Genetic diversity as a parameter for managing agroforestry systems
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Genetic diversity as a parameter for managing agroforestry systems



A lecture about genetic diversity and its applications and importance for agroforestry systems

A lecture about genetic diversity and its applications and importance for agroforestry systems



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Genetic diversity as a parameter for managing agroforestry systems Genetic diversity as a parameter for managing agroforestry systems Presentation Transcript

  • Genetic diversity as a parameter for managing agroforestry systems Aristotelis C. Papageorgiou Forest Genetics Laboratory Democritus University of Thrace Orestiada, Greece
  • plan - genetic diversity - changes of genetic diversity - genetic system in plant populations • Agriculture • Rangeland • Forest - management approach - examples / discussion2 13/07/11
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  • Important things about biodiversity  Is of complex nature and finds its full meaning in complex cases (e.g. landscapes and multiple levels of organization)  Involves different perceptions of its meaning and importance5 13/07/11
  • Genetic component of biodiversity  a total of meaningless mathematic expressions…  Perlman & Adelson 1997  …should not be given priority, since its measurement is complicated and expensive…  Dobson 1995  Misunderstandings:  “Laboratory analysis is the first step of any gene conservation or management measure”  “The object of conservation and management programmes are the genes we see in the laboratories”6 13/07/11
  • So, what is genetic diversity?  The differences among organisms that can be inhereited  Passing from one generation to the other = mating  Changes over time = evolution  Is the basis of all other levels of biodiversity  Underestimated and under-represented  Measured by:  Field observations (environment? / P=G+E)  Lab observations (practical relevance?7 13/07/11
  • Field observations - morphometry • Environmental or genetic? • Multivariable statistics • Landmarks - common environment (trials) • Provenance / progeny tests • Traits of practical relevance – Growth, survival, resistance...etc. • ANOVA8 13/07/11
  • Lab observations - previously: chromosomes, visible traits, enzymes - nowadays: polymorphism at DNA level • Fragments (fragment length) • Sequencies of nucleotides • Some more sofisticated things... - no direct relevance with traits • This changes however - frequencies of genotypes and alleles9 13/07/11
  • The population - central concept to genetics - a set of individuals • Mating (same species – or not?) • Same place (more or less) - demography - frequency of alleles and genotypes10 13/07/11
  • Alleles and genotypes - allele: variant of the same gene that does the same job, just differently • Mendel had yellow and green peas (gene = pea color / alleles = green and yellow) • A diploid organism can have up to two different alleles at each gene - genotype: the types of alleles at a gene • Homozygote: two copies of the same allele • Heterozygote: two different alleles11 13/07/11
  • Importance of genetic diversity  Main condition for adaptation under new environments  Maintenance of populations and species  Stability of communities and ecosystems  Constant production of goods and services  Biological information base  Is transferred over generations and rearranged through mating system  Influenced by population size  Changes and promotes adaptation  Is imported and exported12 13/07/11
  • Evolution Changes of allele or genotype frequencies over time and/or space • Selection / adaptation • Small population size / genetic drift • Non-random mating / inbreeding • Migration / gene flow • Mutation13 13/07/11
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  • Selection Some genotypes produce traits that have better chance to lead an organism to survive and reproduce Higher fitness The alleles of this genotype pass easier to the next generation Genotypes with greater fitness increase / so do their alleles The population is adapted to an environment • Just until it changes...15 13/07/11
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  • Small population size Not all individuals pass to the next generation Not all gametes successfully mate A fraction of the initial number of individuals (and alleles) passes to the next generation Reduction in numbers (randomly) changes allele frequencies over time • Rare alleles are easier lost • Small populations lose their diversity17 13/07/11
  • Ν=10000, p(A)=0,518 13/07/11
  • Ν=1000, p(A)=0,519 13/07/11
  • Ν=100, p(A)=0,520 13/07/11
  • Ν=20, p(A)=0,521 13/07/11
  • Genetic bottleneck22 13/07/11
  • Fragmentation23 13/07/11
  • Non random mating Random mating • Equal probability of all mating events • Keeps frequencies of alleles and genotypes stable • Equilibrium Non random mating – inbreeding • Decreases heterozygotes • Increases the appearence of lethal genes • Inbreeding depression24 13/07/11
  • Hedrick p. 183 up25 13/07/11
  • Self – pollination / selfing Most severe form of inbreeding • Results in full homozygosity in 6 / 7 generations • Reduces heterozygotes by 1/2 every generation In natural plant populations • Dissadvantage in outbreeding species • However, most species self pollinate • Evolutionary advantage under stable environment – Stability of traits26 – 13/07/11of lethal genes... Finall loss
  • Plant breeding The creation of new varieties In agriculture • Self pollination creates “pure breeds” • Absolutely homozygous • Stable in artificial environment In forestry • Self pollination is avoided • Reduces heterozygosity and fitness • More complex and variable environment27 13/07/11
  • Migration – gene flow Migration of individuals (seeds) or gametes (pollen) • New alleles arrive aqnd increase diversity • Adaptation may be delayed Ideal situation: small levels of gene flow allow diffrentiated adaptation and maintenance of high diversity levels28 13/07/11
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  • Lack of gene flow - fragmentation30 13/07/11
  • Mutation Primary source of variation New alleles Rare event Does not change frequencies of alleles much31 13/07/11
  • The genetic system of a forest Genetic diversity is maintained when the genetic system is working!32 13/07/11
  • In agriculture Fields are ecosystems & production units Farming requires uniform conditions and uniform material (one genotype) • Pure lines • Hybrids How to increase genetic sustainability? • Change the scale! • See the broader picture • Use of local & adapted varieties • Uniformity in the field, not among fieldsI33 13/07/11
  • In Forest Management Natural populations on variable sites • Great diversity Maintaining genetic diversity • Avoid disturbance of the genetic system • Use natural regeneration dynamics • Avoid fragmentation and small populations • Proper / adapted reproductive material See the broader picture34 • Manage at the landscape level 13/07/11
  • In rangelands and pastures Natural ecosystems with large diversity Use natural dynamics Introduce proper material (local is safe) Avoid fragmentation Avoid overuse and degradation Landscape level35 13/07/11
  • Agroforestry systems Extensive, not intensive use of land Landscape level management • Keep diversity within and – most important – among landscape elements and among landscapes Maintain dynamics of nature • Natural cycles • Genetic system of plants Avoid fragmentation – establish connectivity Use of proper plant material • Adapted • Variable among units36 13/07/11
  • Strategies  Forest management  Secure pollen & seed movement  Promote natural regeneration  Expand management in non productive forests – This includes rangelands  Landscape connectivity  Sustainable use of rangelands  Improvement through proper material  Restoration  Local seed or best adapted seed37 13/07/11
  • New approach in forest management38 13/07/11
  • Adaptive conservation & management  Ex situ: to preserve current genetic structures for future needs  Frequent collection of reproductive material for plant species  Restore in gene banks  Keep in plantations in different locations  Seed orchards for restoration purposes  Adaptive breeding39 13/07/11
  • Thank you40 13/07/11