Bioscience Evidence 2024, Vol.14, No.1, 32-38 http://bioscipublisher.com/index.php/be 34 2.2 Gene editing technologies Gene editing technologies, notably CRISPR/Cas9 and TALENs (Transcription Activator-Like Effector Nucleases), have opened new avenues for precise alterations in the cassava genome, aimed at improving traits such as yield, nutritional value, and resistance to diseases and pests. CRISPR/Cas9 has been particularly transformative due to its simplicity and efficiency. It has been successfully used to target and modify genes responsible for starch biosynthesis pathways, enhancing the quality and quantity of cassava starch. TALENs also offer a robust method for targeting specific genomic sequences, though they are generally more complex and less versatile than CRISPR/Cas9 (Lyons et al., 2021). 2.3 Applications of transcriptomics, proteomics, and metabolomics The integration of omics technologies—transcriptomics, proteomics, and metabolomics—into cassava research has provided comprehensive insights into the plant's functional biology. Transcriptomics analyses help in understanding gene expression patterns and regulatory mechanisms under different environmental conditions. Proteomics approaches are crucial for studying protein profiles that dictate phenotypic traits and stress responses. Metabolomics, which examines the chemical fingerprints that cellular processes leave behind, is particularly useful in optimizing cassava's nutritional content and taste, by identifying key metabolic pathways that can be targeted for enhancement or modification (Hu et al., 2023). 2.4 Genome selection and marker-assisted breeding Genome selection (GS) and marker-assisted breeding (MAB) are pivotal in modern cassava breeding programs. GS allows breeders to predict breeding values of offspring by analyzing genome-wide genetic markers, significantly accelerating the breeding cycle. This approach is highly effective in cassava due to its complex genetic architecture and long growth cycle. MAB, on the other hand, utilizes specific markers linked to desirable traits (like disease resistance or drought tolerance) to facilitate the selection of superior plants early in their developmental stage. This method has proven successful in developing new cassava varieties that are robust against biotic and abiotic stresses (Adu e al., 2021). These genomic tools and technologies are collectively enhancing the precision and efficiency of cassava breeding, promising not only to boost its yield and quality but also to ensure the crop's resilience against changing climate and evolving pests and diseases. 3 Examples of Application of Genomic Tools in Cassava Improvement 3.1 Improve yield and stress resistance The application of genomic tools in cassava improvement has been pivotal in addressing the challenges posed by its biological characteristics, such as a long growth cycle and a heterozygous genetic background. These challenges have historically slowed breeding goals, including yield increases and disease resistance (Juma et al., 2022). However, the integration of genomics with traditional breeding has shown promise in enhancing abiotic stress adaptation, such as drought and aluminum toxicity. For instance, the use of genotyping-by-sequencing (GBS) has facilitated the identification of single nucleotide polymorphisms (SNPs) associated with traits like resistance to cassava mosaic disease (CMD) and yield under CMD pressure. Additionally, the International Institute of Tropical Agriculture (IITA) has evaluated cassava genotypes for yield components and adaptation to different environments, which is crucial for genetic enhancement aimed at increasing production and productivity (Figure 1) (Veley et al., 2023). Veley et al. (2023) highlights the potential of genetic modifications to enhance disease resistance in crops, reducing reliance on chemical treatments and improving agricultural sustainability. The figure illustrates a study on plant disease resistance, focusing on the interaction between the TAL20 effector and the MeSWEET10a gene in cassava. Panel A shows cassava leaves, highlighting the characteristic lesions caused by disease (white arrows). Panel B describes the molecular mechanism: the top section depicts the TAL20 effector binding to the MeSWEET10a promoter, leading to gene activation and susceptibility, as evidenced by the diseased leaf. The bottom section shows a modified DNA sequence where mutations (indicated by orange circles) in the TAL20 binding site prevent the effector from binding. This results in resistance to the disease, as shown by the healthy leaf.
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