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The root-knot nematode Meloidogyne graminicola is considered one of the most devastating pests in rice-producing areas, and nematicides are neither ecofriendly nor cost effective. More acceptable biological agents are required for controlling this destructive pathogen. In this study, the biocontrol potential of Aspergillus welwitschiae AW2017 was investigated in laboratory and greenhouse experiments. The in vitro ovicidal and larvicidal activities of A. welwitschiae metabolites were tested on M. graminicola in laboratory experiments. The effect of A. welwitschiae on the attraction of M. graminicola to rice and the infection of rice by M. graminicola was evaluated in a greenhouse. The bioagent AW2017 displayed good nematicidal potential via its ovicidal and larvicidal action. The best larvicidal activity was observed at a concentration of 5×AW2017, which caused an 86.2% mortality rate at 48 h post inoculation. The highest ovicidal activity was recorded at a concentration of 5×AW2017, which resulted in an approximately 47.3% reduction in egg hatching after 8 d compared to the control. Under greenhouse conditions, the application of A. welwitschiae significantly reduced the root galls and nematodes in rice roots compared to the control. At a concentration of 5×AW2017, juveniles and root galls in rice roots at 14 d post inoculation (dpi) were reduced by 24.5 and 40.5%, respectively. In addition, the attraction of M. graminicola to rice roots was significantly decreased in the AW2017 treatment, and the development of nematodes in the AW2017-treated plants was slightly delayed compared with that in the PDB-treated control plants. The results indicate that A. welwitschiae is a potential biological control agent against M. graminicola in rice.

Key message After initial up-regulation, expression of TUBG1 and TUBG2 is significantly down-regulated in mature syncytia, but lack of expression of either of γ-tubulin genes reduces numbers of nematode infections and developing females. Abstract Infective second stage juveniles of sedentary plant parasitic nematode Heterodera schachtii invade the root vascular tissue and induce a feeding site, named syncytium, formed as a result of cell hypertrophy and partial cell wall dissolution leading to a multinucleate state. Syncytium formation and maintenance involves a molecular interplay between the plant host and the developing juveniles leading to rearrangements and fragmentation of the plant cytoskeleton. In this study, we investigated the role of two Arabidopsis γ-tubulin genes (TUBG1 and TUBG2), involved in MTs nucleation during syncytium development. Expression analysis revealed that both γ-tubulin’s transcript levels changed during syncytium development and after initial up-regulation (1–3 dpi) they were significantly down-regulated in 7, 10 and 15 dpi syncytia. Moreover, TUBG1 and TUBG2 showed distinct immunolocalization patterns in uninfected roots and syncytia. Although no severe changes in syncytium anatomy and ultrastructure in tubg1-1 and tubg2-1 mutants were observed compared to syncytia induced in wild-type plants, nematode infection assays revealed reduced numbers of infecting juveniles and developed female nematodes in mutant lines. Our results indicate that the expression of both TUBG1 and TUBG2 genes, although generally down-regulated in mature syncytia, is essential for successful root infection, development of functional syncytium and nematode maturation. Electronic supplementary material The online version of this article (10.1007/s00299-018-2312-7) contains supplementary material, which is available to authorized users.

Background Aerobic rice fields are frequently infested by pathogenic oomycetes (Pythium spp.) and the rice root-knot nematode Meloidogyne graminicola. Here, the interaction between Pythium arrhenomanes and Meloidogyne graminicola was studied in rice roots of two aerobic rice varieties. In different experimental set-ups and infection regimes, plant growth, rice yield, Pythium colonization, as well as establishment, development and reproduction of M. graminicola were studied. Results In this study, it is shown that the presence of P. arrhenomanes delays the establishment, development and reproduction of M. graminicola compared to single nematode infected plants. The delay in establishment and development of M. graminicola becomes stronger with higher P. arrhenomanes infection pressure. Conclusions Our data indicate that P. arrhenomanes antagonizes M. graminicola in the rice root and that the plant benefits from this antagonism as shown by the yield data, especially when either of the pathogens is present in high levels. Electronic supplementary material The online version of this article (doi:10.1186/s12284-016-0108-3) contains supplementary material, which is available to authorized users.

In the absence of resistant cultivars, the impending loss of methyl bromide (MBr) and few sustainable alternatives available, managing the northern root-knot nematode, Meloidogyne hapla, is a challenge in temperate vegetable and nursery production systems. Many brassica plants, including arugula, Eruca sativa, possess biofumigant and trap crop qualities, and thus have been gaining popularity as potential alternatives to MBr. As part of a project to develop alternatives to MBr, this study was conducted to determine the effects of arugula cv. Nemat on three glasshouse populations of M. hapla from Rhode Island (RI), New York, Geneva (NYG) and Michigan (MI). In two glasshouse experiments conducted at 20 ± 2°C and 28 ± 2°C, arugula and Rutgers tomato (standard susceptible) seedlings were inoculated with either 0 (control) or 3000 eggs of 67-85% undifferentiated stages of the three populations. Experiment 1 was terminated at 20 days and Experiment 2 at 28 days after nematode inoculation. At 20°C, 200 and 280 degree-days (DD, base 10°C) were accumulated, while 360 and 504 DD were accumulated at 28°C in the respective experiments. Total numbers of nematodes recovered from roots varied by host and by nematode population over the course of the study, but the numbers of females in roots did not vary significnatly. This suggests variability in reaching the adult female stage. Egg and egg mass production was normal in all nematode-infected tomatoes, but no eggs were produced in more than 80% of arugula plants, and less than 17% of the arugula samples had fewer than five loose eggs and no egg masses. The results show that arugula interferes with development and reproduction of populations of M. hapla and thus has potential as a trap crop to control M. hapla. © 2006 Koninklijke Brill NV. Michigan Agriculture Experiment Station: MICL0 1792 0427 Washington State University We thank Tracy Kerchkof and Crystal T. Cuevas for technical assistance, Drs G. Abawi (NYG) and N.A. Mitkowski (RI) for providing the nematode populations, and Dr G.R. Noel, USDA/ARS, University of Illinois, USA, for constructive criticisms on the manuscript. This work was funded by the Michigan Agricultural Experiment Station (Hatch Project No. MICL0 1792) for the first author; and by the College of Agricultural, Human, and Natural Resource Sciences Research Centre, PPNS No. 0427, Department of Plant Pathology and IAREC Prosser, Project No.WNP00542, Washington State University for E. Riga.

Potato cyst nematodes (PCN), Globodera rostochiensis and G. pallida, are economically important pests of potato (Solanum tuberosum) crops in potato growing regions worldwide. Integrated management is under threat, with effective nematicides increasingly being withdrawn on environmental and health grounds. Alternative strategies are urgently needed and trap cropping could be one of them. The non-tuber-bearing Solanum sisymbriifolium is regarded as an effective trap crop for PCN with strong hatching ability and immunity to PCN infection and has been used in the UK and The Netherlands. However, its mode of action is unknown. In order to shed light on the mode of action so that a novel control strategy could be identified, the interactions between G. pallida and S. sisymbriifolium were investigated using in vitro bioassays. In choice assays, G. pallida J2s were equally attracted to the roots of S. sisymbriifolium and to those of S. tuberosum. However, potato root diffusate (PRD), which is routinely used to induce PCN hatch, failed to attract G. pallida J2s in chemotaxis bioassays, indicating hatching factors (HFs) and soluble compounds present in PRD are not involved in attraction of G. pallida J2s to potato roots. The J2s invaded the roots of S. sisymbriifolium in large numbers but failed to develop further. To facilitate continuous observation of nematode development, a novel in vitro method was devised with the use of Pluronic F-127, which requires no sterilisation, and the life cycle of G. pallida was successfully observed in S. tuberosum roots. Quantitative real-time polymerase chain reaction analyses of defence related genes of S. tuberosum and S. sisymbriifolium infected with G. pallida revealed up-regulation of the chitinase gene (ChtC 2.1) at 3 days post inoculation in S. sisymbriifolium but not in S. tuberosum. Electrospray ionisation-mass spectrometry analyses of root exudate extracts of the two Solanum species and subsequent bioassay-guided fractionation showed that the HF of S. sisymbriifolium differs from that of S. tuberosum. Previously, attention had been solely paid to the hatching ability of the root exudate of S. sisymbriifolium, but this study revealed for the first time that the aerial part extract possesses a significant hatching ability. The Biotechnology and Biological Sciences Research Council (BBSRC), Branston Ltd