Rice Genomics and Genetics 2025, Vol.16, No.5, 282-293 http://cropscipublisher.com/index.php/rgg 283 2 Impact of Climate Change on Rice Cultivation 2.1 Impact of rising temperatures and high temperature stress on rice yield Rising temperatures are definitely not a good thing for rice. The growth period will be compressed, the filling period will be shortened, and the yield will naturally decline (Lv et al., 2018). The situation is particularly bad in some places, such as Africa. If no response is taken, by 2070, under a high emission scenario, rice yield may drop by 24% directly-mainly because extreme high temperatures greatly reduce the efficiency of rice photosynthesis (Van Oort and Zwart, 2017). In fact, China is no exception. Different regions are expected to see a 3.7% to 16.4% decline in yield, with the central, eastern and northwestern regions being the most affected (Zhan et al., 2023). A study conducted a meta-analysis and said that for every 1 °C increase in average temperature, rice yield will decrease by about 3.85% (Li et al., 2024a). Moreover, late rice is particularly unlucky. High temperature stress shortens the filling period even more, and yield is naturally hit harder. 2.2 Impact of water shortage and unstable rainfall patterns In addition to temperature issues, water has also become a big problem. Climate change has made water resources more scarce, and rainfall has become increasingly unreliable. In particular, rain-fed rice systems that rely on the weather are most affected. There is too much rain at one time, and not enough at another. Extreme conditions such as droughts and floods are becoming more and more common. Rice is either short of water or flooded, and the yield fluctuates greatly (Wang et al., 2024). In China, the distribution of rainfall is becoming more and more extreme, with droughts and heavy rains taking turns. Although a moderate increase in rainfall of 20% to 25% may help rice stabilize its yield, a drop that is too sharp or too sparse will not work, but will be counterproductive (Li et al., 2024a). Therefore, how to scientifically manage water resources and find ways to adapt to this change has become a hard task facing agriculture (Arunrat et al., 2020). 2.3 Threats from increased incidence of pests and diseases As the climate changes, pests and pathogens have also become more active. Although specific pests and diseases are not listed here, it is certain that rising temperatures, increased humidity, and increasingly unstable weather have created an excellent breeding environment for pests and pathogens (Saud et al., 2022). These biological threats are superimposed on abiotic stresses such as high temperature and drought, greatly increasing the risks of rice cultivation. To ensure yield, it is not enough to rely on only one measure. Comprehensive measures must be taken to flexibly respond to various changes brought about by the climate. 3 Climate-Adapted Rice Varieties 3.1 Development of drought-tolerant and flood-tolerant rice lines Climate change has made rice cultivation increasingly difficult, with droughts and floods becoming the norm. To deal with these problems, breeders have developed drought-tolerant and flood-tolerant rice varieties. In Bangladesh, some flood-tolerant (such as BRRI dhan51 and BRRI dhan52) and drought-tolerant (such as BRRI dhan56 and BRRI dhan71) varieties have shown better yield performance than traditional varieties under various conditions and are gradually being accepted and used by farmers (Figure 1) (Nayak et al., 2022). Of course, this is inseparable from the help of molecular breeding technology. By introducing some key quantitative trait loci (such as qDTY1.1, qDTY2.1, qDTY3.1 and Sub1), researchers have bred lines that can withstand both drought and flood, such as CR dhan 801 and Bahuguni dhan-1 (Sandhu et al., 2019). These new varieties not only have excellent yields under stressful conditions, but also have no yield reduction under normal conditions, making them particularly suitable for areas that are extremely vulnerable to extreme weather (Dar et al., 2021). 3.2 Breeding for salt and heat tolerance For rice cultivation in coastal and tropical areas, salinization and high temperatures have become problems that must be faced. Salt-tolerant rice varieties, such as Inpari 43 and Mendawak, have been shown to maintain good yields in high-salt and flooded environments, especially when used in conjunction with adaptive agronomic measures such as the application of biofertilizers (Simarmata et al., 2021). As for heat-tolerant breeding, the focus is on details such as early morning flowering, pollen fertility, and spikelet fertility (Senguttuvel et al., 2020). Some
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