Aphelenchoides besseyi Causing Green Stem and Foliar Retention Syndrome on Soybean Major Production Fields Across China

Soybean ( Glycine max ) is an important global protein source for human as well as livestock nutrition. Aphelenchoides besseyi represents a globally significant phytopathological constraint on economically relevant agricultural commodity production. This nematode species is specifically correlated with the manifestation of Green Stem and Foliar Retention (GSFR) syndrome in soybean. A major epidemiological outbreak of this syndrome, documented in Brazil in 2017, resulted in quantifiable crop yield losses approaching 60%. Initially, A. besseyi was provisionally designated as the aetiological agent. However, subsequent taxonomic revision reclassified the definitive causative organism of the GSFR syndrome as A. pseudobesseyi . To investigate the association of Aphelenchoides nematodes with the GSFR syndrome in China, 44 symptomatic soybean specimens were collected from different commercial fields during their reproductive phases (R1–R8). Nematodes isolated from the specimens subsequently underwent morphobiometric and molecular identification. Morphological and morphometric results aligned with previous findings for A. besseyi species complex. Phylogenetic examinations using three genomic regions (ITS, COI and 18S rRNA) placed the 36 verified isolates in the main race of A. besseyi . Greenhouse inoculation assays successfully reproduced the characteristic symptoms of the GSFR syndrome, a finding substantiated by pathological, morphometric and molecular evidence. This asserts for the first time that A. besseyi is the causal agent of GSFR syndrome in Chinese soybean fields, thus expanding the confirmed host range of this economically important nematode to include soybean.