Oxidative stress occurs when crop plants are exposed to extreme abiotic conditions that lead to the excessive production and accumulation of reactive oxygen species (ROS). Those extreme abiotic conditions or stresses include drought, high temperature, heavy metals, salinity, and ultraviolet radiation, and they cause yield and quality losses in crops. ROS are highly reactive species found in nature that can attack plant organelles, metabolites, and molecules by interrupting various metabolic pathways until cell death occurs. Plants have evolved defense mechanisms for the production of antioxidants to detoxify the ROS and to protect the plant against oxidative damage. Modern researches in crop plants revealed that low levels of ROS act as a signal which induces tolerance to environmental extremes by altering the expression of defensive genes. In this review, we summarized the processes involved in ROS production in response to several types of abiotic stress in cotton plants. Furthermore, we discussed the achievements in the understanding and improving oxidative stress tolerance in cotton in recent years. Researches related to plant oxidative stresses have shown excellent potential for the development of stress-tolerant crops.

The demand for cotton fibres is increasing due to growing global population while its production is facing challenges from an unpredictable rise in temperature owing to rapidly changing climatic conditions. High temperature stress is a major stumbling block relative to agricultural production around the world. Therefore, the development of thermo-stable cotton cultivars is gaining popularity. Understanding the effects of heat stress on various stages of plant growth and development and its tolerance mechanism is a prerequisite for initiating cotton breeding programs to sustain lint yield without compromising its quality under high temperature stress conditions. Thus, cotton breeders should consider all possible options, such as developing superior cultivars through traditional breeding, utilizing molecular markers and transgenic technologies, or using genome editing techniques to obtain desired features. Therefore, this review article discusses the likely effects of heat stress on cotton plants, tolerance mechanisms, and possible breeding strategies.

Excess salinity can affect the growth and development of all plants. Salinization jeopardizes agroecosystems, induces oxidative reactions in most cultivated plants and reduces biomass which affects crop yield. Some plants are affected more than others, depending upon their ability to endure the effects of salt stress. Cotton is moderately tolerant to salt stress among cultivated crops. The fundamental tenet of plant breeding is genetic heterogeneity in available germplasm for acquired characteristics. Variation for salinity tolerance enhancing parameters (morphological, physiological and biochemical) is a pre-requisite for the development of salt tolerant cotton germplasm followed by indirect selection or hybridization programs. There has been a limited success in the development of salt tolerant genotypes because this trait depends on several factors, and these factors as well as their interactions are not completely understood. However, advances in biochemical and molecular techniques have made it possible to explore the complexity of salt tolerance through transcriptomic profiling. The focus of this article is to discuss the issue of salt stress in crop plants, how it alters the physiology and morphology of the cotton crop, and breeding strategies for the development of salinity tolerance in cotton germplasm.

Transgenic technologies have emerged as a powerful tool for crop improvement in terms of yield, quality, and quantity in many countries of the world. However, concerns also exist about the possible risks involved in transgenic crop cultivation. In this review, literature is analyzed to gauge the real intensity of the issues caused by environmental stresses in Pakistan. In addition, the research work on genetically modified organisms (GMOs) development and their performance is analyzed to serve as a guide for the scientists to help them select useful genes for crop transformation in Pakistan. The funding of GMOs research in Pakistan shows that it does not follow the global trend. We also present socio-economic impact of GM crops and political dimensions in the seed sector and the policies of the government. We envisage that this review provides guidelines for public and private sectors as well as the policy makers in Pakistan and in other countries that face similar environmental threats posed by the changing climate.

Advances in genome editing technologies have tremendous potential to address the limitations of classical resistance breeding. CRISPR-Cas9 based gene editing has been applied successfully in plants to tolerate virus infections. In this study, we successfully tested CRISPR-Cas9 system to counteract cotton leaf curl disease (CLCuD) caused by whitefly transmitted cotton leaf curl viruses (CLCuVs). We also analyzed the ability of CLCuV to escape the Cas9 endonuclease activity. Targeting overlapping genes of most prevalent CLCuVs with three gRNAs resulted in virus interference, as validated by low virus titer. Furthermore, multiplex CRISPR-Cas9 construct simultaneously targeting six genes of CLCuV, was found more effective to interfere with virus proliferation compared to targeting single region individually. Additionally, transgenic N. benthamiana plants expressing multiple gRNAs simultaneously showed enhanced tolerance against CLCuV infection when compared to wild-type plants. T7 Endonuclease-I (T7EI) assay, showing indels in the CLCuV genome, confirmed the occurrence of double strand breaks (DSBs) in DNA at target sequence induced by Cas9 endonuclease. We observed that targeting CLCuV genome at multiple sites simultaneously resulted in better interference, also with inefficient recovery of altered virus molecules. Next, we tested multiplex construct in cotton to interfere CLCuV infection. We found significant decrease in virus accumulation in cotton leaves co-infiltrated with multiplex cassette and virus compared to cotton leaves infiltrated with virus only. The results demonstrate future use of CRISPR-Cas9 system for engineering virus resistance in crops. Moreover, our results also advocate that resistance to mixed virus infections can be engineered using multiplex genome editing.