Morphological and molecular characterisation of Aphelenchoides besseyi and A. fujianensis (Nematoda: Aphelenchoididae) from rice and forage grass seeds in Brazil

Abstract

Morphologically similarAphelenchoidesspp. populations extracted from rice and forage grass seeds from different geographical regions in Brazil were morphologically and molecularly characterised. Overall, the populations studied separated into two groups based on morphological and phylogenetic analyses, referred to herein as ‘Group-rice’ and ‘Group-forage’. Bayesian phylogenetic analyses of SSU, LSU and mtCOI regions strongly supported the presence of two dichotomous groups with Group-rice and Group-forage populations genetically similar toA. besseyiandA. fujianensis, respectively. This study reports the presence of a morphologically similar species toA. besseyiassociated with seeds of grasses, but genetically distinct based on three genomic regions, which our results strongly suggest to beA. fujianensis, this being a new geographical record for Brazil. Additional information regarding spicule morphology of maleA. besseyiis also reported.

Population structure and species delimitation of rice white tip nematode, Aphelenchoides besseyi (Nematoda: Aphelenchoididae), in China

“…The acquired COI phylogeny concurred with previous studies (de Jesus et al , ) in general topologies and supportive values. Two similar species, Aphelenchoides fujianensis and A. besseyi , appear to be polyphyletic.…”

“…In the present study, molecular species delimitation methods were applied to the genus Aphelenchoides and the results suggest a remarkably high diversity of 13, 17 and 19 species in the analysed dataset. De Jesus et al () divided populations of two similar species of A. besseyi and A. fujianensis into Group‐forage and Group‐rice based on a comprehensive morphological, morphometric and molecular analysis, and considered that the populations in each group represented only one species (Group‐forage as A. fujianensis and Group‐rice as A. besseyi ). Recently, Oliveira et al () assigned some of A. fujianensis and A. besseyi as a new species A. pseudogoodeyi.…”

“…Aphelenchoides are notorious for taxonomical confusions due to their difficult morphology and the coexistence of similar species in the same sample (Hockland, ; de Jesus et al , ). The COI ‐based phylogeny in this study confirms the problematic phylogenetic placements and the polyphyletic status of A. besseyi .…”

A Rapid Diagnostic for Detection ofAphelenchoides besseyiandA. fujianensisBased on Real-Time PCR

“…Nematode and DNA extraction. Nematodes were extracted from forage grass and rice seed from disparate geographic areas (Table 1) according to Coolen and D'Herde (1972), or cultivated in vitro (de Jesus et al 2016). DNA was extracted from single nematodes.…”

“…This was recently underscored by de Jesus et al (2016), who reported that, in Brazil, A. fujianensis Zhou et al 2010 had occasionally been mistakenly identified as A. besseyi and that both species were associated with Brazilian forage seed. This reinforces the urgent need for robust methods of diagnosis, because there is no direct evidence suggesting that A. fujianensis is a plant-parasitic species (de Jesus et al 2016) and forage seed consignments may unnecessarily be rejected for export based on species misidentification.…”