Intraspecific sequence analyses of TaAPO-A1 revealed that polymorphisms were forming distinct haplotypes while interspecific studies showed the conserved nature of this gene across terrestrial plant species

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