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Reducing dependence on chemical pesticides is considered as an essential challenge for sustainable crop production. The use of microbial biocontrol agents (MBCAs) is a key component of sustainable pest management. Numerous antagonistic microorganisms are known to suppress plant diseases, but their practical application and commercialization are still limited in part due to poor reliability of their efficacy in the field. Although promising MBCAs achieve remarkable disease control in the laboratory or greenhouse, field control is often unsatisfactory. Thus, for MBCAs to be integrated into crop production, their field performance must be improved to provide the cost-effectiveness and efficacy required by growers. In this review, we highlight recent approaches to enhance the field performance of MBCAs.

Most transplant experiments across species geographic range boundaries indicate that adaptation to stressful environments outside the range is often constrained. However, the mechanisms of these constraints remain poorly understood. We used extended generation crosses from diverged high and low elevation populations. In experiments across low elevation range boundaries, there was selection on the parental lines for abiotic stress‐tolerance and resistance to herbivores. However, in support of a defense‐tolerance trade‐off, extended generation crosses showed nonindependent segregation of these traits in the laboratory across a drought‐stress gradient and in the field across the low elevation range boundary. Genotypic variation in a marker from a region of the genome containing a candidate gene (MYC2) was associated with change in the genetic trade‐off. Thus, using crosses and forward genetics, we found experimental genetic and molecular evidence for a pleiotropic trade‐off that could constrain the evolution of range expansion. Evolutionary constraints are important to understand range limits, yet the mechanisms are poorly understood. Here we used an integrative approach to show that a trade‐off between abiotic stress‐tolerance and chemical defense against herbivores may inhibit the evolution of low elevation range expansion in the ecological model Boechera stricta.

To face future challenges in crop production dictated by global climate changes, breeders and plant researchers collaborate to develop productive crops that are able to withstand a wide range of biotic and abiotic stresses. However, crop selection is often focused on shoot performance alone, as observation of root properties is more complex and asks for artificial and extensive phenotyping platforms. In addition, most root research focuses on development, while a direct link to the functionality of plasticity in root development for tolerance is often lacking. In this paper we review the currently known root system architecture (RSA) responses in Arabidopsis and a number of crop species to a range of abiotic stresses, including nutrient limitation, drought, salinity, flooding, and extreme temperatures. For each of these stresses, the key molecular and cellular mechanisms underlying the RSA response are highlighted. To explore the relevance for crop selection, we especially review and discuss studies linking root architectural responses to stress tolerance. This will provide a first step toward understanding the relevance of adaptive root development for a plant's response to its environment. We suggest that functional evidence on the role of root plasticity will support breeders in their efforts to include root properties in their current selection pipeline for abiotic stress tolerance, aimed to improve the robustness of crops.

Various environmental stresses singly or in combination generate excess amounts of reactive oxygen species (ROS), leading to oxidative stress and impaired redox homeostasis. Generation of ROS is the obvious outcome of abiotic stresses and is gaining importance not only for their ubiquitous generation and subsequent damaging effects in plants but also for their diversified roles in signaling cascade, affecting other biomolecules, hormones concerning growth, development, or regulation of stress tolerance. Therefore, a good balance between ROS generation and the antioxidant defense system protects photosynthetic machinery, maintains membrane integrity, and prevents damage to nucleic acids and proteins. Notably, the antioxidant defense system not only scavenges ROS but also regulates the ROS titer for signaling. A glut of studies have been executed over the last few decades to discover the pattern of ROS generation and ROS scavenging. Reports suggested a sharp threshold level of ROS for being beneficial or toxic, depending on the plant species, their growth stages, types of abiotic stresses, stress intensity, and duration. Approaches towards enhancing the antioxidant defense in plants is one of the vital areas of research for plant biologists. Therefore, in this review, we accumulated and discussed the physicochemical basis of ROS production, cellular compartment-specific ROS generation pathways, and their possible distressing effects. Moreover, the function of the antioxidant defense system for detoxification and homeostasis of ROS for maximizing defense is also discussed in light of the latest research endeavors and experimental evidence.

Plant requires seventeen essential mineral elements for proper growth and functioning classified as macro and micro-nutrients. Apart from these, cerium (Ce), cobalt (Co), iodine (I), aluminum (Al), selenium (Se), sodium (Na), lanthanum (La), silicon (Si), titanium (Ti), and vanadium (V) are evolving as pivotal bio-stimulants in plant growth and providing stress tolerance. Although, they are not mandatory for all plants directly but when they are supplemented, promote the plant growth positively and simulate multiple abiotic and biotic stresses tolerance. Though, these elements have crucial role in plant growth, still obscurethe uptake, transport and molecular understanding as much of macro and micronutrients. However, in recent years scientists are giving more emphasis to explore their mechanisms associated with enhancing antioxidant defense, stress responsive proteins accumulation, and transcription factors under variety of stresses. Likely, they are also crosstalk with other essential elements and plant growth regulators (PGRs) (salicylic acid, SA; jasmonic acid, JA), which is crucial for signaling network perception and regulate plant growth. Recent technologies developed in the field of nanotechnology assist in the further understanding of their uptake, transport and functions at cellular level andoptimizing their concentrations for better plant growth. Bio-fortification of crops with beneficial elements provides some cues regarding their importance in plant growth and also in human balance nutrition. To considering the importance of these compound, this review aimed to explore the uptake and transport mechanisms of beneficial elements and their function in plant development. Consequently, we pinpoint the crosstalk’s between PGRs and other mineral elements, which advance their crucial role during plant mineral nutrition and growth signaling. At the end, this review focused on the crucial role and mechanisms associated with these elements under multiple abiotic stresses that open exciting avanues in several directions related to crop stress breeding program.

Over-production of reactive oxygen species (ROS) in plants under stress conditions is a common phenomenon. Plants tend to counter this problem through their ability to synthesize ROS neutralizing substances including non-enzymatic and enzymatic antioxidants. In this context, ascorbic acid (AsA) is one of the universal non-enzymatic antioxidants having substantial potential of not only scavenging ROS, but also modulating a number of fundamental functions in plants both under stress and non-stress conditions. In the present review, the role of AsA, its biosynthesis, and cross-talk with different hormones have been discussed comprehensively. Furthermore, the possible involvement of AsA-hormone crosstalk in the regulation of several key physiological and biochemical processes like seed germination, photosynthesis, floral induction, fruit expansion, ROS regulation and senescence has also been described. A simplified and schematic AsA biosynthetic pathway has been drawn, which reflects key intermediates involved therein. This could pave the way for future research to elucidate the modulation of plant AsA biosynthesis and subsequent responses to environmental stresses. Apart from discussing the role of different ascorbate peroxidase isoforms, the comparative role of two key enzymes, ascorbate peroxidase (APX) and ascorbate oxidase (AO) involved in AsA metabolism in plant cell apoplast is also discussed particularly focusing on oxidative stress perception and amplification. Limited progress has been made so far in terms of developing transgenics which could over-produce AsA. The prospects of generation of transgenics overexpressing AsA related genes and exogenous application of AsA have been discussed at length in the review.

Evolutionary success in plants is largely dependent on the successful transition from vegetative to reproductive growth. In the lifetime of a plant, flowering is not only an essential part of the reproductive process but also a critical developmental stage that can be vulnerable to environmental stresses. Exposure to stress during this period can cause substantial yield losses in seed-producing plants. However, it is becoming increasingly evident that altering flowering time is an evolutionary strategy adopted by plants to maximize the chances of reproduction under diverse stress conditions, ranging from pathogen infection to heat, salinity, and drought. Here, recent studies that have revealed new insights into how biotic and abiotic stress signals can be integrated into floral pathways are reviewed. A better understanding of how complex environmental variables affect plant phenology is important for future genetic manipulation of crops to increase productivity under the changing climate.

Abiotic stresses, including drought, salinity, cold, heat, and heavy metals, extensively reducing global agricultural production. Traditional breeding approaches and transgenic technology have been widely used to mitigate the risks of these environmental stresses. The discovery of engineered nucleases as genetic scissors to carry out precise manipulation in crop stress-responsive genes and associated molecular network has paved the way for sustainable management of abiotic stress conditions. In this context, the clustered regularly interspaced short palindromic repeat-Cas (CRISPR/Cas)-based gene-editing tool has revolutionized due to its simplicity, accessibility, adaptability, flexibility, and wide applicability. This system has great potential to build up crop varieties with enhanced tolerance against abiotic stresses. In this review, we summarize the latest findings on understanding the mechanism of abiotic stress response in plants and the application of CRISPR/Cas-mediated gene-editing system towards enhanced tolerance to a multitude of stresses including drought, salinity, cold, heat, and heavy metals. We provide mechanistic insights on the CRISPR/Cas9-based genome editing technology. We also discuss applications of evolving genome editing techniques such as prime editing and base editing, mutant library production, transgene free and multiplexing to rapidly deliver modern crop cultivars adapted to abiotic stress conditions.

The plant-Trichoderma-pathogen triangle is a complicated web of numerous processes. Trichoderma spp. are avirulent opportunistic plant symbionts. In addition to being successful plant symbiotic organisms, Trichoderma spp. also behave as a low cost, effective and ecofriendly biocontrol agent. They can set themselves up in various patho-systems, have minimal impact on the soil equilibrium and do not impair useful organisms that contribute to the control of pathogens. This symbiotic association in plants leads to the acquisition of plant resistance to pathogens, improves developmental processes and yields and promotes absorption of nutrient and fertilizer use efficiency. Among other biocontrol mechanisms, antibiosis, competition and mycoparasitism are among the main features through which microorganisms, including Thrichoderma, react to the presence of other competitive pathogenic organisms, thereby preventing or obstructing their development. Stimulation of every process involves the biosynthesis of targeted metabolites like plant growth regulators, enzymes, siderophores, antibiotics, etc. This review summarizes the biological control activity exerted by Trichoderma spp. and sheds light on the recent progress in pinpointing the ecological significance of Trichoderma at the biochemical and molecular level in the rhizosphere as well as the benefits of symbiosis to the plant host in terms of physiological and biochemical mechanisms. From an applicative point of view, the evidence provided herein strongly supports the possibility to use Trichoderma as a safe, ecofriendly and effective biocontrol agent for different crop species.

Abiotic stressorslike drought, salinity, and extreme temperatures significantly hamper global agricultural productivity by adversely affecting plant growth and crop production. As sessile organisms, plants have developed a sophisticated network of signaling pathways to recognize and address environmental challenges. At the heart of these responses are phytohormones, which play animportant role in conferring abiotic stress tolerance. The signaling pathways governed by these phytohormones are crucial for activating the physiological and molecular responses that enable plants to survive under stress conditions. Hormonal crosstalk, an integral component of the phytohormonal network, involves synergistic and antagonistic interactions that finely balance the growth-defense trade-off, allowing plants to optimize their responses to environmental stimuli. Current developments in genetics and molecular biology have shed light on the mechanisms by which phytohormonal signaling pathways are modulated during abiotic stress. This understanding opens new avenues for developing crop cultivars that are more resilient to stressthrough genetic engineering and biotechnological approaches. By manipulating hormonal pathways, it is possible to fortify plants against abiotic stresses, thus ensuring food production in the face of climate change. The present review emphasizes recent advances in understanding how phytohormones (PHs), the central regulators of plant physiological and biochemical responses, mediate plant resilience to such stresses and a strategic method to improve resistance toabiotic stressin horticultural plants, thereby helping agricultural systems remain resilient and sustainable in the face of escalating climatic challenges.