Diversity of Meloidogyne spp. from peri-urban areas of sub-Saharan Africa and their genetic similarity with populations from the Latin America

Abstract

A B S T R A C TIn Africa, peri-urban vegetable production systems supply perishable vegetables to the rapidly expanding urban centers. These highly intensive systems are characterized by high levels of pests and diseases and an excessive use of synthetic pesticides to reduce their population densities. Root-knot nematodes (RKN) are especially prevalent in these systems but are often not recognized, or diagnosed correctly. The limited ability to accurately identify these pathogens likely results in the inappropriate use and misuse of control measures, such as genetic resistance, crop rotation, or synthetic chemicals. Given the perceived importance of RKN, a species characterization study was conducted in peri-urban vegetable (amaranthus, cabbage, pepper, carrot, cassava, eggplant, okra, tomato) fields and some coffee plantations, in Benin, Kenya, Nigeria, Tanzania and Uganda. Meloidogyne spp. were characterized from 143 field samples using esterase phenotypes (EST) and SCAR markers. Five known species were identified: three phenotypes for M. javanica populations (EST J3, Rm: 1.0, 1.25, 1.4; EST J2a, Rm: 1.0, 1.4; EST J2b, Rm: 1.0, 1.25), two for M. incognita (EST I1, Rm: 1.0; EST I2, Rm: 1.05, 1.0), one for M. arenaria (EST A2, Rm: 1.2, 1.3), one for M. enterolobii (EST E4, Rm: 0.70, 0.75, 0.90, 0.95), one for M. izalcoensis (EST I4 Rm: 0.86, 0.96, 1.24, 1.30) and two unusual esterase phenotypes for two unknown species, named Meloidogyne sp.1 and sp.2. Combinations of species were detected from numerous locations. Genetic diversity was further studied using RAPD primers, by comparing a subset of the sampled populations from Africa and some populations from Brazil and El Salvador. The analysis identified separate clusters of the more common and minor species, with low variability observed for African and American populations. The SCAR markers correctly identified all Meloidogyne species with the exception of M. ethiopica, Meloidogyne sp.1 and Meloidogyne sp.2. For Meloidogyne sp.1, the SCAR markers corresponded wrongly to M. javanica and M. arenaria, and for Meloidogyne sp.2 to M. incognita. This demonstrates the shortcomings of using SCAR markers alone, which can generate erroneous results for RKN species. Further morphological and molecular studies are required to clarify the identity of these two atypical species.

Popular Biofortified Cassava Cultivars Are Heavily Impacted by Plant Parasitic Nematodes, Especially Meloidogyne Spp.

“…In the current study, the Meloidogyne spp. were not identified to species level, although it is likely that M. javanica and/or M. incognita were present, both of which are common to the region [ 33 ] and are the two most commonly occurring Meloidogyne spp. found infecting cassava [ 23 ].…”

Host status of Bambara groundnut accessions to Meloidogyne incognita using conventional screenhouse and novel seedling pouch methods

“…A population of M. incognita originally isolated from tomato in Nigeria and identified using perineal pattern and isozyme techniques (dos Santos et al, 2019) was used in the study. Pure cultures, derived from a single egg mass population, were maintained in the screenhouse on cockscomb (Celosia argentea) and tomato (Solanum lycopersicum).…”

Detection of Root-Knot Nematode Meloidogyne luci Infestation of Potato Tubers Using Hyperspectral Remote Sensing and Real-Time PCR Molecular Methods

“…A promising approach for molecular identification of M. luci and other tropical RKN species was demonstrated by [34], using a DNA barcoding approach with six mtDNA genes, but the method has so far not been adopted in diagnostic laboratories. A species-specific SCAR marker was developed for M. ethiopica, a sister species of M. luci [35], but this diagnostic method was not shown to be reliable and reproducible [36,37]. In contrast, M. luci can be detected with a PCR method using a primer pair specific for the Meloidogyne ethiopica group (MEG), i.e., for the three closely related and similar species M. ethiopica, M. luci, and M. inornata.…”