Molecular Identification and Phylogeographic Analysis of Heterodera schachtii Populations Infesting Sugar Beet

Abstract

Sugar beet production is severely constrained by the sugar beet cyst nematode, Heterodera schachtii, which causes substantial yield and quality losses across temperate agroecosystems. The present study focuses on molecular identification and phylogeographic analysis of H. schachtii populations collected from major sugar beet-growing regions. Soil and root samples exhibiting typical cyst formation and poor plant vigor were processed for nematode extraction and morphological confirmation based on cyst shape, stylet morphology, and second-stage juvenile characteristics. Molecular identification was carried out using ITS rDNA and mitochondrial COI gene sequencing, confirming the presence of H. schachtii across all sampled locations. Sequence alignment and phylogenetic reconstruction revealed clear clustering of populations into distinct haplotypes, indicating moderate genetic variability among geographically separated isolates. Phylogeographic analysis suggested limited gene flow between distant populations, likely influenced by restricted nematode movement and localized agricultural practices. However, evidence of shared haplotypes across regions indicated possible anthropogenic dissemination through contaminated soil, irrigation water, or planting material. Population genetic indices showed low to moderate differentiation, suggesting both historical connectivity and ongoing isolation processes. Environmental association analysis indicated that sandy loam soils and cooler temperatures favored higher nematode incidence and reproduction rates. The study underscores the importance of integrating molecular tools with spatial analysis to understand the distribution and evolutionary dynamics of H. schachtii. These findings provide valuable insights into the epidemiology of sugar beet cyst nematode populations and support the development of region-specific management strategies, including crop rotation, resistant cultivars, and sanitation practices. Overall, the results contribute to a better understanding of nematode diversity and dispersal patterns in sugar beet agroecosystems.