Differences in constitutive and inducible defences in pine species determining susceptibility to pinewood nematode

Abstract

The pinewood nematode, Bursaphelenchus xylophilus, originating from North America (NA), is a major invasive pine pest in Eurasia. It was first detected in Portugal in 1999 associated with maritime pine, Pinus pinaster, and has been differently affecting the main local pine species, P. pinaster and P. pinea. Field studies and direct inoculation experiments in Pinus spp. seedlings, under controlled conditions, were performed to assess whether the differences in constitutive and inducible defences are determining the different susceptibility of pine host species to B. xylophilus. Host co-evolution with the pathogen was also assessed, including the NA P. radiata, widely used in forestry in the northeast of the Iberian peninsula. Pine mortality in the field was positively related with the abundance of B. xylophilus, and concentration of phenolics and condensed tannins in pines. In the greenhouse assay, seedling tissues were analysed for constitutive investment in defences, as well as the potential inducibility of those defences as driven by B. xylophilus inoculation. Slower growing P. pinea presented higher levels of constitutive defences than faster growing P. pinaster, with only P. pinaster being affected by B. xylophilus. Furthermore, co-evolution with the pathogen is important, with the fast-growing NA P. radiata presenting an inducible and effective response to B. xylophilus. Results point to the importance of integrating data on pine life history traits, including growth rate, and production of constitutive and inducible defences, into predictive models for this invasive forest pest.

Predicting the spread of an invasive tree pest: The pine wood nematode in Southern Europe

“…This further work could also build on previous studies on the human‐mediated spread of the PWN and other invaders (Hudgins et al., ; Pukkala, Möykkynen, & Robinet, ; Robinet et al., ), that have shown how a stochastic modelling component can accommodate random long‐distance dispersal events, such as accidental long‐distance transport of an invader, while accounting for driving factors such as the density and spatial distribution of roads, wood industries, and human population. Finally, future applications of our approach, dealing either with natural or human‐mediated dispersal, could incorporate recent results on the different susceptibility of pine species to the PWN (Pimentel et al., ).…”

Sublethal infection of different pine species by the pinewood nematode

“…Consistent with this, Pimentel et al . (2017a) found higher concentrations of tannins and phenols in the phloem and cambium of P . pinea compared to P .…”

“…radiata found to be very susceptible and P . pinea tolerant or resistant (Nunes da Silva et al ., 2015; Pimentel et al ., 2017a; Menéndez‐Gutiérrez et al ., 2018). An additional local species was tested in each experiment.…”

“…Experiments to assess the virulence of these nematodes or the susceptibility of host trees have been generally performed under warm temperatures that are associated with pine wilt (Nunes da Silva et al ., 2015; Pimentel et al ., 2017a; Menéndez‐Gutiérrez et al ., 2018). Due to the potential for B .…”

Invasive Species May Disrupt Protected Area Networks: Insights from the Pine Wood Nematode Spread in Portugal

“…Our approach and assessment could be refined, either in Portugal or in other areas that may be affected by the PWN in the future, by considering the different susceptibility to PWN infection of individual European pine tree species as reported by recent studies [63,64]. The stone pine (Pinus pinea L.), for example, is considerably less susceptible to PWN infection than Pinus pinaster [63,64]. In the Portuguese purely coniferous forests analyzed here, Pinus pinaster is, however, much more abundant than Pinus pinea: 89.5% and 9.5% cover, respectively, according to the COS map of Portugal.…”