Effect of sugarcane yellow leaf virus on sugarcane yield and juice quality

In 1996, sugarcane plants infected with sugarcane yellow leaf virus (SCYLV), reported to cause yellow leaf syndrome (YLS), were discovered in Louisiana. Field experiments were established to assess the potential impact of the disease on the Louisiana sugarcane industry. In the first experiment, yield and juice quality of SCYLV-infected and non-infected plants of cultivar LCP82-89 were compared. Sugar yields per unit area were reduced 11% and 14% in the first ratoon and second ratoon crops respectively. Stalk number and tonnage were reduced in SCYLV-infected plants. Cane quality components, % brix, % sucrose, % fibre and % purity, did not differ between infected and non-infected plants. However, % brix, % sucrose, and % purity were higher in juice from virus-infected green leaf tissue compared with healthy leaf tissue. In a second experiment, juice from leaves and stalks of infected and non-infected plants collected from plant cane, first ratoon, and second ratoon crops of cultivars LCP82-89 and LHo83-153 was analysed. Cane quality components did not differ in either cultivar. In juice from SCYLV-infected leaves, % sucrose was higher in LCP82-89 and % purity and starch concentrations were higher in both cultivars, while differences in total polysaccharides and oligosaccharides were not detected. Dextran content was inconsistent. The uppermost green leaves are normally removed from the stalk during mechanical harvesting; however, they may not be removed if the cane is lodged. Leaves delivered to the mill containing elevated levels of starch might reduce processing efficiency.