Tree Genetics and Molecular Breeding 2024, Vol.14, No.2, 81-94 http://genbreedpublisher.com/index.php/tgmb 82 This study explores the potential of genome editing technologies, such as CRISPR/Cas9, in enhancing disease resistance in Eucalyptus trees. By identifying and functionally validating key genes associated with disease resistance, the research paves the way for developing Eucalyptus varieties that are more resilient to pathogen attacks. This study contributes to more sustainable Eucalyptus cultivation practices, ensuring the continued availability of this valuable resource in forestry and bioenergy production. 2 Overview of Eucalyptus Disease Resistance 2.1 Common pathogens and diseases affecting Eucalyptus Eucalyptus plantations are susceptible to a wide range of pathogens, including fungi, bacteria, viruses, and insect pests (Miranda et al., 2021). Among these, fungal pathogens are particularly destructive, causing diseases such as Mycosphaerella leaf disease, caused by Mycosphaerella spp., and Ceratocystis wilt, caused by Ceratocystis fimbriata (Santos et al., 2020b). Another significant threat is Austropuccinia psidii, responsible for myrtle rust, which affects a broad range of Myrtaceae, including Eucalyptus (Swanepoel et al., 2023). Insect pests such as Leptocybe invasa also pose serious challenges by inducing galls that damage the trees and reduce productivity (Mhoswa et al., 2020). These pathogens and pests not only reduce the growth and yield of Eucalyptus but also complicate efforts to cultivate these trees sustainably. 2.2 Genetic basis of disease resistance inEucalyptus The genetic basis of disease resistance in Eucalyptus is complex and involves multiple genes that confer either partial or full resistance to specific pathogens (Myburg et al., 2014; Santos et al., 2020a). Recent advances in genomics have led to the identification of several key resistance genes, such as nucleotide-binding site-leucine-rich repeat (NBS-LRR) genes, which play a crucial role in recognizing and responding to pathogen attacks (Bettaieb and Bouktila, 2020). For example, studies have identified specific loci associated with resistance to pathogens like Leptocybe invasa and Ceratocystis fimbriata, which are now being targeted in breeding programs to develop more resistant Eucalyptus varieties (Mhoswa et al., 2020). The discovery of these genetic determinants has opened new avenues for enhancing disease resistance through modern biotechnological approaches, such as genome editing. 2.3 Historical approaches to improving disease resistance Historically, improving disease resistance in Eucalyptus has relied on traditional breeding methods, such as selecting and cross-breeding resistant varieties. These methods have met with varying degrees of success, largely due to the complexity of resistance traits and the long generation times of Eucalyptus trees. Conventional breeding has been supplemented by chemical treatments and integrated pest management strategies to control outbreaks, but these approaches often provide only temporary relief and can have negative environmental impacts (Mushtaq et al., 2019). The advent of molecular genetics and biotechnology, including marker-assisted selection and genome editing, has transformed these efforts, allowing for more precise and efficient enhancement of disease resistance (Michelmore, 2003). These modern techniques offer the potential to overcome the limitations of traditional methods by directly targeting and modifying the genetic components responsible for resistance, paving the way for the development of more robust Eucalyptus species (Yin and Qiu, 2019). 3 Genome Editing Technologies inEucalyptus The advent of genome editing technologies has revolutionized plant biotechnology, offering unprecedented precision in manipulating specific genes to enhance desirable traits such as disease resistance. In Eucalyptus, these technologies hold significant potential for overcoming the challenges posed by pathogens and pests. 3.1 Tools and techniques for genome editing Genome editing technologies such as CRISPR/Cas9, transcription activator-like effector nucleases (TALENs), and zinc-finger nucleases (ZFNs) have become essential tools in plant biotechnology (Wani et al., 2023). Each of these technologies enables precise modifications to the plant genome, though they differ in their mechanisms and efficiency.
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