Evolutionary and ecological perspectives on the wheat phenotype

Victor O Sadras

doi:10.1098/rspb.2021.1259

Abstract

Technologies, from molecular genetics to precision agriculture, are outpacing theory, which is becoming a bottleneck for crop improvement. Here, we outline theoretical insights on the wheat phenotype from the perspective of three evolutionary and ecologically important relations—mother–offspring, plant–insect and plant–plant. The correlation between yield and grain number has been misinterpreted as cause-and-effect; an evolutionary perspective shows a striking similarity between crop and fishes. Both respond to environmental variation through offspring number; seed and egg size are conserved. The offspring of annual plants and semelparous fishes, lacking parental care, are subject to mother–offspring conflict and stabilizing selection. Labile reserve carbohydrates do not fit the current model of wheat yield; they can stabilize grain size, but involve trade-offs with root growth and grain number, and are at best neutral for yield. Shifting the focus from the carbon balance to an ecological role, we suggest that labile carbohydrates may disrupt aphid osmoregulation, and thus contribute to wheat agronomic adaptation. The tight association between high yield and low competitive ability justifies the view of crop yield as a population attribute whereby the behaviour of the plant becomes subordinated within that of the population, with implications for genotyping, phenotyping and plant breeding.

Highlights

Technologies, from molecular genetics to precision agriculture, are outpacing theory, which is becoming a bottleneck for crop improvement and agronomy [2,3]
In a historic collection of wheat cultivars adapted to high-yielding environments in the UK, the concentration of water-soluble carbohydrates (WSC) in shoot at anthesis was high and did not change with the year of release, but the total amount of WSC increased at 4.6 g m−2 yr−1 with selection for yield between 1972 and 1995 [64]
Binary mixtures of wheat cultivars demonstrated a strong symmetry in yield response to neighbour; this is, Halberd increased yield by approximately 17% with Scepter neighbour in comparison to pure stands, and Scepter reduced yield in a similar proportion when grown with a Halberd neighbour

Summary

Evolutionary and ecological perspectives on the wheat phenotype

South Australian Research and Development Institute, and School of Agriculture, Food and Wine, The University of Adelaide, Australia. We outline theoretical insights on the wheat phenotype from the perspective of three evolutionary and ecologically important relations—mother–offspring, plant–insect and plant–plant. The correlation between yield and grain number has been misinterpreted as cause-and-effect; an evolutionary perspective shows a striking similarity between crop and fishes. Both respond to environmental variation through offspring number; seed and egg size are conserved. Labile reserve carbohydrates do not fit the current model of wheat yield; they can stabilize grain size, but involve trade-offs with root growth and grain number, and are at best neutral for yield. Shifting the focus from the carbon balance to an ecological role, we suggest that labile carbohydrates may disrupt aphid osmoregulation, and contribute to wheat agronomic adaptation. The tight association between high yield and low competitive ability justifies the view of crop yield as a population attribute whereby the behaviour of the plant becomes subordinated within that of the population, with implications for genotyping, phenotyping and plant breeding

Introduction

Conclusion

Findings

Response of maize barrenness to density and