Molecular Pathogens 2024, Vol.15, No.3, 119-128 http://microbescipublisher.com/index.php/mp 123 6 Yield Reduction Mechanisms 6.1 Direct damage to plant tissues Sugarcane yellow leaf virus (SCYLV) directly impacts sugarcane by infecting and damaging plant tissues, leading to significant reductions in growth and yield. Infected plants often exhibit stunted growth, reduced biomass, and lower sugar yields. For instance, a study conducted in Hawaii found that SCYLV-infected plants had a 30% reduction in the number of stalks per stool, a 29% reduction in biomass, and a 26% reduction in sugar yield when harvested after 11 months (Lehrer et al., 2009). Additionally, symptomatic plants showed significant reductions in physiological parameters such as photosynthetic rate, stomatal conductance, and chlorophyll content, which are critical for plant growth and sugar production (Bagyalakshmi et al., 2019). 6.2 Secondary infections and stresses SCYLV infection can predispose sugarcane plants to secondary infections and additional stresses, exacerbating yield losses. The virus can interact synergistically with other pathogens, leading to more severe disease symptoms and greater yield reductions. For example, mixed infections of SCYLV with other viruses such as Sugarcane mosaic virus (SCMV) and Sugarcane streak mosaic virus (SCSMV) have been shown to cause significant varietal degeneration, with reductions in juice yield by up to 36% (Bagyalakshmi et al., 2019). Furthermore, the presence of SCYLV can lead to increased susceptibility to environmental stresses, such as drought, which further diminishes plant vigor and productivity (Asinari et al., 2020). 6.3 Long-term field impacts The long-term impacts of SCYLV on sugarcane fields can be profound, affecting both the current and subsequent crop cycles. Field studies have shown that SCYLV prevalence can increase over time, leading to cumulative yield losses. For instance, in Florida, SCYLV prevalence in virus-free plots increased progressively over three crop seasons, with yield reductions in ratoon crops varying from nonsignificant to 27% depending on the cultivar and soil type (Boukari et al., 2019). Additionally, the slow spread of SCYLV via aphid vectors can result in gradual but persistent infection of neighboring plants, further compounding yield losses over multiple growing seasons. The use of virus-free seed cane and SCYLV-tolerant cultivars has been recommended to mitigate these long-term impacts and sustain sugarcane production (Sood et al., 2021). 7 Case Study: Management Practices and Outcomes 7.1 Case study introduction Sugarcane yellow leaf virus (SCYLV) is a significant pathogen affecting sugarcane production globally. The virus is primarily transmitted by aphids and has a limited natural host range, mainly infecting sugarcane, grain sorghum, and Columbus grass (Holkar et al., 2020). The impact of SCYLV on sugarcane yield and quality has been documented in various regions, including Florida, Réunion Island, and India, where it has caused substantial yield losses and varietal degeneration (Rassaby et al., 2003; Lehrer et al., 2009; Viswanathan, 2021). 7.2 Management strategies implemented Several management strategies have been employed to mitigate the impact of SCYLV on sugarcane production: 1) Use of Virus-Free Seed Cane: Planting virus-free seed cane has been a critical strategy. In Florida, virus prevalence varied from 83% to 100% in plots planted with infected seed cane, but healthy plants of two sugarcane cultivars were only infected at low levels after three crop seasons (Figure 2). Field trials demonstrated that planting healthy seed cane significantly reduced SCYLV prevalence and limited its impact on yield (Boukari et al., 2019). Similarly, in Argentina, the use of healthy planting material was recommended to manage SCYLV (Asinari et al., 2020). Virus prevalence varied from 83% to 100% in plots planted with infected seed cane. 2) Breeding for Resistance: Developing and planting SCYLV-resistant cultivars is another effective approach. Genome-wide association studies by Yang et al. (2019) have identified resistance loci (Figure 3), providing valuable genetic resources for breeding resistant sugarcane cultivars. In India, screening parental clones and pre-release varieties for disease resistance has been a practical strategy (Viswanathan, 2021).
RkJQdWJsaXNoZXIy MjQ4ODYzNA==