Nutrient uptake and accumulation in sugarcane affected by Yellow Canopy Syndrome

Yellow Canopy Syndrome (YCS) is a condition affecting sugarcane, with symptoms expressed as strong yellow-orange colouring of the leaves, predominantly in the mid canopy. The cause remains unknown and yield losses in severe cases can be greater than 30%. We examined the nutrient pathway of healthy green and YCS symptomatic sugarcane to understand the impact of YCS on elemental uptake, accumulation and composition in affected plants, to determine if localised nutrient deficiency and/or elemental toxicity are causal agents of YCS. Sampling comprised 100 soil samples and 400 plant samples, including internode, sheath and leaf. Samples were collected from adjacent green and YCS-affected blocks, from the Burdekin and Herbert regions. Soils were collected from four cores, proximal to each sampled plant, at depths of 0?10, 10?20, 20?40, and sub-soils at 40?60, 60?80 cm. Soil samples were analysed for a range of plant available nutrients using sugarcane industry standard analytical methods. Plant samples were analysed for macro- and trace-nutrient elements. Our results showed major and trace-nutrient elements at adequate levels as measured in the diagnostic leaves, suggesting that YCS is not caused by typical nutrient deficiency. The nutrient uptake trends and accumulation were similar in green and YCS-affected cane for most of elements tested. The exception was Si, with elevated levels found in all symptomatic leaf samples when compared with green controls. In all tested leaf samples Si was significantly higher in plants under YCS-stress conditions, with some concentrations of Si at 45% higher than in asymptomatic green leaves. Interestingly, high levels of manganese were also found in symptomatic leaves from Herbert. The high Mn accumulation pattern was like that of Si accumulation, with high concentrations found across the canopy in the stressed plants. Our data suggest that Si accumulation is a possible response to stress associated with YCS. Further, the high rate of Si accumulation in symptomatic plants of Herbert is most likely a response to combination of YCS and other stresses associated with plants grown in strongly acidic soils.