Emerging Technologies and Management of Crop Stress Tolerance

Volume 2 - A Sustainable Approach

Parvaiz Ahmad, Saiema Rasool

• Publisher: Academic Press
• Year: 2014
• Print ISBN: 9780128008751
• eBook ISBN: 9780128010877
• Topic: Technology & Engineering
• Subtopic: Agronomy
• Index: Technology & Engineering

Emerging Technologies and Management of Crop Stress Tolerance: Volume II - A Sustainable Approach helps readers take technological measures to alleviate plant stress and improve crop production in various environmental conditions.This resource provides a comprehensive review of how technology can be implemented to improve plant stress tolerance to increase productivity and meet the agricultural needs of the growing human population. The book considers issues of deforestation, disease prevention, climate change and drought, water and land management, and more. It will help any scientist better understand environmental stresses to improve resource management within a world of limited resources.- Includes the most recent advances methods and applications of biotechnology to crop science- Promotes the prevention of potential diseases to inhibit bacteria postharvest quality of fruits and vegetable crops by advancing application and research- Presents a thorough account of research results and critical reviews

Chapter 1

Improvement of Legume Crop Production Under Environmental Stresses Through Biotechnological Intervention

Adeena Shafique, Sammia Rehman, Azka Khan and Alvina Gul Kazi

Legumes belonging to the family Fabaceae hold immense importance in kingdom Plantae and are ranked third in the world for crop production. Legumes contribute to the protein diet of humans and are an essential part of forage and green manure crops. They are also important contributors of vegetable oil and animal feed protein. For a long time, legumes have been known as the “soil building crops” because the biological, physical, and chemical properties of soil are markedly improved when legumes are grown in it. One characteristic that sets them apart is their ability to carry out nitrogen fixation, which only a few other crops can do. Environmental stresses including viral, bacterial, and fungal diseases (biotic) and drought, rainfall, salinity, and chilling (abiotic) cause serious damage to the crop thereby hindering its productivity. Such hindrances make it imperative to use biotechnological approaches for the improvement of legumes. Presently, traditional biotechnology techniques have had a great influence on plant production by accelerating the breeding procedure and distributing disease-free seeds. Because legumes and the nodulation processes are highly susceptible to salinity stress and drought conditions, minimal study has been done on nitrogen fixation and nodulation in the settings mentioned. Legumes are known to be recalcitrant to in vitro regeneration, making plant genetic engineering quite difficult. Very few legumes are compliant to regeneration through the callus phase. However, recent advances in biotechnology hold promise for manipulating legumes genetically to result in improved productivity. To increase the yield of legumes in today’s world requires audacious breeding programs, marker-assisted technology enhancement, better nitrogen fixation, and forbearance to soil constraints. This chapter highlights the major biotic and abiotic stresses that impede crop growth and development and also summarizes some recent developments in genomics and molecular biology applicable to legumes for their improvement.

Keywords

legumes; biotic stress; abiotic stress; biotechnology; Medicago truncatula; Ascochyta blight; anthracnose; alfalfa; soybean; cowpea

1.1 Introduction

With more than 20,000 species, legumes are the third largest family of higher plants. Owing to their important biological features, legumes represent the most valuable food sources consumed globally, ensuring food security to almost every part of the world. Because of their importance for humans and animals, legumes complement cereal crops as a source of dietary protein and contribute substantially to total protein intake, mainly in vegetarian diets. Legumes have an intriguing array of features, the most conspicuous being their ability to fix atmospheric nitrogen to ammonia through their interaction with specific soil-borne bacteria, the rhizobia, consequently ameliorating soil fertility (Gonzalez-Rizzo et al., 2009). Such symbiotic interactions also help them to thrive in harsh and fragile environments.

As such, legumes are a pivotal component of the ecosystem and sustainable agriculture worldwide and are of immense importance for providing food to the ever-growing population. Legumes are also a significant source of fodder and are grown on a large scale in the semiarid tropics (SAT) including Africa, Asia, and Latin America. Legumes provide mineral micronutrients and macronutrients (Grusak, 2002; Wang et al., 2003; Le et al., 2007) as well as health-promoting secondary metabolites (Deavours and Dixon, 2005; Sato et al., 2007). Many of these metabolites are known to protect plants against ambush by pathogens and pests (He and Dixon, 2000).

To improve the productivity of legumes, biological and mechanistic key phenotypic features of the plants have been studied during the last decade. The productivity of legume crops, however, has not been significantly increased due to biotic as well as abiotic stress constraints for at least 50 years (FAO, 2012). Research in the past few years has focused on model legumes, which have subsequently resulted in the establishment of extensive genetic and genomic resources. Studies have also discovered critical genes in the symbiotic pathways and stress responses. For example, studying the germplasm of Medicago truncatula resulted in identification of the genes crucial to responses to stress (de Zélicourt et al., 2012).

1.2 Major stresses affecting legume crop production

Biotic and abiotic stresses equally affect legume crop production but getting rid of all stress is not practically feasible. The most common approach to eliminating biotic stressors includes mortality-based strategies. In almost all cases, this technique puts serious selection pressure on the subject (e.g., pests), leading to evolution that makes legumes more tolerant and adaptable to a given pressure. Stress can be defined as a physiological mechanism that can cause yield loss in crops. A number of stressors team up to cause stress in plants. On a larger scale, removing stress can be more helpful for increasing crop production compared to eradicating a stressor, or a couple of stressors, alone.

1.3 Biotic stresses for legumes

Biotic stress is defined as a stress that is caused in plants due to damage instigated by other living organisms, including fungi, bacteria, viruses, parasites, weeds, insects, and other native or cultivated plants (Newton et al., 2011). All around the world in dry lands, the major food crops cultivated and consumed are grain legumes. A key threat to development and growth of these crucial crops is the ever-changing climate.

The legume crops can be affected by climate in two ways (Kudapa et al., 2013): (1) increased crop susceptibility to novel diseases and (2) increased prevalence of diseases, parasites, and pests. There is a rising consensus that these issues may, in the future along with increasing abiotic stresses, add up to disease and pest pressure.

Most grain legumes have a very low resistance to diseases and a narrow genetic base. It is important to conduct research on these crops to determine ways to improve their development. Fortunately, recent biotechnological tools and other approaches that facilitate plants’ responses against deadly diseases have benefited grain legume research significantly. Improving grain legume production globally requires inspection of various genes to select them for genetic engineering so that plants can be made more disease resistant (Licourt et al., 2011). Many of the diseases found in legume crops can be managed by better resistance, and because there is a high variability in legume pathogens, combined methods of resistance are required.

1.3.1 Fungi

As fungi cannot make their own food, they develop certain strategies to obtain it from either living or dead organisms. Some consume wood and dead leaves, while others cultivate a mutual relationship with living plants. There is another group of fungi—the phytopathogenic fungi—that steal food from plants through attack and parasitism. The ascomycetes and basidiomycetes groups of fungi are the majority of plant pathogenic strains. Parasitic fungi attack almost all plant organs.

A parasitic fungus can enter the plant’s body by making a hole in the epidermis or through the stomata, and its spores in the air attack leaves. Some can grow within roots and block the water-conducting cells’ xylem, resulting in a wilted plant. Table 1.1 provides some examples of important phytopathogenic plants along with diseases and affected organs. The effect of aerial fungal diseases on crop yield varies according to cropping region and years, but some fungi cause diseases in all legume-producing countries and can lead to extensive damage both in quantity and quality.

Table 1.1

Fungal Infections in Plant Organs

Parasitic Fungi	Plant Organ	Disease
Amillaria sp.	Roots	Root rot
Phytophthora, rhizoctonia, and pythium	Roots and stem	Damping off diseases
Epichloe typhina	Stem	Choke disease
Phragmidium	Leaves	Rust
Taphrina confusa	Flowers	Flower and leaf distortion

1.3.2 Foliar diseases

In legume-producing countries, the major limiting factors are the foliar diseases caused by biotrophic fungi (e.g., downy mildews, powdery mildews, rust). Fungal diseases, such as rot in the root, stem, or crown and vascular wilt and blight, are normally found in legumes. Climate plays an important role in determining which type of rust species may prevail in a region. Erysiphe pisi, for example, causes powdery mildew and is prevalent in regions with dry, hot days and cool nights, whereas Peronospora viciae, the agent for downy mildew, prevails in regions with cool maritime climates. Rust species target grain and forage legumes, especially the genus Uromyces. Table 1.2 shows a number of rust species along with the host legumes.

Table 1.2

Genus Uromyces Infects a Number of Legume Crops

Fungus	Host Legume
U. ciceris—arietini	Chickpea
U. appendiculatus	Common beans
U. striatus	Alfalfa
U. pisi	Pea
U. vignae	Cow pea
U. viciae fabae	Faba bean, lentils

Ascochyta rabie, one of the top necrotrophic fungi, causes Ascochyta blight in a number of grain legumes (e.g., pea and chickpea). Another widespread foliar disease, botrytis gray mold, is caused by Botrytis cinerea. In a survey in Queensland, Australia, it was found that Medicago sp. were parasitized by fungi such as Colletotrichum trifolii, Oidium sp., Stemphylium vesicarium, Uromyces striatus, and Uromyces anthyllidis, and Pseudopeziza medicaginis, Colletotrichum destructivum, and Rhizoctonia solani caused disease in Ornithopus sp. and Oidium sp. in Trifolium subterraneum (Mackie et al., 1999). On annual medics, the most frequently observed and prevalent disease was rust (Mackie et al., 1999).

1.3.3 Plant viruses

Just the same as animal viruses, plant viruses are obligate intracellular parasites because they lack the machinery required to self-replicate without a host. They consist of a protein coat (capsid) that surrounds the genome (DNA/RNA). Most plant viruses are either ssRNA or dsRNA; very few are ssDNA and no dsDNA plant virus has been discovered yet. Due to the presence of a cell wall, it is difficult for a plant virus to move within plant cells. Virus transmission among plants can be horizontal through an external source (e.g., insects, nematodes, plasmodiophorids, seeds, pollens) or vertical from parent to young plant (i.e., via seed infection).

Common symptoms presented by plants when infected with a virus include changes in leaf color (mottling, mosaic, vein clearing, leaf spots), changes in leaf morphology (rolling, curling, distortion, puckering, enation), and others (stunting, r...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• Preface
• Acknowledgments
• About the Editors
• List of Contributors
• Chapter 1. Improvement of Legume Crop Production Under Environmental Stresses Through Biotechnological Intervention
• Chapter 2. Abiotic Stress Tolerance in Plants: Insights from Proteomics
• Chapter 3. Arbuscular Mycorrhiza in Crop Improvement under Environmental Stress
• Chapter 4. Role of Endophytic Microbes in Mitigation of Abiotic Stress in Plants
• Chapter 5. Plant Growth-Promoting Bacteria Elicited Induced Systemic Resistance and Tolerance in Plants
• Chapter 6. Arbuscular Mycorrhizal Fungi and Metal Phytoremediation: Ecophysiological Complementarity in Relation to Environmental Stress
• Chapter 7. Biological Control of Fungal Disease by Rhizobacteria under Saline Soil Conditions
• Chapter 8. Crop Plants under Saline-Adapted Fungal Pathogens: An Overview
• Chapter 9. Preventing Potential Diseases of Crop Plants Under the Impact of a Changing Environment
• Chapter 10. Plant Responses to Metal Stress: The Emerging Role of Plant Growth Hormones in Toxicity Alleviation
• Chapter 11. Reactive Nitrogen Species and the Role of NO in Abiotic Stress
• Chapter 12. Role of Tocopherol (Vitamin E) in Plants: Abiotic Stress Tolerance and Beyond
• Chapter 13. Land and Water Management Strategies for the Improvement of Crop Production
• Chapter 14. Integrating Physiological and Genetic Approaches for Improving Drought Tolerance in Crops
• Chapter 15. The Use of Chlorophyll Fluorescence Kinetics Analysis to Study the Performance of Photosynthetic Machinery in Plants
• Chapter 16. Manipulating Osmolytes for Breeding Salinity-Tolerant Plants
• Chapter 17. Osmolyte Dynamics: New Strategies for Crop Tolerance to Abiotic Stress Signals
• Chapter 18. The Emerging Role of Aquaporins in Plant Tolerance of Abiotic Stress
• Chapter 19. Prospects of Field Crops for Phytoremediation of Contaminants
• Chapter 20. Sustainable Soil Management in Olive Orchards: Effects on Telluric Microorganisms
• Chapter 21. The Vulnerability of Tunisian Agriculture to Climate Change
• Index