Articles
Investigation of Phytophthora diseases in Australian almonds
Article number
1406_53
Pages
377 – 384
Language
English
Abstract
Phytophthora spp. are aggressive pathogens of almond which cause root rot, crown rot, and trunk cankers.
Symptoms include root necrosis, woody tissue death in the crown, trunk and scaffolds, gummosis, and overall tree decline, with infection often resulting in tree death.
During disease surveys from 2018 to 2020, samples taken from symptomatic trees in orchards of South Australia, Victoria, and New South Wales yielded numerous Phytophthora and Phytopythium isolates. Phytophthora isolates were identified by sequencing the ITS and Cox1 regions, while Phytopythium spp. were identified using ITS along with the BT and Cox2 regions.
Species were identified as Phytophthora acerina, P. cactorum, P. hedraiandra, P. multivora, P. niederhauserii, P. syringae, Phytopythium litorale and Pm. vexans. Two pathogenicity experiments were conducted on potted almond trees (Prunus dulcis ‘Price’ and ‘Carmel’) between 2020 and 2022 in a shade house.
Tested species included P. acerina, P. cactorum, P. hedraiandra, P. multivora, P. niederhauserii and Pm. litorale. One-year-old stems were inoculated with mycelial agar plugs, incubated for 4-6 weeks, and lesion length recorded, followed by re-isolation to confirm Koch’s postulates.
Results showed that all Phytophthora spp. were pathogenic to almond.
Out of three Phytopythium isolates tested, only one was pathogenic to ‘Carmel’. To the best of our knowledge, this is the first report of P. acerina and any Phytopythium species causing disease in almond in Australia, and for P. hedraiandra, in the world.
In the future, it will be critical to determine the prevalence of Phytophthora spp., the impact on orchard productivity, and to develop additional management options for the Australian almond industry.
Symptoms include root necrosis, woody tissue death in the crown, trunk and scaffolds, gummosis, and overall tree decline, with infection often resulting in tree death.
During disease surveys from 2018 to 2020, samples taken from symptomatic trees in orchards of South Australia, Victoria, and New South Wales yielded numerous Phytophthora and Phytopythium isolates. Phytophthora isolates were identified by sequencing the ITS and Cox1 regions, while Phytopythium spp. were identified using ITS along with the BT and Cox2 regions.
Species were identified as Phytophthora acerina, P. cactorum, P. hedraiandra, P. multivora, P. niederhauserii, P. syringae, Phytopythium litorale and Pm. vexans. Two pathogenicity experiments were conducted on potted almond trees (Prunus dulcis ‘Price’ and ‘Carmel’) between 2020 and 2022 in a shade house.
Tested species included P. acerina, P. cactorum, P. hedraiandra, P. multivora, P. niederhauserii and Pm. litorale. One-year-old stems were inoculated with mycelial agar plugs, incubated for 4-6 weeks, and lesion length recorded, followed by re-isolation to confirm Koch’s postulates.
Results showed that all Phytophthora spp. were pathogenic to almond.
Out of three Phytopythium isolates tested, only one was pathogenic to ‘Carmel’. To the best of our knowledge, this is the first report of P. acerina and any Phytopythium species causing disease in almond in Australia, and for P. hedraiandra, in the world.
In the future, it will be critical to determine the prevalence of Phytophthora spp., the impact on orchard productivity, and to develop additional management options for the Australian almond industry.
Authors
B.J. Oswald, L. Tesoriero, S. Kreidl, S.Q. Dinh, T.J. Wiechel, M.R. Sosnowski
Keywords
Prunus dulcis, soil-borne pathogens, nut crops, oomycetes, pathogenicity testing
Groups involved
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