Laimaphelenchus pannocaudus, isolated in Ningbo port from Picea gluaca, is redescribed based upon characteristic morphological details elucidated by light and scanning electron microscopy photographs. The recovered population is characterised by 907 (771-1024) μm long females with 11.2 (8.9-12.2) μm long stylet, four incisures in the lateral field, excretory pore located at the same level as, or slightly anterior to the nerve ring, vulva lacking a flap and located at 68.7 (63.9-73.4)% of the body, elongate post-vulval uterine sac 78.5 (55.6-101.1) μm long, and tail 40.6 (33.4-45.6) μm long. Males are common and characterised by 16.5 (15.7-17.8) μm long spicules (chord) with their condylus slightly recurved, squared to rounded in shape with a blunt rounded tip and rostrum triangular with a bluntly pointed tip, and six visible caudal papillae. The female tail is ventrally curved, conoid and bears a stalk-like terminus with 4-8 pedunculate projections. Phylogenetic analyses using partial 18S and 28S rDNA D2-D3 data revealed that L. pannocaudus formed a sister relationship with L. suberensis in both phylogenies.
Meloidogyne enterolobii is characterised by its aggressiveness and ability to reproduce on plants carrying the Mi resistance gene. However, resistant cultivars and resistance induction may be alternatives to keep the pest population at levels that do not cause economic damage. The aim of this study was to evaluate the reaction of tomato genotypes to M. enterolobii and test the efficacy of resistance inducers in four tomato genotypes. Twenty-one tomato genotypes were inoculated with 2000 eggs of M. enterolobii and evaluated after 35 days of inoculation. All genotypes tested were susceptible to M. enterolobii. Four tomato genotypes were selected and the plants were treated with Bacillus subtilis, B. licheniformis + B. subtilis + Trichoderma longibrachiatum, Acibenzolar-S-methyl (ASM) and extract of Reynoutria sachalinensis. The plants treated with B. subtilis showed higher shoot and root weight. ASM reduced the reproduction factor of M. enterolobii when applied to the genotype ‘PXT 408’. All tomato genotypes tested here are susceptible to M. enterolobii, thus confirming the ability this plant-parasitic nematode to reproduce on resistant plants with the Mi gene. The resistance inducers B. subtilis, B. licheniformis + B. subtilis + T. longibrachiatum and extract of R. sachalinensis did not influence the final nematode population in any of the genotypes used; however, ASM reduces reproduction of M. enterolobii to the genotype ‘PXT 408’.
Paracrobeles laterellus is redescribed from the North-West District (Koanaka Hill), Botswana, which forms part of the Kalahari Desert. A scanning electron microscopy study of the species is presented for the first time. This population is characterised by its adult body length, lateral field with three longitudinal incisures, lips with three tines, the middle one being shorter, primary and secondary axils with two guard processes, labial probolae bifurcate with basal ridge and smooth prongs, pharynx with very swollen and elongate metacorpus, spermatheca swollen, post-vulval uterine sac well developed, vagina sigmoid, female and male tails conoid, and characters of the spicules and gubernaculum. Morphologically, P. laterellus is very similar to P. kelsodunensis and P. mojavicus according to the morphology of the lip region, i.e., with two guard processes at the primary axils and robust spicules.
Characterising the non-neutral genetic variation within and among populations of plant-parasitic nematodes is essential to determine factors shaping the population genetic structure. This study describes the genetic variation of the parasitism gene vap1 within and among geographic populations of the beet cyst nematode Heterodera schachtii. Forty populations of H. schachtii were sampled at four spatial scales: 695 km, 49 km, 3.1 km and 0.24 km. DGGE fingerprinting showed significant differences in vap1 patterns among populations. High similarity of vap1 patterns appeared between geographically close populations, and occasionally among distant populations. Analysis of spatially sampled populations within fields revealed an effect of tillage direction on the vap1 similarity for two of four studied fields. Overall, geographic distance and similarity of vap1 patterns of H. schachtii populations were negatively correlated. In conclusion, the population genetic structure was shaped by the interplay between the genetic adaptation and the passive transport of this nematode.
Two new nematode species of Phasmarhabditis were isolated from land snails in North and West Caucasus, Russian Federation. Phasmarhabditis circassica sp. n. originated from Oxychilus sp. collected by the Nickel settlement in the Adygea Republic while P. clausiliiae sp. n. came from Clausiliidae gen. sp. in the Stavropol district. Phasmarhabditis circassica sp. n. is characterised morphologically by male spicules with a hollow tip, a widely conoid, spicate female tail, ensheathed dauer juveniles 896 (813-982) μm long with a tiny but distinct cuticular apical cap and a long filamentous tail, and exsheathed dauers 773 (670-950) μm long with a tail half as long as in the ensheathed dauers and with a rounded tip. Phasmarhabditis clausiliiae sp. n. is very close to P. circassica sp. n. in having similar morphological traits and is differentiated mainly in having a longer female tail of 94 (79-111) vs 82 (54-125 μm) and the much smaller ratio c of 13.7 (10.3-18.4) vs 22.7 (16.8-27.5) and by its molecular characteristics. The molecular analysis based on partial sequences of LSU rDNA, and ITS rDNA regions has been performed and showed that the closest match for both new species was P. bohemica. Despite the morphological similarity between the species described, significant difference between these two new species was reported both for LSU rDNA and ITS rDNA.
Calcaridorylaimus heynsi n. sp. is the second species of the genus to be described by both morphological and molecular techniques. Morphologically, it can be distinguished from all known species of Calcaridorylaimus by a combination of the following characters: presence of advulval ornamentations, short body (0.90-1.33 mm), slightly anteriorly positioned vulva (V = 47.6 (45.8-49.8)), short odontostyle in females and males (13.1 (11.5-14.5) μm and 13.5 (12.0-18.0) μm, respectively), number of supplements (2 + 9-11), short spicules when measured along the median line (40.4 (38-42) μm) and pore-like vulval opening. It is closest to C. sirgeli, especially in the presence of advulval ornamentations and the pore-like vulva. Phylogenetic analysis based on partial D2-D3 segment of 28S rDNA sequences showed that C. heynsi n. sp. is in a well-supported sister relation with Mesodorylaimus sp. in a clade with C. cignatus and Mesodorylaimus spp. In the Bayesian tree, using partial sequences 18S rDNA, M. japonicus was the closest taxon to the new species.
A population of Hemicriconemoides phoenicis was recovered from Khuzestan province, south-western Iran, in association with date palm. The recovered population was characterised by 518-645 μm long females having a 76-82 μm long stylet, rounded to oblong spermatheca filled with sperm, a 28.0-39.8 μm long tail, juveniles common, with 14 longitudinal rows of rounded scales, and males absent. Compared to the original data, no morphological and morphometric differences were observed. In molecular phylogenetic analyses using the D2-D3 expansion segments of the 28S rRNA gene and a near-full-length fragment of the 18S rRNA gene sequences using Bayesian inference (BI) and maximal number of species of the genus, the two newly generated 28S sequences of the Iranian population formed a maximally supported clade with two original sequences of the species; and the 18S sequence formed a maximally supported clade with an unidentified isolate of the genus in the corresponding phylogeny. This is the second report of the species since its original description, Iran representing a new geographical record and supporting the suggestion that date palm could be its preferred host.
Laimaphelenchus spiflatus n. sp. isolated from declining Chinese pine, Pinus tabuliformis, is described and illustrated. The new species can be characterised by its relatively long body size of 1150 ± 108 (976-1437) μm for females and 1092 ± 78.6 (905-1235) μm for males, lateral field with four lines, females with a long vulval flap, and tail conoid, slightly ventrally curved and ending in a stalk having 8-12 projections when observed with SEM. Males are common, with 27.3 (23.4-28.8) μm long spicules having blunt (not well-developed) condylus and rostrum and truncate simple distal tip, and four caudal papillae. By having a vulval flap, four lateral lines and tail end with a stalk (without four tubercles), the new species comes close to L. preissii, L. simlaensis, and L. unituberculus, but can be differentiated from them by morphological characters and morphometric data. In phylogenetic analyses using near full length 18S and D2-D3 expansion segments of 28S rDNA, Laimaphelenchus spiflatus n. sp. appeared as an independent lineage separated from the other Laimaphelenchus spp. that are currently sequenced for their aforementioned genomic regions.
A new species of Aporcelaimellus, collected in a watermelon field in Nigeria, is described, including its morphological and molecular (D2-D3 28S-rDNA, 18r-DNA) characterisation. Aporcelaimellus nigeriensis sp. n. is distinguishable by its 2.76-3.55 mm length, very coarse ventral body pores, lip region offset by deep constriction and 24-27 μm broad odontostyle 30-36 μm long at its dorsal and 28-31 μm at its ventral side, neck 648-779 μm long, pharyngeal expansion occupying 54-60% of total neck length, uterus 300-473 μm or 2.1-3.2 body diam. long and tripartite, V = 49-54, tail short and convex conoid (27-41 μm, c = 72-115, c′ = 0.5-0.7), spicules 108-137 μm long, and 9-10 spaced ventromedian supplements with hiatus. LSU analysis revealed a close relationship of A. nigeriensis sp. n. with other Aporcelaimellus species and questioned, once more, the monophyly of Aporcelaimidae. SSU phylogenetic tree was not able to resolve the relationship between the new species and other closely related species.
Anaerobic digestate is a byproduct of anaerobic digestion of organic materials for biogas production. Land application of digestates may provide plant nutrition and suppression of plant-parasitic nematodes. The characteristics of digestates may vary by organic substrates and digestion conditions. To measure nematode-suppressive potential, the rigour and simplicity of a radish bioassay with Heterodera schachtii was expanded. In a three-factor factorial design, three incubation environments, two growth containers and two nematode life stages as inoculum were tested. Containers with 50 g of dry sandy loam soil were inoculated with 500 second-stage juveniles (J2) of H. schachtii or with cysts with equivalent hatchable J2. One seed of radish Raphanus sativus ‘Cherry Belle’ was planted into each container, and 1 ml of drench treatment was applied. After 64 degree days (4-5 days), roots were washed and stained with acid fuchsin for nematode counting. In three experiments, food waste digestate permeate suppressed nematode root penetration in the growth chamber, glasshouse and laboratory, in cups and tubes, and following inoculation with cysts and J2. However, root penetration by J2 was more greatly reduced after cyst inoculation than after J2 inoculation. Investigations in preserving nematode cysts showed that J2 within cysts remained viable after incubation in sandy loam soil at 23°C in sealed tubes in the laboratory for 35 days. Results of the radish assay predicted nematode-suppressive potential against Pratylenchus vulnus on peach rootstock ‘Nemaguard’ in a glasshouse experiment. In summary, a straightforward rapid bioassay for measuring nematode suppressiveness of organic liquids was developed for routine use.