Entomopathogenic nematodes (EPN) can infect and kill a wide range of insect pests and are used as safe alternatives to chemical insecticides. Hence, a hypothesis was tested for obtaining EPN with high recovery frequency value and accurate distribution pattern based on combining four factors: favourable sampling method, time and site targeting and use of multiple extraction technique. As the extreme diversity of EPN sampling makes any generalisation from a given case study difficult, this functional sampling was limited to recovering EPN from citrus trees only in Egypt. It could both detect more EPN isolates and allow the application of different indices of dispersion to study their spatial distribution pattern. Therefore, stratified random and systematic sampling from weed-infested soil under tree canopy during the season of abundant insect pests was done, followed by multiple cycles of Galleria-baiting technique. Consequently, the nematodes were recovered from the seven surveyed groves (100%) and from 37 of 60 (61.7%) soil samples. The spatial distribution of these EPN isolates, previously identified as Heterorhabditis indica, was characterised using five dispersion indices, which were mainly a random rather than an over-dispersed distribution.
Cryphodera japonicum n. sp., detected at Ningbo port, China, from the rhizosphere of imported Japanese Podocarpus macrophyllus, is described. The new species is characterised by females with a globose body, protruding vulval lips, slightly concave anus-vulva profile, a stylet length of 37.2 (31.1-41.3) μm and a vulva-anus distance of 38.1 (34.7-44.1) μm. Males possess two lip annuli, a stylet length of 27 (22.5-30.6) μm long, three lines in lateral fields and a spicule 21.5 (19.1-23.0) μm long. Second-stage juveniles have bodies 543 (506-588) μm long, three lip annuli, a stylet 31.7 (29.2-34.5) μm long, three lines in the lateral fields, a conoid tail with a narrow rounded terminus, and a relatively long hyaline region occupying half of the tail length. Phylogenetic analyses based on the D2-D3 expansion segments of the 28S, ITS, partial 18S rRNA, and COI gene revealed the unique position of this species with other heteroderid nematodes, supporting its status as a new species of Cryphodera. The new species showed a close relationship with C. brinkmani.
Root-knot nematodes (Meloidogyne spp.) are major crop pests that cause heavy economic losses. The use of resistant cultivars is one of the most important management methods. The Mi-1 gene in tomato confers effective resistance against several species of Meloidogyne. However, Mi-1-virulent root-knot nematodes restrict the use of resistant cultivars. Molecular markers associated with virulence have been developed in previous studies but not validated in large number of Meloidogyne populations so far. In this study, molecular markers were screened in a total of 69 (a)virulent Meloidogyne incognita and M. javanica isolates. The results showed these markers did not separate virulent and avirulent populations from Turkey. In addition, polymerase chain reaction products obtained from primers HM1.F2/HM1.R2 were digested with 30 restriction enzymes but no differences among populations were found. To the best of our knowledge, this is the first report on screening large root-knot nematode populations with these markers.
Makatinus ukrainicus sp. n. and a population of M. aquaticus, both from Ukraine, are described and illustrated using morphological, morphometric and molecular (28S rDNA) data. The new species is characterised by its 2.17-2.70 mm long body, 20-23 μm broad lip region, odontostyle 20.5-25 μm long at its ventral side and 23-27 μm long at its dorsal side, 591-672 μm long neck, uterus simple and 163-174 μm long or 2.0-4.7 corresponding body diam. long, V = 49.5-52.8, tail convex-conoid (29-39 μm, c = 61-86, c′ = 0.6-0.9), spicules 86-93 μm long, two pairs of adcloacal supplements, and 17-21 closely and regularly spaced ventromedian supplements without an hiatus. In general, the Ukrainian population of M. aquaticus fits well those previously known from Spain and Hungary, and its study confirms the identity of this species. The morphological and molecular data of the Ukrainian populations reveal an interesting diversity within the genus, which might not be a monophyletic taxon.
There is no single feature to distinguish free-living soil nematodes from freshwater nematodes, also because all free-living nematodes are essentially aquatic. This notwithstanding, by examining the frequencies of some characters of 1141 European species, differences of qualitative/quantitative characters between soil and freshwater nematodes were found. In particular, aquatic and semi-aquatic species are, on average, longer and slimmer than soil species, have a longer tail, greater body weight, smooth cuticle and larger amphids. A new body parameter, length of the pharynx in relation to the length of the whole digestive tract (e), was also taken into consideration.
The root-lesion nematode, Pratylenchus zeae, is commonly found in upland rice fields. To measure the impact of the nematode on rice production, a screenhouse experiment was conducted using two farmer-adapted Oryza sativa cultivars, ‘Supa’ (‘SurinamV-880’) and ‘SARO-5’ (‘TXD 306’), under flooded, upland and drought water regimes imposed at 7 days post-inoculation of mixed-stage nematodes (200, 500, 1000, 3000 and 10 000 plant−1). Growth and yield parameters were recorded, and the experiment was terminated after 5 months. ‘Supa’ was shown to be resistant to P. zeae, while ‘SARO-5’ was susceptible. Pratylenchus zeae reduced the growth and yield of both cultivars, though more for ‘SARO-5’ than for ‘Supa’. Yield decreased with increasing final nematode densities. Pratylenchus zeae reproduction was highest at 200 and 500 inoculum levels and under upland water conditions. The yield of ‘SARO-5’ was greater than that of ‘Supa’ under flooded conditions and with no or 200 and 500 nematode inoculum levels, but with high P. zeae inoculum ‘Supa’ yield was better than ‘SARO-5’.
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’.