Fakiha Afzal

Chapter 9 – Preventing Potential Diseases of Crop Plants Under the Impact of a Changing Environment

Occurrence of a certain disease in a plant depends on a multitude of factors including a disease-causing virulent pathogen, a vulnerable host plant, and the environment. This forms a three key factor triangle for the development of diseases. Changing climate become a significant issue and may be intensely associated with increases in yield losses in the coming years. An increased level of ozone and carbon dioxide, altered precipitation patterns, flooding, drought, temperature extremes, global warming, and salinity are the outcomes of climatic changes. These all directly or indirectly affect the occurrence and severity of diseases in plants. Conditions more optimum to pathogenic spread, such as humidity and increased temperature, may lead to increases in the number of epidemics in plants in new geographical areas. Thus, there is a significant necessity for new agricultural strategies to prevent the potential hazards that may be the result of pathogens due to climatic change. This chapter reviews different research strategies in order to characterize the root cause of diseases in major crops worldwide.

Physiological, biochemical and agronomic traits associated with drought tolerance in a synthetic-derived wheat diversity panel

Abstract. Synthetic hexaploid wheat and their advanced derivatives (SYN-DERs) are promising sources for introducing novel genetic diversity to develop climate-resilient cultivars. In a series of field and laboratory experiments, we measured biochemical, physiological and agronomic traits in a diversity panel of SYN-DERs evaluated under well-watered (WW) and water-limited (WL) conditions. Analysis of variance revealed significant differences among genotypes, treatments and their interaction for all agronomic and physiological traits. Grain yield (GY) was reduced by 62.75% under WL, with a reduction of 38.10% in grains per spike (GS) and 19.42% in 1000-grain weight (TGW). In a Pearson’s coefficient correlation, GY was significantly correlated with GS, number of tillers per plant and TGW in both conditions. Path coefficient analysis showed that TGW and GS made the highest contribution to GY in WW and WL conditions, respectively. The traits examined in this experiment explained 59.6% and 63.01% of the variation in GY under WL and WW conditions, respectively; TGW, canopy temperature at spike and superoxide dismutase were major determinants of GY under WL conditions. The major flowering-time determinant gene Ppd-D1 was fixed in the diversity panel, with presence of the photoperiod-insensitive allele (Ppd-D1a) in 99% accessions. Wild-type alleles at Rht-B1 and Rht-D1, and presence of the rye translocation (1B.1R), favoured GY under WL conditions. Continuous variation for the important traits indicated the potential use of genome-wide association studies to identify favourable alleles for drought adaptation in the SYN-DERs. This study showed sufficient genetic variation in the SYN-DERs diversity panel to improve yields during droughts because of better adaptability than bread wheat.

Technological Platforms to Study Plant Lipidomics

The emergence and rapid growth of “omics” has led to a radical change in the viewpoint of life sciences research. Plant metabolomics is a progressing field of study in plant biology where lipidomics is one of the subunits of metabolomics, covering the entire lipidome of the plant body. Previously, mass spectrometry has been used to study plant lipidome and is presently coupled with various chromatographic techniques to produce more accurate results. Different environmental conditions and stresses contribute to the varying lipids profiling of plants. Numerous environmental stresses trigger lipid-facilitated signaling such as pathogen attack, temperature change, salinity, and drought. N-acylethanolamine, oxylipins, lysophospholipid, phosphatidic acid, inositol phosphate, fatty acid, sphingolipid, diacylglycerol, and N-acylethanolamine have all been suggested to have a signaling role. This chapter reviews various analytical techniques for studying plant lipids. Latest research carried out on lipids variations due to different environmental stresses have also been focused upon in the chapter.

Reactive Oxygen Species and Antioxidants in Response to Pathogens and Wounding

Their sessile nature and the lack of specialized immune cells make plants vulnerable to stress, damage and injury. Unlike animals, which can migrate for food and avoid harsh weather conditions, the immobility of plants makes them unable to evade stressful conditions. Plants have thus evolved certain mechanisms for their survival which help them in surviving biotic and abiotic stresses including drought, high salinity, frost, dehydration, microbes and injury. However, in case of an injury, wound-healing cascades activate that help secure the wound and keep the pathogens at bay, thus, speeding up the healing process. Cellular metabolism in plants results in the production of oxygen species that are extremely reactive. During stress or injury, their production accelerates and the accumulation of ROS (or sometimes called ROI) is highest around the wounds. Due to high toxicity of ROS, pathogens are killed that try to access the wounds. Apart from their beneficial role, ROS in excessive quantities are equally harmful to plants as well due to the damage these can cause to biomolecules such as lipids, proteins and DNA. To keep the levels of ROS balanced, plants produce several enzymatic and nonenzymatic antioxidants or ROS scavengers that balance ROS, as the complete eradication of ROS means the loss of an important second messenger in intracellular signaling cascades. This whole intertwined web of mechanisms is quite intricate. In the following chapter, we aim to discuss in detail the role of different types of ROS in evading stress and injury, the independent roles of each antioxidant in wound healing, the genes involved in their synthesis and the pathways of wound healing.

Next-Generation Sequencing Technologies and Plant Improvement

Hidden information lying underneath the genetic material is yet to be explored. Deciphering genetic information is the basic and primary step in bioscience research. For many years, capillary electrophoresis (CE)-based Sanger’s method prevailed in the scientific world for elucidation of genetic information. Due to lack in resolution, throughput, scalability, speed, and efficiency, it has now been replaced by spectacular next-generation sequencing (NGS) technologies since 5 years. Applications of NGS technologies in the field of plant biology is genome-wide scan for variants, rapid parallel sequencing, marker discovery, epigenetics, transcriptomics, de novo sequencing, resequencing, and high-resolution mapping in less time and money. This chapter briefly describes NGS technologies and utilization of these technologies in studying plant genome for its improvement and better development.

Bread Wheat (Triticum aestivum L.) Under Biotic and Abiotic Stresses: An Overview

Wheat, a major cereal crop, is subject to several biotic and abiotic stresses. These stresses affect the crop’s yield globally. Different mechanisms have been adopted by plants to counter the wide range of biotic and abiotic stresses faced. The scarcity of irrigation water leads to moisture stress in the wheat crop. The quantitative trait loci tool is used to map the moisture-tolerant inherited genes. Genes that are drought tolerant have been identified in other crops and scientists are planning to introduce them into the wheat genomes. Similarly, understanding the heat stress tolerance pathway is underway. Moreover, cryoprotectant genes that code for proteins which help the plants gain tolerance to severe cold can be transformed into commercial wheat varieties to tackle cold stress. Several genetic engineering techniques are being developed to minimize micronutrient and waterlogging stress. Biotic stresses include parasitic and nonparasitic diseases. In order to ward these off, plants use systemic acquired resistance and induced systemic resistance, but these are not sufficient when stress reaches its extreme. Seedborne diseases result in lightweight shriveled kernels resulting in an overall reduction in the crop yield. There is also a range of pathogenic fungi and viruses that cause various leaf and root diseases in wheat. Disease control strategies are underway to limit the damage to the wheat crop. Furthermore, soil moisture level, the depth of seed plantation, PH control for fungal growth reduction, and use of certain antibiotics in the soil can greatly reduce the risk of biotic stress-related wheat diseases. In addition to all of these aspects, pivotal to maximize wheat productivity is genetic improvement where harnessing and exploiting smartly via state-of-the-art technologies pointing towards genetic resource diversity is paramount as a means for providing high levels of allelic variation around all major stress constraints.

Modern Tools for Enhancing Crop Adaptation to Climatic Changes

Besides various uncertainties in the climate, there are certainties too. Whatever mitigation efforts are made, Earth’s temperature will keep on rising in the upcoming years. Furthermore, increases in atmospheric carbon dioxide and ozone are also unavoidable. Other climatic changes lead to various severe conditions such as drought, soil erosion, increased precipitation, salinity, flooding, and weather extremes. All these changes, especially global warming, pose a serious threat to crops and badly affect yields. Due to certain global trends, e.g., increasing population, urbanization, deforestation, and manipulation of ecosystems, such climatic changes are increasing. Due to the increasing world population, it would be a real challenge to provide food security for the future. Therefore, there is a need for better cultivars with more sustainable traits against biotic and abiotic stresses. This chapter will focus on climatic changes, and different tools used to increase crop adaptation to the changing climate, which may be helpful in future.