Genetic variation in the genus Leptographium with special reference to Leptographium wageneri

The objectives of this research were to determine genetic variation in Leptographium and how it corresponds to the taxonomy of the genus. The similarity of 88 strains of 27 species of Leptographium was studied using enzyme electrophoresis. UGPMA cluster analysis of similarity matrices (Nei genetic identity, I) generated from data of 267 electrophoretic forms (electromorphs) of 15 enzymes showed a close correspondence between morphology and electrophoretic similarity. Strains of a species clustered at I $\geq$ 0.60, but in two cases, taxa clustered at I $\u3e$ 0.60, suggesting conspecificity. Additional isozyme studies were made of 76 isolates of Leptographium wageneri representing three host-specialized varieties. Of 21 enzymes tested, 10 were polymorphic, having from two to six electromorphs. Only 14 combinations (electrophoretic types) of the 29 electromorphs were found; each electrophoretic type was restricted to a single variety. Within each variety, one electrophoretic type was abundant and broadly distributed; additional types were geographically isolated or restricted. Ordination of Nei genetic distance (D) among strains revealed three discrete clusters that corresponded to the three varieties. Nei gene diversity (H) in each variety was low (0.017 to 0.040), but differentiation between varieties was high; the Nei coefficient of gene differentiation (G\sb{\rm st}) for the species was 0.860. Vegetative compatibility was tested among the same L. wageneri isolates by pairing auxotrophic, nitrate non-utilizing mutants on nitrate media. The development of dense hyphal growth in the zone of confrontation between complementing phenotypes indicated compatibility. Heterokaryons were recovered from hyphal tips and conidiophores of complementing pairings. Only fourteen groups of vegetatively compatible isolates (VC groups) were detected. Each contained isolates that were of similar electrophoretic types, and most had unique geographic ranges. No intervarietal complementation occurred. The indications of low genetic diversity in Leptographium wageneri (i.e., few electrophoretic types and VC groups), the unique geographic distributions of the electrophoretic and compatibility phenotypes, and the correlation between electrophoretic type and VC group may be due to a lack of recombination, to strong clonal selection and to founder effects

Recovery Plan for Scots Pine Blister Rust Caused by Cronartium pini

Peer reviewedPostprin

Root Diseases in Coniferous Forests of the Inland West : Potential Implications of Fuels Treatments

After nearly 100 years of fire exclusion, introduced pests, and selective harvesting, a change in forest composition has occurred in many Inland West forests of North America. This change in forest structure has frequently been accompanied by increases in root diseases and/or an unprecedented buildup of fuels. Consequently, many forest managers are implementing plans for fuels treatments to lower the risk of severe wildfires. Impacts on root disease should be considered before selecting appropriate fuels treatments. Complex interactions exist among conifer root diseases, fuels treatments, forest structure, species composition, stand history, and other environmental factors. As forest managers prescribe fuels treatments, their success in lowering the risk of severe wildfire will depend in part on the impacts of these treatments on root disease. Root diseases are one of many factors to be considered when developing plans for fuels treatments. Choices must be made on a site-by-site basis, with knowledge of the diseases that are present. This paper provides examples of how fuels treatments may increase or reduce specific diseases and demonstrates their importance as considerations in the fuels management planning process. Several root diseases prevalent within Inland West of North America are addressed: Armillaria root disease, annosus root disease, laminated root rot, black stain root disease, Schweinitzii root and butt rot, Tomentosus root disease, Rhizina root rot, and stringy butt rot. For each disease, general information is provided on disease identification, management options, and potential effects of fuels treatments. However, many long-term studies are needed to assess effects of specific interactions among fuels treatments, root diseases, and host trees

Effects of Climate Change on Ecological Disturbance in the Northern Rockies

Disturbances alter ecosystem, community, or population structures and change elements of the biological and/or physical environment. Climate changes can alter the timing, magnitude, frequency, and duration of disturbance events, as well as the interactions of disturbances on a landscape, and climate change may already be affecting disturbance events and regimes. Interactions among disturbance regimes, such as the co-occurrence in space and time of bark beetle outbreaks and wildfires, can result in highly visible, rapidly occurring, and persistent changes in landscape composition and structure. Understanding how altered disturbance patterns and multiple disturbance interactions might result in novel and emergent landscape behaviors is critical for addressing climate change impacts and for designing land management strategies that are appropriate for future climates. This chapter describes the ecology of important disturbance regimes in the Northern Rockies region, and potential shifts in these regimes as a consequence of observed and projected climate change. We summarize five disturbance types present in the Northern Rockies that are sensitive to a changing climate—wildfires, bark beetles, white pine blister rust (Cronartium ribicola), other forest diseases, and nonnative plant invasions—and provide information that can help managers anticipate how, when, where, and why climate changes may alter the characteristics of disturbance regimes