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John N. King - One of the best experts on this subject based on the ideXlab platform.
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constitutive defenses and damage in sitka spruce progeny obtained from crosses between white pine weevil resistant and susceptible parents
Forestry, 2012Co-Authors: Xoaquín Moreira, René I. Alfaro, John N. KingAbstract:Summary Attack by the white pine weevil has notably reduced Sitka spruce productivity in British Columbia (BC) (Canada) and western US. By the 1970s, the BC Ministry of Forests established provenance trials of Sitka spruce with the objective of detecting usable genetic resistance to weevil. These early trials reported significant weevil resistance and allowed the production of the first (F1) controlled-cross progeny generation with demonstrable weevil resistance (R) or susceptibility (S). This study reports results of the screening for weevil resistance and the levels of constitutive defenses of this F1 Sitka spruce progeny. Progeny from resistant parents (R × R progeny) sustained significantly fewer weevil attacks than progeny from susceptible parents (S × S progeny) or progeny with one resistant and one susceptible parent (R × S progeny). Individual and family heritability estimates of the weevil resistance were 0.5 and 0.9, respectively. Constitutive defenses, measured by Resin Canal and sclereid cell density in the cortex, were significantly higher in R × R progeny than in R × S or S × S progeny. We observed a negative correlation between the percentage of trees attacked in each cross and the average density of the Resin Canals or sclereid cells for each cross.
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Geographic variation in Resin Canal defenses in seedlings from the Sitka spruce × white spruce introgression zone
Canadian Journal of Forest Research, 2002Co-Authors: Gregory A. O'neill, Sally N. Aitken, John N. King, R I AlfaroAbstract:Seedlings from 18 provenances along a coast-interior transect in the Picea sitchensis (Bong.) Carriere ◊ Picea glauca (Moench) Voss introgression zone in northwestern British Columbia were mechanically wounded at the beginning of their third growing season to simulate natural attack by the white pine weevil, Pissodes strobi (Peck). Constitutive Resin Canals (CRC) in the cortex and traumatic Resin Canals (TRC) in the xylem of terminal shoots were characterized microscopically 4 months after wounding. Wounding resulted in a large increase in CRC size and in TRC number and density. Provenances differed significantly in TRC number and in CRC number, size, total area, and the proportion of total bark area occupied by CRC. CRC number and size, TRC number, and provenance weevil resistance (obtained from previously published data) increased with increasing latitude, elevation, and distance from the Pacific Ocean (i.e., towards the P. glauca end of the introgression zone) and decreased with increasing longitude (i.e., towards P. sitchensis). These traits also increased with aridity and continentality and decreased with most temperature, precipita - tion, and growing season length variables. Statistically significant multiple regression models related variation in some Resin Canal traits to geographic (r 2 = 0.71) and climatic (r 2 = 0.62) variables. Provenance mean values for weevil resis- tance were positively associated with predicted values for TRC number and CRC size. These results indicate that it is possible to predict locations in the introgression zone containing trees that possess desirable Resin Canal traits using geographic or climatic variables.
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geographic variation in Resin Canal defenses in seedlings from the sitka spruce white spruce introgression zone
Canadian Journal of Forest Research, 2002Co-Authors: Gregory A Oneill, Sally N. Aitken, John N. King, R I AlfaroAbstract:Seedlings from 18 provenances along a coast-interior transect in the Picea sitchensis (Bong.) Carriere ◊ Picea glauca (Moench) Voss introgression zone in northwestern British Columbia were mechanically wounded at the beginning of their third growing season to simulate natural attack by the white pine weevil, Pissodes strobi (Peck). Constitutive Resin Canals (CRC) in the cortex and traumatic Resin Canals (TRC) in the xylem of terminal shoots were characterized microscopically 4 months after wounding. Wounding resulted in a large increase in CRC size and in TRC number and density. Provenances differed significantly in TRC number and in CRC number, size, total area, and the proportion of total bark area occupied by CRC. CRC number and size, TRC number, and provenance weevil resistance (obtained from previously published data) increased with increasing latitude, elevation, and distance from the Pacific Ocean (i.e., towards the P. glauca end of the introgression zone) and decreased with increasing longitude (i.e., towards P. sitchensis). These traits also increased with aridity and continentality and decreased with most temperature, precipita - tion, and growing season length variables. Statistically significant multiple regression models related variation in some Resin Canal traits to geographic (r 2 = 0.71) and climatic (r 2 = 0.62) variables. Provenance mean values for weevil resis- tance were positively associated with predicted values for TRC number and CRC size. These results indicate that it is possible to predict locations in the introgression zone containing trees that possess desirable Resin Canal traits using geographic or climatic variables.
Gar W Rothwell - One of the best experts on this subject based on the ideXlab platform.
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Evolutionary diversification of taiwanioid conifers: evidence from a new Upper Cretaceous seed cone from Hokkaido, Japan
Journal of Plant Research, 2020Co-Authors: Ruth A Stockey, Harufumi Nishida, Gar W RothwellAbstract:A single cylindrical seed cone 2 cm long, 1.1 cm wide has been found preserved in a calcium carbonate marine concretion from the Hakobuchi Formation (late Campanian-early Maastrichtian) of Hobetsu, Hokkaido, Japan. The cone, attached to a bent peduncle lacking leaves, has helically arranged bract/scale complexes that arise at right angles from the cone axis in the middle of the cone. The cone axis, ca. 1 mm wide, has a broad cylinder of secondary vascular tissue, and lacks a continuous Resin Canal system. Bract-scale complexes are laminar, cordate-orbiculate, and upturned distally, consisting primarily of bract tissue with no visible scale tip. The vascular trace to the bract/scale complex originates as a rod that divides laterally into several traces at the level of seed attachment. A single Resin Canal originates at the base of the bract-scale complex abaxial to the vascular strand, but more distally there are up to ca. 15 large Resin Canals that form a single row. Two to three inverted winged seeds are attached adaxially near the cone periphery. Cone structure and vascularization are most similar to those in the Cupressaceae, Subfamily Taiwanioideae, differing from living Taiwania cryptomerioides by having up to three seeds/scale rather than two, an abruptly upturned bract tip, in details of bract/scale vasculature, and a cone peduncle lacking leaves. This cone is described as Mukawastrobus satoi Stockey, Nishida and Rothwell. Together with previously described Early to Late Cretaceous taiwanioid seed cones from Mongolia and Hokkaido the new species demonstrates that the taxonomically diagnostic characters of such conifers are as subtle as those of Cretaceous and Cenozoic sequoioid Cupressaceae. This realization emphasizes that evolutionary diversification and turnover among taiwanioid conifers during the Cretaceous and Paleogene are probably far greater than currently recognized.
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Cunninghamia taylorii sp. nov., a Structurally Preserved Cupressaceous Conifer from the Upper Cretaceous (Campanian) Horseshoe Canyon Formation of Western North America
International Journal of Plant Sciences, 2013Co-Authors: Rudolph Serbet, Benjamin Bomfleur, Gar W RothwellAbstract:The fossiliferous ironstone deposits of the Upper Cretaceous Horseshoe Canyon Formation in the Drumheller badlands, Alberta, Canada, contain a diverse, anatomically preserved flora. Within this assemblage occur abundant stems, leafy shoots, leaves, ovuliferous cones, and pollen cone clusters that are here described as a new species of Cunninghamia. The stems have persistent leaf bases and plagiotropic branching. Some stems show several growth increments, and the cortex and pith are made up of Resin Canals, large parenchymatous cells, and lysigenous cavities. Leafy shoot axes have parenchymatous cells, Resinous cells, lysigenous cavities, and Resin Canals within the cortex and pith. The leaves are helically arranged, lanceolate to falcate, with two abaxial stomatal bands, a large central Resin Canal, and two smaller lateral Canals. The ovuliferous cones have numerous helically arranged bract scale complexes. The bracts and three-lobed ovuliferous scale are variously ornamented. Anatomical features of bract...
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structure and relationships of the jurassic conifer seed cone hughmillerites juddii gen et comb nov implications for the origin and evolution of cupressaceae
Review of Palaeobotany and Palynology, 2011Co-Authors: Gar W Rothwell, Gene Mapes, Ruth A Stockey, Jason HiltonAbstract:Abstract Anatomically preserved Jurassic conifer seed cones originally described as Conites juddi Seward and Bancroft are reinvestigated and assigned to Hughmillerites juddii gen. et comb. nov. using the original specimens and new material from the type locality. This allows for a more thorough characterization of seed cone structure, for systematic placement of the species, and for establishing homologies of cupressaceous bract/scale complexes. Incomplete cones range 2.2–3.6 cm in diameter and 3.0–4.3 cm long, and have distinctly woody axes bearing helically arranged bract/scale complexes with a thickened bract tip. Mature complexes display three inverted seeds attached to the adaxial surface immediately proximal to three free ovuliferous scale tips. In each bract/scale complex there is a single large Resin Canal abaxial to the vascular bundle and three or more smaller adaxial Resin Canals at the level of seed attachment. Seeds are inverted at maturity, display 180° rotational symmetry, and show differentiation of sclerotesta and sarcotesta. The results of a phylogenetic analysis support placement of H. juddii among the basal grade of taxodioid Cupressaceae ( Farjon, 2005 ). A transformational series of ovuliferous bract/scale complexes from voltziacean Voltziales to crown group Cupressaceae is presented to reveal the pattern and antiquity of evolution for modern cupressaceous conifer seed cone morphologies. Developmental studies of living cupressaceous seed cones indicate that the range of mature morphologies is strongly correlated with differences in the timing and rate of development for the bract, scale, and ovules, thus supporting the hypothesis that heterochrony plays a major role in the evolution of bract/scale form. This hypothesis is further supported by our growing understanding of developmental regulatory genetics. There are no currently recognized synapomorphies for living + fossil conifers. Nevertheless, these combined results do not support the hypotheses that some conifers have ancestrally simple seed cones nor that there have been parallel origins of Northern and Southern Hemisphere conifers. The overall body of evidence from both extinct and living conifers strongly supports the hypotheses of deep homology for seed cones and of monophyly for conifers s.s.
René I. Alfaro - One of the best experts on this subject based on the ideXlab platform.
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constitutive defenses and damage in sitka spruce progeny obtained from crosses between white pine weevil resistant and susceptible parents
Forestry, 2012Co-Authors: Xoaquín Moreira, René I. Alfaro, John N. KingAbstract:Summary Attack by the white pine weevil has notably reduced Sitka spruce productivity in British Columbia (BC) (Canada) and western US. By the 1970s, the BC Ministry of Forests established provenance trials of Sitka spruce with the objective of detecting usable genetic resistance to weevil. These early trials reported significant weevil resistance and allowed the production of the first (F1) controlled-cross progeny generation with demonstrable weevil resistance (R) or susceptibility (S). This study reports results of the screening for weevil resistance and the levels of constitutive defenses of this F1 Sitka spruce progeny. Progeny from resistant parents (R × R progeny) sustained significantly fewer weevil attacks than progeny from susceptible parents (S × S progeny) or progeny with one resistant and one susceptible parent (R × S progeny). Individual and family heritability estimates of the weevil resistance were 0.5 and 0.9, respectively. Constitutive defenses, measured by Resin Canal and sclereid cell density in the cortex, were significantly higher in R × R progeny than in R × S or S × S progeny. We observed a negative correlation between the percentage of trees attacked in each cross and the average density of the Resin Canals or sclereid cells for each cross.
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Weevil resistance of progeny derived from putatively resistant and susceptible interior spruce parents
Forest Ecology and Management, 2004Co-Authors: René I. Alfaro, Lara Vanakker, Barry Jaquish, John S. KingAbstract:Abstract Controlled-cross progeny of interior spruce ( Picea glauca (Moench) Voss × Picea engelmanni Parry ex Engelm.) parents ranked as resistant or susceptible to the white pine weevil, Pissodes strobi (Peck) were screened for resistance to the same insect by augmentation of the trial site with weevils. Progeny from two resistant parents (R × R progeny) sustained significantly fewer weevil attacks (13% of the trees were attacked) in the year following the augmentation, than progeny from susceptible parents (S × S progeny) (68% of the trees were attacked). Progeny obtained by crossing one resistant and one susceptible parent (R × S progeny) sustained intermediate attack levels (47% were attacked). Characteristics of the bark Resin Canals of the crosses were explored using microscopy techniques. Bark Resin Canal density was highest in R × R progeny, lowest in S × S progeny and intermediate in R × S progeny. There was a negative correlation between the percentage of trees attacked in each cross and the average density of the outer Resin Canals for each cross. A discriminant function was developed that distinguished between resistant and susceptible progeny using bark characteristics. The function was characterized by positive coefficients for outer Resin Canal density and inner Resin Canal size, and a negative coefficient for bark thickness. Thus, trees with thin bark, large inner Resin Canals and dense outer Resin Canals are more likely to be resistant to P. strobi .
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Histological response of resistant and susceptible white spruce to simulated white pine weevil damage
Tree physiology, 1998Co-Authors: Elizabeth S. Tomlin, René I. Alfaro, John H. BordenAbstract:The traumatic wound response of families of white spruce, Picea glauca (Moench) Voss, resistant or susceptible to the white pine weevil, Pissodes strobi (Peck), were compared after simulated weevil damage. Leaders from 331 trees were wounded just below the apical bud in the spring, coinciding with the natural time of weevil oviposition. A portable 1-mm diameter drill was used to drill 24 holes per leader. Leaders were removed in the fall and examined for evidence of traumatic Resin Canal formation. Drilled trees had a traumatic wound response 8 times greater than that of undrilled trees; however, undrilled trees also formed some Resin Canals in response to unknown causes. In the drilled trees, the traumatic wound response extended into the lower part of the leader, where it could possibly affect older larvae. Trees from resistant families responded with greater intensity than trees from susceptible families, by producing multiple rings of traumatic Resin Canals. Trees from resistant families also responded more rapidly than trees from susceptible families based on number of cells to the first ring of traumatic Resin Canals. Trees from some resistant families exhibited no traumatic Resin Canal formation, showing considerable within-family variation and suggesting that other resistance mechanisms might be important. In the year after drilling, there was a reduction in tree diameter growth and trees suffered a reduction in constitutive Resin Canals in the bark, which suggests some energetic cost of traumatic Resin production. There was no indication that the extent of constitutive defenses, as measured by density of cortical Resin Canals before wounding, was related to the ability to produce traumatic Resin Canals. Screening trees based on their capacity to produce traumatic Resin Canals may be useful in selecting genotypes resistant to white pine weevil.
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White spruce resistance to white pine weevil related to bark Resin Canal density
Canadian Journal of Botany, 1997Co-Authors: René I. Alfaro, Elizabeth S. Tomlin, G. KissAbstract:Examination of the bark from the uppermost lateral branches of white spruce, Picea glauca (Moench) Voss, indicated that trees resistant to attack by the white pine weevil, Pissodes strobi Peck, had significantly higher number and density of vertical Resin Canals per unit of bark area (mm2) than susceptible trees. The number and density of Resin Canals were also positively correlated with tree growth rate, an indicator of tree vigor. The density of the Resin Canals found near the periphery of the bark (outer Resin Canals) had higher correlation with resistance and growth than inner Resin Canals. Measurements of Resin Canals on the bark of lateral branches correlated well with measurements on the bark of the leader of the same tree, indicating that lateral samples could be used to screen white spruce for resistance to weevils. Key words: Picea glauca, Pissodes strobi, pest management, tree genetics.
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related to bark Resin Canal density
1997Co-Authors: René I. Alfaro, Elizabeth S. Tomlin, G. K. KissAbstract:Examination of the bark from the uppermost lateral branches of white spruce, Picea glauca (Moench) Voss, indicated that trees resistant to attack by the white pine weevil, Pissodes strobi Peck, had significantly higher number and density of vertical Resin Canals per unit of bark area (mm') than susceptible trees. The number and density of Resin Canals were also positively correlated with tree growth rate, an indicator of tree vigor. The density of the Resin Canals found near the periphery of the bark (outer Resin Canals) had higher correlation with resistance and growth than inner Resin Canals. Measurements of Resin Canals on the bark of lateral branches correlated well with measurements on the bark of the leader of the same tree, indicating that lateral samples could be used to screen white spruce for resistance to weevils.
Ruth A Stockey - One of the best experts on this subject based on the ideXlab platform.
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Evolutionary diversification of taiwanioid conifers: evidence from a new Upper Cretaceous seed cone from Hokkaido, Japan
Journal of Plant Research, 2020Co-Authors: Ruth A Stockey, Harufumi Nishida, Gar W RothwellAbstract:A single cylindrical seed cone 2 cm long, 1.1 cm wide has been found preserved in a calcium carbonate marine concretion from the Hakobuchi Formation (late Campanian-early Maastrichtian) of Hobetsu, Hokkaido, Japan. The cone, attached to a bent peduncle lacking leaves, has helically arranged bract/scale complexes that arise at right angles from the cone axis in the middle of the cone. The cone axis, ca. 1 mm wide, has a broad cylinder of secondary vascular tissue, and lacks a continuous Resin Canal system. Bract-scale complexes are laminar, cordate-orbiculate, and upturned distally, consisting primarily of bract tissue with no visible scale tip. The vascular trace to the bract/scale complex originates as a rod that divides laterally into several traces at the level of seed attachment. A single Resin Canal originates at the base of the bract-scale complex abaxial to the vascular strand, but more distally there are up to ca. 15 large Resin Canals that form a single row. Two to three inverted winged seeds are attached adaxially near the cone periphery. Cone structure and vascularization are most similar to those in the Cupressaceae, Subfamily Taiwanioideae, differing from living Taiwania cryptomerioides by having up to three seeds/scale rather than two, an abruptly upturned bract tip, in details of bract/scale vasculature, and a cone peduncle lacking leaves. This cone is described as Mukawastrobus satoi Stockey, Nishida and Rothwell. Together with previously described Early to Late Cretaceous taiwanioid seed cones from Mongolia and Hokkaido the new species demonstrates that the taxonomically diagnostic characters of such conifers are as subtle as those of Cretaceous and Cenozoic sequoioid Cupressaceae. This realization emphasizes that evolutionary diversification and turnover among taiwanioid conifers during the Cretaceous and Paleogene are probably far greater than currently recognized.
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structure and relationships of the jurassic conifer seed cone hughmillerites juddii gen et comb nov implications for the origin and evolution of cupressaceae
Review of Palaeobotany and Palynology, 2011Co-Authors: Gar W Rothwell, Gene Mapes, Ruth A Stockey, Jason HiltonAbstract:Abstract Anatomically preserved Jurassic conifer seed cones originally described as Conites juddi Seward and Bancroft are reinvestigated and assigned to Hughmillerites juddii gen. et comb. nov. using the original specimens and new material from the type locality. This allows for a more thorough characterization of seed cone structure, for systematic placement of the species, and for establishing homologies of cupressaceous bract/scale complexes. Incomplete cones range 2.2–3.6 cm in diameter and 3.0–4.3 cm long, and have distinctly woody axes bearing helically arranged bract/scale complexes with a thickened bract tip. Mature complexes display three inverted seeds attached to the adaxial surface immediately proximal to three free ovuliferous scale tips. In each bract/scale complex there is a single large Resin Canal abaxial to the vascular bundle and three or more smaller adaxial Resin Canals at the level of seed attachment. Seeds are inverted at maturity, display 180° rotational symmetry, and show differentiation of sclerotesta and sarcotesta. The results of a phylogenetic analysis support placement of H. juddii among the basal grade of taxodioid Cupressaceae ( Farjon, 2005 ). A transformational series of ovuliferous bract/scale complexes from voltziacean Voltziales to crown group Cupressaceae is presented to reveal the pattern and antiquity of evolution for modern cupressaceous conifer seed cone morphologies. Developmental studies of living cupressaceous seed cones indicate that the range of mature morphologies is strongly correlated with differences in the timing and rate of development for the bract, scale, and ovules, thus supporting the hypothesis that heterochrony plays a major role in the evolution of bract/scale form. This hypothesis is further supported by our growing understanding of developmental regulatory genetics. There are no currently recognized synapomorphies for living + fossil conifers. Nevertheless, these combined results do not support the hypotheses that some conifers have ancestrally simple seed cones nor that there have been parallel origins of Northern and Southern Hemisphere conifers. The overall body of evidence from both extinct and living conifers strongly supports the hypotheses of deep homology for seed cones and of monophyly for conifers s.s.
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A New Species of Pityostrobus from the Lower Cretaceous of California and Its Bearing on the Evolution of Pinaceae
International Journal of Plant Sciences, 2001Co-Authors: Selena Y. Smith, Ruth A StockeyAbstract:A single cylindrical, abraded cone specimen has been found associated with ammonites of the Lower Cretaceous Budden Canyon Formation near Ono, California. The specimen was embedded in bioplastic and sectioned using the cellulose acetate peel technique. The pith is composed of parenchyma and scattered sclereids and is bounded by a ring of Resin Canals. The secondary xylem of the cone axis, with a ring of small‐diameter Resin Canals, is continuous. The cortex is composed primarily of parenchyma with an outer sclerotic zone 10–16 cells thick and has 27–30 dilating Resin Canals. Vascular traces to the ovuliferous scale and bract diverge separately from the vascular cylinder and are accompanied by a single Resin Canal from the pith that is positioned between the arms of the horseshoe‐shaped ovuliferous scale trace. The bract trace is terete, accompanied by two lateral Resin Canals from the cortical axial system, and enters the free part of the bract. The ovuliferous scale is almost completely sclerotic, with r...
Xoaquín Moreira - One of the best experts on this subject based on the ideXlab platform.
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Intraspecific variation of anatomical and chemical defensive traits in Maritime pine (Pinus pinaster) as factors in susceptibility to the pinewood nematode (Bursaphelenchus xylophilus)
Trees, 2015Co-Authors: Rafael Zas, Marta Nunes Da Silva, Alejandro Solla, Xoaquín Moreira, Miguel Ramos, Marta R. M. Lima, Marta W. Vasconcelos, Luis SampedroAbstract:Key message Migration ability of the PWN through wood branch tissues of adult Maritime pine trees significantly differed among Iberian provenances and this variation was related to differences in anatomical and chemical defensive traits. Abstract The pinewood nematode or pine wilt nematode (PWN; Bursaphelenchus xylophilus ) is one of the most dangerous threats to European coniferous forests, especially for the susceptible Maritime pine ( Pinus pinaster ), a valuable forest resource in South Western Europe. The PWN is vectored by beetles of the genus Monochamus (Coleoptera, Cerambycidae) and once inoculated in healthy branches, it quickly migrates downward to the main trunk through the Resin Canal system. Therefore, the anatomy of the Resin Canal system may modulate its migration and proliferation rates. Using material from nine Maritime pine Iberian provenances established in a common garden trial, we investigated whether these provenances differed in their (1) Resin Canal anatomy, (2) concentration of chemical defences (non-volatile Resin and total polyphenolics) in stems and (3) ability of the PWN to migrate through the pine woody tissues in ‘in vitro’ bioassays. Whether variation in anatomical and chemical defensive traits relates to differences in PWN migration across populations was also investigated. Significant intraspecific variation in anatomical and chemical defensive traits and in nematode migration rates through pine tissues was observed. Moreover, the variation in nematode migration rate among pine provenances was related to differences in both anatomical and chemical features. Overall, this study highlights the role of plant genetics in the development of defensive traits against this harmful coniferous pest. The observed intraspecific variation should be taken into account when considering breeding as a strategy to provide areas of high risk of PWN with resistant genetic material.
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Differentiation of persistent anatomical defensive structures is costly and determined by nutrient availability and genetic growth-defence constraints.
Tree physiology, 2015Co-Authors: Xoaquín Moreira, Rafael Zas, Alejandro Solla, Luis SampedroAbstract:Conifers exhibit a number of chemical and anatomical mechanisms to defend against pests and pathogens. Theory predicts an increased investment in plant defences under limited nutrient availability, but while this has been demonstrated for chemical defences, it has rarely been shown for anatomical defensive structures. In a long-lived woody plant, we tested the hypothesis that limited nutrient availability may promote an improved differentiation of persistent anatomical defences. We also hypothesized that the costs of differentiation of those long-term anatomical structures may be determined by genetic constraints on early growth potential. Using Pinus pinaster Ait. juveniles, we performed a greenhouse study with 15 half-sib families subjected to experimental manipulation of phosphorus (P) availability and herbivory-related induced responses. When plants were ∼30 cm high, half of the plant material was treated with methyl jasmonate to induce defences, and 2 weeks later plants were harvested and the abundance of Resin Canals in the cortex and xylem was assessed. Density of constitutive Resin Canals in the cortex and the total Canal system was ∼1.5-fold higher in plants under limited P availability than in fully fertilized plants. Availability of P did not significantly influence the inducibility of Resin Canal traits. We found negative genetic correlations between plant growth and the density of constitutive Canals in the xylem and total Canal system, but only under conditions of limited nutrition. These results demonstrate for the first time that differentiation of constitutive anatomicalbased defences is affected by P limitation. Moreover, results also evidence the existence of genetic constraints between plant growth and constitutive defensive investment, where lineages with the highest growth potential showed the lowest investment in constitutive Resin Canals.
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constitutive defenses and damage in sitka spruce progeny obtained from crosses between white pine weevil resistant and susceptible parents
Forestry, 2012Co-Authors: Xoaquín Moreira, René I. Alfaro, John N. KingAbstract:Summary Attack by the white pine weevil has notably reduced Sitka spruce productivity in British Columbia (BC) (Canada) and western US. By the 1970s, the BC Ministry of Forests established provenance trials of Sitka spruce with the objective of detecting usable genetic resistance to weevil. These early trials reported significant weevil resistance and allowed the production of the first (F1) controlled-cross progeny generation with demonstrable weevil resistance (R) or susceptibility (S). This study reports results of the screening for weevil resistance and the levels of constitutive defenses of this F1 Sitka spruce progeny. Progeny from resistant parents (R × R progeny) sustained significantly fewer weevil attacks than progeny from susceptible parents (S × S progeny) or progeny with one resistant and one susceptible parent (R × S progeny). Individual and family heritability estimates of the weevil resistance were 0.5 and 0.9, respectively. Constitutive defenses, measured by Resin Canal and sclereid cell density in the cortex, were significantly higher in R × R progeny than in R × S or S × S progeny. We observed a negative correlation between the percentage of trees attacked in each cross and the average density of the Resin Canals or sclereid cells for each cross.
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Alterations of the Resin Canal system of Pinus pinaster seedlings after fertilization of a healthy and of a Hylobius abietis attacked stand
Trees, 2008Co-Authors: Xoaquín Moreira, Rafael Zas, Luis Sampedro, Alejandro SollaAbstract:Changes in resource availability and biotic and abiotic stress may alter the defensive mechanisms of pine trees. The effect of fertilisation on the Resin Canal structure of Pinus pinaster seedlings established in two trials in NW Spain, one attacked by Hylobius abietis and the other non-attacked, was studied. The leaders of 50 plants were destructively sampled and the Resin Canal density, the Canal area and its relative conductive area in the phloem and xylem were assessed. Experimentally increased nutrient availability significantly decreased Resin Canal density in the phloem of the seedlings in the two analysed trials, where unfertilised seedlings presented up to 30% more Resin Canal density than the fertilised seedlings (mean value ± SEM = 0.32 ± 0.02 Resin Canals mm^−2 in the fertilised plants versus 0.45 ± 0.04 Resin Canals mm^−2 in the control plants). Fertilisation had no effect on the Resin Canal system in the xylem, but significantly increased tracheid size. Significant differences of Resin Canals among sites were observed mainly in the xylem; the Resin Canal density was 1.7-fold greater in the attacked site than in the non-attacked site. The similar structure of phloem Resin Canals in both sites supports that phloem Resin Canals are constitutive mechanisms of defence in P. pinaster , whereas xylem Resin Canals would be constitutive mechanisms but also inducible mechanisms of resistance following the attack of pine weevils or bark beetles.