First Record of Candidatus Phytoplasma in Lettuce Showing Yellowing and Stunting Symptoms

Abstract

Phytoplasmas are wall-less, phloem-limited bacterial pathogens associated with numerous economically important plant diseases worldwide. The present study reports the first detection and molecular identification of Candidatus Phytoplasma associated with yellowing and stunting symptoms in lettuce plants. Symptomatic lettuce samples exhibiting chlorosis, reduced leaf size, stunted growth, and abnormal plant development were collected from commercial cultivation areas. Disease incidence and symptom characteristics were documented under field conditions, and total DNA was extracted from infected plant tissues for molecular diagnosis. Detection of phytoplasma infection was carried out using polymerase chain reaction (PCR) assays with universal phytoplasma-specific primers targeting the 16S rRNA gene region. Amplification products of the expected size were obtained from symptomatic samples, while healthy plants tested negative. Sequence analysis and phylogenetic comparison confirmed the association of Candidatus Phytoplasma with diseased lettuce plants and revealed close genetic relationships with previously reported phytoplasma groups infecting vegetable crops. The occurrence of phytoplasma infection was associated with significant reductions in plant vigor and marketable quality of lettuce. Symptom expression suggested disruption of normal physiological and metabolic processes due to pathogen colonization within phloem tissues. The identification of this phytoplasma represents a new host-pathogen association and highlights the potential risk of phytoplasma diseases in lettuce production systems. Early molecular detection and accurate identification are essential for disease monitoring, epidemiological studies, and implementation of phytosanitary measures aimed at preventing pathogen spread. The findings contribute valuable information regarding the emergence of phytoplasma-associated diseases in leafy vegetable crops and support the development of integrated disease management strategies for sustainable lettuce production.