Plants often face incompatible growing environments like drought, salinity, cold, frost, and elevated temperatures that affect plant growth and development leading to low yield and, in worse circumstances, plant death. The arsenal of versatile compounds for plant consumption and structure is called metabolites, which allows them to develop strategies to stop enemies, fight pathogens, replace their competitors and go beyond environmental restraints. These elements are formed under particular abiotic stresses like flooding, heat, drought, cold, etc., and biotic stress such as a pathogenic attack, thus associated with survival strategy of plants. Stress responses of plants are vigorous and include multifaceted crosstalk between different levels of regulation, including regulation of metabolism and expression of genes for morphological and physiological adaptation. To date, many of these compounds and their biosynthetic pathways have been found in the plant kingdom. Metabolites like amino acids, phenolics, hormones, polyamines, compatible solutes, antioxidants, pathogen related proteins (PR proteins), etc. are crucial for growth, stress tolerance, and plant defense. This review focuses on promising metabolites involved in stress tolerance under severe conditions and events signaling the mediation of stress-induced metabolic changes are presented.

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R ice (Oryza sativa L.) is one of the most important and widely cultivated cereal crops all over the world (Salim et al., 2003). The tropical and subtropical areas of the world are the major rice producer while 90% of the total rice production is occurring in Asian countries (Ezuka and Kaku, 2000). Heavy losses due to rice pests and diseases are the major constraints in world rice production. This important crop badly suffers from more than forty different microbial disease and disorders. Among them, bacterial leaf blight of rice (BLB) caused by Xanthomonas oryzae pv. oryzae (Swings et al., 1990) is a serious threat for irrigated, deep water, rainfed, temperate, tropical and subtropical rice growing areas of the world (Mew, 1987). This destructive disease has now become a serious pathosystem to rice crop especially in South East Abstract | Bacterial leaf blight is a devastating disease of paddy rice crop throughout the rice growing countries. Several commonly available plant decoctions were investigated as the bioactive eco-friendly compounds, and as the possible alternatives to hazardous chemicals for the control of BLB of rice. Aqueous extracts of fifteen different plant parts either individually or in combination were tested at various concentrations under in vitro conditions by poison food and disk diffusion techniques while best effective seven were trialed in glass house and field experiments to determine their efficacy against Xanthomonas oryzae pv. oryzae. In vitro and in vivo studies under different conditions showed significant response of Mentha piperita, Azadirachta indica and Aloe vera either tested individually or in combination of two or more than two decoctions against the bacterium in question. When used individually, M. piperita demonstrated best in vitro, field and glass house experiments followed by the A. indica which also proved its efficacy against the pathogen. The combination of M. piperita, A. indica and C. limon was superior in reducing the BLB of rice. Besides this, all treatments showed significant effect on the agronomic traits of rice plants. The reduction of disease in all the trials along with healthy crop stand in glass house and field indicated that these decoctions might play an important role in biological management strategies for the control of BLB of rice. The present research may provide an avenue for the formulation of new bactericides for future uses.

Xanthomonas citri subsp. citri, a causative agent of the citrus canker (CC) disease, belongs to one of the essential groups of the bacterial phytopathogen family, Xanthomonadaceae. It has been a potential threat to the globally significant citrus fruit crop, which has remained under investigation for disease management and epidemiology since the 1980s. In Pakistan, the average yield of citrus is 11 t/ha, which is lower than other countries, including China, Brazil, and India, having average productions of 27, 26, and 22 tons/hectare, respectively. Citrus canker is one of the most devastating diseases, posing a significant threat to crop yield and fruit quality. To date, five distinct types (or forms) of the citrus canker have been recognized; the Asiatic (Canker A) form is most destructive and affects most citrus cultivars. Severe infection outcomes include dieback, defoliation, severely blemished fruit, premature fruit drop, and reduced fruit quality. The infection increases under humid, warm, cloudy climate, wind, and heavy rainfall. The analysis of plasmid and chromosomal DNA of X. citri subsp. citri depicted an evolutionary relationship among pathovars of Xanthomonas. The extensive study on the genome of X. citri subsp. citri has contributed to the current knowledge of plant host recognition of pathogens, host specificities, dissemination, and propagation. Regulatory programs, i.e., quarantine or exclusion, continued to be practiced, prohibiting infected citrus plant material into the existing stock. Other measures include removal of inoculums sources, resistant hosts, protective copper-containing sprays, and windbreak systems. In this review, we explored the latest trends in the areas of epidemiology, pathogenome, detection, host–pathogen interaction, biofilm formation, and management of X. citri subsp. citri.

The researchers are still doing efforts to develop an effective, reliable, and easily accessible vaccine candidate to protect against COVID‐19. As of the August 2020, nearly 30 conventional vaccines have been emerged in clinical trials, and more than 200 vaccines are in various development stages. Nowadays, plants are also considered as a potential source for the production of monoclonal antibodies, vaccines, drugs, immunomodulatory proteins, as well as used as bioreactors or factories for their bulk production. The scientific evidences enlighten that plants are the rich source of oral vaccines, which can be given either by eating the edible parts of plants and/or by oral administration of highly refined proteins. The use of plant‐based edible vaccines is an emerging trend as it possesses minimum or no side effects compared with synthetic vaccines. This review article gives insights into different types of vaccines, the use of edible vaccines, advantages of edible vaccines over conventional vaccines, and mechanism of action of edible vaccines. This review article also focuses on the applications of edible vaccines in wide‐range of human diseases especially against COVID‐19 with emphasis on future perspectives of the use of edible vaccines.

Plant tissue culture technique employed for the identification and isolation of bioactive phytocompounds has numerous industrial applications. It provides potential benefits for different industries which include food, pharmaceutical and cosmetics. Various agronomic crops i.e., cereals, fruits, vegetables, ornamental plants and forest trees are currently being used for in vitro propagation. Plant tissue culture coupled with biotechnological approaches leads towards sustainable agricultural development providing solutions to major food security issues. Plants are the rich source of phytochemicals with medicinal properties rendering them useful for the industrial production of pharmaceuticals and nutraceuticals. Furthermore, there are numerous plant compounds with application in the cosmetics industry. In addition to having moisturizing, anti‐ageing, anti‐wrinkle effects; plant-derived compounds also possess pharmacological properties such as antiviral, antimicrobial, antifungal, anticancer, antioxidant, anti-inflammatory, and anti-allergy characteristics. The in vitro propagation of industrially significant flora is gaining attention because of its several advantages over conventional plant propagation methods. One of the major advantages of this technique is the quick availability of food throughout the year, irrespective of the growing season, thus opening new opportunities to the producers and farmers. The sterile or endangered flora can also be conserved by plant micro propagation methods. Hence, plant tissue culture is an extremely efficient and cost-effective technique for biosynthetic studies and bio-production, biotransformation, or bioconversion of plant-derived compounds. However, there are certain limitations of in-vitro plant regeneration system including difficulties with continuous operation, product removal, and aseptic conditions. For sustainable industrial applications of in-vitro regenerated plants on a large scale, these constraints need to be addressed in future studies.

Introduction: Medicinal plants are being used to treat several diseases for many decades and this is an ancient method to treat the patients. Herbal plant Silybum marianum found most effective one to cure liver disorders. This plant produces silymarin which is a secondary metabolite and have hepatoprotective properties. Silymarin is a mixture of flavonolignans (silybin A, silybin B, isosilybin A isosilybin B, silychristin, silydianin apigenin 7-D glucose and taxifolin) that has antiviral, antibacterial, antifungal and antiallergenic properties. Therefore, the excessive production of silymarin is necessary to cure different types liver disorders, so the present study executed to boost up production of Silymarin flavonolignans in vegetative parts of the Silybum marianum plant by using different elicitors. Materials and Methods: In the present study, elicitation technique in hydroponics system was used to enhance the production of pharmacologically active flavonolignans in Silybum marianum. Fungal elicitors prepared from lyophilized Aspergillus niger biomass, methyl jasmonate, silver nanoparticles and combination of silver nanoparticles and methyl jasmonate were added (0.2g/l), (100µM/l), (1 ppm) and (100µM/lppm) in hydroponics with Hoagland’s solution in hydroponics to enhance the production of flavonolignans of Silybum marianum. Controls were also set for each treatment. Plants were harvested after 72 hours of introduction of elicitors. High performance liquid chromatography technique was used for analytical purpose. Four solvents (methanol, acetonitrile, chloroform and 2% Trifloro acetic acid) were used in HPLC. Column was C18 and run time of sample was 1 hour. Silybum marianum’s seed extract was used as a standard. Extract of control and treated plants were run on the same polarity in HPLC. Results: Results showed that after elicitation significant increase was observed in production of silymarin’s flavonolignans (silybin A, silybin B, isosilybin A, isosilybin B and apigenin 7-D glucose) in vegetative part of the plant but rate of production was different for each elicitor, fungal elicitors prepared from lyophilized Aspergillus niger biomass proved best among all treatments.

Soil is a porous matrix containing organic matter and minerals as well as living organisms that vary physically, geographically, and temporally. Plants choose a particular microbiome from a pool of soil microorganisms which helps them grow and stay healthy. Many ecosystem functions in agrosystems are provided by soil microbes just like the ecosystem of soil, the completion of cyclic activity of vital nutrients like C, N, S, and P is carried out by soil microorganisms. Soil microorganisms affect carbon nanotubes (CNTs), nanoparticles (NPs), and a nanopesticide; these are called manufactured nano-objects (MNOs), that are added to the environment intentionally or reach the soil in the form of contaminants of nanomaterials. It is critical to assess the influence of MNOs on important plant-microbe symbiosis including mycorrhiza, which are critical for the health, function, and sustainability of both natural and agricultural ecosystems. Toxic compounds are released into rural and urban ecosystems as a result of anthropogenic contamination from industrial processes, agricultural practices, and consumer products. Once discharged, these pollutants travel through the atmosphere and water, settling in matrices like sediments and groundwater, potentially rendering broad areas uninhabitable. With the rapid growth of nanotechnology, the application of manufactured nano-objects in the form of nano-agrochemicals has expanded for their greater potential or their appearance in products of users, raising worries about possible eco-toxicological impacts. MNOs are added throughout the life cycle and are accumulated not only in the soils but also in other components of the environment causing mostly negative impacts on soil biota and processes. MNOs interfere with soil physicochemical qualities as well as microbial metabolic activity in rhizospheric soils. This review examines the harmful effect of MNOs on soil, as well as the pathways used by microbes to deal with MNOs and the fate and behavior of NPs inside the soils.