Occurrence of plant-parasitic nematodes in sugarbeet fields of North Dakota and Minnesota

Abstract

Plant-parasitic nematodes (PPNs) are an important group of pathogens on sugarbeet. Surveys were conducted in the Red River Valley (RRV) area of North Dakota (ND) and Minnesota (MN) to determine the incidence, abundance, and distribution of PPNs in sugarbeet fields. A total of 217 soil samples were collected in 2016 and 2017 from fields with sugarbeet or a history of sugarbeet production. In addition, 48 samples were collected in 2016 from tare soils in sugarbeet piling stations, and two samples were collected in 2017 from sugarbeet production fields in eastern Montana (MT) and western ND border area. The incidence and abundance of major genera of PPNs identified from sugarbeet production fields in 2016 and 2017 were: Heterodera (incidence = 15%, abundance = 1,351/200 gm of soil); Helicotylenchus (38%, 157); Tylenchorhynchus (37%, 121); Paratylenchus (28%, 108); Pratylenchus (6%, 38); Paratrichodorus (7%, 37); Xiphinema (3%, 32); and Hoplolaimus (0.4%, 20). Helicotylenchus, Tylenchorhynchus, Paratylenchus, and Heterodera were the most frequent and widely distributed nematode genera whereas, Paratrichodorus and Pratylenchus were found less frequently and at low densities. Xiphinema and Hoplolaimus were rarely detected at lower densities. Paratylenchus and Tylenchorhynchus were widely distributed in most of the sampled counties (n = 11), followed by Helicotylenchus (10), Heterodera (8), Pratylenchus (8), Xiphinema (4), Paratrichodorus (3), and Hoplolaimus (1). Species-specific PCR assays and direct sequencing of ribosomal DNA were conducted to identify species. Species identification revealed that the cyst nematodes from one of the counties in eastern MT were Heterodera schachtii and the cyst nematodes analyzed from 31 samples in 12 counties in ND and MN were H. glycines. We have not identified any H. schachtii thus far from surveyed samples in eastern ND and western MN. Other nematode species identified include Paratrichodorus allius, Pratylenchus neglectus, Tylenchorhynchus sp., Paratylenchus nanus, Helicotylenchus microlobus, and H. pseudorobustus. Accurate identification of these nematodes and awareness of their occurrence across the region is essential for developing effective pest management strategies for improved sugarbeet production.