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The effects of interspecific competition between the potato cyst nematodes (PCN), Globodera pallida and G. rostochiensis, under variable population conditions were examined. PCN-susceptible potato cultivars were inoculated with single- and mixed-species populations of PCN. There was a significant difference in species multiplication between single- and mixed-species populations. Globodera rostochiensis multiplication in mixed-species populations was significantly lower than single-species populations. Densitydependent trials showed a significantly greater increase in multiplication of G. pallida at low inoculation densities relative to G. rostochiensis. These results indicate that G. pallida has a negative effect on G. rostochiensis populations and is the more successful species when competing. A staggered inoculation trial showed that the greater competitiveness of G. pallida was not wholly attributed to its later hatch. Globodera pallida outcompeted G. rostochiensis regardless of the timing of inoculation; however, G. pallida multiplication was lowest when plants were simultaneously inoculated with both species. [ABSTRACT FROM AUTHOR]

Soil samples taken from the ridge of field-grown potato (cv. British Queen) as well as from bulk soil of the same field were incubated with sterile potato root leachate or water. Samples were filtered and filtrates used in an in vitro bioassay to determine their effect on hatch of potato cyst nematodes (PCN) Globodera rostochiensis and G. pallida. Concurrently, an experiment was established where the sterile potato root leachate or water was incubated with a sterile soil wash. Ridge soil was shown to induce significantly more hatching than bulk soil, indicating the presence of PCN hatching factors. When a soil wash of ridge soil was used it did not increase hatch, suggesting a role for soil microorganisms in the hatching process. Greater hatch of G. rostochiensis in bulk soil compared to G. pallida suggests a role for soil microorganisms in spontaneous hatch of PCN in vivo. [ABSTRACT FROM AUTHOR]

Three bacterial isolates, SB13 (Acinetobacter sp.), SB14 (Arthrobacter sp.) and SB15 (Bacillus sp.), were previously isolated from the rhizosphere of sugar beet (Beta vulgaris ssp. vulgaris) plants and shown to increase hatch of potato cyst nematodes in vitro. In this study, the three isolates were assayed for rhizosphere competence. Each isolate was applied to seeds at each of four concentrations (105-108 CFU ml-1) and the inoculated seeds were planted in plastic microcosms containing coarse sand. All three isolates were shown to colonise the rhizosphere, although to differing degrees, with the higher inoculation densities providing significantly better colonisation. The isolates increased sugar beet root and shoot dry weight. Isolates SB14 and SB15 were analysed for their ability to induce in vivo hatch of Globodera pallida in non-sterile soil planted with sugar beet. After 4 and 6 weeks, both isolates had induced significantly greater percentage hatch compared to controls. [ABSTRACT FROM AUTHOR]

Six potato (Solanum tuberosum) cultivars (Home Guard, Bintje, British Queen, Maris Piper, Pentland Dell and Saturna) were inoculated with Vaminoc (a commercial mixture of three selected arbuscular mycorrhizal fungal (AMF) isolates) and with two of the individual AMF isolates present in Vaminoc, Glomus intraradices (BioRize BB-E) and Glomus mosseae (isolate BEG 12). Root length colonisation by AMF at 6 weeks after shoot emergence ranged from 49 to 54%, with Vaminoc exhibiting the highest percentage. In comparison with control plants, AMF-inoculated plants accelerated the in vitro hatch (21% mean increase) of the potato cyst nematode (PCN) species Globodera pallida (but not of G. rostochiensis) in potato root leachate collected 3 weeks after shoot emergence. The effects of mycorrhization on PCN hatch were broadly similar across the six potato cultivars. This consistency supports the potential use of AMF inoculation of potato plants as part of an integrated pest management strategy for G. pallida. [ABSTRACT FROM AUTHOR]

The effects of inoculation of roots of the potato (Solanum tuberosum) cv. Golden Wonder with the mixed-isolate arbuscular mycorrhizal fungus (AMF) inoculum Vaminoc, or with three single-isolates AMF inocula (Glomus intraradices, G. mosseae and G. dussii; components of Vaminoc), on the potato cyst nematode (PCN) Globodera pallida were assessed in a pot experiment in the presence or absence of the nematicide aldicarb (Temik 10G). Mycorrhization of potato roots stimulated an 11% overall mean increase in the hatch of G. pallida within the first 2-4 weeks from planting. In the presence of aldicarb, AMF-inoculated plants exhibited only 57% of the PCN population size (viable eggs (g soil)-1) of the non-inoculated plants; in the absence of aldicarb the respective value was 42%. Root length colonisation by AMF was unaffected by the application of aldicarb. Roots of PCN-infested plants exhibited reduced levels of mycorrhizal colonisation (41%) compared to non-PCN-infested plants (45%). The AMF isolates used differed in their ability to produce a plant growth response (expressed as root dry weight, shoot dry weight or total dry biomass) and to affect tuber yield. In this regard, the single Glomus isolates enhanced plant growth (36% increase in total dry biomass) and improved fresh tuber yield by 22% on average, while Vaminoc had, in most cases, no effect. It was concluded that AMF have potential to reduce G. pallida multiplication via a dual mechanism involving stimulation of nematode hatch and inhibition of root invasion. Field experimentation will be required to take this research forward and assess the feasibility of including AMF in G. pallida integrated management strategies. [ABSTRACT FROM AUTHOR]

Successful mycorrhization of potato plants cv. Golden Wonder was achieved with three commercial preparations of arbuscular mycorrhizal fungi (AMF): Vaminoc (mixed-isolate inoculum) and two of its components, Glomus intraradices and Glomus mosseae. Potato cyst nematode hatching assays were conducted on the potato root leachate (PRL) produced by inoculated and non-inoculated potato plants to examine the effect of AMF inoculation on the hatching response of the two PCN species, Globodera rostochiensis and G. pallida. The overall hatch response of G. rostochiensis to the potato root leachate was greater than G. pallida. Root leachates from Vaminoc- and G. mosseae-inoculated plants were found to stimulate the hatch of G. pallida in the first 3 weeks after shoot emergence. Fractionation of root leachates with standardised carbon content by Sephadex G-10 chromatography revealed multiple AMF effects on hatching factor (HF) production. Root leachates from Vaminoc-inoculated plants contained markedly more G. pallida-active HF than all other treatments; by contrast, PRL from the three AMF treatments exhibited little variation in the quantity of G. rostochiensis-active HF produced. Several HF were PCN species-specific or species-selective, with those resolved from the G. intraradices and G. mosseae PRL profiles exhibiting an apparent preference for G. rostochiensis rather than G. pallida. Mycorrhization also significantly increased the root dry weight of plants. [ABSTRACT FROM AUTHOR]

Soil core samples were taken from a commercial potato field before emergence of the potato crop, during crop development and after harvesting. Leachates from the cores were analysed in an in vitro hatching assay in the laboratory for activity towards the potato cyst nematodes (PCN), Globodera rostochiensis and G. pallida. Hatching activity in the soil increased rapidly after plant emergence and peaked between 2 and 5 weeks after emergence; thereafter, at about the onset of flowering, hatching factor activity decreased markedly. The soil cores collected in the first 2 weeks after plant emergence contained significantly greater hatching activity towards G. pallida than G. rostochiensis, indicating that G. pallida-selective hatching factors were produced by the host crop earlier than G. rostochiensis-selective hatching factors. Soil cores collected from the potato ridge and the furrows at various depths and distances from the host plants differed in the distribution of G. pallida-selective and G. rostochiensis-selective hatching activity within the soil profile. Globodera pallida-selective hatching activity had greater vertical and horizontal mobility in the soil profile and elicited significantly greater hatching responses than G. rostochiensis beyond the region of the rhizosphere. Significant levels of hatching factor activity could be detected in the field 90 days after harvesting of the potato crop. [ABSTRACT FROM AUTHOR]

The behaviour of stimulated second stage juveniles (J2) (i.e., hatched in root leachate from potato cv. Cara) and unstimulated J2 (spontaneously hatched in water) of Globodera rostochiensis and G. pallida in response to fractionated and unfractionated potato root leachate (PRL) was investigated in attraction assays. In PRL, fractionated by combined ion-exchange-gel permeation chromatography on Sephadex G-10, three classes of semiochemicals with activity towards J2 were distinguished: i) chemoattractants; ii) chemostats, and iii) chemorepellents. The motility of PRL-hatched G. rostochiensis J2 in one fraction (12) at 10 days after their removal from the root leachate was significantly greater than that of water-hatched J2 apparently due to sensitisation of PRL-hatched J2. PRL-hatched J2 of G. pallida were attracted to different fractions than those of G. rostochiensis, whereas the water-hatched J2 from the two species were attracted to common fractions, indicating that sensitisation by exposure to PRL was species selective. The attraction of PRL-hatched PCN J2 to unfractionated PRL appeared to be dependent on the ratio of chemoattractant to chemorepellent semiochemicals in the leachate. For both species there was no detectable correlation between hatching activity and either attractiveness of root leachates from 12 potato genotypes or chemoattraction in PRL fractions, indicating that hatching factors were not active chemoattractants. [ABSTRACT FROM AUTHOR]

Potato cyst nematodes hatch in response to hatching factors (HF) present in potato root leachate (PRL). The much higher spontaneous hatch (hatch in the absence of potato plants or PRL) of both Globodera rostochiensis and Globodera pallida in sand (32.2 and 21.1%, respectively) compared to in vitro (6.0 and 4.8%) experiments suggested the presence of other hatching factor-producing organisms in the non-sterile sand. When sterile PRL (from aseptically cultured microplants) and non-sterile PRL (from aseptically cultured microplants grown in the presence of tuber washings) samples were collected and assayed for hatching activity, the in vitro hatch of both PCN species but particularly of G. pallida was greater in non-sterile PRL. When these samples were fractionated on Sephadex G-10 by low pressure liquid chromatography and the fractions tested for hatching activity, the non-sterile PRL produced more hatching factors (HF) than the sterile PRL; in the fractionated sterile PRL only one significant HF (active towards G. pallida) was observed, compared to six (towards G. pallida) and three (towards G. rostochiensis) HF from the non-sterile PRL, with two HF being active towards both species. The non-sterile PRL appeared to produce more hatching factor stimulants (HS) and fewer hatch inhibitors (HI) than the sterile PRL. These results suggest that soil micro-organisms play an important role in the production of hatching chemicals and it is proposed that the differences in HF profiles between sterile and non-sterile PRL were due, at least in part, to increased HS production in the non-sterile PRL. [ABSTRACT FROM AUTHOR]

In studies using three sibling F1 clones from each of five crosses between Solanum tuberosum and different wild tuberbearing Solanum species, root leachate hatching activity towards each of the two potato cyst nematode (PCN) species, Globodera rostochiensis and G. pallida, segregated independently. Sephadex G-10 fractionation of the leachates of S. sucrense-hybrid clones revealed differences between clones in the hatching factor elution profiles for the two PCN species. Analysis of individual hatching factors indicated examples both of selectivity (both PCN species hatched in response to a particular hatching factor, but at different levels of hatching response) and of specificity (only one PCN species hatched in response to a particular hatching factor) of hatching factors. The hatching factor profiles of the S. sucrense-hybrids indicated segregation of hatching factors from the parents, but also detected novel factors unique to specific hybrid clones. Total hatching activity of the root leachate of the S. sucrense clones was positively correlated with the proportion of S. tuberosum-derived hatching factors. [ABSTRACT FROM AUTHOR]

Provides information on a study which examined the effect of different soils on the mobility of hatching factors and the relative hatching responses of Globodera (G.) rostochiensis and G. pallida, two species of potato cyst nematodes. Materials and methods; Recovery of tomato root leachate hatching activity from the soil; Effects of different soil characteristics on hatching factor mobility.

Hatching factors with activity towards Globodera rostochiensis were isolated from the root leachates produced by 1500 potato plants grown in gravel. In total, nine hatching factors, each with molecular weight 530.5 Da, were isolated. The main differences in the daughter ions produced from different hatching factors after fragmentation by mass spectrometry occurred between 245 and 500 Da. The main hatching factor, HF E, was found in extremely low concentrations in the leachate (less than 2.9 × 10[sup ­5]% of recovered organic material) and was active in vitro at less than 2.1 × 10[sup ­8] M. Separation of the different hatching factors during purification was found to decrease the percentage hatch achieved in vitro at optimum concentration. Aus Wurzelablaufwasser von 1500 in grobem Sand gehaltenen Kartoffelpflanzen wurden gegenüber Globodera rostochiensis wirksame Schlüpffaktoren isoliert. Insgesamt wurden neun Schlüpffaktoren isoliert, jeder mit einem Molekulargewicht von 530.5 Da. Die grössten Unterschiede bei den Tochterionen, die bei einer Zerlegung durch Massenspektrometrie erzielt wurden, traten zwischen 245 und 500 Da auf. Der Hauptschlüpffaktor, HF E, wurde in extrem niedrigen Konzentrationen (weniger als 2.9 &times 10[sup ­5]% des gewonnenen organischen Materials) im Ablaufwasser gefunden. Er war in vitro noch bei weniger als 2.1 &times 10[sup ­8] M wirksam. Eine Trennung der verschiedenen Schlüpffaktoren im Laufe der Reinigung verminderte den prozentualen Schlupf in vitro bei optimaler Konzentration. [ABSTRACT FROM AUTHOR]

The decline of Globodera rostochiensis (Woll.) populations in two fields was 57% during the first and 40.3% during the second year of crop rotation in the absence of a potato crop in Co. Cork, Ireland. The decline was found to be due to both spontaneous hatch and in-egg mortality. Spontaneous hatch accounted for between 75.8 and 80.2% of the decline experienced during rotation. In-egg mortality was found to be responsible for a reduction of approximately 10% in the total number of viable eggs in both fields, and was positively correlated with soil temperature in the field. The number of culturable bacteria and the composition of the bacterial microflora in the cysts was found to change with increasing soil temperatures. The increase in cellulase-positive isolates reflected the effect of temperature on egg degradation. Der Einfluss von Absterben im Ei und spontanem Schlupfen auf die Abnahme von Globodera rostochiensis im Feld im Laufe des Fruchtwechsels bei Abwesenheit des Wirtes Kartoffel - In Co. Cork, Irland, betrug die Abnahme der Populationen von Globodera rostochiensis (Woll.) in zwei Feldern in einer Fruchtfolge ohne Kartoffeln im ersten Jahr 57% und im zweiten Jahr 40,3%. Es wurde festgestellt, dass die Abnahme durch spontanes Schlupfen und durch Absterben im Ei verursacht wurde. Spontanes Schlupfen war fur 75,8 und 80,2% des wahrend des Fruchtwechsels beobachteten Ruckganges verantwortlich. Etwa 10% der Gesamtzahl infektionsfahiger Eier in den beiden Feldern gingen durch Absterben im Ei zugrunde. Dieser Ruckgang war positiv korreliert mit der Bodentemperatur im Feld. Der Anteil der kulturfahigen Bakterien und die Zusammensetzung der Bakterienflora in den Zysten nahmen mit steigenden Bodentemperaturen zu. Der Anstieg der zellulase-positiven Isolate spiegelte die Wirkung der Temperatur auf die Zersetzung der Eier wider. [ABSTRACT FROM AUTHOR]