Quantifying Sugarcane Yellow Leaf Virus Tissue Tropism Patterns and Yield Impacts to Support Sustainable Sugarcane Production in Louisiana

Commodities

Practices

Sugarcane yellow leaf virus (SCYLV) poses a major threat to global sugarcane production, with yield losses ranging from 15-50%, even in asymptomatic infections, as seen in Florida and Louisiana. Its impact on key physiological traits such as reduced chlorophyll content and increased starch accumulation in vascular tissues, have negative implications regarding yield and crop productivity. This research supports sustainable agriculture by enhancing early virus detection and understanding host physiological responses to guide integrated disease management. We optimized a quantitative, SYBR-based RT-qPCR assay to determine absolute SCYLV titer and assess temporal tissue tropism in planta. Field collections of cultivar LCP-85-384 throughout 2024 revealed no significant variation in viral titer by canopy level or sampling month (p=0.0884). Chlorophyll analysis indicated no difference in infected vs. non-infected tissues in April, but significant reductions in total chlorophyll and chlorophyll b were observed in July (p=0.013 and 0.006), respectively. This study proposes repeated SCYLV titer analysis over the course of two growing seasons in the exceedingly popular cultivar L-01-299. Chlorophyll content will be assessed in conjunction with microscopy and image analysis to quantify starch buildup in bundle sheath cells, paired with RT-qPCR of sucrose phosphate phosphatase (SPP) gene expression. By linking SCYLV titer to physiological and molecular disruptions, this project aims to identify reliable early indicators of virus impact, helping growers make informed management decisions while also providing a safe, reliable, and standardized method of detection, ultimately promoting the long-term sustainability and resilience of sugarcane agroecosystems.

1. Develop qualitative and quantitative SYBR based RT-qPCR assays for optimal tissue sampling and SCYLV detection. Currently, SCYLV incidence in commercial fields is unknown due to a lack of efficient detection methods. SCYLV is a regulated pathogen in seed certification programs, in recent years there has been an increasing number of fields failing certification (Flasco and Gama, personal communication). In the clean seed program, SCYLV is detected using TBIA, which is laborious, time consuming, and requires many years of training. This objective will optimize a qualitative multiplex detection assay that enables largescale testing. The developed absolute quantification assay (RT-qPCR) will assess seasonal virus accumulation in planta and will determine the optimal and most sustainable sampling strategy.
2. Investigate pathophysiological and molecular impacts of SCYLV infection on yield in cultivar L-01-299. There have been numerous studies in other countries that examine the effects of SCYLV on yield loss, the highest reported reduction being 50%³. Cultivar L-01-299 is planted in over 50% of Louisiana and is well known for higher yields and more sustainable economic profitability for growers¹. Despite its prevalence to the state, the impact of SCYLV on yield within the cultivar remain unknown. This objective aims to quantitatively determine the reduction in total recovery rate and the sugar recovery rate per hectare in SCYLC infected sugarcane. This objective will also examine the physiological impacts such as chlorophyll concentrations and starch accumulation in vascular bundles while also examining molecular impacts to the sucrose biosynthesis pathway by determining the relative expression of sucrose 6 phosphate phosphatase (SPP). By examining the phytophysiological impacts of SCYLV, coupled with yield loss, this objective will provide valuable insight into SCYLV dynamics in planta.