Identification and reproduction of dagger nematode, Xiphinema americanum, in potato

Summary Plant-parasitic nematodes limit potato production by feeding on roots, reducing tuber yield and quality, and resulting in poor growth. Dagger nematodes ( Xiphinema spp.) can pose a significant threat to crop production even in low numbers. Dagger nematodes have been reported in North Dakota, USA, potato fields. In this study, a dagger nematode species was identified and its reproduction potential in 21 potato cultivars was evaluated. The dagger nematode was identified as X. americanum via morphometric measurements and DNA sequence analysis. At the molecular level, D2-D3 of 28S ribosomal RNA (rRNA) and internal transcribed spacer (ITS)-regions of rDNA were targeted. Sequencing data of D2-D3 (749 bp) showed 98.18% similarity with three isolates of X. americanum . ITS sequence (860 bp) analysis showed 97.68% similarity with an isolate of X. americanum but lower similarity with other species of Xiphinema . The phylogenetic analysis of ITS region further confirmed the species of dagger nematode as X. americanum . Using naturally infested soil, two glasshouse experiments were conducted to assess the reproduction rate of X. americanum on 21 potato cultivars belonging to four distinct market potato classes (yellow, red, white and russet). The reproduction rates were found to vary among the potato classes and cultivars. Numerically, X. americanum population density was higher in ‘Soraya’, whereas ‘Ranger Russet’, ‘Manistee’, ‘Kennebec’, ‘Russet Norkotah 278’, ‘Modoc’, ‘Pomerelle Russet’ and ‘Dakota Rose’ reduced nematode reproduction in both trials. This is the first study demonstrating the reproduction of X. americanum in potato cultivars and could be helpful to manage dagger nematodes.