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Importance of cereals and wheat nematodes in the world is revised. Distribution of cereal nematodes, species and pathotypes includes root lesion, cereal cyst nematodes and other cereal parasitic species. Life cycle, symptoms of damage and yield losses are also revised for root knot, stem and seed gall nematodes. Integrated control of cereal nematodes and some chemical, biological and cultural practices, including grass free rotations and fallowing with cultivation, are discussed. The effects of time of sowing, crop rotations and cultivation of resistant/tolerant varieties are also revised.

This study examined the restriction polymorphism (RFLP) of the nuclear ribosomal DNA in Heterodera avenae, H. filipjevi, H. mani, H. latipons, and the taxonomically unclear Gotland strain in order to establish a molecular characterization and phylogenetic relationships in the complex of cereal cyst nematodes (CCN). The internal transcribed spacer (ITS) and 5.8S rDNA were amplified by PCR from a single female or a cyst of 27 different geographic isolates of the CCN complex and one population of H. schachtii, used as outgroup. The amplified product was 1.2 kb long and 14 of 15 enzymes produced restriction fragments for each isolate. Relationships between populations were determined from UPGMA analysis based on distance values calculated from RFLP data. Digestions with TaqI clearly differentiated H. avenae, H. latipons, and a group composed of H. filipjevi and the Gotland strain. Six endonucleases (HaeIII, HinfI, ItaI, PstI, TaqI, and Tru9I) produced the same restriction pattern with H. filipjevi and the Gotland strain, and both were clearly separated from H. avenae with PstI. Restriction sites have revealed a mixture of the species H. latipons and H. avenae, and possible infraspecific variation in H. avenae. The inferred phylogenetic relationships of species in the CCN complex are in agreement with their morphological characterization.

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A previous RFLP analysis showed that the Aegilops ventricosa chromosome 6M^ which compensates for the absence of 6D in 6M^ (6D) wheat substitution lines was a 2/6 translocated chromosome, either 2S-6S.6L or 2S-6L.6S. The distal part of its long arm consists of a translocated segment belonging to homoeologous group 2. Chromosome 6M^ carries a gene(s) for resistance to cereal cyst nematode. In order to define the part of 6M^ (2S or 6S or 6L) involved in this resistance, addition lines with a 6M^ deleted either for its short arm or for the distal part of its long arm were evaluated. It was shown that the gene(s) is carried by the group 2 translocated segment. The hypothesis that the gene(s) could be allelic to Cre2, another gene conferring resistance to the nematode introduced into the wheat complement from Ae. ventricosa is discussed.

Les lignées d'addition blé-Aegilops ventricosa Tausch. VI. — Etude de la localisation chromosomique de la résistance à l'égard d'Heterodera avenae Woll.

Two main race groups of the stem nematode, Ditylenchus dipsaci, attack Vicia faba. The aim of this work was to evaluate random amplified polymorphic DNA (RAPD) as a source of markers for race identification and variability analysis of D. dipsaci. Thirteen populations of D. dipsaci were tested and one population of both D. myceliophagus and D. destructor as outgroup species. Sufficient levels of variation were detected to allow a clear distinction between the two D. dipsaci groups. This result was in agreement with the characterization based on morphological differences among races and on the type of faba bean disease symptoms. The intraspecific variation within D. dipsaci populations associated with V. faba was low and no strong correlation could be found between the geographical origin and molecular or morphological characterization. RAPDs are a powerful tool for identification of D. dipsaci races and/or populations.

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