Rate of improvement in genetic yield potential (YP) of wheat is now much too slow to keep pace with anticipated future demand. This indicates an urgent need to develop more-effective breeding targets for YP improvement. Triticale is a cereal crop that shares at least two genomes with wheat and it is a crop that usually enjoys a substantial yield advantage over wheat when the two are grown together. Here, in work conducted over several years under irrigated, high-input conditions, drivers of YP have been compared between modern triticales and modern wheats to help identify potential breeding targets for accelerating YP gains in wheat.

In a first series of studies it was found that traditional, tall triticales had greater anthesis biomass than semi-dwarf wheats, due to both greater radiation interception and higher radiation-use efficiency, and that, despite their substantially greater height, the harvest index (HI) achieved by tall triticales was actually a little higher than semi-dwarf wheats. More-recent studies have incorporated new, shorter triticales in studies with wheats spanning a similar range of heights. These studies have shown that the reduction in crop height of triticale has resulted in even further gains in both YP and HI compared with wheat, as anticipated.

Three major conclusions can be drawn from this work. First, it is obvious that height is a major driver of biomass production, in both wheat and triticale, and that a major source of the biomass advantage of traditional ‘tall’ triticales is their greater height compared with semi-dwarf bread wheats. Second, triticale is much more effective than wheat at converting its height-driven biomass advantage into a yield advantage. Third, the negative HI versus height relationship still holds for triticale, as it does for wheat, but for the same height, ‘semi-dwarf’ triticale achieves a substantially higher HI than bread wheat, setting and filling more and larger grain.

Two strong breeding targets emerge for YP gain in wheat: biomass and HI. Wheat breeders should strive to benefit from the clear biomass advantage that comes with greater crop height, as exemplified by traditional triticales. Second, there is still considerable room to move with HI. It is very clear that triticale achieves substantially greater HI per unit height than bread wheat under the same agronomy. The genetic basis for this HI-enhancement shouldn’t be difficult to identify and transfer to wheat using appropriate germplasm and new genetic tools now available.