Morphological and molecular characterisation of one new and several known species of the reniform nematode, Rotylenchulus Linford & Oliveira, 1940 (Hoplolaimidae: Rotylenchulinae), and a phylogeny of the genus

Abstract

The reniform nematodes of the genusRotylenchulusare semi-endoparasites of numerous herbaceous and woody plant roots and are mainly distributed in tropical and subtropical regions. In this study, we provide morphological and molecular characterisation of six out of ten presently known valid species ofRotylenchulus:R. clavicaudatus,R. leptus,R. macrodoratus,R. macrosoma,R. reniformisandR. saccharifrom South Africa, USA, Italy and Spain.Rotylenchulus parvuswas only studied morphologically. A new species,R. macrosomoidessp. n., isolated from soil and roots of sugarcane in South Africa, is described. The phylogeny ofRotylenchulus, as inferred from the analyses of D2-D3 of 28S rRNA, ITS rRNA,coxImtDNA andhsp90gene sequences, is presented. The study revealed thatR. reniformisandR. macrosomahave a sister relationship, but that relationships between otherRotylenchulusspecies remain unresolved. The phylogenetic analysis also confirmed the hypothesis that this genus originated from the Afrotropical zoogeographical region. Our study revealed thatR. reniformisandR. macrosomoidessp. n. have two distinct rRNA gene types andR. macrosomahave three rRNA gene types in their genomes. PCR with species-specific primers was developed for rapid diagnostics ofR. reniformis.

Plant-parasitic nematodes associated with sugarcane in Kilimanjaro, Tanzania

“…An alternative explanation to the high sequence variations in R. parvus could be the existence of two distinct types of rRNA operons as was found in at least three other Rotylenchulus spp. ( Nyaku, Kantety, Tilahun, Lawrence, Soliman, Cebert, and Sharma 2013; Nyaku, Sripathi, Kantety, Gu, Lawrence and Sharma, 2013 ; Van den Berg et al, 2016 ). However, this hypothesis is not supported by the independent COI analyses, unless a remarkably high intraspecific COI variability or the presence of two distinct mitochondrial genomes within R. parvus is also assumed.…”

Anatomical Alterations in Plant Tissues Induced by Plant-Parasitic Nematodes

“…However, this response seems to be mediated by characteristics of the host or root, because uninucleate GCs originating from a cortical cell and extending from the cortex into the stele have also been observed in thick roots infected by R. macrodoratus or in different host species by R. borealis (Inserra and Vovlas, 1980 ; Vovlas et al, 1985 ). Nevertheless, in wild and cultivated olives, both types of cell response can be induced by R. macrodoratus and R. macrosoma (Castillo et al, 2003b ; Van Den Berg et al, 2016 ). Rotylenchus reniformis could also parasitize cells in the cortex, through formation of a connection to the stele, similar to R. macrodoratus or R. borealis , but this does not appear to be associated with root diameter.…”

Global Distribution of the Reniform Nematode Genus Rotylenchulus with the Synonymy of Rotylenchulus macrosoma with Rotylenchulus borealis

“…Reniform nematodes of the genus Rotylenchulus are an economically important polyphagous group of highly adapted obligate plant parasites that parasitize numerous plants and crops usually associated with temperate, subtropical, and tropical climates [ 1 ]. The genus Rotylenchulus Linford and Oliveira [ 2 ] comprise 11 valid species; some of them are distributed worldwide, whereas others have shown a limited distribution [ 1 , 3 , 4 ]. This genus has been reported in 77 countries of Africa, Asia, Europe, North and South America, and Australia [ 1 , 3 , 4 ].…”

“…The genus Rotylenchulus Linford and Oliveira [ 2 ] comprise 11 valid species; some of them are distributed worldwide, whereas others have shown a limited distribution [ 1 , 3 , 4 ]. This genus has been reported in 77 countries of Africa, Asia, Europe, North and South America, and Australia [ 1 , 3 , 4 ]. The influence of future global climate change could shorten the life cycle of these nematodes and may expand the distribution of well-adapted species to drought conditions [ 5 , 6 ].…”

“…Rotylenchulus spp. show high intraspecific variability of some morphological diagnostic features in immature females (the developmental stage usually employed for species identification) [ 3 ], and for this reason, it is necessary to use molecular markers for precise species identification. In this regard, the use of rRNA markers is challenging due to the previously noted presence of several gene copies that are not well homogenized in the genome, and for this reason, several different amplicon sizes and associated sequences can be observed [ 4 ].…”