Plant ectoparasitic nematodes prefer roots without their microbial enemies

Abstract

Root-feeding nematodes are major soilborne pests in agriculture. In natural ecosystems, their abundance can be strongly controlled by natural enemies. In coastal foredune soil, the abundance of the ectoparasitic nematode Tylenchorhynchus ventralis is controlled by local interactions with soil microorganisms. If not controlled, T. ventralis reduces growth and performance of the host plant Ammophila arenaria. In the present study, we examine if the nematodes may sense the presence of soil microorganisms and, if so, they are able to actively avoid their enemies. First, using Petri dishes with agar medium we examined if T. ventralis can choose between A. arenaria seedlings inoculated with or without soil microorganisms. We observed that there was a trend (although non-significant) in nematode migration towards the non-inoculated plants. If the seedlings were not present, the nematodes did not make any choice and stayed in the centre of the Petri dish. Then, using Y-tubes filled with sterilized dune soil, we examined if T. ventralis could choose between A. arenaria roots with or without microorganisms. We also included treatments of microbial suspensions without plants and a microbe-free filtrate. We observed that the nematodes preferred roots without microorganisms. Microorganisms alone or roots with microbial filtrate did not influence nematode choice significantly. We conclude that the nematode T. ventralis is able to choose roots without soil microorganisms when having roots with them as alternative. Such avoidance could explain why biological control of nematodes in field is not always effective, especially when microbial antagonists accumulate in specific parts of the rhizosphere.

Predicting root defence against herbivores during succession

“…2001) or perennial cultivars such as citrus plants (Ali, Alborn & Stelinski 2010). Also, specialist root‐feeding nematodes of coastal foredune grass Ammophila arenaria (marram grass) are able to distinguish and avoid roots of the host plant when infested with harmful micro‐organisms (Piskiewicz et al. 2009).…”

Additive interaction between a root‐knot nematode Meloidogyne javanica and a root‐feeding flea beetle Longitarsus bethae on their host Lantana camara

“…Studies investigating plant–herbivore interactions have focused primarily on above‐ground herbivory, with very few studies evaluating the effect of below‐ground herbivores on plant performance . In particular, several studies have focused on the interactions between root‐knot nematodes and above‐ground feeding insects, while the interactions between below‐ground feeding insects and this guild of nematodes have received little attention . Root‐feeding nematodes are the dominant below‐ground herbivores, and are often regarded as serious pests worldwide.…”

“…14 In particular, several studies have focused on the interactions between root-knot nematodes and above-ground feeding insects, 15,16 while the interactions between below-ground feeding insects and this guild of nematodes have received little attention. [17][18][19] Root-feeding nematodes are the dominant below-ground herbivores, and are often regarded as serious pests worldwide. In temperate grasslands, they are the main group of root herbivores and their feeding actions can disturb above-ground plant size and nutritional quality.…”

Range-expanding plant species and their belowground neighbours : digging into novel interactions

“…Choice experiment on agar: to examine nematode choice in vitro, we used Petri dishes of 9 cm diameter filled with 20 ml 0.5% microbial agar (Merck kGaA, Germany) (Piskiewicz et al 2009). We used eight independent replicates for each treatment.…”

“…To examine nematode choices under more natural conditions than on agar, we performed a choice experiment in soil-filled Y-tubes (van Tol et al 2001;Piskiewicz et al 2009) in a greenhouse at 16/8 h light/dark and 20/15 °C. We used 6 independent replicates for each treatment.…”