By Dr Anthony Whiley and Dr Elizabeth Dann

The first commercial planting of 600 Hass trees grafted to a new rootstock selected and evaluated in Australia, occurred near Childers in the Central Queensland growing region in July 2020.

The rootstock was recovered and clonally propagated from a surviving Hass tree in an avocado orchard at South Kolan, Queensland. Surrounding trees had succumbed to Phytophthora root rot. Identified as ‘SHSR-04’ for evaluation purposes, it proved to have a high level of resistance to Phytophthora root rot, in repeated trials conducted between 2006 and 2015 under high disease pressure (Smith et al, 2011).

At Childers, the trees on SHSR-04 have been planted alongside rows of Hass grafted to Dusa, Velvick and other rootstocks, and the owner has generously agreed to provide access and assistance with the collection of comparative performance data. Tree health and growth rates across the block will be monitored along with the collection of yield and fruit size data. The site is a replant block in a commercial orchard, where 30-year-old trees had significantly declined from Phytophthora root rot.

The site will also test the tolerance of the new rootstock to high chloride concentrations in irrigation water. To retain Phytophthora resistance, SHSR-04 is produced as a cloned rootstock since its seedlings were shown to have no significant resistance when grafted to Hass. The new rootstock does not have complete resistance to Phytophthora cinnamomi, but will be a key component to establishing and maintaining healthy, productive orchards. Remember the Pegg Wheel for integrated management of Phytophthora root rot! (You can find the Pegg Wheel on the Manage Phytophthora root rot poster in the Education Materials area of the BPR Library, or in the Growing section here.)

The Intellectual Property owners of SHSR-04 (George H. Green, Horticulture Innovation Australia Ltd and Sunshine Horticultural Services Pty Ltd) have secured protection under Plant Breeders Rights and are progressing the commercialisation of SHSR-04 to provide broad access for Australian avocado growers. Propagation licenses have been signed with two ANVAS nurseries, Anderson Horticulture Pty Ltd at Duranbah, New South Wales and Turkinje Nursery at Walkamin, North Queensland. Licensing negotiations are continuing with other ANVAS nurseries.

The IP owners have also applied for a US Patent for the rootstock and are considering other opportunities for international licensing. The latter is believed necessary since past experiences have shown that unauthorised transfer of elite plant material across international borders will occur if IP protection has not been taken out. A Trade Mark (rootstock name) has had preliminary approval, with final approval expected to be granted in November 2020 and the name announced in a subsequent publication.

More information

Dr Anthony Whiley and Dr Elizabeth Dann are preparing a detailed article about the new rootstock for the Summer edition of Talking Avocados (out in early 2021). Watch this space!

You can also find the final reports for AV07000, AV08000 and AV10001 in the R&D Reports area of the BPR Library, and read more about the various projects via Hort Innovation (AV07000, AV08000, AV10001 and AV15005).

References

Smith, L. A., Dann, E. K., Pegg, K. G., Whiley, A. W., Giblin, F. R., Doogan, V. and Koppitke, R. (2011). Field assessment of avocado rootstock selections for resistance to Phytophthora root rot, Australasian Plant Pathology, 40:39-47. (Read the article here.)

Pegg, K. G., Dann, E. K., Coates, L., Whiley, A. W. (2008). Phytophthora resistance in rootstocks, Talking Avocados, 19 (2):23-25. (Read the magazine here.)

Acknowledgement

The research leading to this result was funded by the Horticulture Australia Limited (HAL) project Rootstock improvement for the Australian avocado industry – phase 3 (AV08000), that recovered and clonally propagated the rootstock in collaboration with George Green and Sunshine Horticultural Services. (As IP owners, George Green and Sunshine Horticultural Services provided resources supporting the development of the rootstock, including recovering the original rootstock and subsequent propagation of the rootstock allowing it to be field tested.) The HAL/Hort Innovation funded projects Improving yield and quality in avocado through disease management (AV07000 and AV10001) carried out field evaluations of Phytophthora root rot resistance.

The Avocado rootstock SHSR-04 commercialisation (AV15005) project was funded by Hort Innovation, using the avocado research and development levy, and contributions from the Australian Government. Its main role was to assist with securing the Intellectual Property vested in the rootstock and negotiating commercialisation agreements with nurseries in collaboration with the other parties with IP ownership.

This article was produced for the Guacamole of 18 September 2020 and the Spring 2020 edition of Talking Avocados.