Akademik Veri Yönetim Sistemi
APPLIED FRUIT SCIENCE, cilt.68, sa.4, ss.1-9, 2026 (SCI-Expanded, Scopus)
Türkiye is among the world’s leading walnut producers, ranking sixth among the top global producers. Walnut cultivation has expanded rapidly in recent d ecades, supported by government incentives and increasing consumer demand. Numerous new o rchards have been established both on g rowers’ fields and on degraded forest lands converted into agricultural areas. While this expansion has boosted national production, it has also introduced new phytosanitary challenges, particularly the management of root rot and dieback diseases, which threaten the health and productivity of walnut trees. Walnut dieback is recognized as one of the most destructive diseases of walnut worldwide, with significant economic consequences. This study aimed to investigate the etiology of walnut dieback and identify the causal agent responsible for outbreaks observed in an orchard in Manisa Province, Türkiye. The orchard, established in 2011 on degraded forest land, was p lanted with walnut saplings grafted indoors in plastic tubes. Several y ears later, some trees began to exhibit symptoms such as growth retardation, progressive shoot dieback, crown decline, and eventual plant death. Field surveys were conducted in 2021, and symptomatic plants were examined with a focus on their root and collar tissues. Pathogen isolation was performed through morphological and molecular analyses, including sequencing of diagnostic DNA regions used for species identification. Both approaches consistently revealed Phytophthora cinnamomi as the causal agent associated with dieback symptoms. This species is one of the most aggressive soilborne oomycete pathogens worldwide, capable of causing severe root rot in a wide range of hosts. The confirmation of P. cinnamomi in walnut orchards of Türkiye has critical implications. The findings highlight the urgent need for preventive strategies, improved nursery practices, and effective cultural measures to reduce pathogen spread. Implementing integrated management will be essential to sustain the productivity and long-term viability of the expanding walnut industry in the country