Molecular Pathogens, 2025, Vol.16, No.1, 10-18 http://microbescipublisher.com/index.php/mp 11 2.1 Fusarium wilt in cotton The disease of cotton is mainly caused by a fungus called Fusarium oxysporumf. sp. vasinfectum, referred to as FOV. This disease is found in many countries, especially in the western and southwestern United States, and has a great impact on cotton yield (Chen et al., 2024). Sick cotton usually turns yellow at first, then wilt, and eventually the whole plant dies. There is a mutation type called FOV4, which is more toxic. Researchers have discovered it in the San Joaquin Valley of California and in New Mexico. This situation has forced everyone to speed up and breed new cotton varieties that can resist diseases (Zhu et al., 2021). 2.2 Rhizoctonia solani (root rot) in cotton Cotton is also prone to a disease called root rot, which is caused by Rhizoctonia solani. This disease will cause the roots to rot, causing the seedlings to die, the entire plant to grow poorly, and the final yield reduction is very serious. Although some studies have not mentioned much, farmers who grow cotton are still worried about this problem because it will directly affect the survival rate of seedlings and the health of the entire land. 2.3 Colletotrichumspp. (anthracnose) in cotton Anthracnose is another common fungal disease caused by Colletotrichumspecies. It will attack the cotton bolls, leaves and stems, causing them to appear lesions and even drop leaves early. Humid weather is particularly prone to spreading this disease. Although previous studies have not talked much about anthrax, it still needs to be paid attention to because it may cause serious production cuts (Wu, 2024). 2.4 Symptoms, transmission mechanisms, and ecological impacts of diseases Cotton with blight will have some obvious symptoms, such as yellowing, withering, and even the entire plant will die. This disease is caused by fungi in the soil, which turns into thick wall spores hidden in the soil and is difficult to remove (Dhage and Garg, 2023). There is also a bacteria called Rhizoctonia solani, which can cause root rot and prevent cotton from growing tall or growing well. And the Colletotrichum gossypii will cause black spots to grow on the bolls and leaves, which is Anthracnose. In severe cases, the leaves will fall and the yield will decrease. These bacteria are generally transmitted through soil or infected plant residues. Therefore, it becomes very important to change crops and do a good job of soil management. These diseases also have an impact on the ecology. For example, there are fewer biological species in some places. Moreover, in order to control diseases, farmers often have to use more pesticides, which may cause new problems to the environment. 3 Genetic Basis for Enhancing Disease Resistance 3.1 Identification and functional study of resistance genes 3.1.1 Methods for identifying resistance genes In order to find out the disease-resistant genes in cotton, scientists have used many genomic methods. Like Genome-wide association analysis (GWAS) and using special populations (such as advanced generation hybrid population MAGIC) to find genes. These methods have helped us discover some important gene regions related to cotton blight (Zhang et al., 2019; Zhu et al., 2022). Some specific genes, such as GhnsLTPsA10, have been shown to be related to cotton's resistance to verticillium wilt. The researchers used transcriptome analysis and physiological experiments to see how this gene changes before and after infection. They found that once the bacteria are infected, the expression of this gene in the leaves will increase significantly, which means it may be related to disease prevention. Then, they also compared genetically modified cotton with ordinary cotton. The results show that the lesions on the leaves of cotton overexpressing GhnsLTPsA10 are smaller, indicating that this gene can indeed help cotton better resist bacteria (Figure 1) (Chen et al., 2021). 3.1.2 Functional validation and classification of resistance genes In order to confirm whether a gene has a disease-resistant effect, scientists often use two methods: one is to make the gene express more, and the other is to make it “silence” and not express it. For example, there is a laccase gene called GhLAC15. After being overexpressed, cotton will produce more lignin and the cell wall will become harder,
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