Root‐omics for drought tolerance in cool‐season grain legumes

Abstract

Root traits can be exploited to increase the physiological efficiency of crop water use under drought. Root length, root hairs, root branching, root diameter, and root proliferation rate are genetically defined traits that can help to improve the water productivity potential of crops. Recently, high-throughput phenotyping techniques/ platforms have been used to screen the germplasm of major cool-season grain legumes for root traits and their impact on different physiological processes, including nutrient uptake and yield potential. Advances in omics approaches have led to the dissection of genomic, proteomic, and metabolomic structures of these traits. This knowledge facilitates breeders to improve the water productivity and nutrient uptake of cultivars under limited soil moisture conditions in major cool-season grain legumes that usually face terminal drought. This review discusses the advances in root traits and their potential for developing drought-tolerant cultivars in cool-season grain legumes. | INTRODUCTIONRoot system architecture (RSA) involves in situ spatial distribution of roots within the rooting volume (Hinsinger et al., 2011;Lynch, 1995Lynch, , 2007Manschadi et al., 2013). Roots are important for plant survival and growth because they enable the exploration of soil zones and acquisition of soil water and nutrients (Gregory et al., 2009;Hammond et al., 2009;Lynch & Brown, 2012). Besides the mechanical support to plants, these also serve as active sites of food storage and interactions with pathogenic as well as beneficial organisms in the rhizosphere. The plastic and dynamic nature of roots allow plants to take up important soil resources under various soil moisture conditions and thus respond to corresponding environments (Zhu et al., 2011). There is a need to explore such root traits that efficiently facilitate the uptake of water and nutrients from soils for higher productivity under water-limited situations (Wasson et al., 2012). However, plant breeders are not generally interested in selecting for root traits due to the complex phenotyping protocols, low heritability, and variable expression depending on soil type and rainfall pattern (Malamy, 2005;Tuberosa, Salvi, et al., 2002a). Plant breeders often assume that direct selection for yield will indirectly select varieties with the optimum root system for achieving increased yields (Wasson et al., 2012).However, there is evidence that a more direct selection for RSA traits can help to develop water-efficient genotypes with improved desirable agronomic and physiological traits leading to enhanced biomass, yield, drought resistance, and tolerance to nutrient deficiencies in dry regions (Chen et al., 2018). For example, wheat genotypes with a deeper and denser root system are able to capture more soil water and nitrogen leading to increased duration of green leaf area and yield (Lilley & Kirkegaard, 2011;Manschadi et al., 2006). Therefore, root traits have become important for developing genetically improved genotypes for rainfed cropping systems. ...

Carbon fluxes and environmental interactions during legume development, with a specific focus on Pisum sativum

“…Drought is the most important constraint limiting legumes growth and subsequent yield (Figure 1B). Water deficit leads to deep modifications of the plant primary and secondary metabolisms (Kumar et al, 2021; Lahuta et al, 2022) (Table 1), as it decreases net photosynthesis and nutrient uptake. Hence, when facing drought, a major issue for the plant is to produce enough carbohydrates by photosynthesis to sustain sink growth (Kumar et al, 2021; Nadeem et al, 2019).…”

The Adaptation and Tolerance of Major Cereals and Legumes to Important Abiotic Stresses

“…Denser roots can absorb greater amounts of water because of the more extensive root system [ 185 ]. The gene responsible for root hair elongation is associated with drought tolerance in maize [ 186 ], rice [ 187 ], wheat [ 188 ], and grain legumes [ 5 ]. Drought tolerance is the plants’ ability to tolerate low tissue water content by adaptive traits, including preserving cell turgor by osmotic adjustment, preserving cell elasticity, and improving protoplasmic resistance.…”

“…It is necessary to understand the adaptive mechanisms of plants to identify traits associated with tolerance to abiotic stresses. Several proteins and genes involved in abiotic stress adaptation and mitigation have been integrated to develop varieties that are tolerant to abiotic stresses [ 3 , 4 , 5 , 6 ]. The genetic engineering of crop plants with stress-responsive genes has been demonstrated to enhance the adaptation to various abiotic stresses [ 1 , 7 , 8 , 9 ].…”

Genomics Associated Interventions for Heat Stress Tolerance in Cool Season Adapted Grain Legumes

“…Thus, this crop shows high sensitivity to heat stress. Heat stress affects several phonological, biochemical and physiological traits such as limited growth rate, membrane instability, photosynthesis, reproductive development, and reduced net assimilation rate [ 17 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. Heat stress sensitivity has been observed more in cool season grain legumes compared to warm season food legumes [ 8 ].…”

“…Efforts have been made to improve the heat tolerance through conventional breeding approaches, and screening methodologies have been developed to identify heat tolerant cultivars [ 15 , 16 ]. In recent years, genomics has emerged as a way to decipher the genetics underlying complex traits imparting heat stress tolerance in food legumes and published several reviews focussed on different aspects of heat stress including seed setting [ 17 ], functional mechanism [ 18 ], heat stress during reproductive and grain-filling phases [ 19 ], functional genomics [ 20 ], physiological and molecular approach [ 21 ], and breeding, genetics and genomics [ 2 ]. In the recent past years, new knowledge have been generated in the area of genomics for tackling heat stress tolerance in cool season grain legumes, which were not covered in previously published review articles.…”