Characterization of Aster Yellows Phytoplasma Affecting Carrot Crops Based on 16S rRNA and secY Gene Analysis

Abstract

Characterization of Aster Yellows phytoplasma affecting carrot crops was conducted using 16S rRNA and secY gene analysis to determine molecular identity, genetic diversity, and phylogenetic placement of the pathogen. Field surveys were carried out in carrot-growing regions exhibiting typical symptoms of phytoplasma infection, including leaf yellowing, stunting, proliferation of secondary shoots, and abnormal root development. DNA was extracted from symptomatic plant tissues and subjected to nested PCR assays targeting the 16S rRNA gene, followed by amplification of the secY gene for higher-resolution differentiation. Sequencing and phylogenetic analysis confirmed the presence of Aster Yellows group phytoplasmas, clustering within distinct subgroups associated with vegetable crop hosts. Comparative sequence analysis revealed limited but notable genetic variation among isolates, suggesting regional differentiation and possible strain diversification. The secY gene provided improved discriminatory power compared to 16S rRNA, enabling finer resolution of closely related phytoplasma strains. Infection severity was correlated with phytoplasma presence, with heavily infected plants showing severe yield reduction and root deformation. The study highlights the importance of multilocus molecular approaches for accurate identification of phytoplasmas in carrot systems. These findings contribute to improved understanding of Aster Yellows epidemiology and support the development of diagnostic tools and management strategies aimed at reducing phytoplasma-associated losses in carrot production systems.