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Subject: search.filters.subject.Yellow Canopy Syndrome

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    Solving YCS : final report 2014/049
    (ASSCT, 2021) Scalia, G; Joyce, P; Powell, K
    Yellow canopy syndrome (YCS) is a sporadic condition presenting as golden-yellowing of the mid canopy in sugarcane during the peak growing period of December to March. The key driver of YCS is growth rate and symptoms usually exhibit after rainfall. YCS can be induced or mitigated by altering sink strength and sugarcane can recover from a YCS event. Abiotic or biotic stress has a serious effect on the photosystems and the physiological fitness of the crop. There is a strong correlation between YCS expression, leaf sucrose and sink strength, independent of crop age. YCS symptomatic leaves always have high leaf sucrose and ?-glucan content. Under experimental conditions the pyrethroid bifenthrin supresses insect stress, promotes increased sink growth and maintains low leaf sucrose and ?-glucan levels. Induced senescence causes YCS plants to have a lower number of attached leaves. Yield loss precedes YCS expression and there is no correlation between YCS severity and cane yield or CCS. Lamina starch staining is a useful tool to assist in YCS identification. There is no strong evidence of genetic predisposition for YCS susceptibility. Industry-wide incidence and severity of YCS is too difficult to accurately assess due to its episodic nature, no single causal agent and the link to climate change and severe weather events. The data does not support the cause of YCS being a pathogen, specific insect or mite, soil borne agent, poor root health, nutrient deficiency, or heavy metal toxicity. YCS is a physiological disorder visualised as the terminal expression of metabolic perturbances caused by growth disruption.
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    Effect of neonicotinoid, pyrethroid and spirotetramat insecticides and a miticide on incidence and severity of Yellow Canopy Syndrome : ASSCT peer-reviewed paper
    (ASSCT, 2019) Olsen, DJ; Ward, AL
    Yellow Canopy Syndrome (YCS) is a condition affecting Australian sugarcane that can lead to yield losses in excess of 30% in severely affected crops. The causal agent of this condition is unknown. Insect pests are well known causal agents of a wide variety of yield-limiting crop conditions, either as vectors of pathogens, directly through their feeding damage, or as transmitters of toxins, but little has been done to evaluate insects as a possible causal agent of YCS. This paper presents the findings of a one-year field trial in which insecticides from different chemical groups and an acaricide were tested to evaluate their effect on YCS incidence and severity. Results showed a delay in the onset of symptoms and a significant reduction in the severity of symptom expression following the application of neonicotinoid and pyrethroid treatments. These treatments also resulted in a significant yield improvement relative to cane in the untreated control. The acaricide treatment was ineffective. These findings suggest further work is warranted to determine which insects are being controlled and to identify the mechanism for the positive yield response.
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    Starch accumulation in sugarcane in response to stress
    (ASSCT, 2016) Joyce, P; Don, NH; Sousa, M; Olsen, D
    Yellow Canopy Syndrome (YCS) is a new problem affecting the Australian sugar industry. It was first reported in 2012 and has increased in occurrence and spread from the initial reports in North Queensland to further south in Mackay last year. While the causal agent is still unknown, several physiological studies have been performed. This paper examines the accumulation of starch in sugarcane leaves. This was an initial observation in YCS affected leaf sections of tillers of KQ228A. Subsequently, a method for routine high throughput qualitative analysis of starch has been developed, enabling rapid assessment of this response. Follow up work has compared this phenomenon in affected stalks, both between leaves of different ages within a stalk, as well as within regions of the same leaf. The accumulation of starch in sugarcane plants in response to biotic stress and in naturally senescing leaves has been undertaken to understand this phenomenon better and will be described in this paper. Our results showed that unlike YCS affected leaves, starch did not accumulate in the leaves of diseased plants nor in senescing leaves collected from the field.
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    Is magnesium deficiency a causal agent of sugarcane Yellow Canopy Syndrome? : ASSCT peer-reviewed paper
    (ASSCT, 2019) Tippett, O; Olsen, DJ; Ostatek-Boczynski, Z
    Yellow Canopy Syndrome (YCS) is a disorder affecting sugarcane in the Australian industry, the cause of which is unknown. This paper reviews YCS research focusing on magnesium imbalance as a possible cause of the condition. Four studies were undertaken to evaluate the role of Mg in YCS incidence and severity. In Trial 1 sugarcane leaves were collected at multiple locations in the Burdekin and Herbert with samples taken from sugarcane blocks with both YCS symptomatic and asymptomatic plants. Despite adequate soil-Mg, leaf-Mg concentrations were significantly lower (p?0.05) in leaves 2, 3, 4, 5 and 6 of YCS symptomatic plants in both regions suggesting an imbalance of this critical nutrient. Trial 2 measured Mg concentrations in sugarcane leaves before, during, and after YCS symptom expression. Symptomatic cane showed decreased leaf-Mg concentrations, but this returned to normal levels once the cane recovered. Trial 3 treated YCS symptomatic cane with foliar and soil applications of Mg in an attempt to mitigate the condition. Neither treatment resulted in alleviation of the YCS symptoms. Trial 4 treated sugarcane with foliar-Mg and soil-Mg prior to onset of symptoms. Despite elevating the Mg concentration in leaves, these pre-symptomatic treatments did not prevent YCS expression and plants exhibited YCS symptoms similar to that of the untreated control. We conclude that YCS affected cane is associated with reduced leaf Mg concentrations, but it is unlikely that this is the cause of YCS per se, as concentrations were well above critical thresholds for plant health. YCS occurs independently of Mg and low Mg is an indirect effect rather than a cause. Given that disruption to plant nutrient balance has been described as a symptom of some plant diseases, we speculate that these findings suggest a biotic causal agent.
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    Sugarcane root systems for increased productivity; development and application of a root health assay : final report 2015/002
    (Sugar Research Australia Limited, 2018) Rae, A; Pierre, J
    A better understanding of the sugarcane root system has the potential to improve productivity and overcome soil constraints. By adapting the digital methods that have been developed in other crops, we have developed a toolkit of reliable methods that enable analysis of large numbers of root samples. These methods have been used to provide a baseline understanding of the range and variation of root parameters for sugarcane, including root/shoot ratios, root opening angle, root length, proportion of fine roots, branching density, average diameter and diameter in each size class. We found a consistently high proportion of fine roots, but there was genetic variation for many other key traits amongst current commercial lines. Importantly, there were no significant reductions in root system size or quality in modern varieties compared to older varieties. The methods and baseline were then applied to test the response to stresses encountered in Australian growing environments. When comparing plants with or without YCS symptoms, we found no differences in root system structure, despite significant reductions in shoot mass. Limiting growth by removal of tillers or by restricting nitrogen availability identified plasticity in specific root traits that enabled the plants to adapt to the restrictions. Root system distribution by depth, and relative allocation of resources to the root system showed adaptations to stress while root angle appeared to be stable. With the new methods and knowledge of trait plasticity, we can now start to test which traits provide a benefit in various agronomic situations and develop an integrated understanding of root health which can be used to monitor soil health and promote the adoption of better agronomic practices.