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Titre : Root-lesion and cyst nematodes in cereals fields in Morocco : Species identification, population diversity and crop resistance

Auteur : MOKRINI, Fouad

Université de soutenance : Ghent University

Grade : Doctorat 2016

Résumé partiel
Cereal cyst nematodes (CCN, Heterodera spp.) and root-lesion nematodes (RLN, Pratylenchus spp.) are important plant-parasitic nematodes of wheat and exist in most of the cereal growing regions of the world. As there was limited information on the distribution of CCN and RLN species in wheat fields in Morocco, a survey was organized in 2011. A total of 75 soil and root samples were collected from fields in Gharb, Saiss, Zaers and Chaouia before the wheat and barley harvest (May to June). Cysts were extracted from soil by flotation and decanting through 200-μm sieves. Vermiform stages were extracted from roots and soil with an automated zonal centrifuge. They were identified up to species level using morphological and molecular methods. The survey revealed that 69% of the samples were infested with four species of Pratylenchus, viz. P. thornei, P. penetrans, P. pseudocoffeae and P. pinguicaudatus. The most prevalent species was P. penetrans, present in the four regions. Cereal cyst nematodes were found in 16% of the soil samples and were represented by two species, viz. H. avenae and H. latipons. Heterodera avenae was the most prevalent, occurring in 13% of the fields and associated with wheat in the 3 regions where it was found. Heterodera latipons was detected only in one sample, originating from Ain Jmaa (Saiss). The morphological and molecular characteristics of 11 populations of CCN collected from different wheat growing regions of Morocco were studied. Morphometrics of cysts and second-stage juveniles (J2) were generally within the expected ranges for H. avenae ; only the isolate from Aïn Jmaa showed morphometrics conforming those of H. latipons. When using species-specific primers for H. avenae and H. latipons, the specific bands of 109 bp and 204 bp, respectively, confirmed the morphological identification. In addition, the internal transcribed spacer (ITS) regions were sequenced to study the diversity of the 11 populations. These sequences were compared with those of Heterodera species available in the GenBank database (www.ncbi.nlm.nih.gov) and confirmed again the identity of the species. Ten sequences of the ITS-rDNA were similar (99-100%) to the sequences of H. avenae published in GenBank and three sequences, corresponding with one population, were similar (97-99%) to H. latipons

Présentation

Présentation : Revue Marocaine des Sciences Agronomiques et Vétérinaires