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Aline Ferreira Barros, Vicente Paulo Campos, Denilson Ferreira de Oliveira, Fabiola de Jesus Silva, Iselino Nogueira Jardim, Viviane Aparecida Costa, Carlos Augusto Rodrigues Matrangolo, Regina Cássia Ferreira Ribeiro and Geraldo Humberto Silva

Summary

There is a demand for novel products for the control of plant-parasitic nematodes, so we characterised the effectiveness of some plant essential oils against Meloidogyne incognita and verified the efficiency of the major component from the most toxic oils and their analogues using in vitro and in vivo assays. In this study, the essential oils from Piptadenia viridiflora, Hyptis suaveolens and Astronium graveolens against M. incognita were evaluated, but only P. viridiflora oil showed toxicity toward M. incognita. Benzaldehyde was its main component according to GC-MS analysis. In in vitro assays, benzaldehyde (100 and 200 μg ml−1) and its oxime (400 μg ml−1) caused a higher rate of M. incognita second-stage juvenile (J2) mortality than the nematicide carbofuran (170 μg ml−1). Reductions of more than 90% in the number of galls and eggs, even greater than that observed with carbofuran, were observed in the assay where the J2 were placed in solutions of benzaldehyde and its oxime 48 h prior to tomato plant inoculation. Application of benzaldehyde together with M. incognita J2 to the substrate resulted only in a reduction in the number of eggs (42-65%); however, its oxime reduced both the number of galls (43-84%) and eggs (23-89%). Therefore, the P. viridiflora oil, its major component benzaldehyde, and the analogue benzaldehyde oxime are toxic to M. incognita. In two different in vivo assays, benzaldehyde oxime was confirmed as toxic to M. incognita with a greater efficacy than benzaldehyde.

Manouchehr Hosseinvand, Ali Eskandari and Reza Ghaderi

Summary

The second population of Pratylenchoides riparius, including females and males, is described and illustrated based upon morphological, morphometric and molecular data. The present population from Iran is characterised by some differences with the type population of the species from Hungary in stylet length (24-26 vs 21-22 μm), slightly longer body (1002-1230 vs 830-960 μm), pharynx (202-211 vs 182-190 μm) and tail (64-85 vs 48-57 μm), areolated outer bands of the lateral field (vs non-areolated), widening of the lateral field near tail terminus (vs lateral incisures connecting each other) and presence of males (vs absent). The taxonomic status of the species with regarding the data from the type and presently recovered population, as well as the closely similar species is discussed. The newly recovered population was studied based upon its molecular phylogenetic charactes using the D2-D3 of 28S rRNA and the partial 18S rRNA gene sequences and the results revealed that it forms a clade with P. magnicauda in 28S, but occupies a distant placement from it in 18S phylogeny.

Jessica M.S. Monteiro, Vanessa S. Mattos, Marcilene F.A. Santos, Ana C.M.M. Gomes, Valdir R. Correa, Daniela A. Sousa, Juvenil E. Cares, Jadir B. Pinheiro and Regina M.D.G. Carneiro

Summary

The type population of Meloidogyne polycephannulata is synonymised with M. incognita based on morphological and morphometric characters, as well as biochemical, molecular and phylogenetic studies. Morphological variability and a wide host range were reported for M. incognita during its first description and later re-description. Meloidogyne polycephannulata was described in Brazil from specimens collected in a carrot field (type population). The esterase phenotype (Est) characterised for this species was identical to the phenotype Est I2 of M. incognita, the most ubiquitous phenotype used for diagnostics. Morphological and morphometric characters of the descriptions of the two nominal species showed major similarities, as well as variability within the range of variation detected in M. incognita. In PCR assays, three SCAR markers species-specific for M. incognita (incK14 F/R, Mi/FR and incB06 F/R) amplified the same fragments of 399 bp, 955 bp and 1200 bp, respectively, for populations in both species. In phylogenetic studies based either on concatenated sequences of ITS1-5.8S-ITS2, D2-D3 rRNA, mitochondrial COII regions or on RAPD and AFLP data, the populations of both species grouped in the same clade with high bootstrap support. Altogether, these results provide congruent evidence that the M. polycephannulata type isolate deposited at the Embrapa Cryopreserved National Collection of Root-knot Nematodes is not a valid species but rather a junior synonym of M. incognita.

Mojtaba Keramat, Zeinab Mahboubi, Fariba Heydari, Shideh Mojerlou and Majid Pedram

Dana K. Howe, McKinley Smith, Danielle M. Tom, Amanda M.V. Brown, Amy B. Peetz, Inga A. Zasada and Dee R. Denver

Summary

Bacterial symbioses play important roles in shaping diverse biological processes in nematodes, and serve as targets in nematode biocontrol strategies. Focusing on the Xiphinema americanum species complex, we expanded upon recent research investigating patterns of coevolution between Xiphinema spp. and Xiphinematobacter spp., utilising two symbiont genetic markers of varying evolutionary rates. Phylogenetic analysis of nematode mitochondrial DNA (mtDNA) revealed five strongly supported major clades. Analysis of slow-evolving 16S rDNA in bacterial symbionts resulted in a phylogenetic topology composed of four major clades that grouped taxa highly congruent with the nematode mtDNA topology. A faster evolving protein-coding symbiont gene (nad) provided more phylogenetic resolution with seven well-supported clades, also congruent with the nematode mtDNA tree topology. Our results reinforce recent studies suggesting extensive coevolution between Xiphinema spp. and their vertically transmitted endosymbionts Xiphinematobacter spp. and illustrate the advantages of including genetic markers of varying evolutionary rates in coevolutionary and phylogenetic studies.

Hongchang Li, Guiming Dou, Mengge Gao, Fei Ren, Ruhua Li, Xingyao Zhang and Dong-Hui Yan

Summary

Natural volatiles released by the fungus, Annulohypoxylon sp. FPYF3050, were evaluated against the pine wood nematode (PWN), Bursaphelenchus xylophilus. Our results showed that volatile organic compounds (VOCs) caused 64.1 and 58.4% mortality of second-stage juveniles (J2) and mixed-stages (eggs, J2, third- and fourth-stage juveniles, and adults) of populations of PWN, but no inhibitive effects were detected on nematode eggs in the experiment. Analysis of the gases within the Petri plate by gas chromatography-mass spectrometry (GC-MS) showed a yield of an unique volatile with dominant 1,8-cineole in 77.4% relative area (RA) after 72 h treatment of nematodes with Annulohypoxylon sp. FPYF3050 and Botrytis cinerea. The commercial 1,8-cineole at concentrations of 2, 5, 10 and 15 μl ml−1 was applied to examine nematicidal activity. The results showed that 1,8-cineole had a 40-100% inhibition on the nematode eggs during 48 h treatment, more than 82.9% mortality of J2 after 24 h, 48 h and 96 h, and 18.7-91.9% mortality of the mixed-stage population, depending on the period after exposure. This result indicates that 1,8-cineole in the volatile gas emissions of Annulohypoxylon sp. FPYF3050 may play a crucial inhibitory effect on the pine wood nematode The nematicidal volatile gas from fungi may provide a useful biocontrol agent for controlling B. xylophilus.

Olivera Topalović, Holger Heuer, Annette Reineke, Jana Zinkernagel and Johannes Hallmann

Summary

In certain soils populations of plant-parasitic nematodes (PPN) decline. Understanding this effect may open up environmentally friendly management options. We identified such a suppressive soil containing virtually no PPN. Inoculated Meloidogyne hapla declined in this soil more than in a control soil and reproduction on tomato was reduced. The extracted soil microbiome alone decreased root invasion of second-stage juveniles (J2) and progeny as well as the native soil. We tested the antagonistic potential against PPN that differ in life strategies. The microbiome was most suppressive against two populations of M. hapla and one population of Pratylenchus neglectus, and least suppressive against M. incognita and the ectoparasite Hemicycliophora conida. In a split-root system with M. hapla, plant-mediated but not direct effects of the microbiome significantly reduced root invasion of J2, while direct exposure of M. hapla to the microbiome significantly affected reproduction. Overall, both plant-mediated and direct effects of the microbiome were responsible for the soil suppressiveness against M. hapla.

Zhen Wang, Wim Bert, Jianfeng Gu, Marjolein Couvreur and Hongmei Li

Summary

Aphelenchoides medicagus n. sp. isolated in Ningbo Port, P.R. China, from dried leaves and shoots of Medicago sativa imported from the USA, is described. It is characterised by a lateral field with four lines (three bands), stylet 9.0-12.0 μm long, excretory pore situated at same level as, or slightly posterior, to the nerve ring, vagina sclerotised, female vulval flap absent, post-uterine sac short, spicules 9.2-14.2 μm long (median curved line), rosethorn-shaped, apex and rostrum rounded, poorly developed, female and male tail conical with terminus bearing star-like processes. The new species belongs to the Group 3 category of Aphelenchoides species sensu Shahina. Phylogenetic analyses based on 18S, ITS and 28S D2-D3 of rDNA and mtCOI sequences confirmed its status as a new species and closely related to A. besseyi and A. fujianensis.

Yanfeng Hu, Jia You, Chunjie Li, Fengjuan Pan and Congli Wang

Summary

The aim of this study was to examine the impact of water extracts of Narcissus tazetta bulb on hatching, behaviour and mortality of second-stage juveniles (J2) and reproduction of the soybean cyst nematode (SCN; Heterodera glycines) in laboratory and glasshouse assays. Results demonstrated that N. tazetta bulb extracts did not affect hatching but significantly reduced J2 motility and nematode attraction to the soybean root tip, and resulted in considerable nematode mortality relative to the control. J2 exposure to different concentrations of bulb extracts caused 59-93% reduction in nematode reproduction on soybean roots. Compared with the monoculture control, soybean-N. tazetta intercropping in a pot trial reduced SCN reproduction by 37%. In addition, N. tazetta bulb powder as a soil amendment is effective in controlling SCN reproduction. Thus, the results suggest that N. tazetta bulb extract or derived active compounds may be considered as potential natural nematicides against SCN.

Ali Roshan-Bakhsh, Ebrahim Pourjam, Mahdi Ayyari and Majid Pedram

Summary

Extracts of nine agricultural wastes prepared with five different solvents were assessed for their potential nematicidal activity against three nematode species, Aphelenchus avenae, Meloidogyne incognita and Pratylenchus neglectus, in in vitro condition. The 50% v/v hydro-ethanolic extracts showed the highest performance for two tested plant wastes of cabbage leaves and faba bean pods. These two extracts were tested on nematodes in three different concentrations. The highest in vitro nematistatic activity was recorded for 3000 and 1500 ppm of cabbage leaf extracts by 100% paralysis of all three nematode species after 48 h, and the highest nematicidal activity was recorded for the above-mentioned extract by 25-100% mortality depending on nematode species and extract concentration. A 14-94% mortality was recorded for all three species of nematodes after treatment with faba bean pod hydro-ethanolic extract in in vitro conditions. Hatching inhibition and repellent activity of cabbage leaf and faba bean pod extracts were observed in P. neglectus and M. incognita. In vivo assays confirmed the in vitro results when both of the extracts showed moderate to high inhibition of nematode population development and nematode infection parameters on tomato root system in pot experiments.