Variation in key leaf photosynthetic traits across wheat wild relatives is accession dependent not species dependent

Lorna Mcausland,Silvere Vialet‐Chabrand,Ian P King,Michael J Fryer,Elizabete Carmo‐Silva,Kevin Pyke,Iván Jauregui,Julie King,Amanda Burridge,Keith J Edwards,Erik H Murchie,Tracy Lawson,Stella Hubbart‐Edwards

doi:10.1111/nph.16832

Lorna Mcausland, Silvere Vialet‐Chabrand + Show 11 more

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https://doi.org/10.1111/nph.16832

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Abstract

The wild relatives of modern wheat represent an underutilized source of genetic and phenotypic diversity and are of interest in breeding owing to their wide adaptation to diverse environments. Leaf photosynthetic traits underpin the rate of production of biomass and yield and have not been systematically explored in the wheat relatives. This paper identifies and quantifies the phenotypic variation in photosynthetic, stomatal, and morphological traits in up to 88 wheat wild relative accessions across five genera. Both steady-state measurements and dynamic responses to step changes in light intensity are assessed. A 2.3-fold variation for flag leaf light and CO2 -saturated rates of photosynthesis Amax was observed. Many accessions showing higher and more variable Amax , maximum rates of carboxylation, electron transport, and Rubisco activity when compared with modern genotypes. Variation in dynamic traits was also significant; with distinct genus-specific trends in rates of induction of nonphotochemical quenching and rate of stomatal opening. We conclude that utilization of wild relatives for improvement of photosynthesis is supported by the existence of a high degree of natural variation in key traits and should consider not only genus-level properties but variation between individual accessions.

Highlights

Modern hexaploid bread wheat cultivars are the product of a genetic bottleneck – a reduction in genetic diversity brought about by domestication through polyploidization and the intensive selection for agronomically important traits over the past 10 000 yr (Charmet, 2011; Faris, 2014)
During the processes of domestication and selection, modern wheat may have lost key alleles required for adaptive robustness to abiotic and biotic stress – a negative side effect resulting from single trait selection
We have provided a database of photosynthetic traits, shown substantial variation for key photosynthetic traits, and discovered novel patterns among the wild relatives that partly explain the underlying causes of the differences observed

Summary

Introduction

Modern hexaploid bread wheat cultivars are the product of a genetic bottleneck – a reduction in genetic diversity brought about by domestication through polyploidization and the intensive selection for agronomically important traits over the past 10 000 yr (Charmet, 2011; Faris, 2014). Potential yield gains have been circumvented by increasingly unpredictable environmental conditions, susceptibility to biotic stresses, and agronomic practices (Brisson et al, 2010). With pressure to raise yields between 1.6 and 2.4% per annum over the 50 yr (Brisson et al, 2010; Ray et al, 2013), the emphasis falls to increasing the genetic diversity of modern wheat to maintain or improve yields under current environmental conditions (Evans & Lawson, 2020). Exploration of the wild relatives may uncover previously untapped potential for wider and enhanced characteristics to face changing environmental conditions and disease resistance, aiming to improve the productivity and resilience of future modern varieties

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