Showing papers on "Heterodera avenae published in 1992"

The importance of plant-parasitic nematodes to Australian and New Zealand agriculture

Abstract: The most important nematode problems in Australia and New Zealand are reviewed, several potentially serious new nematode problems are discussed and estimates of losses caused by nematodes are provided Numerous economically important species occur in Australia, but the most damaging nematodes include Meloidogyne spp, which are major pests of a wide range of fruit, vegetable, ornamental, field and pasture crops, the cereal cyst nematode, Heterodera avenae, and Anguina funesta, the vector of annual ryegrass toxicity Together with a number of less well-known nematodes, they cause losses to Australian agriculture that are estimated at more than $300 million per annum In New Zealand, Globodera rostochiensis and G pallida on potato and Heterodera trifolii and Meloidogyne hapla on white clover are possibly the most important species The crisis in nematode control programs caused by the withdrawal of several widely used nematicides is discussed and the need for the development of more sustainable nematode management strategies is recognised Options such as the use of nematode resistant cultivars and rootstocks, crop rotation, organic amendments and biological control are discussed and research priorities in plant nematology are considered

Phenology, Pathogenicity and Pathotypes of Cereal Cyst Nematodes, Heterodera a Venae and H. Latipons (Nematoda: Heteroderidae) in Israel

Abstract: Cereal cyst nematodes were found in varying population densities in the majority of wheat fields surveyed in Israel. The dominant species was Heterodera avenae (Ha), while H. latipons (Hl) occurred mainly in the more arid (southern) areas. The phenology and life cycle of the two species was basically similar: both species completed a single generation per year, life-stage development being closely related to climate and plant development. The two species differed in their etiology; whereas Ha attacked the root tip region inducing typical branching and swelling of roots with ensuing adherence of soil particles, juveniles of Hl penetrated at sites along roots more distant from the apex and, therefore, did not produce clearly visible root symptoms in the early seedling stage. In field conditions, the presence of Hl could be recognized only when cysts appeared on the roots. Moreover, the growth inhibition caused by Ha was more severe than that due to Hl. All local wheat cultivars tested were found to be excellent hosts for both Ha and Hl, as were all tested cultivars of barley and Phalaris sp.; oat cultivars were extremely poor hosts of Ha, but good hosts of Hl. Seven Ha populations showed the predominance of two pathotypes: Ha21, in the northern and the coastal regions, and Ha41 in the southern areas. Soil temperature affected both Heterodera' species hatching and damage to roots: at 6 ° C, life-stage development took 4 months, and it shortened as temperature increased up to 18° C, when it took only 40 days. At 24° C, juveniles failed to penetrate the roots. The effects on plant growth of early vs later sowing in dry and wet soils were recorded and are discussed.

On the origin and spread of heterodera avenae in australia

Abstract: Heterodera avenae is widely established in south eastern Australia and in recent years has been recorded in discrete infestations at far-distant northern locations. The pattern of its detection in Australia and data on host range, relation of hatch to temperature and pathotype reactions are consistent with introduction to southern Australia from Europe in the late nineteenth century.

X-ray microanalysis of feeding syncytia induced in plants by cyst nematodes

Abstract: The elements present in cyst nematode-induced syncytia in plant roots were investigated by scanning electron microscopy and energy dispersive X-ray microanalysis of specimens frozen in nitrogen slush. The techniques applied can examine the response of lighter, more mobile elements, in sites of in vivo activity, and at greater resolution (to sub-cellular level) than previously applied methods. Marked differences were recorded in elemental composition between cyst nematodes, their feeding cells and the unmodified cells of the host plant. In white clover, Heterodera trifolii-induced syncytia had more Mg and P than morphologically unmodified cells in infected and healthy roots. In older syncytia, associated with egg-producing females, high concentrations of Mg and P were localised in bodies assuming a globoid shape in the fractured surfaces. Surrounding cytoplasm had only low levels of these two elements. Similar changes were observed in syncytia induced by H. trifolii in roots of red clover. In syncytia induced by H. avenae in wheat, Mg was unchanged, but P and S concentrations were greater than in unmodified neighbouring root cells. Syncytia induced in tomato by Globodera rostochiensis had less Na and S than other plant cells. X-ray spectra from elements present in nematodes were distinct from those of their feeding cells; in particular, there was more Ca, but less K, in H. trifolii and H. avenae. The elemental composition of the cuticular layers of an H. avenae female showed marked differences in several elements.

Effect of Heterodera avenae on the growth, photosynthesis and chlorophyll content in triticale

Abstract: The studies on the growth of triticale as affected by Heterodera avenae revealed that the characters like shoot and root fresh and dry weights, leaf area, number of leaves and tillers and grain weight were adversely affected than shoot and root length with the increase in the level of inoculum. At 4 J2/g soil, there was significant decrease in these growth parameters but at 1 J2/g soil level there was stimulatoy effect. Photosynthesis, photosynthetic efficiency as also the chlorophyll content of leaves was found to be lower at higher levels of nematode density.

Cereal cyst nematode

Abstract: Cereal cyst nematode (Heterodera avenae Wollenweber) is a widely distributed pest of cereal crops, occurring in Britain, Ireland, various other northern European countries, Israel, India, Australia and N. America. In Britain it is more damaging to oats than to other cereals and is prevalent mainly on light-textured soils. For many years crop losses occurred chiefly on sandy soils in the West Midland counties and adjoining areas of Wales. After the Second World War damage became more widespread, especially on the thin chalk soils of Wiltshire and Hampshire, following wartime ploughing of large areas of downland. With the subse­quent decline in the growing of oats, this pest became less important. However, it still reduces yields of barley and wheat, espe­cially on light and inherently lower yielding soils; it is seldom important on heavy-textured soils.

A DNA probe which distinguishes Globodera pallida Pa2/3 from G. rostochiensis Ro1 and other cyst-forming nematodes

Abstract: A small DNA fragment (approx. 350 base pairs) from the genome of the potato cyst nematode Globodera pallida Pa2/3 was cloned in a bacterial plasmid. When used as a probe in dot-blot DNA hybridisations against a range of nematodes, the cloned DNA bound to G. pallida Pa2/3 but not to Globodera rostochiensis Rol. The cereal cyst nematode Heterodera avenae, the clover cyst nematode Heterodera trifolii, the root knot nematodes Meloidogyne hapla and Meloidogyne incognita, and the beet cyst nematode Heterodera schactii did not cross-hybridise. This probe can detect as few as six larvae of G. pallida.