Resistance level in Scots pine clones and artificial introductions of Tomicus piniperda (Col., Scolytidae) and Leptographium wingfieldii (Deuteromycetes)

Abstract

Scots pine trees belonging to clones considered to be resistant or susceptible after mass inoculations of Leptographium wingfieldii, a fungus associated with Tomericus piniperda, were submitted to a low density of fungal inoculations or beetle insertions. The length of the phloem‐induced reaction zone, the fungal extension and fungal density inside the reaction zone, and the length of maternal galleries of T. piniperda were measured. The length of the phloem reaction zone never differed between resistant and susceptible trees. The density of the fungus mycelium in histological sections of the phloem, and the length of the maternal galleries in the reaction zone were higher in the susceptible trees than in the resistant ones. These factors could be good indicators of resistance of Scots pine to mass attacks.

Comparative population genetic study of two oligophagous insects associated with the same hosts

“…Flying ability has certainly been favoured by natural selection owing to the relative rarity of suitable hosts. In addition, most pines are able to counteract single beetle attacks by induced resistance reactions (Bois and Lieutier, 2000). In most bark beetle species, establishment on conifers is thought to be possible only once a critical threshold of attack density is reached, above which the defence system of the tree is exhausted (Raffa and Berryman, 1983).…”

Resin canal traits relevant for constitutive resistance of Norway spruce against bark beetles: environmental and genetic variability

“…The genetic variation of traits useful for estimating host resistance to bark beetles and to their associated fungi is a new and important field of research (Tomlin et al, 1996(Tomlin et al, , 2000Franceschi et al, 1998;Phillips and Croteau, 1999;Bois and Lieutier, 2000;Nagy et al, 2000;Strom et al, 2002;Lieutier et al, 2003). Traits such as the density of resin canals or the amount of polyphenol storing parenchyma cells in the bark are useful tools for selecting conifer trees less susceptible to bark beetle attacks.…”

Population genetic structure ofTomicus piniperdaL. (Curculionidae: Scolytinae) on different pine species and validation ofT. destruens(Woll.)

“…At least for some host species, it is now clear that individual trees strongly differ in their ability to resist to attacks (Paine et al . 1997; Bois & Lieutier 2000). T. piniperda causes damages on various pine species throughout Europe, mainly due to its shoot feeding behaviour (Langström & Hellqvist 1990; Lieutier 1991).…”