Root Architecture and Functional Traits of Spring Wheat Under Contrasting Water Regimes.

Nidia Brunel-Saldias,Juan Pedro Ferrio,Massiel Orellana,Abdelhalim Elazab,Alejandro Del Pozo

doi:10.3389/fpls.2020.581140

Abstract

Wheat roots are known to play an important role in the yield performance under water-limited (WL) conditions. Three consecutive year trials (2015, 2016, and 2017) were conducted in a glasshouse in 160 cm length tubes on a set of spring wheat (Triticum aestivum L.) genotypes under contrasting water regimes (1) to assess genotypic variability in root weight density (RWD) distribution in the soil profile, biomass partitioning, and total water used; and (2) to determine the oxygen and hydrogen isotopic signatures of plant and soil water in order to evaluate the contribution of shallow and deep soil water to plant water uptake and the evaporative enrichment of these isotopes in the leaf as a surrogate for plant transpiration. In the 2015 trial under well-watered (WW) conditions, the aerial biomass (AB) was not significantly different among 15 wheat genotypes, while the total root biomass and the RWD distribution in the soil profile were significantly different. In the 2016 and 2017 trials, a subset of five genotypes from the 2015 trial was grown under WW and WL regimes. The water deficit significantly reduced AB only in 2016. The water regimes did not significantly affect the root biomass and root biomass distribution in the soil depths for both the 2016 and 2017 trials. The study results highlighted that under a WL regime, the production of thinner roots with low biomass is more beneficial for increasing the water uptake than the production of large thick roots. The models applied to estimate the relative contribution of the plant’s primary water sources (shallow or deep soil water) showed large interindividual variability in soil, and plant water isotopic composition resulted in large uncertainties in the model estimates. On the other side, the combined information of root architecture and the leaf stable isotope signatures could explain plant water status.

Highlights

The rainfed agriculture of the Mediterranean regions is suffering from water shortages, which strongly limit current yields of wheat and other cereals (Richards, 1996; Chairi et al, 2020)
According to the results of the previous field trial conducted at the rainfed (Cauquenes) and full-irrigation (Santa Rosa) sites in 2012, the yield tolerance index (YTI) classified the studied genotypes into tolerant, intermediate, and susceptible to water deficits (Table 1)
The water regimes application significantly affected all studied traits except root biomass (RB), where the WL regime reduced aerial biomass (AB) by 17%, increased R:S by 15%, decreased water used (WU) by 29%, and increased WUE by 17% compared with the WW regime genotype mean

Summary

Introduction

The rainfed agriculture of the Mediterranean regions is suffering from water shortages, which strongly limit current yields of wheat and other cereals (Richards, 1996; Chairi et al, 2020). The genetic gain in grain yield (GY) of spring wheat cultivars developed during the green revolution has been high in favorable environments (del Pozo et al, 2014, 2019b), but this has not been the case in drought-stressed environments where the productivity of modern cultivars is even lower than traditional cultivars (Elazab, 2015; Crespo-Herrera et al, 2017). Previous breeding efforts for increasing GY in drought-prone Mediterranean regions relied on selecting yield per se, distinguished by low heritability and high genotype × environment interactions (Jackson et al, 1996; Elazab, 2015)

Methods

Results

Discussion

Conclusion