Survey and Molecular Characterization of Phytoplasma Associated with Decline Disease of Grapevine in Arid Regions

Abstract

Grapevine decline characterized by leaf yellowing, reduced vigor, shoot stunting, abnormal leaf curling, and progressive vine dieback was observed in vineyards located in arid production regions, suggesting the involvement of phytoplasma-associated diseases. Field surveys were conducted across major grape-growing areas to assess disease incidence, symptom variability, and spatial distribution within vineyards. Symptomatic leaf and phloem tissues were collected for molecular detection and characterization of the associated phytoplasma. Total DNA extracted from infected samples was subjected to polymerase chain reaction (PCR) using universal phytoplasma primers targeting conserved 16S rRNA gene regions. Amplification of expected fragments confirmed the presence of phytoplasma in symptomatic vines, whereas asymptomatic plants yielded no detectable amplification. Sequence analysis of PCR products revealed high similarity with known phytoplasma groups reported from grapevine and other woody hosts. Phylogenetic analysis grouped the detected phytoplasma within established clades, indicating close genetic relationships with previously characterized strains associated with grapevine yellows and decline syndromes. Disease incidence was found to be higher in vineyards with poor irrigation management and elevated insect vector populations, particularly leafhoppers and psyllids, which likely facilitated pathogen transmission. Environmental conditions typical of arid regions, including high temperature fluctuations and water stress, appeared to exacerbate symptom expression and disease severity. Infected vines exhibited reduced canopy growth, poor fruit set, and significant decline in yield potential. The integration of field surveys and molecular diagnostics provided reliable detection and characterization of phytoplasma associated with grapevine decline.