Grain yield responsiveness to water supply in near-isogenic reduced-tillering wheat lines – an engineered crop trait near its upper limit

Grain yield responsiveness to water supply was evaluated in spring wheat (Triticum aestivum L.) near-isogenic lines (NILs) for presence of the reduced-tillering ‘tin’ (tiller inhibition) gene using boundary-line analysis. Data were collected from multiple seasons at Managed Environment Facilities (MEFs; field experimental facilities to control and target water supply) at three locations across the Australian wheatbelt. The minimum water required to obtain a measurable yield was less in reduced-tillering than free-tillering NILs (70 vs 95 mm). Above this minimum, for every mm increase in water supply, grain yield in free-tillering lines increased more rapidly (that is, showed greater responsiveness) than reduced-tillering lines (15.4 vs 12.6 kg ha−1 mm−1). This difference suggests the reduced-tillering gene is associated with greater yield potential in situations with water supply of less than 200 mm. Reduced-tillering wheat also affords a 0.3 t ha−1 yield benefit in extremely water-limited, low yielding situations where no measurable yield is expected with free-tillering wheats (i.e. at water supply 95 mm). These specific adaptations need to be considered when contemplating the use of reduced-tillering wheats in dryland systems where water is a key limiting factor. © 2018 Elsevier B.V

A reduced tillering trait shows small but important yield gains in dryland wheat production

Reducing the number of tillers per plant using a tiller inhibition (tin) gene has been considered as an important trait for wheat production in dryland environments. We used a spatial analysis approach with a daily time-step coupled radiation and transpiration efficiency model to simulate the impact of the reduced-tillering trait on wheat yield under different climate change scenarios across Australia's arable land. Our results show a small but consistent yield advantage of the reduced-tillering trait in the most water-limited environments both under current and likely future conditions. Our climate scenarios show that whilst elevated [CO2 ] (e[CO2 ]) alone might limit the area where the reduced-tillering trait is advantageous, the most likely climate scenario of e[CO2 ] combined with increased temperature and reduced rainfall consistently increased the area where restricted tillering has an advantage. Whilst long-term average yield advantages were small (ranged from 31 to 51 kg ha-1 yr-1 ), across large dryland areas the value is large (potential cost-benefits ranged from AUD 23 to 60 MIL yr-1 ). It seems therefore worthwhile to further explore this reduced-tillering trait in relation to a range of different environments and climates, because its benefits are likely to grow in future dry environments where wheat is grown around the world