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Inoculation of microplants of potato cv. Golden Wonder with Vaminoc, a mycorrhizal inoculum of three arbuscular mycorrhizal fungi (Glomus spp.), resulted in an increase in in-sand hatch of Globodera pallida, but not G. rostochiensis, within 2 weeks. By this time, mycorrhized plants also supported a larger number of feeding nematodes of both PCN species (50% higher for G. rostochiensis) than did non-mycorrhized plants, with a higher proportion of the G. pallida population being fertilised females than for G. rostochiensis. After 12 weeks, the multiplication rate of G. rostochiensis on mycorrhized plants was significantly greater than on non-mycorrhized plants, whereas no such difference was observed for G. pallida.The principal component of PCN multiplication affected by mycorrhization was increased cyst number per plant from 6 to 12 weeks. Over this period, there was no increase in cyst number per plant for either PCN species on non-mycorrhized plants, whereas the value increased on mycorrhized plants for both G. rostochiensis (by almost 200%) and G. pallida (57%). Mycorrhization resulted in significant increases in the root and shoot dry weights of plants grown in the absence of PCN. Although mycorrhized plants carried a larger PCN burden than non-mycorrhized plants when grown on PCN-infested medium, as a result of the increased PCN multiplication rate, they produced larger root systems than did nonmycorrhized plants, suggesting increased tolerance to PCN of the mycorrhized plants, particularly to G. rostochiensis. Of morphological characters investigated in the absence of PCN, only stem height (increased) was significantly affected by mycorrhization. Colonisation by mycorrhizal fungi resulted in increased tuber yield both in the absence (significant increase) and presence (non significant) of PCN, as a result of increased tuber number per plant. These results are discussed in the light of the possible use of AMF as part of an integrated PCN management plan.

Two controlled environment experiments were conducted to explore the hypothesis that invasion and damage caused to potato roots by the potato cyst nematode Globodera rostochiensis might result in quantitative or qualitative changes in the release of root exudates to subsequently affect the growth of Rhizoctonia solani (AG3) in the potato rhizosphere. The growth of five R. solani isolates was compared on media amended either with root exudates from G. rostochiensis-infested or uninfested potato (cv. Désirée) plants at different time intervals after the introduction of the nematodes. In Experiment 1, the growth of R. solani was higher on medium amended with potato root exudates from G. rostochiensis-infested compared to uninfested plants, collected 4, 6, 8 and 12 days after the G. rostochiensis treatments were administered. Similarly, in Experiment 2, R. solani isolates grew faster on medium amended with potato root exudates from G. rostochiensis-infested than uninfested plants. This trend was particularly pronounced at the 12-day collection.At this time, 49% of the G. rostochiensis juveniles in roots were found to belong to the juvenile moults J2 and J3, indicating that root exudates were modified during the earlier stages of juvenile invasion. Carbohydrate analysis of root exudates indicated significantly higher levels of sucrose in root exudates from G. rostochiensis-infested than uninfested plants, whereas no significant differences were found in total nitrogen content. The results are discussed to help elucidate the mechanism behind the disease complex found between G. rostochiensis and R. solani in previous field research.

The persistence of nematicides such as oxamyl can vary greatly in field conditions. The objectives of the present studies were: i) to compare oxamyl degradation in soils with different properties; ii) to quantify and examine the influence of various abiotic factors on oxamyl degradation; iii) to establish the validity of using simulated models to predict the degradation in the field; and iv) to examine if a second application of oxamyl to the same soil 13 or 26 weeks after the first application enhances degradation. The first two studies included field measurements of oxamyl concentration and parallel laboratory incubations. For the field measurements, soils were collected from each of ten potato (Solanum tuberosum) fields in Shropshire, UK, immediately after application of oxamyl on the day of planting and then at weekly intervals for the duration of the two experiments. After each collection, oxamyl was extracted and its concentration determined. For the laboratory incubations, soils were collected from the same ten sites immediately prior to field application and received one application of oxamyl in the laboratory at the same day (day 0). The PERSIST model was then used to predict oxamyl degradation in the field (modelled degradation). Modelled degradation was then compared with the measured degradation up to 91 days (study 1) or 56 days (study 2) after application. In study 3, an extra application of oxamyl to that in the field at day 0 was made in the laboratory at 13 or 26 weeks after application. There were wide variations in the persistence of oxamyl between the ten sites, with the field half-life ranging from 10 to 24 days. Degradation in the field was significantly greater at site 4, where it could not be detected 28 days after application. At other sites, the chemical persisted for 42-63 days and was still detectable at two sites 91 days following application. Soil temperatures had a greater impact on oxamyl degradation than rainfall accounting for up to a maximum of 79% of the variation. The short persistence at site 4 was attributed to the combination of warm and moist conditions in a higher pH soil. The PERSIST model predicted the same rate of decline of oxamyl as actually occurred in the field at only four (sites 5, 6, 7 and 8) sites. At the other sites, degradation in the field occurred at more rapid rates than predicted. This could be as a result of the model not allowing for the movement of nematicide by leaching, or because enhanced degradation of nematicides occurred at these latter sites, or due to a combination of these factors. The wide variation in half-lives and the behaviour of soils after subsequent additions of oxamyl in study 3 were suggestive of complex microbial dynamics even under controlled conditions. Further studies would be required to establish the influence of soil microflora together with that of abiotic parameters on oxamyl degradation. as a whole in the region of €300M (Deliopoulos et al., 2007).Nearly 180 t of granular nematicides were applied on approximately 40 000 ha...

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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 noninoculated 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.Keywords -arbuscular mycorrhizal fungi, cv. Golden Wonder, hatching factors, organic carbon, Sephadex G-10 column.Potato cyst nematodes (PCN), Globodera pallida Stone and G. rostochiensis (Woll.), are the most damaging pests of the potato (Solanum tuberosum L.) crop in Europe. Within the EU, the annual yield losses as a consequence of PCN damage have been estimated to be approximately €300 million (Mulholland et al.,

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.