New phytophthora resistant rootstock released for use by the Australian avocado industry

In 2006, as part of the Hort Innovation Avocado Fund project Improving yield and quality in avocado through disease management (AV07000) the rootstock of a surviving Hass tree in an avocado orchard at South Kolan was recovered and clonally propagated to test for phytophthora root rot resistance. Identified as ‘SHSR-04’ it proved to have a high level of resistance to Phytophthora root rot, a serious disease in most Australian orchards.

Several rootstock lines in common use were grafted to Hass and planted with SHSR-04 into phytophthora infested soil and protected with systemic fungicides for the first year, after which they were withdrawn. 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’. This work was continued by avocado levy-funded project Rootstock improvement for the Australian avocado industry phase III (AV08000).

Under the more recent Hort Innovation Avocado Fund project Avocado rootstock SHSr-04 commercialisation (AV15005), the first commercial use of 600 Hass trees grafted to SHSR-04 were planted near Childers in July 2020. The site is a replant block in a commercial orchard where several other rootstocks in common use have been planted to enable 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. Results will be periodically published as trees develop.

The Intellectual Property owners of ‘SHSR-04’ have secured protection under Plant Breeders Rights and are progressing the commercialisation of ‘SHSR-04’ to provide access for Australian avocado growers. Propagation licenses have been signed with two ANVAS nurseries, Anderson Horticulture Pty Ltd at Duranbah, NSW and Turkinje Nursery at Walkamin, North Queensland. Licensing negotiations are continuing with other ANVAS nurseries.

The IP owners have applied for a US patent for the rootstock and are considering other opportunities for international licensing. Development of other markets will return a share of the revenue to the Australian avocado industry for future R&D programs. Past experiences have shown that international licensing helps protect against IP theft.   

Interested avocado growers should contact the nurseries listed above for more information on accessing these rootstocks.