A novel polyphasic framework to resolve Yellow Canopy Syndrome paradox — ASN Events
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  3. A novel polyphasic framework to resolve Yellow Canopy Syndrome paradox

A novel polyphasic framework to resolve Yellow Canopy Syndrome paradox (#224)

Kelly Hamonts 1 , Pankaj Trivedi 1 , Paul Holford 2 , Jasmine Grinyer 1 , Ian Anderson 1 , Brajesh Singh 1
  1. Hawkesbury Institute for the Environment, University of Western Sydney, Penrith, NSW, Australia
  2. School of Science and Health, University of Western Sydney, Penrith, NSW, Australia

Yellow Canopy Syndrome (YCS) is a largely undiagnosed condition impacting sugarcane crops across Queensland, Australia, causing significant yield losses. YCS is associated with a typical yellowing of cane leaves. Symptomatic leaves senescence and die while the crop can continue to grow. In severe cases, cane stalks become thin and rubbery and root health is compromised. Key YCS symptoms differ from leaf yellowing due to drought stress, phytotoxicity, insect attack, known diseases, nutrient deficiency or natural maturing. Although some of the above factors have been largely eliminated from further consideration, the causal agent of YCS remains unknown. The aim of this study is to determine the involvement of biotic interactions and soil nutritional health in YCS development.
A comprehensive microbiome-based approach combining Illumina MiSeq and HiSeq and conventional culturing techniques was applied to determine the complexity of organisms present in YCS-affected sugarcane tissues, as well as in rhizosphere soil. Soil physico-chemical analyses, substrate-induced microbial respiration and microbial extracellular enzyme activity measurements were conducted. Salicylic acid content of leaves was determined using HPLC and microscopy-based studies were performed. In addition, qRT-PCR was applied to study the expression of pathogenesis- and stress-related genes in symptomatic vs. healthy sugarcane leaves.
Interesting differences were found in bacterial and fungal assemblages of leaves, stalks and roots of asymptomatic vs. symptomatic plants, as well as in the soil nutrient status (C, N) and soil microbial enzyme activity between affected and healthy cane fields. Pathogenesis- and stress-related genes were found upregulated in YCS-symptomatic leaves and symptomatic leaves contained more salicylic acid, demonstrating the potential use of this compound as biomarker for YCS detection. Microscopic images revealed no blockage or crushing of vessels in YCS-symptomatic leaves and roots. Results of this study may reveal the causal agent of YCS and lead to identification of specific management practices for YCS.

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