Pratylenchus brachyurus is the prevalent root-lesion nematode in brazilian soybean fields, occurring singly and in mixed populations with P. zeae, P. penetrans, and P. brasiliensis

Abstract

Root-lesion nematodes of the genus Pratylenchus are among the most economically important plant parasitic nematodes of soybean worldwide, yet their species diversity, distribution, and the genetic structure of the populations remain poorly resolved in Brazil. To address this knowledge gap, this study aimed to characterize the diversity, distribution, and genetic variation of Pratylenchus spp. associated with soybean in Brazil and evaluate soybean cultivar responses to the prevalent species. The study combined extensive field sampling with phylogenetic analyses based on independent molecular markers, morphological and morphometric characterization, and host-response assays. Soybean roots and rhizosphere soil were collected from 309 commercial fields across 16 major soybean-producing states. Pratylenchus spp. were detected in 95.8% (296/309) of the fields, from which 367 pure populations were established. This higher number reflects the separation of distinct morphotypes/species recovered from the same field samples. Sequencing of the D2–D3 expansion segments of 28S rDNA, Internal Transcribed Spacer rDNA, and partial mitochondrial Cytochrome c Oxidase subunit I revealed four species associated with soybean: P. brachyurus (detected in 292 fields), P. zeae (73 fields), P. brasiliensis (six fields), and P. penetrans (one field). This is the first report of P. penetrans associated with soybean in Brazil. Mixed-species infestations were detected in 72 fields, predominantly involving P. brachyurus and P. zeae . Three-species co-occurrence ( P. brachyurus , P. zeae , and P. penetrans ) was detected in one field. There was substantial intraspecific phylogenetic variation in P. brachyurus and P. zeae . Morphological and morphometric analyses largely corroborated molecular identification but highlighted persistent diagnostic overlap between P. penetrans and P. brasiliensis . Reproduction factors were highest for P. brasiliensis (Rf = 4.66–10.84) and P. brachyurus (Rf = 3.33–11.44), whereas P. zeae showed low Rf values (0.06–0.27). All soybean cultivars were susceptible to P. brachyurus and P. brasiliensis (Rf > 1.0) with the highest values estimated for ‘TMG 2833’ and ‘BMX Domínio’. Pratylenchus populations associated with soybean in Brazil are more taxonomically and genetically diverse than previously documented and the absence of effective resistance among current cultivars underscores the need for integrative diagnostics and region-specific management strategies that consider mixed infestations and genetically structured populations.