Field Crop 2025, Vol.8, No.1, 20-31 http://cropscipublisher.com/index.php/fc 21 comes at the right time. For example, some teams have really created more drought-resistant and salt-tolerant varieties by editing specific genes, which is much faster than traditional breeding. We broke down these actual cases and studied them in detail, just to prove that this technology can really solve the urgent needs of rice planting. After all, the global pressure to eat is getting greater and greater. If we can cultivate rice varieties that are both high-yielding and hardy, it will really help a lot. 2 CRISPR Applications for Enhancing Rice Yield 2.1 Gene editing to increase grain number When it comes to increasing rice yields, CRISPR/Cas9 technology has really made a lot of progress recently. Take the case of rice ears, for example. Scientists have found that by modifying the GS3 gene, rice ears can be significantly larger-this is not a minor change, but a real increase in yield (Zeng et al., 2020). What's more interesting is that when researchers edited GS3 and several other key genes together, the effect was even more amazing. Not only did the rice ears become larger, but the number of rice ears also increased (Chennakesavulu et al., 2021). The most powerful thing about this technology is that it can accurately locate specific genes such as GS3 like a scalpel, and change whatever you want. In the past, breeders had to rely on luck to increase the number of rice ears. Now with CRISPR, they can directly target the target gene, and the efficiency is unknown. Scientists are getting better and better at CRISPR/Cas9, especially in the "killing multiple birds with one stone" multi-gene editing. Look at the genes they have been tinkering with recently-OsPIN5b, GS3 and OsMYB30. This combination of punches has an amazing effect: not only do rice ears become longer and bigger, but also their cold resistance is improved (Khush, 2013). The best thing about this trick is that it not only solves the yield problem (the number of rice ears is rising), but also makes rice harder and not afraid of bad weather (Zeng et al., 2020). To be honest, who would have thought that they could improve several traits so accurately at the same time? Now with CRISPR technology, breeders have found a new magic weapon. They can edit any gene they want for any characteristic, and the efficiency is very high. 2.2 Modifying plant structure for higher yield Scientists can now even precisely adjust the "body shape" of rice-after editing the OsPIN5b gene with CRISPR/Cas9, the rice panicles became significantly longer. This is not a simple cosmetic surgery, but a real secret to increasing yields. Think about it, the longer the panicle, the more rice grains can be produced, which directly increases the yield (Zeng et al., 2020). Interestingly, this precise control of plant structure allows us to design rice plant types like building blocks for the first time. In the past, breeders could only rely on natural mutations to take their chances, but now they can directly manipulate key genes, changing the panicle length if they want to, and adjusting the plant height if they want to, turning rice into a programmable "living machine". This groundbreaking method may allow rice yields to reach new highs in the future. In order to increase rice yield, scientists have even arranged for "height management". Using CRISPR/Cas9 to tinker with genes that control plant height and tillering, the effect is immediate-the height that should be high is high, the tillering that should be tillering, the yield immediately increases (Biswal et al., 2019). The most amazing thing about this technology is that the modified rice is not only pleasing to the eye, but also very economical in using fertilizers and sunlight. For example, some improved varieties have just the right plant height, which will not fall over and can fully photosynthesize; the number of tillers is also controlled just right, which is not too dense to affect growth, and can maximize the use of land (Romero and Gatica-Arias, 2019). To put it bluntly, now breeders are like playing high-end customization, and they can edit any plant type you want, which is much more reliable than the previous breeding method that relied on nature. 2.3 Challenges in the implementation process But then again, although CRISPR/Cas9 technology is powerful, it is not perfect. The most troublesome thing is the "off-target effect"-simply put, it is the wrong place that is accidentally modified during editing. Take the previous multi-gene editing experiment of OsPIN5b, GS3 and OsMYB30 as an example. Some plants did have unplanned genetic mutations (Table 1) (Zeng et al., 2020). This kind of accident is like injuring other organs
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