ABOVE AND BELOW GROUND PHENOTYPING TECHNOLOGIES FOR WHEAT BREEDING

Wheat varieties with greater yields arise today mainly by selecting for harvested grain yield in field environments. This approach combines multiple favourable alleles. Gains are slow because the contributions of alleles to yield are largely unknown. The contrasting “pre-breeding” approach aims to introduce a single major enhancing trait (other than yield) into a variety. This approach can take ~20 years from idea to field, and there are few successful examples in wheat (Hall and Richards 2013). Phenotyping may bridge this gap between yield based and single-trait based breeding because multiple traits (alleles) can be measured on one line. Examples are presented where phenotyping technologies quantified shoot and root traits non-destructively on wheats of different genetic and pedoclimatic origins. For early growth traits in controlled conditions: root architecture differed in response to soil water gradients, but shoots did not (Nagel et al., 2015); shoot growth declined in response to reduced N supply, but root growth did not (Gioia et al 2015); and leaf area and water use varied differentially in response to drought (Nakhforoosh et al 2016). Field phenotyping during grain filling has shown that shoot and root development vary independently depending on plant stage, genotype and environment (Severini et al. in prep), and spectral properties of wheat heads and canopy are dynamic, requiring time-lapse systems (Ahrends et al., 2014). Hence phenotyping technologies quantify the high degree of variation at important establishment and grain development stages in wheat, and may increase certainty of incorporating multiple alleles of known effect within breeding