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Ppd-1 is a key regulator of inflorescence architecture and paired spikelet development in wheat


The domestication of cereal crops such as wheat, maize, rice and barley has included the modification of inflorescence architecture to improve grain yield and ease harvesting1. Yield increases have often been achieved through modifying the number and arrangement of spikelets, which are specialized reproductive branches that form part of the inflorescence. Multiple genes that control spikelet development have been identified in maize, rice and barley25. However, little is known about the genetic underpinnings of this process in wheat. Here, we describe a modified spikelet arrangement in wheat, termed paired spikelets. Combining comprehensive QTL and mutant analyses, we show that Photoperiod-1 (Ppd-1), a pseudo-response regulator gene that controls photoperiod-dependent floral induction, has a major inhibitory effect on paired spikelet formation by regulating the expression of FLOWERING LOCUS T (FT)6,7. These findings show that modulated expression of the two important flowering genes, Ppd-1 and FT, can be used to form a wheat inflorescence with a more elaborate arrangement and increased number of grain producing spikelets.

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Figure 1: Characterization of paired spikelets.
Figure 2: Genome-wide plot displaying the 104 QTL (coloured dots/triangles) that contribute to paired spikelet development using the four-way MAGIC population across five independent experiments (five different colours).
Figure 3: The effect of allelic variation for Ppd-1 and photoperiod on inflorescence architecture.
Figure 4: Identification and phenotyping of Ppd-D1a mutants.
Figure 5: Deletion of FT-B1 promotes paired spikelet development.


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We thank Bjorg Sherman for technical assistance with plant husbandry, Mark Talbot for expert assistance with scanning electron microscopy and Carl Davies for photography. We thank Lindsay Shaw and Megan Hemming for helpful discussions. A CSIRO O.C.E. Postdoctoral Fellowship funded S.A.B.

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S.A.B., C.C., K.R., J.G., E.J.F., B.T. and S.M.S. performed experiments and collected phenotypic information. C.C. and B.R.C. designed the MAGIC experiments, performed QTL and statistical analysis. S.A.B., E.J.F., B.T. and S.M.S. contributed new materials. All authors contributed to the preparation of the manuscript.

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Correspondence to Steve M. Swain.

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Boden, S., Cavanagh, C., Cullis, B. et al. Ppd-1 is a key regulator of inflorescence architecture and paired spikelet development in wheat. Nature Plants 1, 14016 (2015).

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