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Summary

In this study, the accumulation of hydrogen peroxide (H2O2) in different parts (healthy root, gall, root attached to gall, aerial parts) of healthy tomato plants and plants infected by the root-knot nematode, Meloidogyne javanica, was investigated after treating the roots with β-aminobutyric acid (BABA). In addition, the effects of different concentrations of H2O2 (0-2 mM) on mortality, body structures and the digestive system of second-stage juveniles (J2) were also investigated in in vitro experiments. Results showed that exposure to concentrations of more than 1 mM H2O2 is lethal for J2, while the digestive system is not able to tolerate concentrations of more than 0.2 mM. Evaluating the activity level of enzymes related to biosynthesis and removing H2O2 in treated plants also showed that the nematode has significant suppressive effects on the biosynthesis enzymes of this compound, and this effect is greater in the site of nematode activity than in other parts of the plant. By contrast, the activity of catalase enzyme, as one of the H2O2-removing enzymes, shows a significant increase in all parts of nematode infected plants (especially in galls).

In: Nematology

Summary

Maize is an important cereal crop in sub-Saharan Africa (SSA). Plant-parasitic nematodes significantly impact maize production. However, research on maize nematodes in SSA is limited. The current study aimed to assess the occurrences and densities of nematodes associated with maize and to assess the correlation of some soil physicochemical properties with nematodes in southern and southwestern Ethiopia. One hundred and eighty-six soil and root samples were collected from 62 maize fields (31 from Hawassa Zuria and 31 from Mana districts). Eleven plant-parasitic nematode genera were identified. The most important genera of plant-parasitic nematodes identified were Meloidogyne and Pratylenchus, followed by Helicotylenchus and Tylenchorhynchus. The nematodes Pratylenchus and Criconemoides were significantly and positively associated with pH, soil organic carbon (SOC) and soil organic matter (SOM). Additionally, Tylenchorhynchus, Pratylenchus and Rotylenchulus were significantly positively correlated with soil available phosphorus (SAP). However, Criconemoides and Meloidogyne had a strong negative correlation with soil bulk density (SBD). This study provides useful baseline information on maize-associated nematodes, and will be useful for agricultural policy makers, private farmers, non-governmental organisations and agricultural extension workers enabling them to establish sustainable maize nematode management strategies.

In: Nematology

Summary

A member of the genus Pellioditis Dougherty, 1953 (syn. Phasmarhabditis Andrássy, 1976) was detected in three introduced gastropod species in Moscow for the first time. Both the nematode and its gastropod hosts were found to have originated from the Caucasus region. No native gastropod species as well as the alien invasive slug Arion vulgaris were infected by P. akhaldaba. The Moscow strain of P. akhaldaba is very close to P. akhaldaba from Georgia in the ITS rDNA (7 bp difference) but they differ significantly in the sequences of COI mtDNA (50 bp difference). However, phylogenetic analysis of both loci showed that these two strains were the closest relative to all other species and strains of the genus Pellioditis studied.

In: Nematology

Summary

Potato production in East Africa is seriously impacted by the potato cyst nematode (PCN), Globodera rostochiensis, where it has been recorded in at least three countries. In Kenya, it is widespread in all major potato-growing regions, often at very high densities. Consecutive cropping of potato on the same land and a sub-tropical climate have influenced PCN biology. For example, unusually large cysts have been regularly recovered. We have analysed the biological properties of these ‘giant cysts’. The giant cysts contained more eggs than those recovered from UK fields. Egg size did not differ from UK populations and there was no difference in overall lipid content or lipid profile in J2 from giant cysts, compared to control samples. The nematodes in giant cysts were also genetically indistinguishable from any other G. rostochiensis sampled. When grown under UK glasshouse conditions, the offspring of nematodes from giant cysts were no different in size from those grown from control cysts, indicating that gigantism is not a heritable trait and may simply reflect favourable conditions for PCN under Kenyan farming systems. To date, all the PCN tested from Kenya, including those from giant cysts, are avirulent on potato cultivars containing the H 1 resistance gene.

Open Access
In: Nematology

Summary

Aphelenchoides yixingensis n. sp. found in Chinese red pine (Pinus massoniana) in Yixing city, Jiangsu Province, P.R. China, is described. It is characterised by a very slim body (a = 50.8 (41.3-63.8) and 49.3 (42.3-55.1) for males and females, respectively), three (occasionally five) lateral lines in the lateral field, a short stylet (9-12 μm), the excretory pore located at the level of nerve ring, the vagina is not sclerotised and the vulva has slightly protruding lips and lacks a flap, the post-uterine sac is well developed and forms ca 29.0% (24.1-34.1%) of the vulva to anus distance. The spicules are smoothly arcuate, the apex and rostrum rounded and short, and the dorsal limb is 20.5 (16.9-22.2) μm long, the distal end bluntly rounded. Spicule sheath-like structure is present, triangular and outstretched when heat-killed in some individuals. The male tail bears three pairs (2 + 2 + 2) of caudal papillae. The tail of both sexes is sub-cylindrical, the terminus bearing a bluntly pointed mucron with tiny nodular protuberances, mainly at the distal part. The new species belongs to the Group 2 category of Aphelenchoides species sensu Shahina and is defined as A2-B1-C1-D1-E2-F2 according to the categorisation codes of OEPP/EPPO. Phylogenetic analysis based on 18S and 28S D2-D3 of rDNA, along with ITS and mtCOI, confirmed its status as a new species. A proposal for genus Ptychaphelenchus as a synonym of Aphelenchoides is also discussed.

In: Nematology

Summary

Solidago gigantea is one of the most problematic species of invasive plants in Europe, where its rapid spread threatens the stability of ecosystems. The effect of invasion by S. gigantea on soil ecosystems and food webs can be evaluated using nematode communities as suitable and useful soil bioindicators. We compared the effect of S. gigantea on nematode communities in plots invaded with S. gigantea and non-invaded grasslands across three sites with varying soil and climatic conditions. Our findings indicated that invasion by S. gigantea did not strongly affect nematode taxonomic diversity but negatively affected functional diversity. This effect was evident in the increased abundance of bacterivore and fungivore nematodes and decrease in values of ecological and functional indices. The evaluation of the soil food web using nematode communities confirmed that soil in plots with S. gigantea were less mature and more disturbed with a degraded or depleted food web indicated by lower values of maturity, enrichment and structure indices, compared with non-invaded grasslands. On the other hand, taxonomic diversity, abundance, biomass and the functional indices differed between three study sites, but site had little or no effect on the values of the maturity indices. The interaction between site and invasion status confirmed the effect of invasion on nematode biomass, with the abundance of bacterivore and fungivore nematodes and the functional indices more prominent at sites characterised by cold and humid climates. These findings underscore the importance of considering both taxonomic and functional diversity and the characteristics of the plants and sites when evaluating the impact of plant invasion on soil biota.

In: Nematology
Nematology Monographs and Perspectives is a series of books presenting in-depth studies of various aspects of Nematology.

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Summary

A new species of the genus Skrjabinomermis, collected from two locations in north and northwest of Iran, is described and illustrated, including morphological data and D2-D3 rRNA LSU sequences. Skrjabinomermis pirnaimi sp. n. is characterised by its six cephalic papillae, two hypodermal pegs in the area of the cephalic papillae, adult’s cuticle with very fine cross fibres, head rounded, mouth central, amphids cup-shaped, six hypodermal cords, vulva a transverse slit, located post-equatorially, cuticular protruding and vulval lips well developed, vagina pear- or barrel-shaped, with slightly bent lumen, tail similar in both sexes, bluntly rounded, spicules paired, medium sized, slightly curved, fused posteriorly for about 68-73% of their length, with pointed tip, male genital papillae arranged in three rows: the median ventral row having two pre- and two post-anal papillae, and the lateroventral rows with five papillae each. Molecular analyses using the D2-D3 expansion regions of the 28S rRNA gene sequences placed the genus Skrjabinomermis as a sister genus to Romanomermis with 93% Bayesian posterior probability based upon currently available data.

In: Nematology

Summary

Cryptaphelenchus species are wood- or bark-inhabiting nematodes, generally mycetophagous and reported to have endophoretic associations with insects. In the present study, we describe two new and one known Cryptaphelenchus species detected in imported and domestic wood samples. Cryptaphelenchus americanum n. sp. and C. minutus were detected in the log samples of Pinus taeda imported from the USA, whereas C. orientalis n. sp. was isolated from the bark of dying Pinus sylvestris trees in Inner Mongolia, China. Both new species displayed characteristic features, including a relatively short body length, four lateral lines, a short post-vulval uterine sac in females, and a distinct cloacal apophysis in male tails. Newly recovered and known species were characterised molecularly, and phylogenetic trees were constructed to study their relationship with related Cryptaphelenchus species. Notably, the genetic divergence observed among Cryptaphelenchus species was found to be more significant compared to morphometrical differences, highlighting the importance of molecular data in taxonomy. The identification of new and known species expands our understanding of the genus and suggests that Cryptaphelenchus species may be under studied, underscoring the necessity for continued exploration.

In: Nematology

Summary

In the exploration of nematode diversity within the coal mine spoil of Sonebhadra district, an isolate of Ironus dentifurcatus Argo & Heyns, 1972 was collected from the soil surrounding the roots of Prosopis juliflora. This study aims to unravel taxonomic intricacies of I. dentifurcatus through analysis of morphometric data, morphological characteristics utilising both light and scanning electron microscopy, and genetic scrutiny employing the SSU 18s rDNA gene marker. The study adds valuable information to the evolutionary history of I. dentifurcatus by constructing a comprehensive phylogenetic tree. This analysis is further augmented by an exploration of phylogeography and genetic divergence within the genus Ironus Bastian, 1865. The results reveal the genetic variability within the species of Ironus and the possible adaptative radiations in the group.

In: Nematology