Western Gall Rust Research Articles

Distribution and occurrence of western gall rust in thinned jack pine stands

Jack pine (Pinus banksiana Lamb.) is one of the most important commercial species in northwestern Ontario and is the principal host of one of the most serious stem rusts, western gall rust (WGR) caused by Endocronartium harknessii (J.P. Moore) Y. Hirat. In 1986 a trial was established to determine, in part, effects of precommercial thinning on the distribution and occurrence of WGR in jack pine. A 9 year-old aerially seeded jack pine stand was thinned to square spacings of 1 m, 1.5 m, 2 m, 2.5 m, 3 m and a control. Fifth-year results indicated that a significant quadratic trend (p = 0.014) existed between spacing and stem gall infection rate. The incidence of WGR (stem galls) increased as stand density decreased to a maximum at 1.5 m spacing, and then declined to roughly the infection rate of the control at the lowest density (3 m). A significant relationship (0.084) between crown class and the rate of branch gall infection rate was also detected. The branch gall infection rate decreased from 6.2% year−1for dominant trees to 2.8% year−1for trees categorized as suppressed. Based on these results, pre-commercial thinning operations should target those trees with main stem galls and/or numerous branch galls, regardless of size and crown position, and then focus on the removal of suppressed trees to meet the desired density target. This strategy should not only enhance growth of the remaining trees, but also reduce WGR inoculum levels and reduce future WGR-related mortality. Key words: jack pine (Pinus banksiana Lamb.), western gall rust (Endocronartium harknessii (J.R Moore) Y. Hirat.), pre-commercial thinning, white pine weevil (Pissodes strobi Peck.)

Lodgepole pine stem diseases and management of stand density in the British Columbia interior

The incidence of western gall rust, stalactiform blister rust, comandra blister rust and Atropellis canker was measured in 16 permanent sample plots in young lodgepole pine stands in the Interior of B.C. in 1980, shortly following juvenile spacing, and again in 1985 and 1992. The incidence (as percent of living trees with live rust infections) of the three rusts increased substantially between 1980 and 1985 in both treated and control plots, but declined from 1985 to 1992, partly because of infected tree mortality, but mostly because of a low rate of new infection and the death of all branch infections on many surviving trees. More than 85 percent of all stalactiform and comandra blister rust infections and 60 percent of all gall rust stem infections occurred within 2 m of the ground. The low incidence of new infection in these plots since 1985 is probably attributable to the loss of live branches due to crown closure and branch suppression in that 2 m zone as well as altered climatic conditions and reduced inoculum levels. Atropellis canker infection increased at each remeasurement, and in 1992, was less in spaced plots than in unthinned controls (3.4 and 8.9% of trees infected). A set of recommendations concerning allowances for disease mortality at the time of regeneration and juvenile spacing is presented. Key words: stand density management, Lodgepole pine, western gall rust, blister rust, Atropellis canker

Geographic pattern of adaptive variation of lodgepole pine ( Pinus contorta Dougl.) within the species' coastal range: field performance at age 20 years

A plantation comprising 79 lodgepole pine provenance samples from all four geographic races was established in 1972 at a site on southern Vancouver Island, British Columbia. Provenance adaptability was assessed in 1991 after 20 growing seasons based on: total height, diameter, survival, crown condition, crown density, tree form, western gall rust and sequoia pitch moth damage, and principal component (PC) scores derived from PC analysis. Regression models depicting geographic trends in adaptive variation accounted for 33% (pitch moth) to 81% (PC1) of provenance variance. The results showed a strikingly narrow ecological adaptation of lodgepole pine within its coastal range. Only provenances from a narrow strip along eastern Vancouver Island in the rain shadow zone, with a climate similar to the test environment, showed no symptoms of declining vigor. Implications in the context of evolutionary significance, genetic resource management, and seed movement are discussed.

Variation and heritability of resistance of lodgepole pine to Western gall rust

AbstractFamilies of pine seedlings from 40 open‐pollinated trees (mother trees) from the interior of British Columbia (B. C.) were inoculated with two spore mixtures, one from the coast and the other from the interior of B. C. The relative susceptibilities of the 40 families to each spore mixture was assessed and narrow sense heritability with respect to disease resistance was estimated. The results are presented and discussed.

Spore dispersal gradients and disease gradients of western gall rust

To determine whether spore dispersal gradients of Endocronartiumharknessii (J.P. Moore) Y. Hiratsuka were present adjacent to heavily infected pine stands, spore samplers were placed 0.5 m above ground, at five distances, 2–80 m from the edge of an 18-year-old stand and were operated for a total of 33 days over 2 years. Six weather parameters were recorded inside the stand, and multiple regression was used to determine the relationship between weather and parameters of spore dispersal. To determine whether gradients of lodgepole pine (Pinuscontorta Dougl. var. latifolia Engelm.) seedlings infected by gall rust were present adjacent to heavily infected pine stands, seedling infection was determined in 75-m2 plots centered 2.5–120 m from the stand edge, in five such plots in the center of that stand, and in transects of two-tree plots through a second stand. Spore concentration decreased with increasing distance from the stand edge in accordance with the power law model. Spore concentrations and the slopes of spore dispersal gradients were significantly affected by wind values, although there was considerable unexplained variation. There was little evidence for the existence of disease gradients.

Limits to selection for disease resistance from natural tree populations

It is demonstrated that for diseases characterized by a small number of discrete infections per tree, random placement of spores on trees results in substantial variation in the number of infections per tree. The consequences of this phenomenon for selection of resistant individuals and for natural selection are examined, using a previously reported distribution of susceptibility model for the western gall rust (Endocronartiumharknessii (J.P. Moore) Y. Hiratsuka)–lodgepole pine (Pinusconforta Dougl.) pathosystem as an example.

A new method for inoculating jack pine seedlings with the western gall rust fungusEndocronartium harknessii

(1993). A new method for inoculating jack pine seedlings with the western gall rust fungus Endocronartium harknessii. Canadian Journal of Plant Pathology: Vol. 15, No. 1, pp. 29-33.

Stand, family, and rust-source effects on four attributes of lodgepole pine resistance to western gall rust

Lodgepole pine (Pinuscontorta var. latifolia Engelm.) seedlings from 23 open-pollinated pine families from five stands in west-central Alberta were inoculated with western gall rust (Endocronartiumharknessii (J.P. Moore) Y. Hiratsuka) spores from four locations within 69 km of those stands. Six weeks after inoculation and at 3-week intervals for 21 weeks thereafter, seedlings were examined for symptoms of infection and galls. Eighteen months after inoculation, most trees in a sample of 1321 had either fully developed galls or no galls; partial gall formation was uncommon. Frequency of gall formation was highly correlated with the area under the disease progress curve (AUDPC) of symptom appearance and the AUDPC of gall appearance. It was also correlated, although less strongly, with the frequency of seedlings that had initially shown symptoms of infection but had no galls 21 weeks after inoculation. Regardless of whether AUDPC of gall appearance, frequency of gall formation, or failure to develop galls following infection was used as the criterion of resistance, the results were similar. Family effects were greater than stand effects, and rust-source effects were smaller than family effects and not always significant. There was no interaction between rust-source effects and either stand or family effects.

Differences in Monterey pine pest populations in urban and natural forests

Monterey pines ( Pinus radiata D. Don) planted along streets (i.e. street trees) within Carmel, California and its immediate vicinity, and naturally grown Monterey pine within adjacent native stands, were sampled with regard to intensity of visual stress characteristics, western dwarf mistletoe ( Arceuthobium campylopodum f. typicum [Engelm.] Gill), and western gall rust ( Peridermium harknessii J.P. Moore) infection, and frequency of sequoia pitch moth ( Synanthedon sequoiae Hy. Edw.) and red turpentine beetle ( Dendroctonus valens LeConte) attacks. The street trees were stratified into four geographic zones: one highly urban zone, two urban zones, and one suburban zone. Dwarf mistletoe infections generally were more common in the forest stand than on street trees in the highly urban and urban zones for trees less than 50 cm dbh and were positively correlated with stand density. Pitch moth attacks were more common in all street tree zones than the natural forest, and were positively correlated with amount of pruning and wounding, and negatively correlated with amount of crown closure and stress. Red turpentine beetle attacks were positively correlated with stress and diameter, and may follow pitch moth attacks. More beetle attacks occurred in the two urban zones than in the natural forest, probably due to significantly more large trees in these zones, and more pruning and wounding in the street tree setting than in the forest.

Early symptoms and resistance of lodgepole pine seedlings inoculated with western gall rust

One-year-old seedlings in 10 open-pollinated Pinus contorta families were inoculated with spores of the rust fungus Endocronartium harknessii at two stages of seedling maturity and two levels of inoculum concentration. The early symptoms (general red stain, red flecks, red streaks) that appeared on the seedlings were recorded 2, 4, and 8 weeks after inoculation, while the number of galls was recorded 1 year after inoculation. The frequency of general red stain and red flecks varied significantly among families. Resistance of families as percent of seedlings producing galls also varied significantly. The frequency of early symptoms was only poorly correlated with family resistance. Also, the occurrence of early symptoms on individual seedlings did not give a good prediction of gall formation on them. These results suggest that early symptoms cannot accurately identify resistant families or individuals. Key words: Endocronartium harknessii, Pinus contorta, symptoms, resistance.

Evaluating Scots Pine for Resistance to Endocronartium harknessii

Abstract Seedlings of eight different varieties of scots pine (Pinus sylvestris L.) were evaluated for resistance to pine-pine gall rust Endocronartium harknessii [J.P. Moore] Y. Hiratsuka using a concentrated aeciospore suspension (CAS). The presence or absence of galls on seedlings was recorded 24 wk after inoculation. Seedlings of variety Mongolica were the most resistant with 16% of the seedlings with galls, and Guadalajara and Alpine were the least resistant among the eight with 58% and 56% of the seedlings with galls, respectively. The remaining varieties were intermediately resistant. For. Sci. 37(6):1689-1691.

Isozyme structure of Peridermium harknessii in the western United States

We conducted a population genetic study of the western gall rust fungus (Peridermium harknessii) using isozymes as genetic markers. Electrophoresis of 341 single-gall aeciospore isolates collected from several pine species revealed that western gall rust is comprised of two distinct zymodemes (multilocus electrophoretic types) in the western United States. Within zymodemes, all 15 loci studied were monomorphic (0.95 criterion), although variants were found at low frequencies (≤ 0.03) at 3 loci. Zymodeme I was characterized by single bands, indicating homozygosity at all loci; it consisted of isolates from all pine species and environments studied, including the Pacific Coast and Cascade Ranges and the Sierra Nevada and Rocky Mountains. Zymodeme II, which was absent from coastal forests, was characterized by double or triple bands at 6 of 15 loci. The additional bands were interpreted as products of alternative alleles in heterozygous condition; isozyme phenotypes at the other nine loci were identical to those of zymodeme I. Presumed heterozygotes were fixed within zymodeme II, and homozygotes of alleles unique to this zymodeme were not found. Generally, all isolates sampled from a forest stand were in the same zymodeme, and when isolates from both zymodemes were found in the same location, recombinant genotypes between zymodemes were not observed. Such extreme disequilibrium is inconsistent with sexual reproduction, indicating that P. harknessii is asexual. Key words: western gall rust, Pinus spp., genetic variation.

Resistance to western gall rust in artificially inoculated ponderosa pine

Seedlings from 80 open-pollinated families of ponderosa pine (Pinusponderosa Laws.) were inoculated with western gall rust (Endocronartiumharknessii (J.P. Moore) Y. Hiratsuka) at the beginning of their 2nd year of growth. The overall infection level was 41 %, with a family heritability of 0.76. Several resistance responses were evident, heritabilities of which ranged from moderate to high; i.e., for seedlings with no symptoms, the heritability value was 0.60, while for trees with bark reactions that prevented gall formation, the heritability value was 0.71. There were three such types of bark reactions, for which heritability values were 0.36, 0.58, and 0.60. Heritability values of 0.38, 0.41, and 0.45 were found for trees with dead galls, rust-killed trees, and rate of gall appearance, respectively. Resistance of ponderosa pine to western gall rust is not only high but highly variable and exhibits a rich assortment of resistance reactions that probably account for the low level of gall-rust damage. The findings emphasize the importance of maintaining resistance in ponderosa pine tree-improvement programs.

Comparison of White- and Orange-Spored Peridermium harknessii in Native North Dakota Pinus ponderosa

Comparison of White- and Orange-Spored Peridermium harknessii in Native North Dakota Pinus ponderosa

Comparison of White- And Orange-Spored Peridermium Harknessii in Native North Dakota Pinus Ponderosa

Comparison of White- And Orange-Spored <i>Peridermium Harknessii</i> in Native North Dakota Pinus Ponderosa

Major gene resistance of Scots pine to western gall rust

Grafted ramets, full-sib families, and open-pollinated families were derived from two healthy and one western gall rust (Endocronartiumharknessii (J. P. Moore) Y. Hiratsuka) infected Scots pine (Pinussylvestris L.) and inoculated with western gall rust. Resistance appeared to be a qualitative character; grafts and seedlings either had many infected shoots or none. All F1 families for which the diseased tree was one of the parents were about 50% infected. All other full-sib families showed &lt;15% infection. There was no distinction between bulk inoculum collections from Scots and from lodgepole (Pinuscontorta Dougl.) pine. It is proposed that susceptibility to western isolates of the gall rust in the Scots pine trees tested in this experiment is conditioned by a dominant gene.

Pine-Pine Gall Rust on Young Jack Pine in Northwestern Ontario

Abstract Pine-pine gall rust, caused by Endocronartium harknessii, accounted for &gt;99% of all stem rusts encountered during a 1987 survey of jack pine in 71 plantations regenerated with planted stock or by seeding between 1979 and 1984 in northwestern Ontario. Significant differences in rust incidence were detected among the six districts in the region (P &lt; 0.05) with mean incidence ranging from 6.7 to 17.2%. Trees with main stem galls were found more frequently than trees with only branch galls. The majority of main stem infections in 44 plantations where incidence of main stem galls was &gt;5% were in the potential impact class where deformity or mortality was imminent (P &lt; 0.05). The average level of mortality attributed to rust was low (3.4%). Implications of the results to the region's jack pine tree improvement program and to stand management are discussed. North. J. Appl. For. 7:133-136, September 1990.

Histological evidence of resistance to Endocronartium harknessii in Pinus contorta var. latifolia

Resistance to the western gall rust fungus, Endocronartium harknessii, was observed in 3-, 10-, 20-, and 33-month-old greenhouse-grown seedlings of lodgepole pine (Pinus contorta var. latifolia). Three sites of resistance were identified: epidermal, cortical, and cambial. In cases of epidermal resistance, penetration of the epidermis occurred, but infection was prevented by an apparent hypersensitive response. Cortical resistance occurred where infected cells in the cortex were successfully isolated by necrophylactic periderm and the infected tissue was exfoliated with the rhytidome. In cambial resistance, infections progressed to the vascular cambium where infected cells and cambial initials were inactivated. This resulted in abnormal secondary xylem development, characterized by a zone of pathological tissue extending from the pith to the epidermis. In a number of infected seedlings, cambial function was restored and infected lesions were overgrown. Live mycelium was often maintained in cortical lesions and in some cases reinvaded healthy cortical cells. These latent-type infections resulted in the initiation of gall formation up to 1 year after initial resistance to infection occurred. Key words: tree improvement, western gall rust, pine stem rust.

Early symptom development in lodgepole pine seedlings infected with Endocronartium harknessii

Six-week-old Pinus contorta seedlings were inoculated with spores of the western gall rust fungus Endocronartium harknessii. Of 660 seedlings inoculated, 174 showed early symptoms and were sampled for histological observation in the 7 weeks following inoculation. Pigmentation of epidermal cells was the first externally visible response to infection, generally occurring 14–28 days after inoculation. Developing symptoms were extremely variable, ranging from little or no visible response to severe necrosis. The appearance of external symptoms was largely due to changes occurring in underlying infected cortical cells such as the production of phenolic compounds, necrophylactic periderm, or necrotic tissue. Intercellular lignin deposition was observed in infected tissue and was thought to be associated with necrophylactic periderm formation. Suppression of normal exophylactic periderm development was evident in virtually all infected tissue zones. Infection of the vascular cambium occurred as early as 21 days after inoculation and resulted in the subsequent formation of distorted xylem tracheids typical of gall tissue.

Influence of plant growth regulators, basal media and carbohydrate levels on the in vitro development of Pinus ponderosa (Dougl. ex Law.) cotyledon explants

Applications of in vitro screening techniques for Pinus ponderosa resistance to Peridermium harknessii could be beneficial in a tree breeding program. Plant growth regulators, basal media formula and carbohydrate levels were examined to determine the various effects each would have on excised cotyledon growth and development. Proliferating green callus was initiated from cotyledon explants on SH basal medium containing 4.4 μM BA:5.4 μM NAA and 1% sucrose. Subsequent subculturing onto LS medium supplemented with 44.0 μM BA: 5.4 μM NAA and 2% sucrose improved callus maintenance. The highest frequency of caulogenesis from cotyledon explants occurred on a modified GD medium containing 44.0 μM BA: 0.054 μM NAA and 4% glucose. The influence of nitrogen source, osmoticum and medium salt concentrations are discussed relative to callus initiation and caulogenesis.