Detection of root-knot nematode disease in cucumber under protected cultivation in Kumaon region

Abstract

The increasing adoption of protected cultivation in India has led to significant challenges, one of the most serious being the infestation of root-knot nematodes (RKNs), particularly Meloidogyne spp., which threaten sustainable vegetable production. Despite its importance, limited attention has been given to the identification and characterization of RKNs under protected cultivation in hilly regions. Addressing this gap, the present study was undertaken to investigate the RKN populations affecting cucumber crops grown under polyhouse conditions in the Kumaon hills of Uttarakhand, a part of the Indian Himalayan region. A field survey was conducted during 2021–2022 in farmers' polyhouses growing cucumbers. Random sampling was employed by dividing each polyhouse into four units to assess spatial variability in nematode distribution. Integrative taxonomic methods were used, combining symptomatology, morphometric analysis, and molecular identification. Morphological characterization was performed on males, second-stage juveniles (J2), and adult females, with detailed morphometric measurements at various stages. Molecular identification involved amplification and sequencing of the rDNA ITS region. Phylogenetic analysis revealed that the ITS sequence obtained formed a distinct clade, closely related to the Meloidogyne incognita isolate OP030611.1. This study provides the first authentic characterization and report of M. incognita infecting cucumber under protected cultivation in the hilly terrain of Uttarakhand. The findings offer valuable insights into the nematode's occurrence and distribution in the mid-Indian Himalayan region. The study highlights the need for regular surveillance and monitoring of RKN populations to inform integrated nematode management strategies and ensure the sustainability of cucumber production under protected conditions.