B.PAS.0505 - Rapid diagnosis of pasture dieback using SIFT-MS (Selected Ion Flow Tube Mass Spectrometry)
Confirmation of early stage pasture dieback is difficult as the condition can be confused with a range of other issues. The project tested a portable gas collection tool to sample volatile organic compounds with limited success.
| Project start date: | 14 August 2020 |
| Project end date: | 29 November 2021 |
| Publication date: | 01 May 2024 |
| Project status: | Completed |
| Livestock species: | Grass-fed Cattle, Sheep |
| Relevant regions: | NSW, Queensland, Tropical warm season wet, Sub-tropical moist, Sub-tropical sub-humid, Tropical wet |
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Summary
This was a very short (six months) project to explore the possibility of developing an accurate identification tool for early stage pasture dieback which could be implemented for researchers. Intent was to assist researchers and producers to track the spread and impact of pasture dieback to support early implementation of management strategies. This project tested a portable gas collection tool, the analysis volatile organic compounds (VOCs), and mass spectrometry to identify ‘pasture dieback’ in laboratory and field samples.
A short-chain (C6) ‘green leaf’ plant volatile, (E)-2-hexen-1-ol, was associated with dieback. Green leaf volatiles are induced in response to abiotic and biotic stress such as attack by pests and pathogens, and water stress, and are involved in plant defenses including altering behavior of insect herbivores, attracting natural enemies of pests, and in plant-to-plant communication to reduce further attacks.
Results indicate that the use of the portable gas collection device is practical for use in the field. The work also demonstrates that VOC analysis can detect at least one induced plant volatile associated with early-stage dieback. However, the molecules identified so far are not specific to pasture dieback, and are produced in association with the appearance of early visible symptoms of dieback (leaf discoloration).
Further work is required to determine specific patterns of ions in SIFT analysis without the confounding effects of sites and grass species. This detailed laboratory analysis will be conducted and a revised report submitted.
Objectives
1. Detect and identify chemical markers associated with grass pasture dieback induced by mealybug in the laboratory.
2. Determine the potential for consistent detection of chemical markers associated with grass and early dieback and low density mealybug in the laboratory.
3. Determine the potential for detection of chemical markers associated with grass and early dieback and low-density mealybug in field samples.
Key findings
We consistently identified statistically significant differences in volatile metabolome composition between healthy and diseased grasses, both in the laboratory and in the field. In controlled laboratory experiments, green leaf volatiles were significantly associated with dieback. One induced plant volatile, (E)-2-hexen-1-ol was identified and was clearly associated with dieback.
Short-chain (C6) ‘green leaf’ plant volatiles such as 2-hexen-1-ol are are induced in response abiotic and biotic stress such as attack by pests and pathogens and water stress, and involved in plant defenses including altering behavior of insect herbivores, attracting natural enemies of pests, and in plant-to-plant communication to reduce further attacks.
Dieback-affected and grasses in the field produced a significantly different profile of VOCs from healthy grasses at the same location using SIFT analysis. However, VOC profiles were confounded by both sites and grass species.
Consistent markers or patterns that differentiate all affected from unaffected grasses could not be determined in the field and require further detailed laboratory tests that reduce the number of confounding factors.
Results indicate that use of the portable gas collection device is practical in the field, and that VOC analysis may have value in detecting early-stage dieback. However, the induced plant volatiles identified so far are not specific to pasture dieback, and are associated with the appearance of early svisible symptoms of dieback (leaf discoloration). A detailed laboratory analysis of VOCs generated over time in affected plants and that eliminates the confounding effects of site and grass species will be conducted.
Benefits to industry
Results indicate that the use of the portable gas collection device and subsequent laboratory analysis is practical to use in the field. The work also demonstrates that VOC analysis can detect and identify at least one induced plant volatile associated with early-stage dieback. However, further work is required to determine specific patterns of ions in SIFT analysis that are more robust when collecting in different sites and grass species.
MLA action
This was an early stage proof of concept project. While there was limited success using laboratory screenhouse grass samples and field collected samples there are confounding effects that are site specific. With limited funding for dieback research there are higher priority areas where investment has been directed into more practical research for on the ground management strategies that producers can implement to feed livestock and manage PD risk.
Future research
Further work is required to determine specific patterns of ions in SIFT analysis without the confounding effects of sites and grass species. This detailed laboratory analysis will be conducted and a revised report submitted.
More information
| Project manager: | Felice Driver |
| Contact email: | reports@mla.com.au |
| Primary researcher: | Queensland University of Technology |
