|dc.description.abstract||Meloidogyne is a destructive nematode genus parasitising crops worldwide. Meloidogyne arenaria, M. hapla, M. incognita and M. javanica are listed as the economically most important species, but M. enterolobii is considered a virulent and emerging threat. No comprehensive molecular and/or morphological knowledge exists for local M. enterolobii populations. Subsequently, the aims of this study were to: 1) identify Meloidogyne spp. from 37 populations sampled from local crop production areas using morphological and morphometrical techniques, 2) verify the identity of the populations using molecular techniques, 3) evaluate the genetic diversity of thermophilic species using genotyping by sequencing (GBS) and 4) assess the reproduction potential of selected populations. Meloidogyne spp. viz. M. enterolobii, M. javanica, M. incognita and M. hapla (in descending order of occurrence) were identified using both classical (Aim 1) and molecular techniques (Aim 2). Large phasmids (surrounded by fine striae), fine striae on lateral sides of the vulva and the presence of atypical perineal-patterns (medium to high square-like dorsal arches) present on perineal-patterns of M. enterolobii females allowed initial differentiation of the species from its thermophilic counterparts. Molecular assays (Aim 2) using the sequence characterised amplified region – polymerase chain reaction (SCAR-PCR) technique verified results from the classical study. However, the D2-D3 28S rDNA, COI and COII/16S genes identified M. enterolobii only, while, the NADH5 gene discriminated among M. enterolobii, M. incognita and M. javanica. Dry bean, spinach, groundnut, lII eggplant, and lettuce are first reports to host South African M. enterolobii populations, while the presence of this species in the North West and Northern Cape provinces is another first report.
Using GBS (Aim 3), 653 common single nucleotide polymorphisms (SNPs) were identified. Principal component and phylogenetic analyses placed all M. enterolobii populations in one clade and M. javanica populations in another. Meloidogyne incognita populations formed an intermediate clade between these species, confirming its genetic linkage with them. Alleles present only in the genome of M. enterolobii and located in genes involved in virulence in other animal species, have been identified and represents another first report. Substantial variation was evident in the injuriousness within and among the 11 selected populations (Aim 4). A mixed population of M. enterolobii and M. javanica (P29; Rf = 15.7) and a single-species population of M. javanica (P28; Rf: 19.1) had the highest reproduction potentials for the initial and repeat experiments, respectively. A single population of M. enterolobii (P1) was the second most injurious for the initial (Rf = 8.2) and repeat (Rf = 13.7) experiments. By contrast, another single-species population of M. enterolobii (P21) had the lowest reproduction potential for both experiments. Using various classical and molecular techniques shed light on the identity, genetic composition and reproduction potential of South African M. enterolobii populations compared to its thermophilic counterparts. Ultimately, valuable and novel knowledge has been generated which is crucial for the management of Meloidogyne spp.||en_US