Showing papers on "Globodera rostochiensis published in 1990"

Localization by restriction fragment length polymorphism mapping in potato of a major dominant gene conferring resistance to the potato cyst nematode Globodera rostochiensis

Abstract: A major dominant locus conferring resistance against several pathotypes of the root cyst nematode Globodera rostochiensis was mapped on the linkage map of potato using restriction fragment length polymorphism (RFLP) markers. The assessment of resistance versus susceptibility of the plants in the experimental population considered was based on an in vivo (pot) and an in vitro (petri dish) test. By linkage to nine RFLP markers the resistance locus Gro1 was assigned to the potato linkage group IX which is homologous to the tomato linkage group 7. Deviations from the additivity of recombination frequencies between Gro1 and its neighbouring markers in the pot test led to the detection of a few phenotypic misclassifications of small plants with poor root systems that limited the observation of cysts on susceptible roots. Pooled data from both tests provided better estimates of recombination frequencies in the linkage interval defined by the markers flanking the resistance locus.

The life-cycle, population dynamics and host specificity of a parasite of Heterodera avenae, similar to Pasteuria penetrans.

Abstract: SUMMARY The occurrence of a population of Pasteuria, similar to Pasteuria penetrans, and possibly a new species, parasitic on Heterodera avenue in a cereal-cyst nematode suppressive soil, is reported. The life-cycle was respicted to the H. avenue second-stage juvenile, and prevented such infected juveniles from invadmg plant roots. Between March and July, 38-56 ?h of the juveniles present in the soil had between one and five spores adhering to their cuticles; microcolonies could be seen in the juveniles as early as April, however, mature spores were not recorded until July. Developing females, and cysts extracted from plant roots were not infected by the bacterium. The suppressive soil also contained juveniles and adults of Pratylenchus and Tylenchorhynchus infected with Pasteuria. Although the spores adhering to, and within, al1 three nematode species were approximately the same size, between 4 and 5 Pm, it was not clear whether or not the Pasteuria population was either a single or a mixed population. Host specificity studies with spores extracted from the juveniles of H. avenue showed that it adhered to the cuticles of schachtii, H. glycines, Globodera rostochiensis, G. pallida and Meloidogyne javanica. Attempts to bait soil by adding these nematodes failed to result in the infection of females. It is reported the soil contained approximately 7 x IO3 spores per gram as evaluated using differential centrifugation.

Pathotype - specificity in potato cyst nematodes, a reconsideration.

Abstract: Within the two potato cyst nematode (PCN) species, Globodera rostochiensis and G. pallida, eight pathotypes are presently discerned by seven differential Solanum clones, whereby resistance is defined as a Pf/Pi ratio <1.0, and susceptibility as a ratio above 1.0. This pathotyping is felt to be unsatisfactory. Reconsidering the original data and data published by others resulted in the conclusion that there are only three reliably recognizable Ro-pathotypes Ro1/Ro4, Ro2/Ro3 and Ro5. The differential clones 60.21.19 and 65.346.19 differentiate only between the two species. Within G. pallida it does not seem possible to identify pathotypes reliably. The resistance-virulence pattern is of a quantitative nature fitting a polygenic system. There appear to be pathotype-specific effects, which are not large enough to identify and classify pathotypes reliably. It is therefore suggested to rename the Ro-pathotypes into Ro1 (old Ro1 and Ro4), Ro3 (old Ro2 and Ro3) and Ro5 (old Ro5) and to speak of more and less virulent Pa-populations.

Ultrastructural response of potato roots resistant to cyst nematode Globodera rostochiensis pathotype Ro 1

Abstract: Histological and ultrastructural changes in the potato cvs Diamant, Anosta and Morag, three days after inoculation with second stage juveniles of Globodera rostochiensis pathotype Rol, were identical. The cells involved in nematode feeding were already transformed into a highly metabolic syncytium. Protein storage in form of crystalline bodies were detected in the plastids contained in the syncytial cells. It is assumed that these crystalline bodies are formed as a consequence of an osmotic imbalance in the cells caused by the nematode invasion of resistant roots. The hypersensitive host reaction was evident seven days after nematode inoculation and was characterized by an extensive necrosis lining the syncytium. Syncytial cells showed an involution of the cytoplasmic content while the nucleus and nucleolus were severely affected, indicating inactivation of the transcription mechanism. The mechanism of resistance to the Rol pathotype in the three potato cultivars was determined to be antibiosis, expressed as resistance to the survival and reproduction of the nematode.

Fungal Parasites of the Potato Cyst Nematode Globodera rostochiensis: Isolation and Reinfection.

Abstract: Fungal parasitism of eggs of the potato cyst nematode Globodera rostochiensis was < 1, 3, and 17% at three sites in Sweden. The fungi isolated most frequently from infected eggs were a Septocylindrium-like fungus ( 19 %), Exophiala spp. (17 %), and Cylindrocarpon spp. (13 %). Verticillium suchtasporium was isolated from infected eggs at a low frequency (4%). In laboratory experiments V. suchlasporium infected 93% of the eggs within cysts after 10 days on dilute corn meal agar. This species showed chitinase and protease activity. Infection of eggs by the Septocylindrium-like fungus was moderate, whereas Cylindrocarpon destructans and Cladosporium cladosporoides did not infect eggs. No chitinase activity was found in these fungi, but protease activity was recorded in all. Growth of the fungi in cysts did not influence the number of physiologically disordered eggs.

Reproduction of Globodera rostochiensis on Transformed Roots of Solanum tuberosum cv. Desiree

Abstract: Transformed roots of the susceptible potato Solarium tuberosum L. cv. Desiree were inoculated with second-stage juveniles ()2) of Globodera rostochiensis pathotype Rol. Adult males emerged after 3-4 weeks and matings with females occurred. After 8 weeks gentle pressure on the eggs of maturing females released the J2 which were viable. Because this technique enables the production of vigorously growing roots with numerous laterals, it may be suitable for obtaining a high yield of sterile potato cyst nematodes. Success with the sterile in vitro culture of a sedentary nematode, Heterodera schach- tii Schmidt, was achieved many years ago (10). More recently, Murashige and Skoog (MS) medium was used to culture suscep- tible and resistant potato roots on which Globodera rostochiensis (Wollenweber) Beh- rens was reared (2). The use of trans- formed roots to rear H. schachtii and Me- loidogyne javanica in vitro has opened up new possibilities for studying resistance genes against sedentary nematodes (8,13,14). The objective of this research was to determine whether G. rostochiensis could be cultured in vitro on transformed potato roots. MATERIALS AND METHODS Transformed root cultures: Susceptible Solanum tuberosum L. cv. Desiree tubers were soaked in absolute ethanol for 5 min- utes, peeled, and surface sterilized for 15 minutes in a 10% solution of Domestos, a commercial bleach (Unilever plc, London, UK) containing 7% sodium hypochlorite. They were then washed six times in sterile distilled water and finally immersed in liq- uid Murashige and Skoog medium (MS powder, Flow Laboratories, Irvine, UK) supplemented with 20 g sucrose per liter, adjusted to pH 5.8 (MS20) but without hor- mones (12). Several columnar sections were removed from the tubers using a sterile

Assessing intra-specific variations in virulence in Globodera rostochiensis and G. pallida

Abstract: La methode d'elevage des nematodes a kyste sur pommes de terre cultivees en boite de Petri (Mugniery & Person, 1976) est utilisee pour estimer le pourcentage de phenotypes virulents et non virulents dans des populations de Globodera. Plusieurs populations de divers pathotypes de G. rostochiensis et G. pallida sont etudiees. Les frequences des proportions de pathotypes virulents notees pour chaque population sont comparees a celles obtenues a partir d'essais en pots utilisant le rapport P f /P i

Hatching and Reproduction of the Potato Cyst Nematode, Globodera Rostochiensis, From Potato Fields in Western Australia as Influenced By Soil Temperature

Abstract: The optimum hatching temperature for the Western Australian population of Globodera rostochiensis was 22°C in picrolonic acid with a maximum total hatch of 88 ± 6% after 42 days. In pots, under conditions simulating temperatures at the infestation sites, there were two peaks of hatching at 10-40 days and 110-140 days. Females and their eggs were first observed in the roots at 35 and 49 days respectively with most males in soil at 60 days. No second generation of eggs was observed following the second peak of juveniles in soil. Females on plants transferred from 15/10°C at 35 days after sowing developed between 5-30°C but the optimum temperature for egg development was 15°C. The relationship between initial and final egg density was as reported previously.

Changes in polyphosphoinositide metabolism in Globodera rostochiensis following stimulation to hatch by potato root diffusate

Abstract: Eggs of Globodera rostochiensis were incubated for 2.5 h in 13.3 mM myo-[2- 3 H] inositol to allow incorporation of the labelled compound into phosphoinositides. The subsequent in vivo metabolism of these phospholipids released the water soluble products glycerophosphoinositol, (GPIns), inositol 1-phosphate (IP1); inositol 1,4-biphosphate (IP2) and inositol 1,4,5-triphosphate (IP3) which were separated by ion exchange chromatography before the radiolabel incorporated into each was quantified using a scintillation counter. Exposure of eggs to labelled myo-inositol in either active or heat-inactivated hatching factor in potato root diffusate resulted in a significantly higher recovery of the three inositol phosphates from individuals receiving the stimulus to hatch. The results substantiate earlier work indicating a rapid initial action of hatching factor on unhatched juveniles of G. rostochiensis.

Field trials using single potato plants as whole plots, with and without nematicide treatment, to assess tolerance of attack by Globodera rostochiensis.

Abstract: Summary It is important to assess the tolerance of new potato cultivars with partial resistance to potato cyst nematode attack. The experiments described here are intended to quantify tolerance adequately using a minimum of resources. When test plants were spaced widely in the field trials it was also possible to estimate their resistance levels but standard plant spacing allowed roots of neighbouring plants to encroach on a test plant's root space and to interfere with attempts to assay resistance. Standard plant spacing did, however, give more realistic yields per plant and competition from neighbouring plants was standardised by surrounding each test plant by four identical guard plants (cv. Desiree). Regressions of yield on severity of nematode attack were drawn when nematode infestation varied naturally across the trial site or when different levels of attack were created by applying nematicide at a range of dose rates. Cara was the most tolerant cultivar tested, with a complete spectrum of tolerance shown by other cultivars/clones. Some clones with a high degree of resistance were intolerant and it is precisely these that this type of test seeks to identify.

Quantification of Globodera rostochiensis and G. pallida in mixed populations using species-specific thermostable proteins

Abstract: A method has been developed to quantify species ratios in mixed populations. The method is based on the separation of species-specific thermostable proteins by SDS-PAGE. Densitometric analyses of the 17 kD protein ofGlobodera pallida and the 18 kD protein ofG. rostochiensis revealed a high correlation (R2=0.93) with the species ratio in the mixed samples. Within the limits of 10 to 90% of each species, one can estimate with 95% reliability the species composition with 3 to 6% deviation.