Differences in defence responses ofPinus contortaandPinus banksianato the mountain pine beetle fungal associateGrosmannia clavigeraare affected by water deficit

Abstract

We tested the hypotheses that responses to the mountain pine beetle fungal associate Grosmannia clavigera will differ between the evolutionarily co-evolved host lodgepole pine (Pinus contorta var. latifolia) and the naïve host jack pine (Pinus banksiana) and that these responses will be influenced by water availability. G. clavigera inoculation resulted in more rapid stem lesion development in lodgepole than in jack pine; water deficit delayed lesion development in both species. Decreased hydraulic conductivity was observed in inoculated lodgepole pine seedlings, likely because of tracheid occlusion by fungal hyphae and/or metabolite accumulation. Drought but not inoculation significantly impacted bark abscisic acid levels. Jasmonic and salicylic acid were implicated in local and systemic responses of both species to G. clavigera, with salicylic acid appearing to play a greater role in jack pine response to G. clavigera than lodgepole pine. Water deficit increased constitutive levels and/or attenuated induced responses to G. clavigera for several monoterpenes in lodgepole but not jack pine. Instead, inoculation of well-watered but not water deficit jack pine resulted in a greater number of xylem resin ducts. These findings reveal mechanisms underlying differences in G. clavigera-induced responses between lodgepole and jack pine hosts, and how water availability modulates these responses.

Consequences of Sphaeropsis tip blight disease for the phytohormone profile and antioxidative metabolism of its pine host

“…In general term, much lower phytohormone levels were observed in the wood compared to the bark. Moreover, as in line with our hypothesis (iii), the changes in the phytohormone profile in both bark and wood confirm that S. sapinea disease causes similar stress as water deficit to the pine host (Arango‐Velez et al, ). This is particularly indicated by the elevated levels of ABA and JA in the wood, whereas ABA levels in the bark of host pines showed a decreased level upon S. sapinea infection.…”

“…tomato DC3000 ( Pto ) interactions by Naseem and Dandekar (). The elevated levels of JA in the wood of the pine host upon S. sapinea disease are consistent with earlier studies on the infection of conifers with the necrotrophic fungus, for example, G. clavigera (Arango‐Velez et al, ; Hudgins, Christiansen, & Franceschi, ; Martin, Tholl, Gershenzon, & Bohlmann, ). Despite a well‐documented crosstalk between SA and JA in plant–pathogen interactions, our results (in the bark: enhanced SA but unaffected JA levels; in the wood: enhanced JA but SA levels below the limit of detection) nevertheless provide new information on the complexity of antagonistic and/or synergistic interactions of SA–JA signalling pathways upon pathogen infection (Kazan & Manners, ; Koornneef & Pieterse, ).…”

“…and jack pine ( Pinus banksiana Lamb.) inoculated with the necrotrophic fungus Grosmannia clavigera (Arango‐Velez et al, ). Obviously, the phytohormone defence network of pines shows similar responses to drought stress (Riemann et al, ) and invasion by fungi such as S. sapinea , which is in line with our hypothesis (iii).…”

The Effect of Water Limitation on Volatile Emission, Tree Defense Response, and Brood Success of Dendroctonus ponderosae in Two Pine Hosts, Lodgepole, and Jack Pine

“…In the current study, lesion size might be affected by differences in soil water content at the two sites; the lodgepole pine site had higher soil water content than the jack pine site at the time of tree harvest likely due to water release through seasonal thawing. Arango-Velez et al (2015), however, also found longer lesions in lodgepole pine than jack pine in an arboretum-based study in Alberta, where both pine species occur at the same field site. Although it is commonly assumed short lesions indicate host plant resistance (Raffa and Berryman, 1983;Krokene and Solheim, 1998), assessment of qualitative and quantitative changes in phloem chemistry following fungal inoculation might be more relevant to explain tree resistance against bark beetles (Peterman, 1977;Berryman, 1982, 1983;Paine et al, 1997).…”

Spatial and temporal components of induced plant responses in the context of herbivore life history and impact on host

“…These results also add to our understanding of how plant architecture and the attacking agent interact to influence the expression of induced responses. Chemical induction in conifers can extend beyond anatomical responses, as previous studies have detected changes well beyond lesions, sometimes in needles of trees induced on the stem (Arango-Velez et al, 2016;Bonello & Blodgett, 2003;Krokene, Solheim, & Krekling, 2003;Sherwood & Bonello, 2016;Villari et al, 2012). The extent to which the distances involved reflect local chain reactions due to cell injury, hormonal elicitors, or diffusion is unknown.…”