Introduction
Wheat is a vital staple food worldwide, but its production is hampered due to global warming, long-term unrainfall turning regions into drought, sometimes long-span cold, heat waves, etc. It is enriched in protein, vitamins, minerals, and proteins, and is economically significant. In Bangladesh, spring wheat was introduced in 1968. Historically, wheat was a common food in the country. The production peaked at 1.91 MMT in the 1998-99 season covering 0.88 million hectares of lands (Mha) and, then declined to 0.311 Mha of lands cultivated in 1.19 MMT in the 2023-24 season du e to low profitability, lack of mechanization, and huge competition with other crops. Farmers face challenges, such as high seed requirements (120-140 kg/ha) (Akhter et al. 2017) and limited seed availability in the market. In the 2022-23 season, 40-45 thousand MT of wheat seeds were needed, but government and private agencies supplied only about half of it. The remaining amount of seeds farmers preserved themselves. Moreover, importing wheat seeds is problematic as they often fail to adapt to local climatic conditions, hence only plants grow without grain-filled panicles. Further, wheat is eco-friendly, requiring fewer inputs like fertilizers, pesticides, and irrigation water (600-800 L kg-1) for production than Boro rice (3000-5000 L/kg) (Tuong, 2008; Reddy et al. 2014). Further, no major insects infest to wheat crop. The government promotes sustainable groundwater use by encouraging low-water crops like wheat, maize, barley, foxtail millet, etc. Increasing wheat production can reduce reliance on imports, enhance food security, and support environmental sustainability. Global warming significantly impacts wheat cultivation in Bangladesh.
The annual demand for wheat grains was approximately 7.5 MMT, but production was only 1.19 MMT in the 2023-24 fiscal year (FY), meeting only 17.6% of the total requirement (BBS, 2023; BWMRI, 2023; DAE, 2023; MoA, 2023). Further, wheat demand in Bangladesh grows by 5-10% annually (BBS, 2023; USDA, 2023). In the 2022-23 FY, nearly 6.1 MMT of wheat grains were imported to meet the annual demand exchange of over 2.21 billion USD (BBS, 2023; FAO, 2023). Cereals are crucial food grains whose annual requirement in Bangladesh was 51.4 MMT in the 2022-23 FY (Jul-Jun), including wheat grains at 7.0 MMT (contributing 13.6% of the total cereal requirement) (BER, 2024). Food grains production was 48.9 MMT in 2022-23 FY, and in 2023/24 FY, cereal production has been fixed target of 49.5 MMT, and 8.6 MMT for imports, of which wheat was 6.1 MMT (almost 70.9% of the total cereals imports), 0.25 MMT for rice, and 2.1 MMT for maize (FAO, 2023; BER, 2024). Therefore, the country lies behind in wheat production, although it is almost self-sufficient in rice production. It was surprising for us that the country had to spend more than 2.21 billion USD on wheat grain imports in the 2022-23 FY, which was 2.17% of the total imports of the country (annual import of 92.5 billion USD) (BER, 2024) (USDA, 2023; BBS, 2023; BWMRI, 2023; DAE, 2023; MoA, 2023; FAO, 2023). Bangladesh will be the sixth largest wheat importer country by 2033/34 FY (targeting 6.9 MMT), while China, Nigeria, and the Philippines will stand the position of fourth-, fifth-, and seventh-largest wheat importer countries, increasing to 9.7, 7.0 and 6.9 MMT, respectively (USDA, 2023; FAO, 2023).
The IPCC (Intergovernmental Panel on Climate Change) predicts global temperatures could rise 1.5°C above preindustrial levels between 2030 and 2052, reaching 2°C by 2100 due to anthropogenic activities (IPCC, 2018). Bangladesh's average annual temperature is 25-35°C (BMD, 2022). From 1970 to 2022, Bangladesh showed an increase in average monthly minimum and maximum temperatures and relative humidity, while rainfall decreased (BMD, 2024). Projections indicate further temperature increases: 1.0°C by 2030, 1.4°C by 2050, and 2.4°C by 2100, with winter temperatures rising similarly (Sarker et al. 2012). From 1949 to 2013, annual temperatures increased by 0.13°C/decade, with seasonal and extreme temperatures rising faster (Zaman et al., 2013). Annual mean rainfall increased by 4.20 mm/year (Alam et al., 2023). Future projections warn of more hot days, heat waves, dry spells, and drought risks (Khatun et al., 2016). Wheat thrives best at 15-25°C temperature, but heat stress disrupts its growth and development, causing stunted plants and reduced yields (Alam et al., 2013a, Sun et al. 2022). The optimum sowing dates of wheat in Bangladesh are between Nov 15-30 for better growth and development (Alam et al. 2013c, 2014). Late sowing, especially after Dec 10, leads to poor grain quality due to high temperatures (Alam et al., 2013b, Hossain et al. 2021).
Wheat is a cool-loving herb whose growth and development optimum range is 15 to 25°C (Hossain et al. 2023). Heat waves or high temperatures are detrimental to morpho-physiological, biochemical, metabolic, and molecular processes (Alam et al. 2018a; 2018b; 2021). When wheat plants face heat stress, reactive oxygen species (ROS), and reactive oxygen species (RNS) are produced much more in organs than in the normal environment, which impairs metabolic processes and breaks down the bases of DNA, RNA, amino acids, fatty acids, and other macro- and micro-biomolecules (Alam et al. 2018a; Sun et al. 2022). Furthermore, photosynthates and metabolites can’t move from source to sink; an increase in respiration and burning injury are found in plant organs, resulting in plant stunting. Plants also face leaf senescence early. As a result, unfilled, shriveled, shrinkage, and chappy grains are formed, ultimately reducing the grain yield havoc. BWMRI evidenced that wheat seeds sown between 15 to 30 Nov exhibit good growth and development; consequently, yields are achieved fair (Alam et al. 2014). Recently, because of the slow drainage of rainwater in southern regions, low land areas, and the lack of insincerity or unknown detrimental effects of late sowing, T. Aman rice harvested seeds throughout the entire Dec in the southern part of Bangladesh. After 10 Dec wheat seeding, the grain-filling period passes along with high temperature or heat wave (≥25°C), resulting in the generation of shriveled and chappy grains and impaired overall production (Hossain et al. 2021; 2023).
In the past two decades (2001-2020), wheat production has declined sharply compared with that in the previous decade (1991-2000) because of the increase in maize, potato, mustard, and Boro rice cultivation, i.e., crop competition, lack of mechanization in wheat production, processing, postharvest technology application, scarcity of seeds, insufficient support to cultivars, low price of wheat grains, high price of maize and potato, unwillingness of people feeding on wheat products, etc. To render wheat available to its consumers, protecting the environment from pollution from the overuse of pesticides, herbicides, fertilizers, and irrigation water for Boro rice, potato, tobacco, maize, T. Aus, etc., by refraining people from overeating rice, reducing nutrient deficiency in children and adults, minimizing diabetes risk, and checking foreign currency laundering abroad (2.21 USD/Year) might be increased wheat production by initiating fruitful programs. The budget allocations in research for developing technology (s) and biotic-abiotic stress-tolerant high-yielding variety (s) to mitigate the effects of global warming, an extension of newly released varieties, an increase in seed production, inputs support for wheat production to farmers freely, protection of soil health, training programs for the motivation of wheat cultivators, and their importance and nutrient values should be augmented. Therefore, our study investigated the reasons and factors underlying the decline of wheat production, challenges, and possible solutions to increase its production and delivered guidelines to the policymakers and national and international stakeholders.