Multiplex PCR assay for detection and identification of Gnomoniopsis idaeicola, the causal agent of blackberry collapse

Authors: Stockwell, Virginia; Shaffer, Brenda

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2024
Publication Date: 4/23/2024
Citation: Stockwell, V.O., Shaffer, B.T. 2024. Multiplex PCR assay for detection and identification of Gnomoniopsis idaeicola, the causal agent of blackberry collapse. Plant Health Progress. https://doi.org/10.1094/PHP-09-23-0080-BR.
DOI: https://doi.org/10.1094/PHP-09-23-0080-BR

Interpretive Summary: Oregon is the top producing state of blackberries in the USA. The crop was valued at $31 million in 2017 (NASS), providing income to several small farms. Recently, Oregon blackberry growers have been challenged with the 2020 'heat dome' that damaged their crops just before harvest and a new emerging disease called blackberry collapse. Blackberry collapse is caused by the fungus Gnomoniopsis idaeicola. Early symptoms are cane lesions, which then progresses to reduced plant growth, wilting, and plant death in two to three years. Symptomatic plants are removed to reduce disease spread in the field. Unfortunately, the early symptoms of blackberry collapse are difficult to distinguish from other non-lethal cane diseases. Diagnosis of cane lesions as blackberry collapse takes several weeks. We developed a rapid and accurate PCR assay to identify G. idaeicola in culture and in plant tissues. This assay will provide rapid diagnosis of blackberry collapse, which will aid growers decisions whether plants with cane lesions should be removed to stop early establishment or spread of blackberry collapse in their fields. The PCR assay also will aid scientific research on timing fungal spore production and spread in fields. This knowledge is essential to develop novel management strategies for blackberry collapse.

Technical Abstract: Blackberry collapse is an emerging disease in Oregon caused by Gnomoniopsis idaeicola. Symptoms associated with the disease include cane lesions, reduced primocane production, wilting and plant death. Symptomatic plants are removed to reduce disease spread in the field. Unfortunately, blackberry collapse symptoms can be difficult to distinguish from other non-lethal cane diseases. Diagnostic procedures for blackberry collapse currently require several weeks, necessitating the development of a multiplex PCR assay to identify G. idaeicola in culture and in planta. The assay targets tef-1a and ß-tubulin and includes primers as internal controls for PCR reactions of plant tissue or fungal cultures. This species-specific assay will provide rapid diagnosis of blackberry collapse and aid epidemiological studies.