Inducing long-shoot growth for vegetative propagation of western larch

This study evaluated methods to release from suppression both short shoots on lower stems and developing buds on leaders of western larch (Larix occidentalis Nutt.) seedlings, in order to increase the number of long shoots suitable for stem-tip cuttings. Treatments included application of the cytokinin N-6-benzyladenine (BA), horizontal stem bending, and decapitation on container-grown 1.5-year-old seedling ortets. The rate of release of suppressed growth of short shoots on the basal stem segments increased from 15% to 83% after spraying with 200 ppm BA and doubled on unsprayed horizontally-bent stems. Syllepsis on the upper stems increased by 19% following decapitation and by 32% after a combination of decapitation and BA treatments. Although these treatments resulted in large increases in the numbers of long shoots available for stem cuttings, the rootability of BA-treated shoots needs assessing before use in operational programs.     

Effects of nursery environment on needle morphology of Pinus monticola Dougl. and implications for tree improvement programs

Statistically significant differences were found in 14 needle traits of western white pine (Pinus monticola Dougl.) seedlings grown from the same seed orchard source in the three nurseries in northern Idaho. Traits with significant variation included needle length and width, number of stomatal rows, number of stomata per row, total stomata per needle, adaxial surface area, stomatal density, major axes of stomata, stomatal shape, stomatal area, stomatal occlusion, epistomatal wax degradation, weight of wax per dry weight of needle, and the contact angles of water droplets placed on adaxial needle surfaces. Wax crystallites on needle surfaces were hollow and tubular and the amount of surface wax appeared to be associated with surface wettability. Our results may have important implications for tree improvement programs that require successful inoculation of nursery-grown seedlings with spores of Cronartium ribicola J. C. Fisch. ex Rabenh. to reliably screen white pines for resistance to blister rust.     

Interactions among Streptomyces griseoviridis,Fusarium root disease,and Douglas-fir seedlings

In a laboratory experiment, Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) seedlings had similar disease ratings when treated with known Fusarium isolates or concurrently with Fusarium and Streptomyces griseoviridis. When tested under greenhouse conditions and against known Fusarium isolates, more seeds germinated and survived as seedlings in control medium than survived in S. griseoviridis-inoculated medium or when S. griseoviridis and Fusarium were added together. A series of applications of S. griseoviridis as a soil drench to a crop of Douglas-fir seedlings did not affect seedling morphology. However, against resident levels of Fusarium, S. griseoviridis reduced Fusarium infection by 16%, but increased infection by F. oxysporum and F. proliferatum, two potentially pathogenic fungi, by 40%.     

Gliocladium virens in an alginate prill ineffective as a biological control of Fusarium root disease in container-grown Douglas-fir

An alginate prill formulation of Gliocladium virens (GL-21) was added as a top-dressings (54 g per m²) or incorporated into medium (1.2 kg per m³) used to grow Douglas-fir seedlings in styrofoam containers. Seedlings in the top-dress treatment were similar to control seedlings; infection and colonization by naturally-occurring Fusarium was unaffected by treatment. Incorporated G. virens reduced seedling growth and increased occurrence and colonization intensity of Fusarium. In a laboratory experiment, inoculating Douglas-fir seedlings with G. virens (10% w/w) prior to inoculation with Fusarium increased survival time when compared to concurrent inoculations of fungi.University of Idaho, Idaho Forest, Wildlife and Range Experiment Station Contribution No. 742.     

First year field growth of chemically root pruned containerized seedlings

Containers deform seedling root systems and have a potential to inhibit tree growth after outplanting. Ponderosa pine (Pinus ponderosa Dougl. ex Laws. var. ponderosa), western white pine (Pinus monticola Dougl. ex D. Don), and Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) were grown in containers coated with latex paint containing different concentrations of cupric carbonate and outplanted in a forest. Treatment effects on seedling growth and root morphology were determined after one growing season in the field. Seedling height was unrelated to treatment and stem diameter was not significantly affected (p0.05). New root growth in the upper portion of the root plug was significantly increased (p0.05). The optimal concentration of cupric carbonate for seedling root growth in the upper portion of the root plug was estimated by multiple regression.     

Fusarium root infection of container-grown Douglas-fir: effect on survival and growth of outplanted seedlings and persistence of the pathogen

Greenhouse-grown Douglas-fir (Pseudotsuga menziesii var.glauca [Beissn.] Franco) seedlings with roots infected with eitherFusarium oxysporum Schlect. orFusarium proliferatum (Matsushima) Nirenberg were outplanted on a forest site in northern Idaho, U.S.A. No residentFusarium populations were detected in the forest soil.Fusarium persisted the first four years on roots initiated during the greenhouse phase, but occurred sparingly or was absent on roots that grew after outplanting. Height growth was unaffected, and mortality was not often associated withFusarium. A seasonal pattern ofFusarium activity was observed. Low levels (10–40%) of initial root infection apparently have little adverse effect on outplanting performance of Douglas-fir seedlings.University of Idaho, Idaho Forest, Wildlife and Range Experiment Station Contribution No. 640.     

Trial of a granular etridiazole and thiophanate-methyl mixture to control Fusarium root disease of container-grown Douglas-fir seedlings

Fusarium root disease is a common and often serious problem in the production of container-grown seedlings. Fungicide treatments applied late in the growing season, i.e. during bud initiation stress, are relatively ineffective against the disease. Incorporating a granular mixture of etridiazole and thiophanate-methyl fungicide (Barrot®) into the medium prior to sowing was tested for its efficacy of control against the disease. The fungicide was unable to sufficiently reduce Fusarium infection and infection intensity enough to warrant its use in root rot management. Some phytotoxic effects were observed.Idaho Forest, Wildlife and Range Experiment Station Contribution No. 550.     

Efficacy of Trichoderma harzianum as a biological control of Fusarium oxysporum in container-grown Douglas-fir seedlings

Inoculating a soilless medium with encapsulated Trichoderma harzianum did not affect any aspect of Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) seed germination or subsequent growth. Results of inoculating medium with a known pathogenic isolate of Fusarium oxysporum alone, or concurrently with T. harzianum, were the same: high levels of damping-off, low amounts of hypocotyl and root disease in midsummer, and significant reductions in height growth. When seedling roots grew through T. harzianum-inoculated medium before growing into a mixture of T. harzianum-F. oxysporum-inoculated medium, mortality was reduced about 50%. Although contamination by resident Fusarium occurred, subsequent root colonization was significantly reduced in T. harzianum-amended growing medium.