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Site preparation can improve lodgepole pine (Pinus contorta var. latifolia Engelm. ex S. Watson) survival and growth; however, we lack information regarding possible interactions between treatment effects and the impacts of western gall rust (Endocronartium harknessii (J.P. Moore) Y. Hirats.) and comandra blister rust (Cronartium comandrae Peck). Mechanical and burning techniques examined over 24 years at a sub-boreal British Columbia site did not significantly increase rust infection rates or characteristics relative to an untreated control. Most infection occurred before age 10 years and at heights

Summary To test the hypothesis that galls resulting from infection by western gall rust [Endocronartium harknessii (J. P. Moore) Y. Hiratsuka] on lodgepole pine [Pinus contorta Dougl. ex Loud.] create hydraulic constrictions that reduce tree growth, the hydraulic conductivity (Kψ; m2 s−1 Pa−1), leaf area (AL) and sapwood area (AS) were measured on 6- to 15-year-old trees having galls encircling 0–100% of the stem. Increases in gall encirclement were accompanied by decreases in Kψ, foliar nitrogen concentration, AL and AS, although the AL:AS ratio remained constant. Dye flow patterns through galled stem sections indicated that water moved primarily through the non-galled portions of the stem. In a second field study, xylem and phloem wounds were applied to 13-year-old galled and non-galled trees on either the galled or non-galled side of the tree. Although both galls and xylem wounds reduced Kψ, radial and height growth were unaffected. In aggregate the two experiments showed that although trees are quite tolerant to small galls and short term reductions in Kψ, the disruption of water movement by larger galls may be sufficient to initiate a chain of events leading to tree death, especially in very dense stands with high levels of intraspecific competition.

Infection of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) by western gall rust has been shown to decrease with tree height and age, but the effects of those two factors have not been separated. Five replicate artificial inoculations were done on a total of 327 trees of different ages in two height classes. Temperature and percentage of spore germination at the height of inoculation, shoot development (stem elongation at the time of inoculation as a proportion of final shoot elongation), main stem leader length at the time of inoculation, tree height, and tree age were measured. Modeled percentages of infected trees and the number of galls per 10 cm of shoot length decreased by 85% and 88%, respectively, as tree age increased between 2 and 10 years, indicating the undesirability of early, aggressive precommercial thinning of lodgepole pine stands in areas where western gall rust is common. By controlling and (or) statistically accounting for inoculum, microclimate, and phenological factors, it was possible to demonstrate that changes in susceptibility with tree age are sufficient to account for the reduction in infection with tree height.

Moltzan, B. D., Blenis, P. V., and Hiratsuka, Y. 2001. Effects of spore availability, spore germinability, and shoot susceptibility on gall rust infection of pine. Plant Dis. 85:1193-1199. Temporal changes in three factors (shoot susceptibility, spore availability, and spore germinability) were evaluated to estimate their effects on the infection of lodgepole pine (Pinus contorta var. latifolia) by Endocronartium harknessii. Germinability of rust spores from sori free of hyperparasites remained above 80% during the growing season and thus would not have significantly limited infection. In contrast, there was a slight, but statistically insignificant, increase in estimated susceptibility as infection increased from 94% of maximum at 45% shoot elongation to maximum susceptibility at 90% shoot elongation. This was followed by a precipitous decline in estimated susceptibility to 57% of maximum when shoots were 95% elongated. Spore availability was 24% of maximum when shoots were 45% elongated, and thus may have been limiting at the beginning of the growing season. At the end of the growing season, spore availability declined prior to, or simultaneous with, the decline in susceptibility. The combined effect of both factors drastically reduced the number of infections estimated to occur once shoots are more than 95% elongated. As shoots elongated, relatively more infections formed higher on the shoot, supporting the hypothesis that periderm is important in limiting infection.

Geographic variability among western gall rust (WGR) fungus (Endocronartium harknessii (J.P. Moore) Y. Hiratsuka) was studied by random amplified polymorphic DNA (RAPD). Samples were taken from lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) host at four locations in British Columbia and Alberta and from jack pine (Pinus banksiana Lamb.) host at nine locations in Alberta, Saskatchewan, Manitoba, and Ontario. Of 90 random oligonucleotide primers screened, 9 were chosen for analysis. These nine primers consistently amplified 41 sharp and reproducible RAPDs (fragments) of the WGR fungal isolates over several independent runs. Eighteen of the 41 RAPDs were polymorphic (showing the presence of both marker and null phenotypes), of which 15 could discriminate WGR isolates of lodgepole pine hosts from jack pine ones. Of these 15 RAPDs, five were unique to isolates of lodgepole and five to jack pine. The remaining five RAPDs were significantly heterogeneous in the RAPD frequency between WGR isolates of the two host origins. The RAPD pattern of WGR isolates from lodgepole pine was uniform. However, isolates from jack pine differed significantly in the frequency of four RAPDs among locations, with an east-west trend of decreasing similarity in RAPD. Analysis of molecular variance apportioned 76.3, 14.4, and 9.3% of the total RAPD variability to differences among hosts, to differences among locations within hosts, and to differences within locations, respectively. The large differentiation between WGR fungal isolates sampled in lodgepole pine and jack pine hosts might suggest that selective pressure for host specificity in sampled populations was strong.

Lodgepole (Pinus contorta Dougl. ex Lound.) and jack (Pinus banksiana Lamb.) pines occur sympatrically and hybridize in central and northwestern Alberta, providing opportunities for studying unique ecological and evolutionary interactions. We conducted a greenhouse inoculation experiment to investigate interactions between 40 populations of lodgepole and jack pines and their putative hybrids across this hybrid zone and two sources of the western gall rust fungus, Endocronartium harknessii (J.P. Moore) Y. Hiratsuka, one from lodgepole pine and the other from jack pine. Rust susceptibility and height were assessed when the seedlings were 6 months and 1 year old. Lodgepole pine and the hybrids were significantly more susceptible to the rust infection than jack pine. Jack pine grew significantly faster than the hybrids and lodgepole pine. In addition, the seedlings infected with spores from lodgepole pine grew significantly slower than those with spores from jack pine. While the overall rust scores indicated that spores from lodgepole pine was more virulent to the hosts than those from jack pine, both spore sources were better adapted to their own host species, causing significant spore source × host group interactions. However, such host specificity in the western gall rust is far from stabilized (equilibrium) because of continued gene exchanges among the two parental species and their hybrids.Key words: Pinus contorta - Pinus banksiana complex, western gall rust, natural hybridization, coevolutionary genetics.

Eighteen lodgepole pine (Pinus contorta Dougl. ex Loud.) stands, 19-32 years in age, were surveyed for Scytalidium uredinicola Kuhlman et al. in west-central Alberta. The purpose of the study was to determine how hyperparasite incidence was affected by gall age, gall size, and the occurrence of western gall rust caused by Endocronartium harknessii (J.P. Moore) Y. Hiratsuka (Peridermium harknessii J. P. Moore). Such information was deemed valuable for evaluating the likelihood that S. uredinicola was functioning as a density-dependent constraint in the pathosystem and assessing the potential for using this fungus as a biological control agent. The hyperparasite was present in all stands, albeit at generally lower levels than previously reported, but there was little evidence that its incidence increased with increasing incidence of gall rust. The odds of hyperparasitism increased by a factor of 1.3 for each year of gall growth, following adjustment for gall size effects, and by a factor of 2.1 for each 1 cm increase in gall size, following adjustment for gall age effects. Since gall age and gall size were positively correlated, there was a strong positive relationship between the unadjusted effects of both age and size and the incidence of S. uredinicola. However, although the incidence of S. uredinicola consistently increased as galls became older and larger, low levels of the hyperparasite on small and young galls may limit the effectiveness of S. uredinicola as a biological control agent.

A survey in a lodgepole pine, Pinus contorta var. latifolia Engelm., provenance trial showed that the western pine moth, Dioryctria cambiicola (Dyar) (Lepidoptera: Pyralidae), was the most prevalent pitch moth, and stalactiform blister rust, Cronartium coleosporioidesArth., the most prevalent stem rust. Also present were the Douglas-fir pitch moth, Synanthedon novaroensis(Hy. Edwards) (Lepidoptera: Sesiidae), comandra blister rust, Cronartium comandrae Pk., and western gall rust, Endocronartium harknessiiJ.P. Moore, and the stem canker Atropellis piniphila (Weir). Results from a likelihood ratio test indicated an association of western pine moth with stalactiform blister rust and of Douglas-fir pitch moth with both western gall rust and stalactiform blister rust. Western pine moth attacks are most commonly found along the active edge of stalactiform blister rust cankers, suggesting that the moth larvae derive some specific benefit from the fungus. The association of Douglas-fir pitch moth with the rusts appear to be a result of the physical wounding caused by the fungi, since attacks by this pitch moth are also frequently found at pruning wounds or other injuries. Resume : Un inventaire dans un test de provenance avec du pin lodgepole (Pinus contorta var. latifolia Engelm.) a revele que la pyrale du cambium, Dioryctria cambiicola (Dyar) (Lepidoptera: Pyralidae), est le nodulier le plus frequent et que la rouille-tumeur stalactiforme, Cronartium coleosporioidesArth., est la rouille la plus frequente. On a egalement retrouve le nodulier du Douglas, Synanthedon novaroensis(Hy. Edwards) (Lepidoptera: Sesiidae), la rouille- tumeur oblongue, Cronartium comandraePk., la rouille-tumeur autonome, Endocronartium harknessiiJ.P. Moore, et le chancre atropellien, Atropellis piniphila (Weir). Les resultats d'un test de rapport de probabilite a revele qu'il y avait une association entre la pyrale du cambium et la rouille-tumeur stalactiforme ainsi qu'entre le nodulier du Douglas, la rouille-tumeur autonome et la rouille-tumeur stalactiforme. Les attaques de la pyrale du cambium surviennent le plus souvent a la limite des chancres causes par la rouille-tumeur stalactiforme, ce qui suggere que les larves de la pyrale tirent certains benefices specifiques du champignon. L'association entre le nodulier du Douglas et les rouilles semble resulter de la blessure physique causee par les champignons etant donne que les attaques de ce nodulier sont aussi frequemment observees autour des blessures d'elagage ou d'autres types de blessures. (Traduit par la Redaction) Rocchini et al. 1614

A total of 456 half-sib families of superior lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) trees found mostly in high-elevation natural stands in west-central Alberta were outplanted in 1990 at two geoclimatically different sites, Norris and Redrock, Alberta. The trials were measured at age 6 for survival, height, and incidence and severity of western gall rust (WGR) (Endocronartium harknessii (J.P. Moore) Y. Hiratsuka). Survival at both sites was very similar (85-87%). Mean family height at Redrock was almost 10 cm higher (60.5 cm) than that at Norris (51.0 cm). Mean family WGR incidence was 25% with a range of 0-76% at Norris, but only 1.6% with a range of 0-27% at Redrock. A similar site difference was also observed for WGR severity. Strong site x family interactions were detected for height growth and WGR infection. The interaction for WGR infection did not seem to involve a change in family ranks because there was very little contribution to the interaction variance from lack of perfect genetic correlation between the two sites. The contrasting patterns of family variation in WGR infection across the two sites may be the outcome of epidemiological (environmental) or genetic causes or both.

Stability of 76 interior lodgepole pine (Pinus contorta ssp. latifolia Engelm.) provenances in resistance to western gall rust (Endocronartium harknessii (J.P. More) Y. Hiratsuka) and needle cast (Lophodermella concolor (Dearn.) Darker) was investigated from 19 and 23 sites in the British Columbia interior, respectively. Provenances, sites, and provenance by site interaction had significant effects on severity level of infection of both diseases. Susceptible provenances contributed mainly to the interaction. The resistant provenances to both diseases were very stable and essentially homeostatic across sites (regression coefficient approaching 0). Resistant provenances were concentrated in the jack pine (Pinus banksiana Lamb.) - lodgepole pine hybrid zone and adjacent areas, and provenances from the low-elevation interior wetbelt were also very resistant to needle cast. Geographic patterns of provenance variation revealed that the closer a lodgepole pine provenance is to the limit of jack pine distribution, the higher and more stable is its resistance to western gall rust and needle cast. The current multiple-site evaluation supports for the hypothesis that jack pine introgression influences pest defence in lodgepole pine and suggests genetic selection can be effective.

Seedlings from 291 open-pollinated families of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) from three breeding regions (B1, B2, and C) in west-central Alberta were evaluated in the greenhouse during 1992-1994 for their response to infection by western gall rust (WGR) (Endocronartium harknessii(J.P. Moore) Y. Hiratsuka). Region C is a foothill outlier whereas the two western regions are under strong cordilleran influence in the Rocky Mountains. Significant variation in WGR resistance was found among and within regions. A general east-west trend was observed, with western and high-elevational families being more susceptible to WGR infection. Regression of WGR resistance on geographic origins of families accounted for up to 25% of the among-family variation. However, the among-family variation in region C could not be predicted by any geographic variables. Canonical discriminant analysis of WGR resistance and geographic variables could discern families in region C from those in regions B1 and B2. While the widespread introgression from jack pine (Pinus banksianaLamb.) could contribute to WGR resistance in lodgepole pine, the observed geographic variation could also be a selection gradient induced by regional patterns of geoclimatic conditions for WGR development. Resume : Les semis de 291 descendances de pollinisation libre de pin tordu latifolie ( Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) provenant de trois zones d'hybridation (B1, B2 et C) du Centre-Ouest de l'Alberta furent evaluees en serre de 1992 a 1994 pour leur reaction a l'infection par la rouille-tumeur autonome (RTA) (Endocronartium harknessii(J.P.

The susceptibility of Pinus sylvestris to the rusts of P. contorta—Endocronartium harknessii, Cronartium coleosporioides, and C. comandrae—was determined by an assessment of these diseases in 1993 in five seven‐year‐old experimental plantations in British Columbia and the Yukon in western Canada. After seven years, infection by E. harknessii was much higher on P. contorta than on P. sylvestris (27.3% resp. 2.5%). The average number of galls per infected tree was, however, higher on P. sylvestris than on P. contorta (5.99 resp. 3.61). C. coleosporioides was uncommon but occurred on P. contorta at all the five sites, while on P. sylvestris it occurred only at the two southern sites. 28.2% of the P. contorta trees were infected by C. comandrae at one site, but it was recorded only sporadically at the four other sites. P. sylvestris was slightly affected by C. comandrae at two of the sites.

Vingt-quatre peuplements de pin de Murray (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.), âges de 26 a 32 ans et eclaircis entre l'âge de 15 et 23 ans, ont ete examines dans le centre-ouest de l'Alberta. L'âge du peuplement au moment de l'eclaircie etait le meilleur predicteur individuel de la formation de galles sur les arbres qui en etaient exempts lors de l'eclaircie (infection posterieure a l'eclaircie). La hauteur du peuplement etait aussi un bon predicteur de l'infection posterieure a l'eclaircie apres un ajustement pour les effets de la localisation du peuplement et les annees d'infection severe. Le nombre de galles par arbre au moment de l'eclaircie etait le meilleur predicteur de l'incidence des galles sur tous les arbres, incluant ceux qui avaient des galles au tronc au moment de l'eclaircie (infection totale). Les infections au tronc diminuaient avec l'âge et la hauteur des arbres. Pres de 60% des galles au tronc couvraient 40% ou moins de la circonference du tronc. Il n'y avait pas de relation entre le degre d'encerclement et la hauteur ou l'âge des galles. Dans les endroits ou la rouille-tumeur est commune, les amenagistes devraient considerer la possibilite de retarder l'eclaircie.

Endocronartiumharknessii (J.P. Moore) Hirat. populations never approach the level where all susceptible Pinuscontorta Dougl. ex Loud. var. latifolia Engelm. tissue is infected, even in years when environmental conditions are favourable for infection. A simple simulation model was developed to determine whether a hyperparasite could regulate the rust population and maintain it at an equilibrium level far below host saturation. The model assumed that galls begin sporulating and first become susceptible to parasitism 2 years after formation and requires specification of infection rates for the rust and the hyperparasite, mortality rates for normal and parasitized galls, and the degree to which aeciospore production is reduced following hyperparasite infection. Analysis of the model showed that the hyperparasite could regulate the rust population, producing a stable equilibrium, but only if the various rates were such that healthy galls, in their lifetime, produced enough aeciospores to give rise to more than one new gall, while galls that were parasitized during the first year of aeciospore production produced, in their lifetime, fewer than one new gall. The model of hyperparasite regulation provides one possible explanation of the dynamics of the gall rust pathosystem. It shows that control measures such as sanitation and breeding for resistance may reduce the effectiveness of the hyperparasite in regulating the system and, thus, may fail to achieve the anticipated goals.

Incidence of western gall rust (Endocronartiumharknessii (J.P. Moore) Y. Hiratsuka), stalactiform blister rust (Cronartiumcoleosporioides Arth.), needle cast (Lophodermellaconcolor (Dearn.) Darker), and sequoia pitch moth (Synanthedonsequoiae (Hy. Edwards) (Lepidoptera: Sesiidae)) attacks were investigated in a lodgepole pine (Pinuscontorta Dougl. ex Loud, van latifolia Engelm.) provenance–family test plantation located at Red Rock Tree Improvement Station, Prince George, British Columbia. This plantation contains 778 wind-pollinated families from 53 provenances in British Columbia, Alberta, and the Yukon Territory. Pest incidence was assessed in 1993 when the plantation was 21 years old. Provenance had a significant effect on resistance to the four disease and insect attacks. Regression models using latitude, longitude, and elevation as predictors accounted for 38% to 80% of the provenance variation in pest incidence. Geographic patterns of genetic variation in pest resistance essentially followed longitudinal and elevational clines. The most interesting finding is the strong relationship between pest incidence and provenance distance to the western limit of the natural range of jack pine (Pinusbanksiana Lamb,): the closer a lodgepole pine provenance is to the edge of jack pine distribution, the higher is its resistance to the pests. We hypothesize that jack pine introgression may have played a significant role in the evolution of pest defense in lodgepole pine. Effective selection and breeding for pest resistance in lodgepole pine may have to look beyond the intraspecific gene pool.

The life cycle, phenology, and abundance of Epuraea obliquus Hatch was studied near Hinton, Alberta. Most of the life cycle occurs on galls of Endocronartium harknessii (J.P. Moore) Y. Hiratsuka (western gall rust) infecting lodgepole pine (Pinus contorta Dougl. var latifolia Engelm.). Both adults and larvae feed on the spores of the fungus. Individuals of this beetle were found on most galls sampled. Adults overwinter in the soil. They emerge in the spring to seek out and colonize galls. Eggs are laid on the surface of galls, mainly under the periderm, and larvae feed on the fungus, developing through three larval instars. Larvae in the last instar drop from galls to pupate in the soil. Adults leave the soil in late summer and return to feed on inactive galls before overwintering in the soil. The phenology of E. obliquus is closely synchronized with the timing of rust sporulation and the impact of beetle feeding may be an important natural control of western gall rust.

Tree height and number of western gall rust (caused by Endocronartiumharknessii (J.P. Moore) Hirat.) bole and branch infections per living tree were recorded in three experimental 7-year-old lodgepole pine (Pinuscontorta Dougl. ex Loud.) plantations located near Fort St. James, Mackenzie, and Fort St. John, B.C. An extra set of data for trees originating from north of 60°N was also taken at Fort St. John. Each plantation consisted of 40 types of genetic material (i.e., different parentage and latitude of origin), while the extra set at Fort St. John consisted of 17 types of genetic material. The 4357 trees examined had an average of 1.81 gall rust infections per tree, and 49.1% of all trees were infected. Ninety percent of all infections originated in a single year (1990). The number of galls per unit target area declined with increasing height above ground. The percentage of galls located on the bole was 3.10, 10.53, 8.03, and 9.88% for the four populations, respectively. The number of western gall rust infections per tree was linearly related to tree height. The number of infections on boles did not vary with tree height, but the proportion of all infections located on the bole was linearly related to the reciprocal of tree height. The proportion of infections on the bole did not vary significantly with infection severity. Finally, the proportion of galls on the bole did not differ significantly between types of genetic material.

This study aims to identify the role of the beetle Epuraea obliquus Hatch in disseminating Scytalidium uredinicola Kuhlman et al., a mycoparasite of western gall rust, Endocronartium harknessii (J.P. Moore) Y. Hiratsuka. The study was conducted in a lodgepole pine, Pinus contorta Dougl. var. latifolia Engelm., stand near Hinton, Alberta. Mycoparasite spores were observed on the integument of adult beetles collected from western gall rust. In field and greenhouse experiments, adult beetles inoculated with spores of the mycoparasite caused significant numbers of S. uredinicola infections on western gall rust. Since E. obliquus adults migrate between galls, the beetle can transfer the mycoparasite from parasitized to unparasitized galls. Scanning electron microscopy showed that spores of the mycoparasite were common on the body of overwintering beetles. It is believed that these overwintering spores are viable because a culture was successfully established from them. This suggests that beetles emerging in the spring can disseminate S. uredinicola to previously uninfected galls. Epuraea obliquus is an important insect vector of S. uredinicola in western Canada. Key words: mycoparasite, vector, spore dispersal, western gall rust, pine stem rusts.

Families 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.

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.

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.

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.

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.

Resistance of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) to western gall rust (Endocronartium harknessii (J.P. Moore) Y. Hiratsuka) was compared between 21-year field infection trials and inoculation of 2-month-old seedlings. The seedlings were produced from seed stored since the original field plantings. Virtually all of the seedlings from families identified as susceptible in the field produced galls in the inoculation trial, only 1% of seedlings from these families did not develop galls. Nearly half the seedlings in families classed as resistant in the field trials did not form galls 13 months after inoculation. Only one of these seedlings developed galls in the following 2 years. Seedling inoculation provides a simple early test to assess field resistance to gall rust of lodgepole pine seedlots, and an efficient way to cull at least the most susceptible ones.

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.

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.

Hourly measurements of spore release by Endocronartium harknessii (J. P. Moore) Y. Hiratsuka on Pinus contorta Doug. var. latifolia Engelm. were obtained during 2 years. Two spore traps were placed beside both of two sporulating galls and electronic data loggers were used to record environmental data. On rainless days, most spores were trapped between 0900 and 2200, when vapor pressure deficit, temperature, light intensity, and wind velocity were high. A similar pattern of spore release occurred under simulated daytime and nighttime conditions in a growth chamber. On rainy days, most spores were released, on average, over a longer time interval than on dry days. Within 9 h of being placed in a dew chamber, the previously intact peridia on a single gall had ruptured, presumably from pressure caused by spore production. Further evidence that spore production is stimulated by low vapor pressure deficit was obtained by moving 11 galls alternatively between humid and dry conditions. Thus, it is proposed that the diurnal periodicity of spore release on dry days results from the production of spores during the night and the subsequent passive release of those spores during the next day.

A sample of 29 405 lodgepole pine (Pinuscontorta Dougl. var. latifolia Engelm.) trees was assessed from 1982 to 1985, and stem analysis data of 75 trees from five heavily infested second-growth stands in the foothills of the Rockies were analyzed to determine the incidence, development, and impact of western gall rust Endocronartiumharknessii (J.P. Moore) Y. Hiratsuka, in relation to age of trees and stand and site factors. The incidence of western gall rust increased with stand age and time. In stands up to 12 years old, the incidence averaged about 5% and increased rapidly to about 20% at age 20. A rapid increase in incidence over time occurred in younger age-classes. In stands 20 years or older, the incidence of new infection was low. Mortality associated with western gall rust among crop trees was low. There was, however, 30% mortality in an unthinned 22-year-old stand over its life. Impact on growth was highly significant (p

A new species of Scopinella is described and illustrated. This species, Scopinella gallicola, occurs on Pinus contorta galls caused by Endocronartium harknessii. It differs from previously described species mainly in its unusual habitat, size, and shape of the ascocarp, and two- and four-spored asci. The Harziella anamorph is also described. No anamorph has been reported in other species.

(1988). Axenic Culture of Endocronartium Harknessii. Mycologia: Vol. 80, No. 1, pp. 120-123.

Seven lodgepole pine (Pinusconforta Dougl.) provenances collected along an east–west transect from the Cypress Hills, Saskatchewan, to Vancouver, British Columbia, were inoculated as 1-year-old seedlings with one coastal and three British Columbia interior western gall rust (Endocronartiumharknessii (J.P. Moore) Y. Hiratsuka) spore sources in a factorial design. Infection levels ranged from 4 to 95% (average 56.4%, based on 1032 inoculated seedlings). ANOVA of arc sine transformed percent seedlings infected demonstrated a significant interaction between provenance and spore source (P = 0.029). Provenance, spore source, and their interaction accounted for 70, 14, and 6% of the variation, respectively.

Incidence of western gall rust infection in each of 10 replicated forest openings having diameter height ratios of 2:1, 4:1, and 6:1 was determined along two perpendicular 1-m wide transects. Infection frequencies were not significantly different among the different-sized openings. No pine regeneration was present in openings with diameter:height ratios of 0.5:1 or 1:1, thus precluding direct comparison of our results with those obtained from three other tree host–parasite studies in which disease incidence was greatest in small openings.

Seedlings of lodgepole pine (Pinus contorta Dougl.) as young as 11 days old were successfully inoculated with Endocronartium harknessii (J. P. Moore) Y. Hiratsuka, and recognizable discolored areas were observed on these as early as 7 days after inoculation.

In a sample of 121 young lodgepole pine (Pinuscontorta Dougl. var. latifolia Engelm.) stands in naturally regenerated cut blocks near Hinton, Alta., strong positive correlations were observed in the incidence of gall rust (Endocronartiumharknessii (J. P. Moore) Y. Hiratsuka) and leader damage from terminal weevil (Pissodesterminalis Hopp.) and from pitch twig moth (Petrova spp.) with tree size in both thinned and unthinned stands. Although tests on a selected number of the largest trees from each plot showed no significant differences in incidence of the two pest categories between thinned and unthinned stands, thinning that retains the large trees may result in an increase in relative incidence of these pests unless special effort is made to cut damaged trees and retain undamaged ones.