Molecular Pathogens 2024, Vol.15, No.3, 119-128 http://microbescipublisher.com/index.php/mp 120 instance, the Sugarcane yellow leaf virus (SCYLV) is a member of the Polerovirus genus within the Luteoviridae family, characterized by a monopartite, single-stranded positive-sense RNA genome approximately 6 kb in size. The virions are composed of 180 coat protein units and are 24 nm-29 nm in diameter (Holkar et al., 2020). 2.2 Transmission mechanisms Plant viruses can be transmitted through various mechanisms, including mechanical means, seed transmission, and vectors such as insects. SCYLV, for example, is primarily transmitted by the sugarcane aphid, Melanaphis sacchari, in a circulative and non-propagative manner (Lehrer et al., 2006; Holkar et al., 2020). Other aphid species, such as Ceratovacuna lanigera, Rhopalosiphum rufiabdominalis, and R. maidis, have also been reported to transmit SCYLV (Holkar et al., 2020). The virus is phloem-limited, meaning it is restricted to the plant's vascular system, which complicates its detection and management (Holkar et al., 2020; Shabbir et al., 2022). 2.3 Impact on crop yields The impact of plant viruses on crop yields can be severe, leading to significant reductions in both quantity and quality of the produce. SCYLV, for instance, has been shown to cause substantial yield losses in sugarcane. In Hawaii, SCYLV-infected plants exhibited a 26% reduction in sugar yield when harvested after 11 months, although yields did not decrease when plants were harvested after two years (Lehrer et al., 2009). In India, SCYLV has led to yield reductions of up to 50% in severe cases, with juice yield reductions of 40%-50% (Viswanathan et al., 2021). The virus can also cause varietal degeneration, reducing the vigor and productivity of subsequent vegetative generations or ratoons (Bagyalakshmi et al., 2019; Viswanathan et al., 2021). Field studies have demonstrated that SCYLV prevalence can vary significantly depending on soil type and crop season. For example, in Florida, SCYLV prevalence rates were found to be higher in organic soils compared to mineral soils, with yield reductions in ratoon crops varying from non-significant to 27% depending on the cultivar and soil typeC (Boukari et al., 2019). The slow spread of SCYLV via aphids, typically a few meters per year, suggests that planting virus-free seed cane can be an effective strategy to limit the impact of SCYLV on sugarcane production (Lehrer et al., 2006). 3Sugarcane Yellow Leaf Virus (SCYLV) 3.1 Discovery and history Sugarcane yellow leaf virus (SCYLV) is a significant pathogen affecting sugarcane crops worldwide (Madugula and Umadevi, 2018). It was first identified as the causal agent of sugarcane yellow leaf syndrome (YLS), a disease characterized by yellowing of the leaf midrib, followed by leaf necrosis and potential growth suppression (Madugula and Gali, 2017; Schenck and Lehrer, 2000). SCYLV was first detected in Réunion Island in 1997, where it was found to cause substantial yield losses in certain sugarcane cultivars (Rassaby et al., 2003). In India, the virus was recorded in the late 1990s and reached epidemic status by 2005, severely impacting cane productivity (Viswanathan, 2021). 3.2 Biological characteristics SCYLV is a member of the Polerovirus genus within the Luteoviridae family. The virus has a monopartite genome consisting of single-stranded positive-sense RNA approximately 6 kb in size, which includes six open reading frames (ORFs) expressed by sub-genomic RNAs (Holkar et al., 2020). The virion is composed of 180 coat protein units and measures 24-29 nm in diameter (Holkar et al., 2020). SCYLV is phloem-limited, meaning it primarily infects the phloem tissues of the plant, and it has a limited natural host range, mainly infecting sugarcane, grain sorghum, and Columbus grass (Schenck and Lehrer, 2000; Holkar et al., 2020). 3.3 Transmission and spread SCYLV is primarily transmitted by the sugarcane aphid, Melanaphis sacchari, in a circulative and non-propagative manner (Boukari et al., 2019; Holkar et al., 2020). Other aphid species, such as Ceratovacuna lanigera, Rhopalosiphum rufiabdominalis, and Rhopalosiphum maidis, have also been reported to transmit the
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