Proline-Mediated Drought Tolerance in the Barley (Hordeum vulgare L.) Isogenic Line Is Associated with Lateral Root Growth at the Early Seedling Stage.

Felix Frimpong,Ali A Naz,Michael Frei,Fabio Fiorani,Michael Anokye,Carel W Windt,Dagmar Van Dusschoten

doi:10.3390/plants10102177

Abstract

A vigorous root system in barley promotes water uptake from the soil under water-limited conditions. We investigated three spring barley genotypes with varying water stress responses using rhizoboxes at the seedling stage. The genotypes comprised two elite German cultivars, Barke and Scarlett, and a near-isogenic line, NIL 143. The isogenic line harbors the wild allele pyrroline-5-carboxylate synthase1-P5cs1. Root growth in rhizoboxes under reduced water availability conditions caused a significant reduction in total root length, rooting depth, root maximum width, and root length density. On average, root growth was reduced by more than 20% due to water stress. Differences in organ proline concentrations were observed for all genotypes, with shoots grown under water stress exhibiting at least a 30% higher concentration than the roots. Drought induced higher leaf and root proline concentrations in NIL 143 compared with any of the other genotypes. Under reduced water availability conditions, NIL 143 showed less severe symptoms of drought, higher lateral root length, rooting depth, maximum root width, root length density, and convex hull area compared with Barke and Scarlett. Within the same comparison, under water stress, NIL 143 had a higher proportion of lateral roots (+30%), which were also placed at deeper substrate horizons. NIL 143 had a less negative plant water potential and higher relative leaf water content and stomatal conductance compared with the other genotypes under water stress. Under these conditions, this genotype also maintained an enhanced net photosynthetic rate and exhibited considerable fine root growth (diameter class 0.05–0.35 mm). These results show that water stress induces increased shoot and root proline accumulation in the NIL 143 barley genotype at the seedling stage and that this effect is associated with increased lateral root growth.

Highlights

Climate variability and ever more frequent drought events negatively affect cereal production [1,2,3]
Our current study investigated the hypothesis that proline accumulation contributes to barley root growth under water stress
We found that the shoot proline concentration was 30% higher than the root proline concentration for all genotypes under water stress (WS) and that these differences were significant

Summary

Introduction

Climate variability and ever more frequent drought events negatively affect cereal production [1,2,3]. Developing adapted cultivars that maintain yields under reduced water availability is essential [4]. Crop adaptation requires that cultivars adjust their above and below-ground morphology, physiology, and biochemical traits to a specific water stress scenario [4,5]. As a critical below-ground trait, the ability to develop deep roots enables the entire plant to adjust to or avoid reduced water availability [6,7,8]. Essential root traits associated with maintaining plant productivity under drought include small fine root diameters [10], long specific root length, root area, root angle, and considerable root length density, especially within deep soil horizons containing available water [11,12,13]

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