Tillering and Water Soluble Carbohydrates Accumulation As Adaptive Traits In Wheat.

Cereals are cultivated worldwide, from low to high input agricultural systems. Two key traits behind the adaptability of cereals to drought conditions are tillering and the capacity to store water soluble carbohydrates (WSC) in the stems. Tillering influences the number of spikes per unit area, canopy architecture, and water use among other processes involving resource capture. WSC storage and remobilisation buffer the decline in photosynthetic capacity during grain filling and help maintain grain growth. In previous work we have shown that the stem WSC concentration has been negatively correlated to the stem and spike number per unit area at flowering or maturity in genetically diverse wheat germplasm, when plants are evaluated at a single plant density. In this series of experiments we tested the hypothesis that the genotypic ranking of WSC is independent of stem density per unit area. A small subset of recombinant inbred lines from the Seri/Babax population (2-14) that had been either shown to differ in WSC level or stem number m^-2 were grown at different plant densities 50 to 400 pl m^-2 over three years. While absolute tiller numbers and WSC levels changed in response to plant density, the genotypic ranking of WSC as observed at current practice was not altered. The underlying causes for observed differences in tiller number at anthesis between RILs were investigated in terms of leaf and tiller appearance rates, tillering cessation and mortality. Understanding the relationship between these traits and how they are regulated is important to interpret genotype x environment interaction to different mega-environments. We propose a model of how tillering and WSC accumulation are linked and discuss to what extent they can be manipulated for better breeding outcomes.