Metatranscriptomic identification and sustainable integrated control of Jasmine virus H in ornamental plants using nano-chitosan and biological inputs

Abstract

This study combined metatranscriptomic virus detection with an integrated, eco-friendly management strategy to address viral diseases of ornamentals in Karbala Governorate, Iraq. Leaf samples with typical virus-like symptoms were collected from commercial nurseries and subjected to next-generation RNA sequencing. The bioinformatic analysis revealed Jasmine virus H (JaVH) as the predominant pathogen, and the complete genome of an Iraqi isolate, designated JaVH isolate Iraq-1 (3,868 bp; 95.4% nucleotide identity to the reference), was deposited in GenBank under accession PZ155373.1. A field experiment evaluated three management regimens in naturally infected J. sambac and H. rosa-sinensis plants: T1, an integrated treatment combining biological preparations, chitosan nanoparticles, NPK fertilizer, and an amino acid stimulant; T2, a conventional pesticide alternation; and T3, an untreated control. Although virus incidence remained high in all treatments, integrated management (T1) significantly reduced disease severity, particularly in Hibiscus, where severity declined from 76.66% in controls to 33.33%. T1 also enhanced physiological performance, increasing total chlorophyll content by 11% in J. sambac and 13% in H. rosa-sinensis relative to controls, and boosting defense enzyme activities and nutrient accumulation. In H. rosa-sinensis, T1 markedly elevated polyphenol oxidase and phenylalanine ammonia-lyase activities, consistent with activation of systemic defense pathways. These findings provide the first molecular characterization of JaVH in Iraq and demonstrate that integrating nano-chitosan with beneficial biological agents and balanced nutrition can mitigate the impact of JaVH infection and improve plant vigor in ornamental nursery production. The approach offers a promising, environmentally sustainable alternative to pesticide-based management for viral diseases of ornamental plants.