Md. Abdur Rahim
Climate change refers to the extended changes in temperatures and weather patterns caused by either natural factors (alteration in the sun's activity and volcanic eruptions) or human activities (combustion of fossil fuels). The emission of greenhouse gases from using fossil fuels forms a layer around the Earth, which traps the heat generated by the sun, leading to an increase in global temperatures. The temperature of the Earth's surface has increased by approximately 1.2°C compared to the late 1800s and is currently higher than it has been in the last 100,000 years. Due to climate change, crops are affected by abiotic (salinity, droughts, floods, heat, and cold) and biotic (pathogens and insects) stresses and declining biodiversity. Food, feed, fuel, shelter, and clothes are derived from crops. A recent study projected that the world’s population will reach 9.6 billion by 2050, and the crop demand will increase by 100–110%.
As a result of climate change, the temperature of the Earth’s surface is at an upward trend, which affects the growth, development, and reproduction of plants. Heat stress drastically lowers crop production by disrupting the photosynthesis and reproduction processes, particularly flowering and grain filling. Important cereals like rice, wheat, and corn are vulnerable to heat stress at flowering and grain-filling stages, resulting in spikelet sterility. Drought is another threat to crop production caused by climate change. The major drought-prone areas of Bangladesh are Rajshahi (Barind Tract), Rangpur, Dinajpur, Bogra, Naogaon, and Joypurhat districts. These areas cover roughly around 15% of the agricultural lands of the country and are vulnerable to frequent droughts due to high temperatures, limited irrigation, and low rainfall. Drought stress affects almost all stages of plant growth and development, but the flowering stage is the most susceptible and potentially reducing agricultural production by up to 40% in these affected areas. Soil salinity is another threat to crop production in the coastal and offshore lands, which are frequently inundated with saline seawater at high tides. The major salinity-prone areas of Bangladesh are Khulna, Bagerhat, Jhalakati, Pirojpur, Barisal, Patuakhali, Noakhali, Chittagong, Barguna, and Bhola. The coastal area covers 20% to 30% of the agricultural land of Bangladesh. Salinity stress limits water uptake from soil by the plants and affects different developmental processes, including seed germination, vegetative growth, to reproductive development, which ultimately declines crop production. The distribution and intensity of insect and plant pathogen outbreaks are also predicted to be impacted by climate change and potentially reduce crop production in Bangladesh. The risk of flooding and cyclones is heightened by climate change through the elevation of sea levels and the rise of sea surface temperatures. Sea levels have increased by over six inches since 1900 and are projected to increase by 1 to 2.5 feet in this century.
To address these, we need to breed crop varieties/cultivars with enhanced tolerance/resistance against abiotic and biotic stresses. This could be achieved either through conventional plant breeding or by employing molecular techniques. Conventional plant breeding is quite a promising approach for developing crop varieties. However, the main limitations of this method are lengthy breeding cycles (10-15 years depending on crop species) and the unavailability of tolerance/resistance sources, which reside in wild form/relatives of crops. The transfer of new genes from wild form/relatives to the high-yielding varieties through hybridization has mostly been ineffective for complex traits like abiotic and biotic stress tolerance. Therefore, conventional alone cannot be a proper solution. During stress conditions, plant triggers mechanisms of acclimation and adaptation. The acclimation is a non-heritable and temporary stress tolerance mechanism, while adaptation is a heritable alteration through genetic modifications. Genetic mechanisms for stress tolerance are based on the regulation of stress-responsive genes. The rapid advancement of high-throughput genome sequencing and phenotyping technologies is making it easier to identify and select complex traits like stress tolerance. In this case, molecular genetic tools, including transgenic technology, genomic selection, marker-assisted selection (MAS), and marker-assisted backcrossing (MABC) can be employed to solve the problems that arise due to climate change. The development and release of new crop varieties using transgenic technology should pass through strict biosafety regulatory processes that also delay processes considerably. Besides, several countries are reluctant to permit genetically modified organism (GMO) crops to be released as a variety of food/feed and grow in their countries. Recently, modern genome editing technology, especially ‘clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein (Cas)’ has drawn the attention of agricultural scientists due to its comfort, accuracy, and supremacy as it enables to develop enhanced crop varieties with the totaling of desirable/elimination of undesirable traits without introducing transgenes from unrelated/wild sources. The genome editing can develop new plants that are similar or identical to plants developed by conventional breeding methods. Therefore, genome-edited plants are treated as non-GMO. The main advantages of this technology are that it is transgene-free and accelerates the variety development process (1-3 years). Many crop varieties with enhanced quality that have been developed through genome editing have been released. Japan was the pioneer in commercializing genome-edited crops, as they released a tomato variety called ‘GABA tomato’ producing high ɣ-aminobutyric acid (GABA) with greater blood pressure-lowering properties in September 2021. Besides, some other genome-edited crops are bacterial blight resistance in the rice variety, powdery mildew resistance in the wheat variety, and high oleic acid content in soybean.
We urgently need to adapt this novel modern genome-editing technology to develop environment-friendly, climate-resilient crop varieties in Bangladesh to cope with abiotic and biotic stresses due to climate change.
Finally, it can be said that we should utilize powerful molecular genetic tools like genome editing, genomic selection, marker-assisted selection, and marker-assisted backcrossing together with conventional breeding to mitigate the adverse impact of climate change on our crops. Therefore, the government should patronize such high-tech research on the crop sector and ensure proper funding.
Author: Professor, Department of Genetics and Plant Breeding, Sher-e-Bangla Agricultural University, Dhaka, Bangladesh.
