B.PAS.0006 - Resistant grass varieties and endophytes
Resistant or tolerant pasture grass varieties have been identified to control mealybug induced pasture dieback which is prevalent through parts of Queensland and NSW.
| Project start date: | 27 February 2020 |
| Project end date: | 14 December 2022 |
| Publication date: | 30 July 2024 |
| Project status: | Completed |
| Livestock species: | Grain-fed Cattle, Grass-fed Cattle, Sheep, Goat, Lamb |
| Relevant regions: | NSW, Queensland |
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Summary
Pasture dieback causes unhealthy growth and death in a range of introduced and native grasses across Queensland and into northern New South Wales, resulting in large losses in beef production areas. Pasture mealybug, Heliococcus summervillei Brookes, has been identified as the leading cause of pasture dieback. Possible management strategies include the identification of resistant or tolerant pasture varieties, and the use of endophytic fungi to protect pasture grasses. Endophytes are fungi that live within healthy plant tissue and can confer resistance to insects, including mealybugs.
Objectives
1. Identify susceptible grass varieties to pasture dieback from field surveys.
2. Assess the relative susceptibility of selected grass varieties to pasture mealybug and/or other agents responsible for pasture dieback and their impact on mealybug biology.
3.Isolate and characterise endophyte species present in grasses collected during pasture dieback field surveys and determine those which are tolerant to the mealybug.
4. Develop procedures and use them to assess promising endophytes (both facultative and seed-born) as cost effective pasture pest control methods. Make recommendations on opportunity for an endophyte approach (via plant breeding/propagation) to address dieback.
5. Develop procedures and use them to assess endophytes and tolerant/resistant pasture mixes in field surveys, and laboratory and glasshouse assays. Make recommendations for field evaluation of prospective tolerant grasses and mixes.
6. Provide timely communication on research activities for use in industry briefings at least biannually throughout the project.
Key findings
1. The mealybug H. summervillei was found associated with symptoms of ‘pasture dieback’ on 24 varieties and species of pasture grasses across Queensland and New South Wales, and on sugar cane. Legumes and other broadleaf species were not hosts of the mealybug and do not show symptoms of ‘pasture dieback’.
2. Mekong brizantha, Argentina bahia, curly Mitchel grass, Biloela buffel and Gatton panic were all less susceptible to mealybug than American buffel.
3. Callide and Katambora Rhodes, Paspalum nicora, green panic, and Gayndah buffel were all similar in susceptibility to American buffel.
4. A highly statistically significant correlation between diversity of species of beneficial endophytic fungi and severity of dieback was demonstrated. Where a high diversity of species of beneficial fungi were isolated, dieback severity was significantly reduced. In contrast, both diversity of Fusarium species and races, and diversity of ‘neutral’ fungi, were not significantly associated with dieback severity.
Benefits to industry
The project has significantly increased options to manage pasture dieback. Tolerant and resistant pasture varieties have been identified, the benefit of both seed-born and soil/rhizospheric fungal endophytes in reducing mealybug and pasture dieback in the laboratory and in the field has been demonstrated, and rapid assays have been developed to reduce cost and increase speed and statistical power of future screening for development of new pasture varieties and endophytic symbionts for protection of tropical and subtropical pastures.
This work demonstrates a direct link between ‘pasture dieback’, pasture diversity and soil health.
Management practices that increase diversity of beneficial rhizospheric fungi, such as inclusion of legumes, and impacts of management that reduces abundance and diversity of these fungi (such as, possibly, hot burning) should be avoided.
MLA action
A new MDC Research agreement has been concluded with QUT to further investigate mechanisms of tolerance and resistance to mealybug, the effects of mealybug on the host plant immune system and the role of beneficial fungi.
Future research
Further research to screen varieties for tolerance/resistance and to determine tolerance/resistance mechanisms using a combination of rapid laboratory assay method and transcriptome analysis (B.PAS 0003) are strongly recommended.
Characterisation of the isolates of fungi in the three genera of the key beneficial endophyte genera (Clonostachys, Trichoderma and Penecillium) should be completed to determine their taxonomy. The beneficial impacts of these fungi on grasses and mealybugs should be a focus of further investigation using some of the rapid assay methods developed here.
Further assays and detailed analysis of plant/endophyte/mealybug interactions in grasses should be conducted in combination with trials on pasture legume mixes is strongly recommended. Management practices that increase diversity, such as inclusion of legumes, and management that reduces abundance and diversity of these fungi (such as, possibly, hot burning) should be investigated.
More information
| Project manager: | Cameron Allan |
| Contact email: | reports@mla.com.au |
| Primary researcher: | Queensland University of Technology |
