Soil conservation is one of the major challenges for agriculture in the 21st century. For this reason, non-inversion tillage systems including subsidiary crops have become popular over the last three decades in Europe. However, the adoption of new agricultural practices may change the diversity and abundance of certain pests and diseases. For example, plant-parasitic nematodes that are major threats towards cultivated plants may be promoted if good hosts, such as certain subsidiary crops and weeds, occur more frequently. The indigenous plant-parasitic nematode fauna under organic farming systems is already adapted to diverse crop rotations and usually dominated by nematodes with broad host ranges. These may be further enhanced in organic farming systems if non-inversion tillage is introduced, which generally increases the abundance and biomass of certain weeds. We evaluated the early effects of non-inversion tillage and subsidiary crops in an organic wheat-potato rotation on plant-parasitic nematodes in two field experiments in two successive years. The total densities of plant-parasitic nematodes increased from an initial 1260 nematodes (100 ml soil)−1 at the start of the experiment to 1850 and 1700 nematodes (100 ml soil)−1 after wheat under non-inversion and conventional tillage, respectively. Plant-parasitic nematode densities then decreased on average to 1100 and 560 nematodes (100 ml soil)−1 after subsidiary crops and potatoes, respectively. Parasitic nematode densities tended to be higher under non-inversion than conventional tillage, except where oilseed radish and black oats had been used as cover crops. For the latter, no differences between tillage treatments occurred. In the second experiment, about 1700 free-living nematodes (100 ml soil)−1 were found under conventional tillage without mulch while under reduced tillage with mulch their numbers were significantly higher at 3100 nematodes (100 ml soil)−1. We conclude that an appropriate choice of subsidiary crops can be an important management factor for the long term sustainability of non-inversion tillage systems.
Globodera pallida infestation on potato is responsible for huge yield losses globally. Screening of potato germplasm for resistance to the nematode at the early stages of a breeding programme can significantly enhance resistance-based management. This study assessed the suitability of tissue culture (TC)-derived potato plants as screening material for resistance to G. pallida. Reproduction of the nematode on TC plants was similar to the reproduction on tuber- and eye-plug-derived plants. The pot volume, inoculum density and inoculation time had a significant effect on the reproduction. A positive correlation was found between the mean number of white females on the root surface and the final number of nematode cysts after extraction. Resistance ranking using TC plants and the tubers yielded comparable results, thus justifying the use of TC in the screening process. Tissue culture plants have the potential of speeding up the screening process and reducing resource requirements, thus lowering breeding cost.
The plant-parasitic nematode, Paratylenchus bukowinensis, occurs ubiquitously in arable fields. Economic damage has been reported from, among others, cabbage, parsley, and celery, but other crops might be affected as well. Management of P. bukowinensis is difficult. Resistant cultivars are not available and chemical control is prohibited in most European countries. In addition, sustainable management is often hindered by a lack of information regarding the biology and host range of P. bukowinensis. To improve the management of P. bukowinensis in the future, a good understanding of the life cycle and host plant-nematode interactions is required. We investigated the host range, life cycle and natural decline of P. bukowinensis in five glasshouse experiments. A total of 26 plant genotypes comprising 22 plant species from eight plant families were studied. Plant species within the families Brassicaceae and Apiaceae were confirmed as good hosts, while plant species within the families Fabaceae, Asteraceae, Amaryllidaceae, Solanaceae, Amaranthaceae and Poaceae can be considered non-hosts or poor hosts. In roots of good hosts, P. bukowinensis completed its life cycle within 3-4 weeks. In the absence of a host plant, P. bukowinensis declined by 40% within the first 4 weeks, but then remained at this level until the experiment was terminated after 14 weeks. Overall, the host range of P. bukowinensis seems to be smaller than for other species within the genus Paratylenchus, such as P. projectus or P. similis. Control of P. bukowinensis using crop rotation should be feasible by rotating good hosts belonging to the families Brassicaceae and Apiaceae with non-hosts or poor hosts.