Western Gall Rust Research Articles

A DNA-based method for detection ofPeridermium harknessii, the causal agent of western gall rust

Peridermium harknessii is not present in the southern hemisphere yet it poses a serious threat to Pinus radiata cultivation in exotic forest plantations there. If a suspected incursion were to occur, it would be necessary to rapidly confirm the presence of P. harknessii within non-sporulating galls. With this in mind, we have developed a DNA-based identification system, using the first intergenic spacer region (IGS-1), that is able to detect the presence of the pathogen within galled tissue. The PCR primers are highly specific and with the exception of the closest relative, Cronartium quercuum f. sp. banksianae, they did not cross react with any of the 11 species within the closely related genera Cronartium and Peridermium that were tested. Phylogenetic analysis of the IGS-1 region confirmed that C. quercuum f. sp. banksianae is the closest relative to P. harknessii. The PCR primers and protocol reported here should prove useful in the event of a suspected western gall rust disease outbreak in exotic P. radiata plantations.

Whole-tree water relations of western gall rust infected lodgepole pine trees

Lodgepole pine (Pinus contorta Dougl. ex Loud.) trees having galls resulting from infection by western gall rust (WGR; Endocronartium harknessii (J.P. Moore) Y. Hiratsuka) have a lower ability to conduct water than nongalled stems. Experiments were conducted to compare the leaf-specific hydraulic capacity (Q L; g H2O·cm−1 ·MPa−1) of galled and control trees. Specific objectives were to test the hypothesis that Q L was reduced in galled trees, to determine which components of Q L, if any, varied between galled and control trees, and to test the hypothesis that water stress would more negatively affect galled trees than control trees. Under well-watered conditions, galled trees had lower Q L than control trees. This difference was associated with an increased water potential difference between the soil and leaves (ΔΨ MPa) rather than a change in transpiration per unit leaf area (E L; g H2O·cm−2 A L). Although water stress reduced Q L, the effect was similar for galled and control trees, indicating that the former were no more vulnerable to xylem cavitation than the latter. The similarities in the short-term responses of galled and control trees under well-watered conditions are consistent with the observation that stem galls do not result in rapid tree mortality.

Annual Meeting, Saskatoon, Saskatchewan, 2007 / Réunion annuelle, Saskatoon, Saskatchewan, 2007

Annual Meeting, Saskatoon, Saskatchewan, 2007 / Réunion annuelle, Saskatoon, Saskatchewan, 2007

Predicting survival of lodgepole pine stands infected with western gall rust

The probability of lodgepole pine (Pinus contorta Dougl. ex Loud.) having main-stem galls caused by western gall rust, Endocronartium harknessii (J.P. Moore) Y. Hiratsuka, surviving to rotation is unknown. To evaluate survival, 400 galled trees with at least one stem gall and 400 trees without stem galls were measured in 1992 in two precommercially thinned stands approximately 20 years old. The survival of trees was assessed in 2003. Nonlinear regression using iteratively reweighted least squares was employed to estimate the survival of galled trees as a function of the proportion of the main stem encircled by galls. Galls encircling >79% and >91% of the stem in the two stands increased the risk of mortality relative to non-galled trees, with the risk increasing steeply with percent gall encirclement; smaller stem galls did not cause tree mortality. The 11-year pattern of survival of galled trees was similar for infections that occurred on the main stem and those that had reached the stem from a nearby branch infection. Based on an earlier model of gall expansion, 38%–43% of stem-galled trees would be expected to survive until age 80. Scribing of stem galls to prevent their expansion does not appear to be a feasible management strategy.

Incidence of main stem infections of lodgepole pine by western gall rust decreases with tree age

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.

Annual Meeting, Ottawa, Ontario, 2004

Annual Meeting, Ottawa, Ontario, 2004

DNAbased detection of western gall rust

The internal transcribed spacer (ITS) region of the nuclear ribosomal DNA of the western gall rust fungus (Peridermium harknessii) was amplified using the basidiomycetespecific PCR primers ITS1F and ITS4B The PCR product was then sequenced and aligned with other pine stem rust ITS sequences and a conserved region within P harknessii was targeted with the novel PCR primer Phar1 Our PCR protocol was able to differentiate P harknessii from Cronartium comandrae and C coleosporioides and detected P harknessii within infected host tissue However P harknessii was not distinguishable from C quercuum fsp fusiforme The method provides a rapid and sensitive detection protocol for P harknessii and C quercuum fsp fusiforme within infected host tissue

Temporal occurrence and impact of Scytalidium uredinicola, a mycoparasite of western gall rust

Scytalidium uredinicola Kuhlman et al. is considered an important mycoparasite of western gall rust caused by Endocronartium harknessii (J.P. Moore) Y. Hiratsuka (= Peridermium harknessii J.P. Moore). The temporal occurrence of S. uredinicola and its impact on the ability of western gall rust spores to germinate were determined. Scytalidium uredinicola was not isolated from either external or internal tissues of 3- to 5-year-old galls at any time of the year. However, it was isolated from the external, but not internal, tissues of 6- to 9-year-old galls in most months and from both external and internal tissues of 10+-year-old galls in all months. On galls older than 10 years, S. uredinicola overwintered beneath the periderm and colonized developing rust sori prior to peridial rupture in April. Spore viability of western gall rust was consistently reduced by 85% throughout the period of sporulation over two sporulating seasons. Because S. uredinicola requires considerable time to become persistent and perennial, artificial establishment of the hyperparasite in the early stages of gall rust epidemics might be required to make it an effective biological control agent.

Random amplified polymorphic DNA variability among geographic isolates of western gall rust fungus in Canada

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.

Random amplified polymorphic DNA variability among geographic isolates of western gall rust fungus in Canada

Random amplified polymorphic DNA variability among geographic isolates of western gall rust fungus in Canada

Seedling inoculation distinguishes lodgepole pine families most and least susceptible to gall rust

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.

Predicted impacts of hard pine stem rusts on lodgepole pine dominated stands in central British Columbia

We developed two models to predict volume loss due to western gall rust (Endocronartium harknessii (J.P. Moore) Y. Hiratsuka) and comandra blister rust (Cronartium comandrae Peck) on juvenile lodgepole pine (Pinus contorta Dougl. ex Loud.) dominated stands in central British Columbia. The models suggest that volume loss is significantly and positively correlated to the incidence of comandra blister rust. The relationship between volume loss and western gall rust incidence was weak. The addition of stand density data improved the statistical fit of the model. We used the growth and yield model Tree and stand simulator (TASS) to predict volume at culmination age (age at which the merchantable mean annual increment was maximized) in thirty 1-ha stem-mapped stands. The lodgepole pine trees we stem mapped were also assessed for hard pine stem rust incidence. We developed our volume loss functions assuming that trees with stem infections of both comandra blister rust and western gall rust were lethal, and that infected trees would die from ages 21 to 40. In areas where comandra blister rust is common, the losses due to the disease can be considerable. We predict that the volume losses due to hard pine stem rusts in lodgepole pine dominated stands are as high as 7.2% by culmination age.

Predicted impacts of hard pine stem rusts on lodgepole pine dominated stands in central British Columbia

We developed two models to predict volume loss due to western gall rust (Endocronartium harknessii (J.P. Moore) Y. Hiratsuka) and comandra blister rust (Cronartium comandrae Peck) on juvenile lodgepole pine (Pinus contorta Dougl. ex Loud.) dominated stands in central British Columbia. The models suggest that volume loss is significantly and positively correlated to the incidence of comandra blister rust. The relationship between volume loss and western gall rust incidence was weak. The addition of stand density data improved the statistical fit of the model. We used the growth and yield model Tree and stand simulator (TASS) to predict volume at culmination age (age at which the merchantable mean annual increment was maximized) in thirty 1-ha stem-mapped stands. The lodgepole pine trees we stem mapped were also assessed for hard pine stem rust incidence. We developed our volume loss functions assuming that trees with stem infections of both comandra blister rust and western gall rust were lethal, and that ...

Seedling inoculation distinguishes lodgepole pine families most and least susceptible to gall rust

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 in...

Susceptibility ofPinus contorta - Pinus banksianacomplex toEndocronartium harknessii: host-pathogen interactions

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.

Association of pitch moths (Lepidoptera: Sesiidae and Pyralidae) with rust diseases in a lodgepole pine provenance trial

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 coleosporioides Arth., 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 harknessii J.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.

Effects of gall age, gall size, and rust severity on incidence of the mycoparasite Scytalidium uredinicola

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.

Phylogenetic positions of rust fungi parasitic on ferns: Evidence from 18S rDNA sequence analysis

Molecular phylogenetic analyses of fern rusts were carried out based on 18S rDNA sequences. We sequenced the 18S rDNAs of fern rusts (Hyalopsora polypodii andUredinopsis intermedia) and non-fern rusts (Aecidium epimedii, Coleosporium asterum, Ochropsora kraunhiae, Puccinia suzutake andPhysopella ampelopsidis) and analyzed their phylogenetic relationships with other members of the Urediniomycetes. Our bootstrapped neighbor-joining tree obtained from these analyses showed that rust fungi were apparently monophyletic at high confidence level (100% bootstrap confidence). In this molecular phylogenetic tree, the two fern rusts did not occupy the basal position within the rust fungal lineage and did not form a monophyletic lineage. Two species of the Cronartiaceae (Peridermium harknessii, Cronartium ribicola) and one species of the Coleosporiaceae (Coleosporium asterum) grouped with the fern rusts. Therefore, our results suggested that the two fern rusts were not primitive. On the other hand,Mixia osmundae, which is parasitic on the primitive fernOsmunda, was phylogenetically far from the fern rusts.

Comparative assessment of genetic variation of young high-elevation lodgepole pine for height and western gall rust resistance across two sites in Alberta

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 resistance to western gall rust and needle cast in lodgepole pine provenances

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.