'Red Leaf': A new disorder in Australian strawberry plants

Abstract

In 2014, several strawberry plants growing in commercial field beds in South East Queensland, Australia, displayed a reddish/maroon interveinal discolouration and decline in plant health and yield. This new red leaf disorder (RLD) has since been observed to varying extents in several commercial cultivars grown during winter production. An increase in the number of commercial plants affected by RLD has occurred since 2014. In 2019, a survey of 18 farms in South East Queensland assessed the incidence and severity of RLD symptoms. RLD was observed in up to 30% of plants in affected field blocks. Samples were screened for evidence of an association with viruses, phytoplasmas, rickettsia, and fungal and bacterial pathogens using polymerase chain reaction and high-throughput sequencing (HTS). Transmission tests, fungal isolations, and leaf nutrient analysis were also undertaken. These tests have not identified an obvious single causal agent and work is ongoing to investigate potential biotic and abiotic stress factors of this complex disorder and its epidemiology. An examination has also been conducted into whether resistance or tolerance to RLD is present in Australian cultivars and Australian Strawberry Breeding Program selections. Quantitative genetic analyses of symptom severity and RLD incidence in two field trials identified a range of tolerances to the disorder, and moderate narrow-sense heritability. Due to the significance of this disorder to the Australian winter production and potential importance to the national strawberry industry, RLD requires broader investigation to accelerate identification. © 2021 International Society for Horticultural Science. All rights reserved.