What was it all about?

Almonds are susceptible to a variety of endemic and exotic bacteria, phytoplasmas, viruses, viroids and fungi which, if introduced to an orchard at an early age, are likely to reduce orchard health, limiting production.

The almond industry works to ensure a repository of high health plants is maintained. This project involved testing trees at the Australian Almond Improvement Society at Monash, in South Australia, for any viruses. The Monash planting consists of 64 cultivars and clones and four rootstocks, planted over one hectare. It provides budwood supplies of common commercial cultivars, clones and root stocks to the nursery industry as well as germplasm of local and imported varieties used in the Australian almond breeding program.

After detection of some symptoms on budwood trees in 2011, leaves from 25 trees were tested for viruses. Nine (36 per cent) of the trees were assessed positive for Prunus Necrotic Ringspot Virus, which, combined with the visual symptoms being observed, lead to a cessation of budwood supply from the entire site in 2011/12.

For this project, candidate lines from a total of 45 almond varieties were sampled from the Monash budwood repository and assessed for viral diseases using two methods. Propagation material was sourced from the original virus free trees at the Monash repository and grafted to the most appropriate rootstock to ensure the best possible long‐term health of the foundation trees.

Two foundation trees were established per cultivar, clone and rootstock and, beginning in 2013, replanting of healthy trees began at the site.

By remediating the almond budwood repository, researchers have enhanced biosecurity of the Australian almond industry at the orchard level.