So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

Human biochemical genetics

Evolutionary responses are required for tree populations to be able to track climate change. Results of 250 years of common garden experiments show that most forest trees have evolved local adaptation, as evidenced by the adaptive differentiation of populations in quantitative traits, reflecting environmental conditions of population origins. On the basis of the patterns of quantitative variation for 19 adaptation-related traits studied in 59 tree species (mostly temperate and boreal species from the Northern hemisphere), we found that genetic differentiation between populations and clinal variation along environmental gradients were very common (respectively, 90% and 78% of cases). Thus, responding to climate change will likely require that the quantitative traits of populations again match their environments. We examine what kind of information is needed for evaluating the potential to respond, and what information is already available. We review the genetic models related to selection responses, and what is known currently about the genetic basis of the traits. We address special problems to be found at the range margins, and highlight the need for more modeling to understand specific issues at southern and northern margins. We need new common garden experiments for less known species. For extensively studied species, new experiments are needed outside the current ranges. Improving genomic information will allow better prediction of responses. Competitive and other interactions within species and interactions between species deserve more consideration. Despite the long generation times, the strong background in quantitative genetics and growing genomic resources make forest trees useful species for climate change research. The greatest adaptive response is expected when populations are large, have high genetic variability, selection is strong, and there is ecological opportunity for establishment of better adapted genotypes.

/pdf/potential-for-evolutionary-responses-to-climate-change-2jb03f187c.pdf

Potential for evolutionary responses to climate change – evidence from tree populations

Introduction to forest genetics.

The broad applications of somatic embryogenesis, both in basic and applied research, have stimulated studies on the determination of in vitro conditions for the induction of somatic embryos and their conversion into plants. As a result, efficient protocols on SE induction and plant regeneration have recently become available for many plant species, including Arabidopsis thaliana (L.) Heynh., a model plant in genetics and embryogenesis. Studies on factors controlling in vitro plant morphogenesis are highly desirable not only for the development of improved regeneration systems, but also for the analysis of molecular mechanisms underlying plant embryogenesis. This review focuses on the conditions influencing the induction of embryogenic potential in in vitro cultured plant cells. The roles of explant type, endo- and exogenous plant growth regulators and stress factors in the induction of somatic embryogenesis are especially emphasized. Possible mechanisms by which different factors induce or modify embryogenic competence in cultured plant cells are also discussed. Since the production of genetically solid and true-to-type plants is desired, especially for transformation and micropropagation practice, the problem of the genetic characteristics of regenerants, in terms of their chimerism and somaclonal variation, is discussed in some detail. Special consideration is given to A. thaliana– a major model plant species for classical genetics and genomics. Recent availability of efficient embryogenic cultures in this organism makes it possible to benefit from advanced genomic research of Arabidopsis to study plant embryogenesis on the molecular level.

Factors influencing somatic embryogenesis induction and plant regeneration with particular reference to Arabidopsis thaliana (L.) Heynh

Classical budburst models (Spring Warming, Sequential, Parallel and Alternating) are unable to fully predict external data, partly because of the methods of optimization used to adjust them. The purpose of this study was to examine different assumptions of budburst models and select those which are best supported by the data, defining new models able to predict external data. Eight models, each differing in one assumption, were fitted and tested using external data. The dataset used to test the models was deduced from aeropalynological data at two stations in France. The results show that some of the models proposed are able to accurately predict external dates of flowering of most of the studied species. The assumptions of those models have been individually tested and shown to improve the models accuracy. Robust estimates of the best predictor models of 12 tree species are presented. The analysis of hypothetical provenance transfer of two species, Buxus sempervirens and Platanus acerifolia, between the two study sites, shows that P. acerifolia estimates are similar in both environments whereas B. sempervirens estimates are variable. This result, which agrees with the genetic characteristics of both species, shows that local adaptation of phenology can also be studied through modelling approaches.

/pdf/selecting-models-to-predict-the-timing-of-flowering-of-1a24bbwwb7.pdf

Selecting models to predict the timing of flowering of temperate trees: implications for tree phenology modelling

Maturation of five embryogenic lines of Pinus strobus L was tested on media with various sugars and sources of organic nitrogen, and solidified with two gellan gum concentrations (06 and 10%) Mature somatic embryo production was more abundant at 10% gellan gum than at 06% Complex combinations of amino acids had little effect on mature embryo production of most tested embryogenic lines Increasing glutamine concentration of the maturation medium from 17 to 73 g l−1 was beneficial to one embryogenic line Increasing sucrose concentration or substituting part of the sucrose with mannitol or sorbitol had variable effects on somatic embryo maturation depending on the embryogenic line A medium with 88 mM sucrose plus 175 mM sorbitol solidified with 10% gellan gum produced high numbers of somatic embryos in four out of five embryogenic lines tested

Effect of sugars, amino acids, and culture technique on maturation of somatic embryos of Pinus strobus on medium with two gellan gum concentrations.

The somatic embryogenic process was investigated using immature and mature zygotic embryos originating from 13 open-pollinated seed families selected for their embryogenic capacity from over 128 seed families of Pinus strobus. In a first step, intact megagametophytes with precotyledonary embryos from these families were placed on modified Litvay medium. Embryogenic tissues (ETs) were obtained for 12 of them, with initiation rates varying from 2.6% to 23%. On average, 14% of the ETs (36/258) formed stable embryogenic cell lines (ECLs) after 4–6 months of subculture. Mature somatic embryos were produced for 30 out of 52 cell lines, and plants were regenerated. Later, initiation of ETs from mature zygotic embryos was also tested for the selected families. ECLs were obtained for five of them, with a maximum initiation rate of 2.7%, and plants were produced for four ECLs.

Screening of large numbers of seed families of Pinus strobus L. for somatic embryogenesis from immature and mature zygotic embryos

La structure genetique des populations de pin blanc (Pinus strobus L.) au Quebec de meme que les patrons de variation existant entre les provenances ont ete examines a l'aide d'un test de provenances/descendances. Un echantillon de 66 provenances de pin blanc localisees au Quebec et pres de sa frontiere ouest en Ontario ont ete testees, chaque provenance etant representee par un nombre inegal de familles variant de un a huit (pour un total de 159 familles). Des donnees ont ete recueillies sur les semis a plusieurs reprises, soit: la hauteur totale a differents âges depuis l'ensemencement jusqu'a 4 ans, le nombre de branches a l'âge de 4 ans, et les dates de debourrement et d'aoutement a l'âge de 3 ans. L'analyse de variance a permis de faire ressortir la presence de differences significatives entre les provenances et entre les familles a l'interieur des provenances et ce pour tous les caracteres etudies a l'exception d'un. La variance due aux provenances etait en moyenne deux fois plus elevee que celle due aux familles a l'interieur des provenances. Tous les caracteres etaient interrelies au niveau des provenances. Deux composantes principales ont permis d'expliquer 77% de la variance totale observee chez l'ensemble des caracteres. Les regressions des divers caracteres en fonction des variables geographiques ont, pour leur part, explique de 16% a 62% de la variation au niveau des provenances et ont fait ressortir des patrons de variation genetique complexes entre les provenances. Les provenances du sud-est de la region echantillonnee etaient constituees d'arbres plus grands, et le debourrement et l'aoutement de leurs bourgeons etaient plus tardifs que ceux des arbres plus petits des provenances du nord-ouest. Les modeles de regression ont ete testes a l'aide de donnees empiriques de trois tests pour lesquels la hauteur a 10 ans et le taux de survie etaient disponibles; les resultats se sont averes non consistants. Nous avons utilise les modeles decrivant les patrons de variation au niveau des provenances pour etablir des lignes directrices quant au deplacement des semences et pour delimiter provisoirement deux zones d'amelioration genetique du pin blanc au Quebec.

Patterns of adaptive genetic variation in eastern white pine (Pinus strobus) from Quebec

We evaluated the effects of exogenous gibberellin A(4/7) (GA(4/7)) on the production of seed and pollen cones in four stock types of Picea glauca (Moench) Voss. From 1987 to 1991, a combined treatment that included GA(4/7), root pruning and heat stress was applied to 5- to 10-year-old container-grown grafts, representing over 90 clones and originating from 17- to 27-year-old ortets. Hormonal treatments were applied to pruned field-grown grafts in 1991 and 1992, and to unpruned field-grown grafts from the same set of clones in 1990, 1991 and 1992. In 1992, 26-year-old mature trees in a progeny test were treated with GA(4/7). The GA(4/7) treatment was effective in promoting seed-cone production in all four stock types, whereas it promoted pollen-cone production only in unpruned field-grown grafts and mature trees. The older and taller a tree, the less the response to the GA(4/7) treatment was influenced by the climatic conditions prevailing during the differentiation phase.

Influences of crown size and maturation on flower production and sex expression in Picea glauca treated with gibberellin A4/7

Patterns of genetic variation among and within provenances were investigated for growth traits in Pinus strobus L. Sixty-seven provenances represented by 266 families were tested in this study. Four-year height was measured in the nursery as 10-year height was in three tests established in Quebec. Significant differences among provenances and families within provenances were disclosed. In the nursery, provenance variation was twice that of families while both were about the same for 10-year height. While provenance-by-site interaction was significant, suggesting that provenance ranks changed across the test sites, ranks of families within provenances seemed to be stable as supported by the nonsignificant family-within-provenance-by-site interaction and the high genetic correlation coefficients. Estimates of heritabilities were moderate for 4-year height but decreased later in the field. Genetic progress in height could be obtained from selection and breeding, and indirect selection for 10-year height from 4-year height could be considered. Culling of the worst families in the nursery could successfully decrease the costs of field testing without significant loss of potential genetic gain.

A. Plourde

Papers

Effect of sugars, amino acids, and culture technique on maturation of somatic embryos of Pinus strobus on medium with two gellan gum concentrations.

Screening of large numbers of seed families of Pinus strobus L. for somatic embryogenesis from immature and mature zygotic embryos

Patterns of adaptive genetic variation in eastern white pine (Pinus strobus) from Quebec

Influences of crown size and maturation on flower production and sex expression in Picea glauca treated with gibberellin A4/7

Genetic variation in juvenile growth of Pinus strobus in replicated Quebec provenance-progeny tests.