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POSTERS: New and emerging diseases

Pennsylvania Orchards for Rapid Apple Decline
Ekaterina Nikolaeva - Pennsylvania Department of Agriculture. Tammy Jones- Pennsylvania Department of Agriculture, Ruhui Li- USDA ARS, Kari Peter- Pennsylvania State University, Fruit Research and Extension Center, Cody Molnar- Pennsylvania Department of Agriculture, Rachel Knier- Pennsylvania Department of Agricult

In 2018, the Pennsylvania Department of Agriculture and Pennsylvania State University conducted a survey of PA orchards for Rapid Apple Decline (RAD). Forty-four apple orchard blocks in 16 farms located in seven counties were inspected for symptoms of RAD, including presence of many declining trees, unseasonal tree discoloration and defoliation, brown cankers around graft union, and presence of rootstock suckers. A total of 516 samples were collected from both symptomatic and asymptomatic trees and tested. The main target was a newly described apple luteovirus 1 (ALV1), which may play a role in RAD. A one-step RT-PCR assay was developed and used for the ALV1 detection in the samples. One hundred and twenty samples (23%) including scion leaves, bark, blossoms, fruits, and rootstock sucker leaves were found positive for ALV1. The virus was detected from several apple cultivars including Crimson Crisp, Fuji, Gala, Honeycrisp and Golden Delicious. Most ALV1 positive trees (67%) were grafted onto M9 rootstocks. Our results also show the virus does not distribute equally within the tree, and the number of positive tree scaffolds increases during the infection process. ALV1 was detected in some trees in combination with 1-3 apple latent viruses (apple mosaic virus, apple stem grooving virus, apple stem pitting virus, apple chlorotic leaf spot virus); however, there was no consistency in virus combinations. Additional studies are necessary to further understand any connection of ALV1 to RAD.