Search Results (7)

Plant-parasitic nematodes (PPNs) cause yield losses in various crops worldwide. Damage due to PPNs can be severe, causing billions of dollars of crop losses across the globe annually. Information about PPNs occurrence in Mozambique is limited. Based on the literature, twenty-five genera of PPNs have been reported to affect several economically important crops, including root-knot nematodes (RKNs, Meloidogyne spp.), Scutellonema spp., root-lesion nematodes (RLNs, Pratylenchus spp.), spiral nematodes (Helicotylenchus spp.), and the dagger nematode (Xiphinema spp.), which are commonly associated with crops such as banana (Musa spp.), cassava (Manihot esculenta), cowpea (Vigna unguiculata), maize (Zea mays), sugarcane (Saccharum officinarum), and sunflower (Helianthus annuus). Dissemination of these nematodes is not yet fully understood, but the importation of plants, roots, rhizomes, and/or seeds likely contributes to the introduction and spread of PPNs. Although the implementation of PPN-mitigation strategies is crucial to crop production, their application is still limited in Mozambique, with quite a few reported uses of nematicides in the Manica and Maputo provinces. Therefore, adopting integrated management strategies that combine two or more practices, such as biological control, crop rotation, organic amendments, soil solarization, and, as a last resort, chemical nematicides, may be an option to effectively reduce the population of PPNs. This review gathers information on the occurrence and management of PPNs, as reported to date in Mozambique. Full article

Grapevine viruses reduce harvests and degrade fruit quality, but their genetic diversity in Kazakhstan has remained unexplored. We collected symptomatic leaves from local vineyards and recovered eleven fragments of the coat-protein gene: one from grapevine fanleaf virus, five from grapevine virus A, and five from grapevine leafroll-associated virus 3. After Sanger sequencing, we compared these fragments with more than one thousand international counterparts to place the Kazakh strains on the global family tree. The results reveal a clear spectrum of genetic diversity that mirrors each virus’s route of spread. Grapevine virus A, which is moved both mechanically and by insects, proved the most variable; grapevine fanleaf virus, carried by dagger nematodes and pruning sap, had intermediate variability; and grapevine leafroll-associated virus 3, moved only by mealybugs and scales, was highly conserved. All Kazakh sequences fell inside established foreign lineages, showing that the viruses were imported multiple times rather than evolving locally. Grapevine virus A will require broad-coverage or multiplex PCR primers to avoid false negatives, whereas the stable leafroll virus can be monitored with a single high-sensitivity assay. Combined with vector management—mealybug control for leafroll, and nematode testing for fanleaf—these data lay the groundwork for a national clean-plant program and more resilient vineyards across Central Asia. Full article

Xiphinema israeliae has been reported in the rhizosphere of olives in Crete, Greece. Attempts were made to culture this nematode in pots planted with olive and fig seedlings, using Xiphinema index as a control. In these conditions, X. index showed a high reproduction rate on fig in a few months and none on olive. The experiments with X. israeliae indicated that olive and fig are suitable hosts for this dagger nematode, since juveniles of various life stages were found in plants inoculated exclusively with females, although the rate of nematode reproduction was low. Xiphinema israeliae was proved to have a parthenogenetic reproduction and a long life cycle, from female to female, taking more than nine months at a 24–26 °C temperature to complete. Therefore, a quite long period, even a few years, may be necessary to obtain a high number of nematodes in pots under experimental conditions. In contrast, Xiphinema italiae did not reproduce on olive and fig after a seven-month period. Accordingly, to our knowledge, this study increases the host range and knowledge about the culturing of these species, as only seven species of Xiphinema have been successfully cultured in pots till now. The potential of fig and olive for culturing X. israeliae gives an opportunity for further studies of its biology and host range. Full article

Turfloop constitutes an area in Mankweng, situated in the Limpopo Province of South Africa, where several villages are home to smallholder farmers who specialize in vegetable farming. Among the most crucial crops cultivated in this region is tomato, a fruit that has gained significant commercial importance due to its high demand and versatility in various culinary applications. To determine the relationship of plant-parasitic nematodes and soil physicochemical properties, soil samples were collected from tomato fields. Overall, our results showed that seven nematode genera were in the tomato fields. There was a significant positive correlation between the number of Meloidogyne and potassium (r = 0.903) and a negative correlation with Na (r = −0.684). In contrast, there was no association between the number of Meloidogyne spp. and the pH and texture of the fields. The number of Criconema in the field was negatively correlated with pH (r = −0.732). Soil texture percentages, including clay (r = 0.744), sand (r = −0.744), and silt (r = 0.706), were only correlated with the number of Criconema. The number of dagger nematodes, Xiphinema, was only correlated negatively with NH₄⁺ (r = −0.589) and positively with boron (B) (r = 0.779). None of the soil variables were correlated with the number of Pratylenchus. The principal component analysis (PCA) placed soil samples of tomatoes together, in which the number of Meloidogyne was not correlated to any soil sample site. In conclusion, plant-parasitic nematodes that were associated with tomatoes are of high economic importance as they can reduce the yield. Criconema was found to be sensitive to the soil’s physicochemical properties. In addition, Helicotylenchus was found in all soil samples. Our results suggest that the plant-parasitic nematodes in tomatoes have high diversity with the potential to reduce crop production. Full article

Dagger nematodes of the genus Xiphinema include a remarkable group of invertebrates of the phylum Nematoda comprising ectoparasitic animals of many wild and cultivated plants. Damage is caused by direct feeding on root cells and by vectoring nepoviruses that cause diseases on several crops. Precise identification of Xiphinema species is critical for launching appropriate control measures. We deciphered the cryptic diversity of the Xiphinema hispanum-species complex applying integrative taxonomical approaches that allowed us to verify a paradigmatic example of the morphostatic speciation and the description of a new species, Xiphinema malaka sp. nov. Detailed morphological, morphometrical, multivariate and genetic studies were carried out, and mitochondrial and nuclear haploweb analyses were used for species delimitation of this group. The new species belongs to morphospecies Group 5 from the Xiphinema nonamericanum-group species. D2-D3, ITS1, partial 18S, and partial coxI regions were used for inferring the phylogenetic relationships of X. malaka sp. nov. with other species within the genus Xiphinema. Molecular analyses showed a clear species differentiation not paralleled in morphology and morphometry, reflecting a clear morphostatic speciation. These results support the hypothesis that the biodiversity of dagger nematodes in southern Europe is greater than previously assumed. Full article

Upon pathogen attack, plants very quickly undergo rather complex physico-chemical changes, such as the production of new chemicals or alterations in membrane and cell wall properties, to reduce disease damages. An underestimated threat is represented by root parasitic nematodes. In Vitis vinifera L., the nematode Xiphinema index is the unique vector of Grapevine fanleaf virus, responsible for fanleaf degeneration, one of the most widespread and economically damaging diseases worldwide. The aim of this study was to investigate changes in the emission of biogenic volatile organic compounds (BVOCs) in grapevines attacked by X. index. BVOCs play a role in plant defensive mechanisms and are synthetized in response to biotic damages. In our study, the BVOC profile was altered by the nematode feeding process. We found a decrease in β-ocimene and limonene monoterpene emissions, as well as an increase in α-farnesene and α-bergamotene sesquiterpene emissions in nematode-treated plants. Moreover, we evaluated the PR1 gene expression. The transcript level of PR1 gene was higher in the nematode-wounded roots, while in the leaf tissues it showed a lower expression compared to control grapevines. Full article

Grapevine fanleaf virus (GFLV) and arabis mosaic virus (ArMV) are nepoviruses responsible for grapevine degeneration. They are specifically transmitted from grapevine to grapevine by two distinct ectoparasitic dagger nematodes of the genus Xiphinema. GFLV and ArMV move from cell to cell as virions through tubules formed into plasmodesmata by the self-assembly of the viral movement protein. Five surface-exposed regions in the coat protein called R1 to R5, which differ between the two viruses, were previously defined and exchanged to test their involvement in virus transmission, leading to the identification of region R2 as a transmission determinant. Region R4 (amino acids 258 to 264) could not be tested in transmission due to its requirement for plant systemic infection. Here, we present a fine-tuning mutagenesis of the GFLV coat protein in and around region R4 that restored the virus movement and allowed its evaluation in transmission. We show that residues T258, M260, D261, and R301 play a crucial role in virus transmission, thus representing a new viral determinant of nematode transmission. Full article