An in vitro examination of the feeding behaviour of Paratrichodorus anemones (Nematoda: Trichodoridae), with comments on the ability of the nematode to acquire and transmit Tobravirus particles

Abstract

AbstractThe plant-parasitic nematode Paratrichodorus anemones efficiently transmits tobacco rattle virus that causes substantial economic damage to vegetable and ornamental flower-bulb crops. The nematode acquires and transmits virus particles when feeding on plant roots, but previous studies on feeding by trichodorid nematodes suggested that the nematodes destroyed the cells upon which they fed. For successful establishment of virus infection in a plant, virus particles would have to be introduced by the nematode into root cells that would remain fully functional. Consequently, the efficient transmission of the genus Tobravirus by trichodorids could not occur where the majority of attacked root cells become irreversibly damaged and, therefore, unsuitable for establishment of virus infection. Live specimens of P. anemones feeding on Nicotiana tabacum seedlings growing in agar were examined in real time using videoenhanced interference light microscopy to determine how trichodorids acquire and transmit Tobravirus particles. The feeding cycle of P. anemones had four distinct phases: i) root exploration, ii) cell exploration, iii) cell sampling, and iv) cell feeding, followed by a quiescent period. Preceding the initiation of phase iv) an average of four cells, which had been perforated by the nematode onchiostyle, were immediately abandoned and thus remained fully functional. Also, during this phase, about 5% of the perforated cells remained alive and fully functional, providing a suitable environment for the establishment of virus infection. Each feed on a single cell was similar to that previously observed with Trichodorus similis, being in four phases, i.e., cell wall perforation, salivation, ingestion and withdrawal.