The technologies behind high-throughput phenotyping are transforming ecophysiology, but the generation of new knowledge about how plants function is limited by the lack of a conceptual framework. Functional phenomics delivers a next-generation plant physiology framework using phenotyping, physiology, multivariate statistics, and simulation modeling to generate and test new hypotheses about how plant traits integrate to influence plant performance, whether agronomic or fitness. The trait economics spectrum is a conceptual framework from ecology that could be useful for exploring whole plant trait integration in crops. In this context, economics refers to the balance among traits for resource acquisition and utilization, with explicit treatment of the tradeoffs between pairs of traits. A single leaf economics spectrum was found to explain correlations among leaf traits such as photosynthetic assimilation rate, leaf mass per area, percent nitrogen, and leaf longevity. These ideas lead naturally to considering other economics spectra in plant species. For example, a root economics spectrum was proposed in which root respiration correlated to percent nitrogen, root length per mass, and the decomposition rate of dried roots in soil. The idea of ‘fast’ and ‘slow’ traits has important implications for agriculture where modern cultivars have generally been selected to perform in high-input, non-limiting systems, and thus may be dominated by ‘fast’ traits. Therefore, consideration of ‘slow’ traits that lead to greater resource use efficiency could have transformative value for breeding crops for sustainable agroecosystems. To investigate the root economics spectrum, 276 diverse wheat (Triticum aestivum) genotypes with available sequence data were intensively phenotyped for a suite of shoot and root traits including specific root length and specific root respiration using open source tools such as RhizoVision Analyzer.
Results/Conclusions
Substantial intraspecific genetic variation was discovered for all traits measured. Nearly 5-fold variation was found among the wheat lines for specific root respiration on a root length basis, with a heritability of 0.46. Specific root length was found to have even greater heritability than shoot mass (0.6 and 0.57, respectively). Correlation networks among root economics traits confirm expectations based on previous literature. Genome-wide association studies (GWAS) for the univariate traits uncovered several genetic regions associated with variation in these economics traits. Excitingly, multivariate GWAS uncovered underlying genetics of a root economics spectrum itself, possibly for the first time. Using the genomic and phenomic resources available for crop species is an unprecedented opportunity to further ecological theory.