Cotton Genomics and Genetics 2025, Vol.16, No.2, 72-79 http://cropscipublisher.com/index.php/cgg 73 2.1 Boron (B) Boron is a vital micronutrient for cotton growth, significantly impacting fiber quality. It aids in the transfer of sugars and nutrients from leaves to fruit, which is crucial for plant functions and fiber development. Studies have shown that foliar application of boron improves cotton fiber quality by enhancing boll retention, lint yield, and fiber strength (Wahid et al., 2020; Abbas et al., 2023). Boron application is particularly beneficial in soils with low boron content, where it can improve fiber yield and quality traits such as micronaire index, strength, and uniformity (Cordeiro et al., 2024). Additionally, combining boron with other elements like silicon can further enhance fiber quality by improving tensile strength and reducing short fiber content (Table 1) (De Souza Júnior et al., 2022). Table 1 Analysis of variance for the influence of individual and combined application of silicon and boron on morphological and yield and fiber quality traits of transgenic cotton (Adopted from Abbas et al., 2023) Mean sum of squares Source of variance Treatment Error DF 9 20 Plant height 208.18** 23.05 Monopodial branches 0.72** 0.15170 Sympodial branches 15.65** 1.83 Openbolls 99.60** 12.12 Closed bolls 1.1813** 0.0398 Total bolls 26.25 0.76 Seed cotton yield 2258.92** 267.19 Ginning out turn 1.17** 0.01 Fiber length 0.26** 0.005 Fiber uniformity 3.69** 0.14 Micronaire 0.10** 0.003 Fiber strength 1.09** 0.05 2.2 Zinc (Zn) Zinc is another essential micronutrient that directly affects cotton yield and fiber quality. It plays a role in enzyme activation, auxin synthesis, and maintaining biological membrane stability, all of which are critical for plant growth and fiber development (Swetha et al., 2020). Zinc deficiency can lead to poor crop production and fiber quality, making its adequate supply crucial for optimal cotton growth (Ahmed et al., 2020). Foliar application of zinc is often recommended in conditions where soil application is ineffective due to binding with soil particles. 2.3 Iron (Fe) and manganese (Mn) Iron and manganese are also important micronutrients for cotton production. They are involved in various physiological processes, including chlorophyll synthesis and enzyme activation, which are essential for plant health and fiber quality (Bellaloui et al., 2021). Deficiencies in these micronutrients can lead to reduced fiber quality and yield. Ensuring an adequate supply of iron and manganese through foliar applications can help mitigate these deficiencies and improve cotton fiber quality. 3 Mechanisms by Which Micronutrients Enhance Fiber Quality 3.1 Cellular and molecular effects on fiber elongation Micronutrients such as boron (B) and silicon (Si) play a crucial role in the cellular and molecular processes that enhance fiber elongation in cotton. Boron is essential for the development and growth of new cells in the growing meristem, which is critical for fiber elongation. It aids in the transfer of sugars and nutrients from leaves to fruit, directly impacting fiber development (Swetha et al., 2020). Additionally, the overexpression of certain genes, such as GhACO1, which is involved in ethylene biosynthesis, has been shown to improve fiber elongation by promoting cell wall loosening and cytoskeleton arrangement, thereby enhancing fiber quality (Wei et al., 2022).
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