Identification and reproduction of dagger nematode (Xiphinema americanum) in potato

Authors: GORAYA, MANKANWAL - North Dakota State University; YAN, GUIPING - North Dakota State University; PLAISANCE, ADDISON - North Dakota State University; Handoo, Zafar

Submitted to: Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2023
Publication Date: 9/29/2023
Citation: Goraya, M., Yan, G., Plaisance, A., Handoo, Z.A. 2023. Identification and reproduction of dagger nematode (Xiphinema americanum) in potato. Nematology. 25(9):1-13.

Interpretive Summary: Plant-parasitic nematodes are microscopic worms that feed on plants and cause an estimated ten billion dollars of crop losses each year in the United States and 173 billion dollars globally. Dagger nematode (Xiphenema) species belong to a group of nematodes that are of importance to agriculture as plant parasites, causing damage to host plants due to direct feeding on root cells, as well as vectors of plant viruses. In this study, dagger nematode species were identified by both molecular and morphological means and evaluated for reproduction potential in commonly grown potato cultivars. One species identified was Xiphenema americanum. It was discovered that yellow potato cultivars exhibited a significantly higher reproductive factor (RF) than White and Russet types on this nematode. Cultivar Soraya increased population density whereas cultivars Ranger Russet, Manistee, Kennebec, Russet Norkotah 278, Modoc, Pomerelle Russet, and Dakota Rose reduced the nematode reproduction in both trials. This discovery is significant because this is the first research study demonstrating the reproduction of X. americanum in commonly grown potato cultivars and could be helpful to manage dagger nematode diseases. In addition, new molecular and morphological information obtained for this dagger nematode species will facilitate future identifications of this nematode. Therefore, this research will be used by scientists, diagnosticians, growers, action agencies, and extension agencies involved in nematode research and control.

Technical Abstract: Plant-parasitic nematodes limit potato production by feeding on roots, reducing tuber yield and quality, and resulting in poor growth. In North Dakota potato fields, Xiphinema spp. (dagger nematode) was found. Even in low numbers, the dagger nematode poses a significant threat to the crop. In this study, the dagger nematode species was identified and its reproduction potential in commonly grown potato cultivars was evaluated. At molecular level D2-D3 of 28S ribosomal DNA (rDNA) and internal transcribed spacer (ITS) rDNA were targeted. Sequencing data of D2-D3 of 28S rDNA region (749 bp) showed 98.18% similarity with three isolates of Xiphinema americanum. Also, ITS rDNA sequence (860 bp) analysis showed a 97.68% similarity with a UK isolate of X. americanum and a very low similarity with other species of Xiphinema. The sequence analysis revealed that X. americanum is present in North Dakota fields. Further dagger nematode species confirmation as X. americanum was done by morphometric measurements. Using naturally infested soil, two greenhouse experiments were conducted to evaluate the reproduction rate of X. americanum on 21 potato cultivars belonging to four distinct market classes (Yellow, Red, White, and Russet). The reproduction rates were observed to vary among potato cultivars. Yellow cultivars exhibited a significantly higher reproductive factor (RF) than White and Russet types. Soraya increased X. americanum population density whereas Ranger Russet, Manistee, Kennebec, Russet Norkotah 278, Modoc, Pomerelle Russet, and Dakota Rose reduced the nematode reproduction in both trials. This is the first research study demonstrating the reproduction of X. americanum in commonly grown potato cultivars and could be helpful to manage dagger nematode diseases.