Showing papers on "Heterodera avenae published in 1979"

Extent of disease in populations of Heterodera, with especial reference to H. schachtii

Abstract: SUMMARY Analysis was made of the extent of disease in 112 populations of Heterodera schachtii, comprising 88 populations of cysts obtained from soil samples and 24 populations of females and cysts taken from host roots. Overall, some 14% of full cysts taken from soil were diseased, although much variation was found. About half of the cysts were substantially and half partially diseased. Where beet monoculture had long been practised, overall disease was approximately doubled. Less than 50% of diseased cysts were parasitised by recognised egg pathogens and nearly the same proportion showed symptoms of lysis, coagulation or decay, the causes of which could not be ascertained. The remainder contained unexamined or miscellaneous fungi and a few showed oily degeneration. Disease in 10 populations of cysts from roots was higher than in cysts from soil. In females from roots it was especially variable, for most diseased females were invaded by one or two specific fungal pathogens in whose absence all were healthy. Examination of six populations of Heterodera avenae indicated the extent and nature of disease was not dissimilar from that in H. schachtii. The pathogens, which were all fungi, and the disease symptoms of uncertain origin found in cysts and females of H. schachtii are briefly summarised.

Reactions of Cereals To Populations of Heterodera Avenae in South Australia

Abstract: Two wheat cultivars (AUS 10894 and AUS 90248) and one barley (cv. Morocco), were resistant to 20 populations of Heterodera avenae Woll. from southern Australia. No variations occurred in the reactions of 22 cultivars from an 'International Test Range', to 4 diverse poplations of H. avenae in South Australia. Except for one wheat (cv. Psathias), which was more susceptible than the resistant wheat (cv. AUS 10894), the reactions were similar to those reported with Victorian populations. Therefore, only one biotype seems likely for South Australia and it is probably the same as the Victorian biotype. Second-stage larvae which developed in the field at different locations had a constant width but varied in length. This variation in length did not occur when larvae were grown in a controlled environment.

Temperature and root exudates on the cereal cyst-nematode heterodera-avenae

Abstract: English populations of Heterodera avenae hatched best in water at 10° or 15° after storage for at least 8 weeks at 2° or between 0° and 7°. Maximum total hatch over prolonged periods was at 15°, though for brief periods hatch rate was most rapid at 20°. Transfer to 20° briefly stimulated hatch after 8 weeks at 2° and 5° but after 10° the transfer had no significant effect. At 10° and 15°, root exudates of wheat, oats and barley (including varieties resistant to H. avenae pathotypes 1 and 2) stimulated hatch significantly. Root exudate activity is best detected in hatching tests of relatively short duration. No special relationship between cereal variety host status and exudate effects on pathotype has yet been found.

Inheritance of Resistance To Heterodera Avenae in Barley

Abstract: Inheritance of resistance to H. avenae in four cultivars of barley, Athinais, CI 8147, Marocaine 079 and Nile, was attributed to a single dominant gene. In a fifth cultivar, Morocco, the resistance may have been due to a single dominant gene but the possibility of two genes involved in the resistance could not be discounted. The same gene was involved in the resistance of Athinais and Marocaine 079, different genes were involved in Athinais and Nile, while both of these genes differed from the resistance in Morocco. Resistance in CI 8147 also differed from Morocco, but the relation of this gene to genes in other cultivars is not known. Therefore, at least three, with a possibility of five, different major genes were involved in the expression of resistance to H. avenae by the barley cultivars used in this test.

Occurrence of Plant Parasitic Nematodes in Punjab, India

Abstract: Forty-seven plant nematode species were found associated with 33 crops, bringing the total number of plant nematode species reported from the state to 68. Meloidogyne incognita, M. arenaria, Pratylenchus zeae, Tylenchorhynchus brassicae, Tylenchulus semipenetrans, Rotylenchulus reniformis, Xiphincma americanum, Heterodera avenae and H. zeae cause extensive damage. Vegetables were the most adversely affected of all the crops investigated.

Records of crop damage by some species of cyst nematodes in eastern England, 1967–77

Abstract: SUMMARY Records of crop damage in eastern England from 1967 to 1977 inclusive are tabulated and mapped for the cereal cyst nematode (Heterodera avenae Woll.), carrot cyst nematode (Heterodera carotae Jones), brassica cyst nematode (Heterodera cruciferae Franklin) and pea cyst nematode (Heterodera goettingiana Liebscher). Although distributions of crop damage by these cyst nematodes have not altered significantly from previous reports, the frequencies show distinct fluctuations from year to year.

Effect of the cereal cyst nematode, Heterodera avenae, on the early growth of oats, wheat and barley

Abstract: SUMMARY The effect of Heterodera avenae Woll. upon the early growth of cultivars of oats, wheat and barley was measured. During the first two weeks the rate of root growth was retarded in some barley cultivars although shoot growth was stimulated in all the oats and in two cultivars each of barley and wheat. Later, infestation slowed growth of all the cultivars grown, except Drost barley. When uninfested, some cultivars resistant to H. avenae grew more slowly than did susceptible ones.