Advancements in Developing Abiotic Stress-Resilient Plants

Basic Mechanisms to Trait Improvements

M. Iqbal R. Khan, Palakolanu Sudhakar Reddy, Ravi Gupta, M. Iqbal R. Khan, Palakolanu Sudhakar Reddy, Ravi Gupta

• Editore: CRC Press
• Anno: 2022
• ISBN:
  9781000572896
• Edizione: 1
• Argomento: Ciencias biológicas
• Categoria: Botánica

Plants often encounter abiotic stresses including drought, salinity, flooding, high/low temperatures, and metal toxicity, among others. The majority of these stresses occur simultaneously and thus limit crop production. Therefore, the need of the hour is to improve the abiotic stresses tolerance of crop plants by integrating physiology, omics, and modern breeding approaches. This book covers various aspects including (1) abiotic stress responses in plants and progress made so far in the allied areas for trait improvements, (2) integrates knowledge gained from basic physiology to advanced omics tools to assist new breeding technologies, and (3) discusses key genes, proteins, and metabolites or pathways for developing new crop varieties with improved tolerance traits.

1Physiological, Molecular, and Biochemical Responses of Rice to Drought Stress

Ashish B. Rajurkar^1*, Dhananjay Gotarkar², and Seema Rana³

¹Plant Science Division, University of Missouri, Columbia, MO, USA

²IRRI South Asia Regional Centre (ISARC), Varanasi, UP, India

³Tamil Nadu Agricultural University, Coimbatore, TN, India

*Corresponding Author, [email protected]

DOI: 10.1201/9781003159636-1

CONTENTS

1. 1.1Introduction
2. 1.2Physiological Responses and Mechanisms under Drought Stress
3. 1.2.1Leaf Rolling and Leaf Area Index
4. 1.2.2Leaf Water Potential (LWP) and Relative Water Content (RWC)
5. 1.2.3Osmotic Adjustment
6. 1.2.4Stomatal Density, Aperture Size and Stomatal Conductance
7. 1.2.5Root Traits
8. 1.2.6Molecular Breeding for Physiological and Secondary Traits
9. 1.3Molecular Responses and Mechanisms under Drought Stress
10. 1.4Biochemical Responses and Mechanisms under Drought Stress
11. 1.4.1Proline
12. 1.4.2Polyamines
13. 1.4.3Allantoin
14. 1.5Conclusion and Future Perspectives
15. References

1.1 Introduction

Drought or water deficit is one of the major environmental constraints on rice productivity, particularly in rainfed ecosystems and largely in major rice -growing ecosystems, as groundwater, a valuable resource for irrigation during drought, is continuously declining (Ray et al., 2015). Erratic rainfall across the globe may exacerbate droughts, with increasing frequency of water stress during the cropping season. Increased drought will increase water stress. Exposure of plants to drought adversely affects them at every stage from germination to reproduction and finally limits yield (Pandey and Shukla, 2015; Khan et al., 2015). Rice is highly susceptible to water stress. Drought stress reduces accumulation of biomass, in general, and causes yield reduction. The magnitude of yield loss depends on timing, plant growth stage and duration, and the severity of drought stress. Drought stress affects rice plants throughout their lifecycle, but drought stress from the intermittent (during maximum tillering, flowering-reproductive growth) to the late (after panicle initiation) stage may greatly affect the yield. The drought-mediated yield losses in the reproductive stage in rice are given in Table 1.1.

TABLE 1.1Yield Losses in Rice as a Result of Reproductive-Stage Drought

Severity of Reproductive Drought Stress		Yield Reduction (%)		Reference
Lowland moderate stress		45–60		Vikram et al., 2011 Dixit et al., 2012, Rajurkar et al., 2019, 2021
Lowland severe stress		65–91		Vikram et al., 2011 Ghimire et al., 2012 Rajurkar et al., 2019, 2021
Upland mild stress		18–39		Vikram et al., 2011 Sandhu et al., 2014
Upland moderate stress		70–75		Vikram et al., 2011 Sandhu et al., 2014
Upland severe stress		80–97		Bernier et al., 2007 Lafitte et al., 2007 Dixit et al., 2012

Extreme climate change causing lower precipitation and drought has negative effects in many growing areas of the world (Lobell et al., 2011). Drought is frequent in many parts of South and Southeast Asia, affecting 46 Mha rainfed lowland and 10 Mha upland rice area in Asia (Pandey et al., 2007). In India alone, 14.4 and 6.0 Mha of the rainfed lowland and upland rice area, respectively, are affected by drought (Mahajan et al., 2017). Recent predictions suggest further increased frequency and intensity of drought and increase concern over water deficit problems in the coming decades (Wassmann et al., 2009). Given the increasing severity, it is necessary to develop cultivars with inbuilt mechanisms for drought stress tolerance and to deliver adapted varieties to improve productivity in drought-affected environments.

Plants adapt different strategies, such as drought escape, recovery and resistance, which can be further divided into drought avoidance and tolerance (Fukai and Cooper, 1995). Drought avoidance is usually associated with reduced water loss, extensive root system for water uptake and reduced leaf area to avoid evaporation. During drought tolerance, plants maintain their normal functioning even with low water potential within the tissues, and this is associated with accumulation of compatible solutes and protoplasmic resistance (Price et al., 2002). Improving drought resistance is a complex and difficult task to achieve, because sometimes it comes with limitations such as short lifecycle, leading to reduced grain yield, and lower carbon assimilation with ultimate reduction in grain yield is seen in varieties using drought escape and avoidance strategies. In the case of drought tolerance mechanisms, increased solute concentration for osmotic adjustment may have a negative impact on plant growth. Therefore, adaptation of crops to drought stress must maintain a balance between the drought resistance mechanisms introduced to guarantee sustainable productivity (Mitra, 2001; Yang et al., 2010). Plants sense their environments by adaptive morphological, anatomical, cellular, physiological and biochemical changes. And thus, multidisciplinary approaches are needed to ...