Fluorescence Microscopy-based Preliminary Detection of Phytoplasma infecting Sweet Cherry in Himachal Pradesh, India

Sweet cherry (Prunus avium L.), an important temperate fruit crop, is increasingly threatened by phytoplasma-associated diseases. This study aimed to detect phytoplasma infections in cherry orchards of Himachal Pradesh, India. Field surveys (2023–2024) in major growing regions, particularly Shimla district, revealed typical symptoms including chlorosis, reduced leaf size, reddening, dieback, and tree decline, with disease incidence reaching up to 40% in severely affected orchards. Symptomatic and asymptomatic samples were analyzed using DAPI (4′,6-diamidino-2-phenylindole) staining. Fluorescence microscopy showed bright signals in the phloem sieve elements of symptomatic tissues, indicating phytoplasma presence, while no fluorescence was observed in healthy samples. DAPI staining proved to be a rapid and cost-effective preliminary diagnostic tool; however, molecular validation is required for definitive confirmation. The study provides preliminary evidence of phytoplasma occurrence in sweet cherry in Himachal Pradesh and highlights the need for molecular characterization and effective management strategies.