Interactions between the oomycete Pythium arrhenomanes and the rice root-knot nematode Meloidogyne graminicola in aerobic Asian rice varieties

Abstract

Background: Aerobic rice fields are frequently infested by pathogenic oomycetes (Pythium spp.) and the rice rootknot nematode Meloidogyne graminicola. Here, the interaction between Pythium arrhenomanes and Meloidogyne graminicola was studied in rice roots of two aerobic rice varieties. In different experimental set-ups and infection regimes, plant growth, rice yield, Pythium colonization, as well as establishment, development and reproduction of M. graminicola were studied.

Jasmonate-Induced Defense Mechanisms in the Belowground Antagonistic Interaction Between Pythium arrhenomanes and Meloidogyne graminicola in Rice

“…These data demonstrate that the JA pathway is induced upon P. arrhenomanes infection in rice roots as part of a plant defense response and lead to the hypothesis that JA induction would be the causal mechanism behind the antagonistic interaction with M. graminicola , reported in Verbeek et al (2016).…”

“…Previously, we have reported that prior infection by the oomycete P. arrhenomanes consistently reduces the penetration rate and development of the root-knot nematode M. graminicola in rice roots, even under different infection and plant growth conditions (Verbeek et al, 2016). To elucidate a potential mechanism behind this antagonism, we decided to investigate the levels of a set of plant hormones, namely JA, SA, IAA—an important AUX—and ABA, upon single and double inoculations, using root samples taken at two time points (11 and 13 days post germination, dpg) during the greenhouse experiment described in detail in Verbeek et al (2016). Results, shown in Figure 1 , revealed JA levels in the roots are significantly reduced at 3 days post single nematode inoculation (11 dpg) compared to the un-inoculated control ( Figure 1A ).…”

“…Root samples of variety IR81413-BB-75-4 were collected during the greenhouse experiment performed at the IRRI in Los Baños, Philippines (Verbeek et al, 2016). Detailed experimental conditions were described in Verbeek et al (2016). Sterilized seeds were germinated in tap water, which was refreshed daily for one week.…”

“…Although very relevant for agronomy, pathogenic interactions between plants and multiple damage-causing organisms are largely understudied, certainly when considering the role of plant hormones and plant defense. Two such soil-borne pathogenic organisms that co-occur in aerobic rice fields are Pythium arrhenomanes and Meloidogyne graminicola (Kreye et al, 2009a; Verbeek et al, 2016). The soil-borne oomycete P. arrhenomanes infects several monocots such as rice (Kreye et al, 2009a), sugarcane (Bond et al, 2004), and wheat (Mojdehi et al, 1991).…”

“…Previously we showed an antagonistic interaction between the plant-pathogenic oomycete P. arrhenomanes and M. graminicola , where infection with the oomycete negatively affects the number of established nematodes and hampers nematode development in rice roots (Verbeek et al, 2016). We hypothesized that this antagonism could be related to changes in phytohormones and related induced defense responses in the rice roots.…”