Field Phenotyping of Soybean Roots for Drought Stress Tolerance

Berhanu Fenta,James Burridge,Jonathan Lynch,Christine Foyer,Kathryn Barlow,Stephen Beebe,Karl Kunert

doi:10.3390/agronomy4030418

Abstract

Root architecture was determined together with shoot parameters under well watered and drought conditions in the field in three soybean cultivars (A5409RG, Jackson and Prima 2000). Morphology parameters were used to classify the cultivars into different root phenotypes that could be important in conferring drought tolerance traits. A5409RG is a drought-sensitive cultivar with a shallow root phenotype and a root angle of <40°. In contrast, Jackson is a drought-escaping cultivar. It has a deep rooting phenotype with a root angle of >60°. Prima 2000 is an intermediate drought-tolerant cultivar with a root angle of 40°–60°. It has an intermediate root phenotype. Prima 2000 was the best performing cultivar under drought stress, having the greatest shoot biomass and grain yield under limited water availability. It had abundant root nodules even under drought conditions. A positive correlation was observed between nodule size, above-ground biomass and seed yield under well-watered and drought conditions. These findings demonstrate that root system phenotyping using markers that are easy-to-apply under field conditions can be used to determine genotypic differences in drought tolerance in soybean. The strong association between root and nodule parameters and whole plant productivity demonstrates the potential application of simple root phenotypic markers in screening for drought tolerance in soybean.

Highlights

Soybean is a vital source of vegetable protein for food and animal feed world-wide
We determined the decline in soil water content after switching off the sprinkler nozzles over the drought area with plants exposed to natural drought conditions
While more work is required to understand the mechanistic relationships between nodule size and SFN in Jackson and Prima 2000 occurring during drought, the findings of this study suggest that nodule size is a useful phenotypic trait that might be used for the selection for high seed yield under field conditions

Summary

Introduction

It is predicted to become a major crop in Africa [1]. Current breeding strategies for crops such as soybean seek to identify new varieties with higher grain yields and improved nitrogen- and water-use efficiencies. While considerable progress has been made recently in the development of imaging tools for the rapid phenotyping of shoots, the associated data processing and bio-informatic requirements remain challenging [2,3]. Classic manual plant phenotyping techniques remain valuable tools for plant breeding [4]. Such techniques are important in many developing countries, in Africa, which lack the essential underpinning infrastructure required to apply more sophisticated “phenomic” approaches

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