The domestication of cereal crops such as wheat, maize, rice and barley has included the modi fication of infl orescence architecture to improve grain yield and ease harvesting 1 . Yield increases have often been achieved through modifying the number and arrangement of spikelets, which are specialized reproductive branches that form part of the in fl orescence. Multiple genes that control spikelet development have been identi fied in maize, rice and barley2–5 . 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.