Morphological evidence and global research progress of plant-parasitic nematodes in shallot cultivation

Abstract

Plant-parasitic nematodes (PPN) represent significant pests that inflict damage on root systems, diminish plant vigor, and lead to yield losses in various horticultural crops, including shallots (Allium cepa var. aggregatum). This study synthesizes field and laboratory data with an analysis of global research trends to enhance the diagnosis and identify research gaps concerning PPN in shallots. In the original research component, rhizosphere soil and root samples were collected from symptomatic plants in shallot plantations. Symptoms were visually assessed in the crown and roots, followed by nematode extraction. Morphological characterization was conducted to identify nematodes based on microscopic diagnostic features. The findings indicated that symptomatic plants exhibited stunting, chlorosis, wilting, and root damage. Parasitic nematodes were consistently detected with varying population densities across sampling points, alongside the presence of several nematode groups identified through morphological characteristics. In the global trend analysis section, a literature search was performed using Scopus (2019–2025), resulting in 192 selected articles after screening. Thematic analysis revealed that global PPN research is predominantly focused on taxonomy and biodiversity and management themes, whereas diagnosis, detection, and specific studies on shallots remain limited. The integration of local findings and global trends underscores the urgency of enhancing PPN diagnosis in shallots and highlights the necessity for further research through molecular identification and the development of sustainable, commodity-specific management strategies.