Showing papers on "Heterodera avenae published in 2003"

Molecular identification of cyst-forming nematodes (heteroderidae) from iran and a phylogeny based on its-rdna sequences

Abstract: RFLP and sequences of ITS-rDNA of 45 populations of cyst-forming nematodes collected from different parts of Iran were analysed and identified as representatives of 21 species. Eight enzymes generated RFLP for all studied populations. Comparison of RFLP profiles and sequences of the ITS regions with published data confirmed the presence of Heterodera avenae, H. filipjevi, H. glycines, H. hordecalis, H. latipons, H. schachtii and H. trifolii in Iran. RFLP patterns and ITS sequences for H. elachista, H. turcomanica, H. mothi and C. cacti were obtained for the first time in this study. Heterodera humuli, H. goettingiana, H. fici, H. elachista, H. turcomanica and Cactodera cacti are recorded for the first time in Iran. These results correspond with morphological and morphometric identification of the populations. Several populations were not identified at the species level and are attributed to Heterodera sp.; some of these may correspond to new species. Twenty-one new sequences from Iranian cyst-forming nematodes and 36 known sequences were used for the phylogenetic analyses. The cyst-forming nematodes formed several clades corresponding to their morphological features. Heterodera mothi and H. elachista clustered with high support with other Cyperi group species and H. turcomanica formed a moderately to highly supported clade with the Humuli group.

Molecular and morphological characterisation of the Heterodera avenae species complex (Tylenchida: Heteroderidae)

Abstract: Species of the Heterodera avenae complex, including populations of H. arenaria, H. aucklandica, H. australis, H. avenae, H. filipjevi, H. mani, H. pratensis and H. ustinovi, obtained from different regions of the world were analysed with PCR-RFLP and sequencing of the ITS-rDNA, RAPD and light microscopy. Phylogenetic relationships between species and populations of the H. avenae complex as inferred from analyses of 70 sequences of the ITS region and of 237 RAPD markers revealed that the cereal cyst nematode H. avenae is a paraphyletic taxon. The taxonomic status of the Australian cereal cyst nematode H. australis based on sequences of the ITS-rDNA and RAPD data is confirmed. Morphometrical and ITS-rDNA sequence analyses revealed that the Chinese cereal cyst nematode is different from other H. avenae populations infecting cereals and is related to H. pratensis. Bidera riparia Kazachenko, 1993 is transferred to the genus Heterodera as H. riparia (Kazachenko, 1993) comb. n. As a consequence, H. riparia Subbotin, Sturhan, Waeyenberge & Moens, 1997 becomes a junior secondary homonym and is renamed as H. ripae nom. nov. Morphological, morphometrical characters and RFLP profiles for identification of the nine species presently placed in the H. avenae species complex are given.

Genetic and phenotypic diversity in the graminaceous cyst nematode complex, inferred from PCR-RFLP of ribosomal DNA and morphometric analysis

Abstract: Graminaceous cyst nematodes form a group of eleven valid species including Heterodera avenae, Heterodera filipjevi and Heterodera latipons and constitute major pests to cereals They are widely spread in circum-mediterranean areas where they are presumed to cause yield losses on bread and durum wheat The objective was to document the diversity of these cereal cyst nematodes, in particular samples from Mediterranean regions, in comparison to species which develop on cultivated or wild grasses (H arenaria, H hordecalis, H mani) and on rice or sugarcane (H sacchari) Studies involved PCR-RFLP of ITS and morphometrics of the juvenile and cyst characters UPGMA analysis of molecular data showed that the isolates segregated in two main clusters which seem to represent different evolutionary lineages The H avenae sensu lato cluster (I) contained H arenaria, H avenae, H filipjevi and H mani The second cluster (II) contained isolates of H hordecalis and H latipons Within H avenae sensu lato, H filipjevi was separated from the other related species with significant bootstrap value The differentiation of H arenaria, recognized for the first time based on molecular data, and H mani with few restriction enzymes were the least significant Intraspecific polymorphism allowed differentiation of isolates originating from Australia within H avenae sensu stricto The group H hordecalis–H latipons showed the greatest genetic variability between and within isolates Two representatives of Heterodera sacchari, taxonomically included in the ‘schachtii’ group, were genetically as distant to this group as to the other graminaceous species belonging to either H avenae sensu lato or H hordecalis–H latipons group Results inferred from multivariate analysis applied on morphometrics of the cysts and juveniles showed agreement between genetic and phenotypic classifications This study demonstrates the utility of combined molecular and classical methods to enhance our knowledge about the diversity within the complex of graminaceous cyst nematodes and to establish robust techniques to identify a wider set of nematode species

Mapping of a QTL contributing to cereal cyst nematode tolerance and resistance in wheat

Abstract: Cereal cyst nematode (CCN; Heterodera avenae Woll.) is a root pathogen of cereals that can cause severe yield losses in intolerant wheat cultivars. Tolerance to CCN, measured as early vigour in CCN-infested plots, was mapped in a Trident/Molineux doubled-haploid (DH) population. A locus accounting for a significant proportion of the tolerance to CCN was mapped to chromosome 6B of Molineux by association with RFLP loci Xcdo347-6B and Xbcd1 and also by nullisomic/tetrasomic substitution line analysis, and has been designated Cre8. The linkage of CCN tolerance with Xcdo347-6B was validated using a Barunga/Suneca DH population. The Cre8 locus also contributed to CCN resistance in the Trident/Molineux population. The RFLP locus Xbcd175, which is diagnostic for the Aegilops ventricosa segment VPM1 of Trident, explained up to 18% of the variation for early vigour in CCN-infested soils in the Trident/Molineux population. However, the Trident/Molineux population also segregated for early vigour in the absence of CCN, with Xbcd175 explaining up to 7% of the variation for this trait. The VPM1 segment of Trident therefore provides early vigour that may contribute to CCN tolerance in this cultivar.

Biochemical and genetic studies of two Heterodera avenae resistance genes transferred from Aegilops ventricosa to wheat

Abstract: Two Heterodera avenae resistance genes, Cre2 from Aegilops ventricosa AP-1 and Cre5 from Ae. ventricosa #10, were shown to confer a high level of resistance to the Spanish pathotype Ha71. No susceptible plants were found in the F2 progeny from the cross between the two accessions of Ae. ventricosa, suggesting that their respective resistance factors were allelic. However, genes Cre2 and Cre5 apparently were transferred to a different chromosomal location in the wheat line H-93-8 and in the 6Mv(6D) substitution, respectively, as proved by F2 segregation of their cross progeny. The induction of several defence responses during early infection by the same H. avenae pathotype in resistant lines carrying Cre2 or Cre5 genes was studied. Isoelectrofocusing (IEF) isozyme analysis revealed that peroxidase, esterase and superoxide dismutase activity increased after nematode infection, in roots of resistant lines in comparison with their susceptible parents. Differential induced isoforms were also identified when IEF patterns of resistant lines were compared. A DNA marker, absent in Cre5-carrying genotypes, was found to be linked, thought not very tightly, to the Cre2 gene in the H-93-8 line. The differences observed between the Cre2 and Cre5 genes with respect to their chromosomal location in wheat introgression lines, de-toxificant enzyme induction and behaviour against different pathotypes, suggest they are different H. avenae resistance sources for wheat breeding.

Natural Incidence of Parasitic Bacterium, Pasteuria Sp. on Plant Parasitic Nematodes in Haryana

Abstract: No incidence of Pasteurw spp. was recorded (except on Heterodera cajani ) in field crops infected with Heterodera avenae, H. zeae, Rotylenchulus reniformis or citrus Infected with Tylenchulus semipenetrans . Grape vineyards infected with Meloidogyne javanica revealed 56 per cent incidence of Pasteuria penetrans . Ten-year-old vineyards showed maximum prevalence of the bacterium. Sugar centrifugal floatation technique was better than modified Baermann's funnel method for the recovery of Meloidogyne J2 encumbered with P. penetrans spores. Bioassay of soil samples from vineyards proved more useful than routine analysis to estimate the extent of infestation of P. penetrans .