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Grain yield in bread wheat (Triticum aestivum L.) is largely determined by inflorescence architecture. Zang734 is an endemic Tibetan wheat variety that exhibits a rare triple spikelet (TRS) phenotype with significantly increased spikelet/floret number per spike. However, the molecular basis underlying this specific spike morphology is completely unknown.Through map-based cloning, the causal genes for TRS trait in Zang734 were isolated. Furthermore, using CRISPR/Cas9-based gene mutation, transcriptome sequencing and proteinprotein interaction, the downstream signalling networks related to spikelet formation and awn elongation were defined.Results showed that the null mutation in WFZP-A together with deletion of WFZP-D led to the TRS trait in Zang734. More interestingly, WFZP plays a dual role in simultaneously repressing spikelet formation gene TaBA1 and activating awn development genes, basically through the recruitments of chromatin remodelling elements and the Mediator complex.Our findings provide insights into the molecular bases by which WFZP suppresses spikelet formation but promotes awn elongation and, more importantly, define WFZP-D as a favourable gene for high-yield crop breeding.

Summary The spikelet number and heading date are two crucial and correlated traits for yield in wheat. Here, a quantitative trait locus (QTL) analysis was conducted in F 8 recombinant inbred lines (RILs) derived from crossing two common wheats with different spikelet numbers. A total of 15 stable QTL influencing total spikelet number (TSN) and heading date (HD) were detected. Notably, FT‐D1 , a well‐known flowering time gene in wheat, was located within the finely mapped interval of a major QTL on 7DS ( QTsn/Hd.cau‐7D ). A causal indel of one G in the third exon of FT‐D1 was significantly associated with total spikelet number and heading date. Consistently, CRISPR/Cas9 mutant lines with homozygous mutations in FT‐D1 displayed an increase in total spikelet number and heading date when compared with wild type. Moreover, one simple and robust marker developed according to the polymorphic site of FT‐D1 revealed that this one G indel had been preferentially selected to adapt to different environments. Collectively, these data provide further insights into the genetic basis of spikelet number and heading date, and the diagnostic marker of FT‐D1 will be useful for marker‐assisted pyramiding in wheat breeding.

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