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A previous common-garden test located in southern British Columbia revealed that black cottonwood (Populus trichocarpa Torr. & A. Gray) sources from the southern region were distinctly superior in growth and health conditions than their northern counterparts, and restricted gene migration between the two regions was proposed as the main cause of the observed ecotypic mode of regional differentiation. Confirmation of the observed pattern of regional differentiation and the proposed underlying mechanism is very important as it will not only enhance our understanding of the evolution of the species, but also have substantial practical implications. In this study, we examined the performance of 483 clones from 30 populations (drainages) across the entire range in British Columbia in a field trial on the northern coast. Three-year test results confirmed the ecotypic mode of genetic differentiation between the two regions as previously observed in the south, providing further evidence supporting the proposition of restrict gene migration as the underlying mechanism. The southern populations were 87% taller than and twice as healthy as their northern counterparts. Regional differences accounted for most of the detected nonrandom variation, with over 80% in both height and health condition. Of the 30 fastest growing clones that were free of any damages, 27 were from the southern region, whereas only three were from the northern region. Performance was very consistent between sites in the two regions at both population and clonal levels. Resume: Une etude anterieure en plantation comparative situee dans le sud de la Colombie-Britannique a permis de decouvrir que les provenances de peuplier de l'Ouest (Populus trichocarpa Torr. & A. Gray) de la region meridionale etaient nettement superieures a leurs contreparties plus septentrionales du point de vue de la croissance et de l'etat de sante. Une migration restreinte des genes a ete proposee comme cause principale de ce mode ecotypique de differenciation regionale. La confirmation de ce patron de differenciation regionale et du mecanisme sous-jacent qui a ete propose apparait tres importante puisqu'elle ameliorera non seulement notre comprehension de l'evolution de cette espece mais aura egalement d'importantes repercussions pratiques. Dans la presente etude, nous avons examine la performance de 483 clones provenant de 30 populations (bassins versants) reparties sur l'ensemble de l'aire de repartition de l'espece en Colombie-Britannique a l'aide d'un essai au champ localise dans la region cotiere nordique. Apres trois ans, les resultats confirment le mode ecotypique de differenciation genetique entre les deux regions, tel qu'il a ete observe anterieurement dans le sud, fournissant une preuve additionnelle que la migration restreinte des genes est le mecanisme sous-jacent. Les populations meridionales etaient 87 % plus hautes et deux fois plus en sante que leurs contreparties septentrionales. Les differences regionales expliquaient la plus grande partie de la variation non aleatoire dont plus de 80 % etait due a la hauteur et a l'etat de sante. Parmi les 30 clones dont la croissance etait la plus rapide tout en n'ayant aucun dommage, 27 provenaient de la region sud alors que seulement trois provenaient de la region nord. La performance etait tres coherente entre les stations dans les deux regions a la fois pour les populations et les clones. [Traduit par la Redaction], Introduction The natural distribution of black cottonwood (Populus trichocarpa Torr. & A. Gray) along the coast of British Columbia (BC) is not continuous but is divided into two, namely northern [...]

Genetic differentiation of black cottonwood (Populus balsamifera subsp. trichocarpa (Torn. & A. Gray ex Hook) Brayshaw) across a 'no-cottonwood' belt on the coast of central British Columbia (BC), Canada, was examined using data on 3 year height, severity of infection by Valsa sordida Nitschke and Melampsora occidentalis H. Jacks., and abnormality of leaf flushing. The data were collected in a common-garden test consisting of 180 provenances of 36 drainages ranging from northern BC to Oregon, USA. The results demonstrated an ecotypic mode, north-south regional differentiation. Valsa sordida and M. occidentalis infected 41% and 89%, respectively, of the trees from the northern region, while 66% showed flushing abnormality. In contrast, only 1% and 27% of their southern counterparts were infected by the same diseases, and 1% had abnormal flushing. Trees from the northern region averaged 87% shorter than those from the south. Regional differentiation accounted for the highest amount of variation observed in all traits, with 60% in 3 year height, 34% in V. sordida, 76% in M. occidentalis, and 50% in abnormal leaf flushing. Regression analysis revealed geographic patterns that essentially reflected regional differentiation along the no-cottonwood belt. The species' distribution biography, ecological characteristics, and life history suggest that restricted gene migration was the main factor responsible for the observed geographic patterns of genetic differentiation. Les auteurs ont etudie la differenciation genetique chez le peuplier baumier de l'Ouest (Populus balsamifera subsp. trichocarpa (Torn. & A. Gray ex Hook) Brayshaw) dans une zone d'exclusion de cette espece situee sur la cote dans le centre de la Colombie-Britannique en utilisant des donnees de hauteur a 3 ans, de severite d'infection par Valsa sordida Nitschke et Melampsora occidentalis H. Jacks., et d'anomalies de debourrement des feuilles. Les donnees ont ete colligees dans une plantation comparative constituee de 180 provenances representatives de 36 bassins versants distribues du nord de la Colombie-Britannique jusqu'en Oregon aux Etats-Unis. Les resultats ont revele un mode de differenciation ecotypique avec un patron regional de differenciation nord-sud. Les arbres de la region septentrionale etaient infectes par V. sordida et M. occidentalis dans des proportions respectives de 41 % et 89 %, alors que 66 % d'entre eux montraient des anomalies de debourrement. Par contre, seulement 1 % et 27 % des arbres de la region meridionale etaient infectes par les memes maladies et 1% d'entre eux avaient un debourrement anormal. Les arbres de la region septentrionale etaient en moyenne 87 % plus petits que ceux de la region meridionale. La differenciation regionale etait responsable de la plus grande partie de la variation observee chez tons les caracteres, dans des proportions de 60% pour la hauteur a 3 ans, de 34% pour l'infection par V. sordida, de 76 % pour l'infection par M. occidentalis, et de 50 % pour les anomalies de debourrement des feuilles. Les analyses de regression ont revele l'existence de patrons geographiques essentiellement representatifs de la differenciation regionale le long de la zone d'exclusion du peuplier baumier de l'Ouest. Les informations biographiques relativement a la distribution de l'espece, ses caracteristiques ecologiques et son cycle vital indiquent qu'un flux genique reduit serait le principal facteur responsable des patrons geographiques de differenciation genetique qui ont ete observes. [Traduit par la Redaction], Introduction Patterns of geographic variation in forest trees are primarily shaped by three interactive evolutionary forces: natural selection, genetic drift, and gene migration (Morgenstern 1996; White et al. 2007). Continuous [...]

Site index was calculated for 78 experimental plantations in westernCanada and northern Finland and Sweden, representing a wide range ofsite environments where lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) is considered as a potential afforestation species.The plantations and provenances belong to the International Union ofForest Research Organizations' international provenance testing program, and estimates of site index (projected 50-year height) were based on height growth of recommended provenances. The estimated site indices were used in regression analyses with temperature data and estimated soil fertilities to predict the change in forest production due to a warmer climate, which may follow an expected rise in atmosphericCO2. The influence of temperature was strong and considerably stronger in northern Finland and Sweden than in Canada. The relationships differed between the two continents and between sites located north of 56 deg. N and south of that latitude. Soil fertility had a small but significant influence. Estimates of increases in site index and potential productivity in different scenarios for increases intemperature sum and average July temperatures are given. [ABSTRACT FROM AUTHOR]

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 severitylevel 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. [ABSTRACT FROM AUTHOR]

Understanding the irregular yield pattern of greenhouse-grown sweet peppers (Capsicum annuum L.) has been a challenge to researchers and greenhouse producers. Experimental data from 4 years, each consisting of 26 production weeks, were used in a time series analysis, neural network (NN) modeling, and regression analysis. Time series analysis revealed that weekly yield was influenced by yields from the preceding 2 weeks (Yd_1 and Yd_2), cumulative light 2 and 4 weeks prior (L_2 and L_4), and average 24-h air temperature 5 weeks prior (T_5). Cumulative light (L) data were transformed into kL by dividing by 1000 for subsequent NN modeling and regression analysis. These five inputs were used to establish a NN model, which illustrated the positive influence of Yd_1, kL_4, and kL_2 and negative influence of Yd_2 and T_5. Again, these five inputs were used in a regression analysis illustrating the positive influence of Yd_1 and the negative influence of Yd_2. Each input was further modified to include its squared value before entering the regression, which resulted in significant inputs of Yd_1, Yd_1 squared, and Yd_2 squared. Among these three analyses, the most consistent parameters were Yd_1 and Yd_2, confirming that the irregular yield pattern of greenhouse-grown peppers is of a biological nature. Environmental factors kL_2, kL_4, and T_5 did not show a consistent effect on yield in all three analyses, indicating yield pattern is less influenced by growing environment. [ABSTRACT FROM AUTHOR]