Molecular Pathogens 2024, Vol.15, No.3, 119-128 http://microbescipublisher.com/index.php/mp 122 4.2 Laboratory diagnostic methods Several laboratory techniques are employed to diagnose SCYLV, including Tissue Blot Immunoassay (TBIA), Reverse Transcription-Polymerase Chain Reaction (RT-PCR), and Quantitative Real-Time RT-PCR (qRT-PCR). RT-PCR and qRT-PCR are particularly effective, revealing SCYLV presence even in cultivars previously thought to be immune based on TBIA results (Eiden et al., 2010; Zhu et al., 2010). These methods can detect varying virus titres, with qRT-PCR providing a semi-quantitative measure of virus load, which is crucial for understanding the correlation between virus titre and yield reduction (Zhu et al., 2010). Additionally, Double Antibody Sandwich-ELISA (DAS-ELISA) is used for virus quantification in both nursery and field trials, aiding in the identification of resistant genotypes (Burbano et al., 2021). 4.3 Field detection techniques Field detection of SCYLV involves both visual inspection and laboratory confirmation. Visual symptoms such as leaf yellowing can be an initial indicator, but laboratory methods like RT-PCR and TBIA are essential for accurate diagnosis. In field trials, virus-free plants are often produced through meristem tip culture and monitored for reinfection by viruliferous aphids to ensure the effectiveness of the virus-free status. Field trials in Florida demonstrated that planting virus-free seed cane significantly limits SCYLV prevalence and its impact on yield, highlighting the importance of starting with healthy planting material (Boukari et al., 2019). Additionally, combining symptom phenotyping with precise virus titration in field trials helps in screening for SCYLV resistance among different genotypes (Filloux et al., 2018; Burbano et al., 2021). By integrating visual inspection with advanced laboratory techniques and strategic field management, effective diagnosis and control of SCYLV can be achieved, thereby mitigating its impact on sugarcane yield. 5 Impact on Sugarcane Physiology 5.1 Effects on photosynthesis Sugarcane yellow leaf virus (SCYLV) significantly impacts the photosynthetic efficiency of sugarcane plants. Infected plants exhibit notable reductions in photosynthetic rate, stomatal conductance, transpiration rate, chlorophyll fluorescence ratio, and leaf chlorophyll content (Bagyalakshmi et al., 2019). These physiological impairments hinder the plant's ability to convert light energy into chemical energy, thereby reducing overall plant vigor and productivity. The reduction in photosynthetic activity is a critical factor contributing to the decline in sugarcane yield observed in SCYLV-infected plants. 5.2 Nutrient uptake and transport SCYLV infection also affects the nutrient uptake and transport mechanisms within sugarcane plants. The virus is phloem-limited, meaning it resides and spreads within the plant's phloem tissue, which is responsible for the transport of nutrients and sugars (Holkar et al., 2020). This localization disrupts the normal flow of nutrients, leading to deficiencies that can further exacerbate the physiological stress on the plant. The impaired nutrient transport can result in stunted growth and reduced biomass, as observed in various studies (Lehrer et al., 2009; Boukari et al., 2019). 5.3 Growth and development impairments The growth and development of sugarcane plants are severely impaired by SCYLV infection. Infected plants show reduced germination rates and early shoot growth, leading to a lower number of stalks per stool and decreased biomass (Lehrer et al., 2009). The virus causes a significant reduction in the number of stalks, biomass, and sugar yield, particularly when plants are harvested after shorter growth periods (Lehrer et al., 2009). Additionally, the presence of SCYLV can lead to varietal degeneration, where the overall vigor and productivity of the sugarcane cultivar decline over successive planting cycles (Amata et al., 2016; Bagyalakshmi et al., 2019). This degeneration is marked by poor growth, reduced juice yield, and overall diminished plant health.
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