Showing papers on "Heterodera avenae published in 1998"

A cereal cyst nematode (Heterodera avenae Woll.) resistance gene transferred from Aegilops triuncialis to hexaploid wheat

Abstract: The cereal cyst nematode (Heterodera avenae) is an important root parasite of common wheat. A high level of resistance was transferred to wheat from Aegilops triuncialis (TR lines) using the cross [(T. turgidum×Ae. triuncialis)×T. aestivum]. Low fertility (3–5 viable kernels per plant) was observed during the process but the surviving hybrid plants were highly vigorous. To obtain stable resistant lines further crosses to T. aestivum were performed. The resistance in TR lines seems to be transferred from the C genome of Ae. triuncialis (genomes CCUU). Ae. triuncialis was highly resistant to the two Spanish populations of H. avenae tested, as well as to four French races and two Swedish populations. The histological analysis showed a hypersensitive reaction in the roots of a resistant TR line inoculated with the Ha71 pathotype of H. avenae, whereas well-formed syncytia were observed in the roots of the susceptible control. Resistance to the H. avenae Ha71 pathotype seemed to be inherited as determined by a single dominant factor in the crosses between resistant TR lines and susceptible cultivars.

RFLP mapping of a new cereal cyst nematode resistance locus in barley

Abstract: Cereal cyst nematode (CCN) (Heterodera avenae Woll.) is an economically damaging pest of barley in many of the worlds cereal growing areas. The development of CCN-resistant cultivars may be accelerated with the application of molecular markers. Three resistance genes against the pest have been mapped previously to chromosome 2 (Ha1, Ha2 and Ha3). In this study, a third gene present in the Australian barley variety 'Galleon' derived from the landrace 'CI3576' was located. Segregation analysis of CCN resistance data derived from doubled haploid populations of the cross 'Haruna Nijo' × 'Galleon' identified a single major locus controlling CCN resistance in the variety 'Galleon'. This locus mapped to the long arm of chromosome 5H estimated to be 6.2cM from the known function restriction fragment length polymorphism marker XYL (xylanase). While five genes for CCN resistance, including Ha2, have been mapped to group 2 chromosomes in the Triticeae, no gene other than Ha4 has been identified on group 5 chromosomes.

A molecular genetic map of the long arm of chromosome 6R of rye incorporating the cereal cyst nematode resistance gene, CreR

Abstract: A genetic map of the long arm of chromosome 6R of rye was constructed using eight homoeologous group-6 RFLP clones and five PCR markers derived from the rye-specific dispersed repetitive DNA family, R173 The map was developed using a novel test-cross F1 (TC-F1) population segregating for resistance to the cereal cyst nematode Comparisons were made between the map generated with other rye and wheat group-6 chromosome maps by the inclusion of RFLP clones previously mapped in those species Co-linearity was observed for common loci This comparison confirmed a dramatic reduction in recombination for chromosome 6R in the TC-F1 population The CreR locus was included in the linkage map via progeny testing of informative TC-F1 individuals CreR mapped 37 cM distal from the RFLP locus, XksuF37 Comparative mapping should allow the identification of additional RFLP markers more closely linked to the CreR locus

Host responses of different Triticeae to species of the cereal cyst nematode complex in relation to breeding resistant durum wheat

Abstract: occurred in the iliree levels of ploidy and in several genomes: SI (T. longissimum), DVM v (T. vemricosum), UM (T. ovalUm), US V (T. variabile ), and ABD (T. aeslivum AUS 4930). Total or intermediate resistance was found in genome D (T. lQuschii CPI 110813 or AUS 18913) but their expression in synilietic hexaploid wheat was incomplete resistance. It was confirmed that the Crel gene from wheat cv. Loros is ineffective against H. avenae populations from Australia, India, and Israel but also against H. jilipjevi. Inter- and intraspecific differentiation wiiliin ilie cereal cYSt nematode complex, based on (a)viru­ lence to Triticeae and fitness, and the use of total and intermediate resistance in breeding programmes are discussed. Orstorn/Elsevier, Paris

Effects of crop rotations of cereals with vetch and fallow on soil nematofauna in Central Spain.

Abstract: The influence of the use of vetch or fallow in rotation with cereals on the dynamics of nematode populations was studied in a field experiment conducted on a luvisol in Central Spain. All the nematodes present in the trial were monitored by seasonal samplings for three consecutive years, starting one year after the first rotation cycle was completed. Vetch in rotation with cereals controlled soil populations of some virus transmitters (Xiphinema pachtaicum and Trichodorus sp.) and the cyst nematode Heterodera avenae. Fallow also controlled X. pachtaicum and H. avenae, as well as Pratylenchus thornei, Ditylenchus dipsaci, Tylenchorhynchus maximus and Tylenchus sp. Other Dorylaimidae and Rhabditidae species seemed to be influenced by vetch and fallow only indirectly. Neither rotation influenced Longidorus profundorum populations. The maturity index based on the nematode fauna was used as a measure of the disturbance in this ecosystem.

Hatch and emergence

Abstract: The cyst forming species of subfamily Heteroderinae retain their eggs within a ‘cyst’ that is formed by the cuticle of the mature female after her death by a polyphenol tanning process. In some cyst nematode species (e.g. Heterodera avenae), all of the eggs are retained within the cyst, while in many species (e.g. H. cajani, H. glycines, H. trifolii) eggs are also laid in egg sacs. Egg hatch and juvenile emergence from cyst is influenced by a myriad of chemical and physical factors such as host plant root diffusates, temperature and moisture conditions (Fairbairn, 1960). In some species, eggs hatch in large numbers under suitable moisture and temperature conditions provided the essential development has taken place, while in some other species, a stimulus from the host (e.g. root diffusate) is needed to initiate egg hatch. The cyst does not simply act as a passive container of eggs; there is evidence of the influence of the cyst wall on hatching (Kaul, 1962; Shepherd and Cox, 1967; Okada, 1972). Work of Banyer and Fisher (1971a) indicates that a greater percentage of free eggs hatch than the encysted ones. Physical, chemical and biological environment in the cyst can greatly influence the activity and emergence of hatched juveniles from openings in the cyst. Further, if any specific stimulus is required, then it must first enter the cyst before acting on the egg shell and juvenile. A second-stage juvenile must complete two integral steps in order to find a host root: (1) hatch from egg, and (2) emergence from cyst. ‘Hatch’ is eclosion of a juvenile from an egg in the cyst, and ‘emergence’ is exit of the hatched juvenile from the cyst. A commonly used expression ‘hatching from cyst’ includes these two distinct steps. Emergence, of course, is the end product of successful completion of the sequence of events in egg and cyst. After completion of embryonic development, the first-stage juvenile moults inside the egg and the infective second-stage juvenile ecloses from egg and gradually escapes from openings in the cyst. In the case of egg sacs, the juveniles hatch from eggs and egress from the egg sacs; the egg sac may exert influence on the movement of juveniles.

Biocontrol of Heterodera avenae infecting wheat using different inoculum sequence of Verticillium chlamydosporium

Abstract: Ecofriendly management of Heterodera avenae using fungus Verticillium chlamydosporium isolated from the local fields was carried out under pottrials. Fungus was multiplied on cheaper wheat bran substrate. Eight gram of such fungal containing wheat bran were inoculated in three different sequencesviz. (i) Fifteen days prior to nematode inoculation. (ii) Simultaneously with nematode and (iii) Fifteen days after nematode inoculation in 15 cm diameter earthen pots containing 1Kg of sterilized soil. Spore load per gram was estimated using standard formula. Observations revealed that the timing of the fungal treatment greatly affected the plant growth characters. The reduction in the plant growth characters were more discernible when the nematode inoculation was given prior to the fungal inoculation. However, better plant growth and appreciable reduction in cyst formation per plant was noted in plants where fungal inoculation preceded nematode inoculation. Young females, cysts, and eggs were found colonized by the fungal hyphae. Prior application of biocontrol agent proved beneficial in managing the nematode population to an appreciable level.

Characterization of the hatching fluid from Heterodera avenae

Abstract: During hatching of cyst nematodes, fluid is released from the egg into the hatching medium. The presence of carbohydrates in the hatching medium of two populations of Heterodera avenae from India and the UK was determined using Western blots probed with different biotinylated lectins. Eighteen specific bands with molecular weights in the range 12-78 kDa were detected in the hatching media collected over the six weeks hatching period. There were no differences between the two populations. The majority of the lectin bands were inhibited by the appropriate competitive sugar, indicating sugar-specific binding. Four different sugars were detected. Of the bands detected with Con A, only two were not completely inhibited which may indicate non sugar-specificity. The possible origin of these carbohydrates during the hatching process is discussed. There were differences in the protein banding pattern of hatched second stage juveniles; an extra band was present at 20 kDa in the population from India, whereas the population from the UK had a band at 34 kDa.