Treesearch

The terms "resistance" and "tolerance" have been used by different scientists to refer to different things, and they have often been measured (and thus operationally defined) in ways that confuse the two concepts with each other. In keeping with the emerging consensus on resistance and tolerance, the following conceptual distinction is useful: resistance refers to traits that prevent infection or limit its extent, and tolerance refers to traits that do not reduce or eliminate infection, but instead reduce or offset its fitness consequences. Thus, resistance and tolerance can both improve...

Natural plant-pathogen associations are complex interactions in which the interplay of environment, host, and pathogen factors results in spatially heterogeneous ecological and epidemiological dynamics. The evolutionary patterns that result from the interaction of these factors are still relatively poorly understood. Recently, integration of the appropriate spatial and temporal context of the metapopulation has permitted an essential conceptual advance stressing the importance of these factors in evolutionary interactions. Yet, a major aspect of host and pathogen biologies that still needs...

Cronartium ribicola is one of the most destructive forest pathogens of North American white pines. The pathogen infects pine trees through their stomata, colonizes the stem, and produces stem cankers the following growing season. In this research, we collected samples from different white pine populations across Canada and the United States to develop an efficient ex vitro and in vitro screening method for phenotype expression of western white pine (Pinus monticola Douglas ex D. Don) following inoculation with C. ribicola. A major group of partial resistant plants in British Columbia,...

There is now a very long history of genetics/breeding for disease resistance in annual crops. These efforts have resulted in conceptual advances and frustrations, as well as practical successes and failures. This talk will review this history and its relevance to the genetics of resistance in forest species. All plant breeders and pathologists are familiar with boom-and-bust cycles of single major resistance genes. Though there may be occasional situations where a single-gene approach to resistance is reasonable, most interest is in finding alternatives to this approach. This is especially...

Quantitative resistance to white pine blister rust in 128 controlled- and open-pollinated sugar pine families was evaluated in a “disease garden”, where alternate host Ribes bushes were interplanted among test progenies. Overall infection was severe (88%), but with great variation among and within families: a 30-fold range in numbers of infections per tree, and a 10- fold range in trees with completely inactive, or aborted infections. Inheritance of these partial resistances was strong, with significant amounts of both additive and non-additive genetic variance evident. They will be most...

The Fourth International Workshop on the Genetics of Host-Parasite Interactions in Forestry (July 31-August 5, 2011) included a session on “Ecology and Evolutionary Biology of Resistance and Tolerance, Natural Systems.” Within this session, I gave a talk entitled “An overview of ecological and evolutionary research on disease in ‘natural’ systems” that reviewed research on disease that is primarily in ecology and evolutionary biology journals (as opposed to forestry and plant pathology journals). Several people requested that I provide details of the references listed in that talk, and...

The exotic fungus Cronartium ribicola causes the disease white pine blister rust on five-needled pines throughout North America. Although the effects of this disease are perhaps better known on pines in the western portion of the continent, the disease has also impacted regeneration and growth of eastern white pine (Pinus strobus L. ), especially in the upper Great Lakes region of Minnesota, Wisconsin, Michigan, and Ontario. This paper summarizes some of the early white pine blister rust research in Minnesota and Wisconsin, particularly the Moose Fence site near Tofte, Minnesota, the...

The weevil resistance breeding program against the white pine weevil, Pissodes strobi Peck (Coleoptera: Curculionidae), particularly for Sitka spruce (Picea sitchensis (Bong.) Carr), is arguably one of the most successful pest resistance breeding programs for plantation forest species, and it has done a lot to rehabilitate this important western conifer. Nearly all planting stock currently comes from this breeding program and so far the resistance seems effective, durable, and stable. We have used this program to also study causes behind this resistance, including: various hindrance...

Port-Orford-cedar (Chamaecyparis lawsoniana (A. Murr.) Parl.) (POC) is a long-lived conifer native to northwestern California and southwestern Oregon. It has been widely used in horticulture in both western North America and elsewhere. The accidental introduction of the non-native pathogen Phytophthora lateralis into North America and Europe has raised concerns about the future viability of POC in some forest ecosystems, in managed forests, and in horticultural settings. Fortunately, some level of natural genetic resistance to P. lateralis exists in POC. Utilizing this genetic resistance...

In an attempt to improve semiochemical-based treatments for protecting forest stands from bark beetle attack, we compared push-pull versus push-only tactics for protecting lodgepole pine (Pinus contorta Douglas ex Loudon) and whitebark pine (Pinus albicaulis Engelm.) stands from attack by mountain pine beetle (Dendroctonus ponderosae Hopkins) in two studies. The first was conducted on replicated 4.04-ha plots in lodgepole pine stands (California, 2008) and the second on 0.81-ha plots in whitebark pine stands (Washington, 2010). In both studies, D. ponderosae population levels were moderate...