Presenting author: Ragavendran Abbai; email: abbai@ipk-gatersleben.de

Over the course of domestication and breeding, tremendous progress is achieved in improving wheat grain yield primarily by increasing number, fertility, and size of floral organs, while mostly preserving the overall spike architecture, where the grain-bearing spikelets are directly attached to the rachis in a distichous pattern. However, slow rates of yield increase in the past two decades suggests a “yield plateau” even in some of the highly productive agroecosystems worldwide.

Conceivably, introducing radical changes in the inflorescence architecture might offer new paths for furthering yield potential and overcome yield barrier. Here, we explored the physiological and genetic basis of grain yield determination in ‘Miracle-Wheat’ (Triticum turgidum convar. compositum (L.f.) Filat.) that deviates from the standard developmental programme, producing a non-canonical spike with lateral branches.

Notably, the Miracle-Wheat accessions are landraces with an exceptionally high number of spikelets because of spike-branching, but suffers from reduced grains per spikelet and grain weight, thus impeding its use in wheat breeding. To address this limitation, we investigated the effect of source-sink strength on such trade-offs by analyzing a large population comprising 385 RILs derived from the spike-branching landrace TRI 984 and CIRNO C2008, an elite durum (T. durum L.) cultivar.

Multi-year field experiments identified favorable allele combinations viz., branched headt 3 (bht-A3), a new modifier locus for spike-branching and grain protein content (gpc-B1) that delayed senescence, which together improved grain number and grain weight in the spike-branching recombinants.

Furthermore, a set of promising spike-branching RILs were selected for yield trails in two diverse environments alongside leading local varieties. Overall, our study provides insights on mitigating grain yield trade-offs in Miracle-Wheat and propose spike-branching as a new breeding target to enhance yield gains in wheat.