Plant Gene and Traits 2024, Vol.15, No.3, 108-117 http://genbreedpublisher.com/index.php/pgt 114 Moreover, the integration of genes such as the Arabidopsis FLOWERING LOCUS T into the genome-editing cassette has accelerated flowering and, consequently, the breeding cycle in cassava (Bull et al., 2018). These techniques offer a promising approach to rapidly introduce beneficial traits into cassava varieties. 5.3 Conventional breeding vs. molecular breeding: comparisons, advantages, and challenges Conventional breeding in cassava faces challenges such as long breeding cycles and limited genetic variability within cultivated varieties. In contrast, molecular breeding approaches, including transgenic breeding and molecular marker-assisted selection, leverage the knowledge of genes and enzymes involved in starch biosynthesis to improve cassava starch quality (Tappiban et al., 2019). For example, increasing the sink strength for carbohydrate by expressing a modified bacterial ADP-glucose pyrophosphorylase (AGPase) gene has led to increased starch production in cassava roots (Ihemere et al., 2006). However, molecular breeding techniques require a deep understanding of the genetic basis of starch biosynthesis, as well as the integration of omics data to elucidate the dynamic regulation of these pathways during root development (Saithong et al., 2013). Despite the potential for higher precision and faster breeding cycles, molecular breeding must also address regulatory, biosafety, and public acceptance issues associated with genetically modified organisms. 6 Challenges and Opportunities 6.1 Current limitations in understanding and manipulating starch synthesis pathways Despite significant progress in understanding the starch biosynthesis in cassava, there are still limitations in fully comprehending and manipulating these pathways. The complexity of starch biosynthesis is evident from the identification of 45 genes involved in the process, including isoforms of enzymes like ADPG pyrophosphorylase (AGPase), granule bound starch synthase (GBSS), and others (Tappiban et al., 2019). While the functions of these genes have been characterized to some extent, the intricate regulation of their expression during root development and the interaction between different enzymes in the pathway are not completely understood (Tappiban et al., 2019). Additionally, the genetic modification of cassava to enhance starch production has shown potential, but the translation of these findings to field conditions remains a challenge (Ihemere et al., 2006). The use of CRISPR-Cas9 mediated targeted mutagenesis has been successful in modifying genes involved in amylose biosynthesis, but the long-term effects and stability of these modifications need further investigation (Bull et al., 2018). 6.2 Research gaps: areas needing further research based on current findings There are several research gaps that need to be addressed to advance our understanding of starch synthesis in cassava. Firstly, the identification of quantitative trait loci (QTLs) and candidate genes associated with starch quality traits is a significant step forward, but the functional validation of these QTLs and their use in breeding programs requires more research (Tappiban et al., 2019). Secondly, the comparative analysis of the cassava genome between wild ancestors and cultivated varieties has revealed positive selection for genes involved in starch accumulation, but the underlying mechanisms of this selection and its impact on starch biosynthesis are not fully explored (Wang et al., 2014). Thirdly, the expression profiles of genes related to starch metabolism, such as those encoding uridine diphosphate glucose pyrophosphorylase (UGPase), have been analyzed, but the environmental and developmental factors influencing these profiles are still to be determined (Ha et al., 2019). 6.3 Future prospects in cassava breeding with genetic insights The future of cassava breeding looks promising with the integration of genetic insights into breeding programs. The use of genome editing techniques, such as CRISPR-Cas9, offers the possibility of creating cassava varieties with modified starch properties tailored for specific industrial applications or improved cooking qualities (Bull et al., 2018). The acceleration of flowering in cassava through genetic modification could also reduce breeding times, allowing for faster development of new varieties (Bull et al., 2018). Furthermore, the reconstruction of the starch biosynthesis pathway using genome information provides a framework for integrating omics data, which can lead to a better understanding of the dynamic regulation of this pathway and identify key targets for genetic improvement (Saithong et al., 2013). The exploitation of the starch biosynthesis pathway for data integration
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