Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Andrew Geering

829 views

Published on

  • Be the first to comment

  • Be the first to like this

Andrew Geering

  1. 1. Better control of avocado sunblotch disease through improved diagnostic technologies By Andrew Geering and Vish Steele Horticulture and Forestry Science, Industry Services
  2. 2. Queensland Primary Industries and Fisheries Avocado sunblotch viroid (ASBVd) • Smallest pathogen in the world (genome of 247 nts). • Only detected using molecular methods or by grafting bark patches onto indicator host such as cv. Hass. • Three strains: symptomless carrier (ASBVd-SC), variegation (ASBVd-V) and bleaching (ASBVd-B). • Differences between strains very minor – a single mutation can result in change from ASBVd-V to ASBVd-B. © The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
  3. 3. Queensland Primary Industries and Fisheries Economic impact of ASBVd • Smaller and fewer fruit – estimates of yield loss range from 18-95%. • Fruit disfigurement – more than half of fruit may be downgraded on quality standards. • Symptomless carrier trees may still show significant yield decline. • Quarantine restrictions may affect export of fruit from affected orchards. © The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
  4. 4. Queensland Primary Industries and Fisheries Transmission of ASBVd • Cannot be transmitted by insects. • Cannot survive for any length of time outside of the plant (i.e. in the soil). • Transmitted at a very high rate in seed. • Transmitted in scions used for grafting. • Probably transmitted at a low rate on the blades of pruning tools. • Transmitted by root grafting. © The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
  5. 5. Queensland Primary Industries and Fisheries Control of ASBVd • Infected plants cannot be cured. • Infected plants should be removed to prevent further spread – all living tissue must be destroyed. • New blocks should be established with plants certified to be free of ASBVd: – i.e. from a nursery participating in the Avocado Nursery Voluntary Accreditation Scheme (ANVAS). © The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
  6. 6. Queensland Primary Industries and Fisheries Objectives of research project • To develop quality-assured diagnostic tools. • To survey for ASBVd in south-east Queensland/northern NSW. © The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
  7. 7. Queensland Primary Industries and Fisheries Quality-assured diagnostic tools • Two types of error in diagnosis: – Healthy plant mistakenly diagnosed as infected. – Infected plant mistakenly diagnosed as healthy. • The latter mistake is most serious. Causes of error: • Human error. • Sample degradation. • Sampling error. • Assay inhibition. © The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
  8. 8. Queensland Primary Industries and Fisheries New PCR assay for ASBVd including internal control (plant gene) Positive ASBVd status Negative ? Plant gene ASBVd © The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
  9. 9. Queensland Primary Industries and Fisheries How significant a problem is ASBVd in Australia? • ANVAS established in 1978. • 34% of Australian avocado trees 6 years or younger. • Less than 10 records of ASBVd from Australia and mostly from germplasm collections. • Last published report of ASBVd was in 1989. Question: Is ASBVd still present in Australia? © The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
  10. 10. Queensland Primary Industries and Fisheries Verified records of ASBVd in Australia – cv. Mexicola, Alstonville Research Station, NSW (1962, 1989) – budwood obtained from ‘interstate’. – cv. Zutano AV35, 2 field trees, Coomealla, NSW (1981) – cv. unknown, CSIRO Division of Horticultural Research, Merbein, Victoria (1981). – cv. Carlsbad, post-entry quarantine, Canberra (1981). – cv. Fuerte, field tree, Alstonville, NSW (1981). – cv. Hass, 1 field tree, Red Cliffs, Vic (1981) – cv. Hass, 2 field trees, Qld (1981) – cv. Hass, 1 field tree, NT (1981). – cv. Bacon, 1 field tree, Paringi, NSW (1989). © The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
  11. 11. Queensland Primary Industries and Fisheries Surveys for ASBVd in south-east Queensland and northern NSW • All trees in the multiplication blocks of Anderson Avocado Tree Nursery, Duranbah, NSW, and Birdwood Nursery, Woombye, QLD, have been tested and all were NEGATIVE. • 2100 trees from commercial properties in south-east Queensland and northern NSW have been tested and all were negative, except: – One cv. Fuerte tree of age >20 years old. This tree was symptomless. © The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
  12. 12. Queensland Primary Industries and Fisheries Conclusions • ASBVd is very rare but not yet completely eradicated from Australia. • ANVAS is successful and ASBVd progressively being eradicated. • To ensure ASBVd-freedom, buy planting stock from accredited nurseries. • If you suspect you have ASBVd, please talk to me at conference and we will test samples for free. © The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
  13. 13. Queensland Primary Industries and Fisheries Acknowledgements • Funding from Horticulture Australia Limited and Avocados Australia is gratefully acknowledged. • THANK YOU FOR YOUR ATTENTION © The State of Queensland, Department of Employment, Economic Development and Innovation, 2009

×