3D modelling of tillering behaviour and light interception of freely (-tin) and restricted (+tin) tillering wheat near-isolines

A functional-structural plant model of wheat architecture was parameterised to simulate a pair of lines varying for a tiller inhibition (tin) gene. Effects of planting configuration were explored through red : far-red (R:FR) signalling on tiller production, final spike numbers, and light interception. Both increased plant density (125 to 200 plants/m²) and row spacing (20 to 30 cm) reduced the simulated tiller and spike numbers per plant in both lines. This reduction was greater in the free-tillering (–tin) than in the reduced-tillering (+tin) line. At wider row spacing of 30 cm, simulated radiation interception was less in the +tin line than in the –tin line from about 60 days after sowing onwards. In the +tin line, increased R:FR signalling between individual plants due to less within-row spacing at wider rows resulted in reduced spikes/m² irrespective of population density. Spikes/m² simulated for the –tin line were similar at either row spacing in a population of 125 plants/m², but decreased with wider row spacing at the higher density of 200 plants/m². For both lines, the greatest number of tillers and ultimately spikes per m² was simulated at a density of 200 plants/m² and 20 cm row spacing (–tin: 820 spikes/m²; +tin: 570 spikes/m²). The simulations indicated that growing +tin wheat at an increased density of 200 plants/m² and 20 cm row spacing can produce similar, or greater, spikes/m² compared to –tin wheat grown at a density of 125 plants/m².