Abstract
Abstract Pratylenchus species are among the most common plant parasitic nematodes in the Great Plains Region of North America. Our goal was to survey Pratylenchus species diversity across the Great Plains region using a mitochondrial COI DNA barcode. The objectives were to (i) determine species boundaries of the common Pratylenchus species within the region, (ii) assess the host associations of the barcoded Pratylenchus specimens, and (iii) determine Pratylenchus distribution patterns throughout the region. A total of 860 soil samples, primarily associated with eight major crops, were collected from Colorado, Kansas, Montana, Nebraska, North Dakota, and Wyoming. From this total, 246 soil samples provided the majority of 915 individual nematode specimens that were amplified by PCR and sequenced for a 727 to 739 bp region of COI. Maximum likelihood, neighbor-joining, and Bayesian phylogenetic trees all recognized 19 distinct and well-supported haplotype groups. The most common and widespread haplotype group, representing 53% of all specimens was P. neglectus, detected from 178 fields in 100 counties and associated with fields growing wheat, corn, dry beans, barley, alfalfa, sugar beets, potatoes, and a vineyard. The second most prevalent haplotype group was P. scribneri, representing 30% of all specimens and recovered from 104 fields in 45 counties, and most frequently associated with corn. Mixed field populations were encountered in approximately 20% of infested fields, with P. neglectus and P. scribneri most often occurring together in corn-soybean cropping systems. Less frequently encountered from the region were P. hexincisus, P. thornei, P. penetrans, P. alleni, and P. zeae. Eight additional haplotype groups, potentially new Pratylenchus species, were discovered in the survey.
Highlights
Global estimates indicate that there are approximately 100 described species in the genus Pratylenchus Filipjev, 1936 (Janssen et al, 2017; Singh et al, 2018)
Neighbor-joining, and Bayesian phylogenetic trees each identified 19 distinct cytochrome oxidase subunit 1 (COI) haplotype groups that were wellsupported by bootstrap values (BS: 96-100% based on tree construction method), intra- vs interspecific genetic distance and posterior probabilities (PP:100 for all groups) (Fig. 2)
These haplotype groups were tentatively labeled as P. neglectus, P. scribneri, P. thornei, P. hexincisus, P. alleni, P. penetrans, P. zeae Graham, 1951, P. crenatus Loof, 1960, P. vulnus Allen & Jensen, 1951, Pratylenchus sp. 1 to sp. 10, including one unnamed singleton, nematode identification (NID) 6402 from
Summary
Global estimates indicate that there are approximately 100 described species in the genus Pratylenchus Filipjev, 1936 (Janssen et al, 2017; Singh et al, 2018). 27 of these species have been reported from North America by Castillo and Vovlas (2007) This number has increased to 29 with the descriptions of P. floridensis De Luca, Troccoli, Duncan, Subbotin, Waeyenberge, Moens & Inserra, 2010 and P. parafloridensis De Luca, Troccoli, Duncan, Subbotin, Waeyenberge, Moens & Inserra, 2010. Root lesion nematodes in the genus Pratylenchus are migratory, intercellular endoparasites that penetrate the root of the host plants and feed and reproduce within the root epidermis and cortex. This feeding behavior results in root lesions that enhance fungal and bacterial infection, secondarily contributing to yield and economic losses in agricultural production (Jones et al, 2013; Smiley, 2015). Many Pratylenchus species exhibit a preference for sandy soils with a relatively high level of oxygen (Castillo and Vovlas, 2007; Olabiyi et al, 2009)
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