Morphological and molecular diversity among populations of cereal cyst nematodes (CCN) from wheat production areas in Ismailia province, Egypt, was investigated using light microscopy, ITS-RFLP and sequencing of the rDNA-ITS. CCN were found in five out of seven regions in Ismailia, the highest incidence being found in El Shark (West Sinai). The Egyptian populations were identified as H. avenae according to morphometrics of cyst vulval cone and second-stage juveniles. No differences in ITS-RFLP patterns generated by 17 restriction enzymes were detected among the Egyptian populations although the Egyptian populations could be distinguished from German populations of H. avenae and H. filipjevi. The analyses of ITS region sequences confirmed the species identification of the Egyptian populations as they clustered with H. avenae populations from Iran, Saudi Arabia, India, Israel and China.
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.
Population-level genetic tools to study the epidemiology of potato cyst nematodes (PCN) are needed to evaluate their adaptive potential and validate management strategies. The effector gene vap1 is essential in early infection by PCN. We expected high allelic variation due to diversifying selection. A technique was developed specifically to amplify vap1 fragments of PCN, and electrophoretically separate variants in a denaturing gradient (DGGE). Sequenced gene variants differed in intron as well as exon regions. Siblings were more similar in vap1 pattern than juveniles from different cysts. Nearly all juveniles analysed had unique patterns with up to ten or five vap1 variants for Globodera pallida or G. rostochiensis, respectively. Patterns differed significantly among populations, with similarities increasing from between-species, within-species to within-pathotype comparisons. In conclusion, the method is suitable to determine the similarity of heterogeneous PCN populations for studies on their temporal change and spread.
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.
Soybean, Glycine max, is a relatively new crop in Europe gaining increasing interest for its potential to fix atmospheric nitrogen and thus increase sustainability of modern agricultural production systems. Under temperate conditions, root-lesion nematodes (Pratylenchus spp.) are one of the most prominent plant-parasitic nematode taxa of economic concern in soybean. Here, we investigated the susceptibility of soybean cultivars towards naturally occurring populations of Pratylenchus spp. and their effects on soybean yield. At the site Bundesallee the cultivars ‘Abelina’, ‘Primus’ and ‘Taifun3’ supported the highest infestation and multiplication of a mixed population of P. neglectus and P. crenatus, while ‘Sultana’ and ‘Solena’ were least susceptible. At the field site Groß Lüsewitz, ‘Primus’ and ‘Merlin’ cultivars were significantly more susceptible to P. neglectus than ‘Sultana’. Soybean yield was reduced by high initial densities of Pratylenchus spp. Results are expected to contribute to a better nematode management.