ReviewInfluence of the soil physical environment on rice (Oryza sativa L.) response to drought stress and its implications for drought research
Research highlights
► Soil strength is often overlooked in root research for drought-prone environment. ► Large variation in soil strength within rainfed rice areas and experimental sites. ► We examine soil strength in two field sites used for root QTL studies. ► Variation in soil strength may partially elucidate differences in results. ► Variation in soil strength must be examined and reported in drought research.
Introduction
Drought is a complex phenomenon, occurring at any ontogenic period during crop production, for varying lengths of time and affecting a large array of physiological, biochemical, and molecular pathways. The holistic effect of drought stress is an interaction among many factors, including weather (temperature, water vapour pressure deficit, wind speed, and radiation), soil physical and chemical environment, and biological interactions with pests and pathogens (Price et al., 2002a). These interactions may have implications for the interpretation of drought tolerance phenotyping activities and the selection of improved germplasm. Knowledge of the environmental characteristics within and among experimental sites and the main environmental considerations within the target populations of environments (TPE) is necessary to optimise drought breeding programs, by helping to understand and predict the performance of genotypes across environments (Wade et al., 1996, Heinemann et al., 2008).
Soil penetration resistance is the resistance offered by the soil matrix against penetration by growing roots (Tsegaye and Mullins, 1994). All roots experience axial and radial penetration resistance to varying degrees (Russell, 1977). When resistance is greater than approximately 1 MPa, root elongation is reduced and it continues to decrease as soil penetration resistance increases (Bengough and Mullins, 1990). The extent of reduction in root growth under increased soil resistance varies between species (Assaeed et al., 1990, Materechera et al., 1992, Martino and Shaykewich, 1994) and within species (Thangaraj et al., 1990, Yu et al., 1995, Babu et al., 2001). In rice, an increase in soil penetration resistance from 0.1 MPa to 1.5 MPa in the field decreased root length density by 40% (Hasegawa et al., 1985). Using a wax petroleum layer, a compact soil layer was simulated and rice root growth was shown to be severely inhibited at 1.4 MPa (60% wax formulation) (Yu et al., 1995).
Vertical root growth into the soil profile is considered to be a salient trait for drought avoidance, allowing access to a greater volume of soil water during periods of water deficit. Improving rice root systems for increased performance under water-limited conditions has received much attention (Price and Courtois, 1999, Price, 2002); however, few studies have been conducted in the field, where root systems regularly experience penetration resistance in the form of hardpan and/or gravelly layers as well as concomitant impacts of soil drying that restrict access to deeper soil layers. Soil penetration resistance increases during drought stress (Bengough et al., 1997), and may increase more rapidly than a decrease in soil moisture (Cairns et al., 2004). Thus, during drought, soil penetration resistance in some fields may be a more fundamental constraint to root growth than soil water availability (Cairns et al., 2004). Variability in soil penetration resistance within field experiments on managed drought stress may cause differences in the ability of roots systems to contribute to drought avoidance via access to a larger volume of soil water and may have important implications for the interpretation and application of experimental results.
The aim of this paper is to briefly review the effects of the soil physical environment on root growth and its interaction with crop response to drought stress. While the soil physical environment influences root systems, limited information is available for soil physical properties within experimental sites used for drought stress phenotyping and drought-prone rainfed rice production areas. This paper highlights the potential impacts of the soil environment on experimental results and data interpretation, and the importance of measuring and reporting soil penetration resistance within field drought experiments. In this mini-review, variability in soil penetration resistance within and between sites will be illustrated. Case studies involving field and controlled environment phenotyping and QTL (Quantitative Trait Loci) mapping associated with root growth and drought avoidance are discussed in which genotype × soil interactions are shown to influence experimental outputs.
Section snippets
Effect of soil penetration resistance on root growth
Soil penetration resistance is the result of cohesive forces between individual soil particles and frictional resistance met by particles that are forced to slide over one another or to ride out of interlocking positions in order to make way for growing roots (Marshall et al., 1996). Except for cracks and macropores (e.g., earthworm channels and a previous crop's decayed root voids) that provide pathways for roots to grow through (Passioura, 1991), root elongation in soils is possible only to
Soil penetration resistance in rainfed areas of South and Southeast Asia
Phenotypic performance is a function of three factors: genotype, environment and genotype × environment (G × E) interaction. In rainfed ecosystems, G × E interaction accounts for a large proportion of the phenotypic variation (Fischer, 1996). To investigate the nature of G × E interactions within drought screening in rainfed lowlands, grain yield of 37 genotypes across 36 sites in India, Bangladesh, Thailand, Indonesia, and the Philippines was analysed (Wade et al., 1999). G × E interaction accounted for
Effect of soil mechanical impedance on drought screening—a case study
The advent of molecular marker technology provided new opportunities in the development of improved germplasm for genetically complex traits such as drought tolerance. With the complexity of yields under drought stress many QTL studies focussed on secondary traits associated with drought tolerance on the assumption that promising alleles could be moved into breeding programs using marker-assisted selection, thus indirectly increasing and stabilizing grain yields under drought stress. Given the
Conclusions
Root growth is controlled by many factors including the soil physical environment. Roots and root system have been the focus of a large amount of research; however, in contrast relatively little is known about soil properties within experimental sites and the intended target environment for crop improvement. In the formulation of conclusions from drought phenotyping screens and to facilitate comparisons between experiments it is imperative that soil penetration resistance is reported.
Acknowledgements
This paper uses previously unpublished data for which the authors would like to acknowledge Drs CE Mullins, HR Lafitte, GN Atlin and A Audebert. Dr Bill Hardy is thanked for editing the manuscript.
References (62)
- et al.
Mechanical resistance as a soil factor influencing the growth of roots and underground shoots
Adv. Agron.
(1967) - et al.
Effects of soil water deficit on growth stages on rice growth and yield under upland conditions. 1. Growth during drought
Field Crop Res.
(1996) - et al.
Field water management to save water and increase its productivity in irrigated lowland rice
Agric. Water Manage.
(2001) - et al.
Mapping quantitative loci associated with root growth in upland rice (Oryza sativa L.) exposed to soil water-deficit in fields with contrasting soil properties
Field Crops Res.
(2009) - et al.
The potential restriction to root growth in structurally weak tropical soils
Soil Till Res.
(1995) - et al.
Effect of timing and severity of water deficit on four diverse rice cultivars. I. Rooting pattern and soil water extraction
Field Crops Res.
(1994) - et al.
Yield response of rice (Oryza sativa L.) genotypes to drought under rainfed lowlands. 1. Grain yield and yield components
Field Crop Res.
(2002) - et al.
Yield response of rice (Oryza sativa L.) genotypes to drought under rainfed lowlands. 2. Selection of drought resistant genotypes
Field Crop Res.
(2002) - et al.
Yield response of rice (Oryza sativa L.) genotypes to drought under rainfed lowlands. 3. Plant factors contributing to drought resistance
Field Crop Res.
(2002) - et al.
Upland rice grown in soil-filled chambers exposed to contrasting water-deficit regimes. II. Mapping quantitative trait loci for root morphology and distribution
Field Crops Res.
(2002)
Upland rice grown in soil-filled chambers exposed to contrasting water-deficit regimes. I. Root distribution, water use and plant water status
Field Crops Res.
Penetration of hardpans of rice lines in the rainfed lowlands
Field Crops Res.
Genotype × environment interactions across diverse rainfed lowland rice environments
Field Crops Res.
Effect of soil compaction on growth, yield and light interception of selected crops
Ann. Appl. Biol.
Variation in root penetration ability, osmotic adjustment and dehydration tolerance among accessions of rice adapted to rainfed lowland and upland ecosystems
Plant Breed.
The penetrometer in relation to mechanical resistance to root growth
Sloughing of the root cap cells decreases the frictional resistance to maize (Zea mays L.) root growth
J. Exp. Bot.
Mechanical impedance to root growth: a review of experimental techniques and root growth responses
J. Soil Sci.
A biophysical analysis of root growth under mechanical stress
Plant Soil
Growth and mechanical impedance
Effect of soil mechanical impedance on root growth of two rice varieties under field drought stress
Plant Soil
Locating genes associated with root morphology and drought avoidance in rice via linkage to molecular markers
Theor. Appl. Genet.
Complete mechanical impedance increases the turgor of cells in the apex of pea roots
Plant Cell Environ.
A gradual rather than abrupt increase in soil strength gives better root penetration of strong layers
Plant Soil
Evidence from near-isogenic lines that root penetration increases with root diameter and bending stiffness in rice
Funct. Plant Biol.
Old and new tools to analyze genotype × environment interactions: impact on upland rice breeding
Shoot and root responses to water deficits in rainfed lowland rice
Aust. J. Plant Physiol.
Research approaches for variable rainfed systems—thinking globally, acting locally
Breeding strategies for rainfed lowland rice: suggestions for future research
Root behaviour: field and laboratory studies
Soil Physics and Rice
Cited by (75)
Quantifying root-induced soil strength, measured as soil penetration resistance, from different crop plants and soil types
2023, Soil and Tillage ResearchCompacted soil adaptability of Brassica napus driven by root mechanical traits
2023, Soil and Tillage ResearchPlant responses to drought stress
2022, Brassinosteroids in Plant Developmental Biology and Stress ToleranceMicrobial impact on climate-smart agricultural practices
2022, Microbiome Under Changing Climate: Implications and SolutionsBalancing rice and non-rice crops: Managing the risks from soil constraints in Mainland Southeast Asian rice systems
2020, Field Crops ResearchCitation Excerpt :This correlation is improved by considering subsoil clay sodicity, then used to define land with low percolation rates in which rice is best grown. Even if the hardpan provides little or no limitation to root growth, the subsoil may have physical (e.g. bulk density or mechanical resistance), chemical (e.g. salinity, pH or nutrient toxicity), or other characteristics that limit the NRC roots from exploring the subsoil volume to depth (Cairns et al., 2011; Murray and Grant, 2007; Singh et al., 2017). Deep subsoils without limitations enable deeper root exploration and hence favour greater NRC production (Tolk et al., 1999), particularly with limited irrigation technology, or even in the absence of irrigation.