Interactions between potato plants, arbuscular mycorrhizal fungi, potato cyst nematodes and a nematicide

Inoculation of potato plants with Vaminoc, a commercial mixture of three selected isolates of arbuscular mycorrhizal fungi (AMF), and with two of these isolates, Glomus intraradices (BioRize BB-E) and Glomus mosseae (isolate BEG 12) increased the early in vitro (in potato root leachate, PRL) and in soil hatch of the potato cyst nematode (PCN) Globodera pallida (0-4 weeks after shoot emergence), but had no effect on the hatch of the other PCN species Globodera rostochiensis. In the absence of AMF, G. pallida exhibited delayed in vitro and in soil (microplants or plants grown from tubers) hatch, compared to G. rostochiensis inoculation of potato roots with AMF eliminated this delay in G. pallida hatch. While the effects of these AMF isolates on PCN hatch were consistent across a range of potato cultivars, the effect on plant growth was more variable, with certain AMF-cultivar associations being more effective than others on plant growth enhancement. The growth parameter mostly affected (increased) by mycorrhizal inoculation was root growth. When the PRL from AMF-untreated and AMF-treated plants were fractionated and corrected for carbon content, it was revealed that mycorrhizal inoculation had multiple effects on hatching factor (HF) production: generation of novel HFs (more evident with Vaminoc than with the single AMF isolates), up or down regulation of existing HFs. The result of the AMF-PCN interaction depended on the time that mycorrhizal inoculation took place: pre-inoculation with AMF 2 weeks before planting followed by one more AMF application at planting significantly lessened the multiplication of G. pallida on the roots, relative to AMF-untreated plants; in contrast, one application of AMF (at planting) increased the final G. rostochiensis population size (but not G. pallida), compared to AMF-untreated plants. In the presence of the nematicide aldicarb, the multiplication rate of G. pallida was significantly lower on roots inoculated with AMF than on roots that did not receive mycorrhizal treatment at planting