Characterization of portuguese old varieties of hazelnut (Corylus avellana L.) by morphological, molecular, biochemical and nutritional parameters
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2017-02-03
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A aveleira (Corylus avellana L.), pertencente à família Betulaceae e à ordem
Fagales. Esta espécie é originária da Europa e Ásia Ocidental e é cultivada há mais de
5000 anos. Ao longo dos últimos séculos, a maioria das variedades cultivadas foram
selecionadas a partir de populações silvestres. Em Portugal, a aveleira encontra-se na
região norte e centro. Desde a década de 90 que a sua produção está em declínio,
podendo conduzir ao desaparecimento das variedades locais (“landraces”). A avaliacao
da diversidade genética de espécies silvestres e populações locais revela-se de grande
importância para a sua utilização e para a gestão das coleções existentes.
Com o objetivo de avaliar a diversidade genética e conhecer as relações
filogenéticas das aveleiras portuguesas e variedades comerciais, procedeu-se ao estudo de 58 genótipos, incluindo variedades locais, silvestres e comerciais, ao nível morfológico, molecular e bioquímico.
No Capítulo 1 apresenta-se uma revisão bibliográfica sobre a origem e a
domesticação da aveleira, os marcadores moleculares, os alelos de incompatibilidade
(alelos S) e a composição nutricional dos frutos.
A avaliação da diversidade genética ao nível do DNA cloroplastidial (cpDNA)
através de microssatélites (cpSSR), encontra-se no Capítulo 2. Quatro dos dez loci
estudados revelaram-se polimórficos. Encontraram-se, no total, onze haplótipos, sendo o haplótipo A o mais frequente, quer nas variedades locais quer nas comerciais. Nos
genótipos silvestres detetaram-se quatro haplótipos exclusivos (H, I, J e L). Esta
diversidade pode indicar o norte de Portugal como um potencial refúgio durante o último período glaciar.
A diversidade genética e as relações filogenéticas, avaliadas através de marcadores
inter-microssatélites (ISSRs) e Polimorfismo de Comprimento de Fragmentos
Amplificados (AFLPs), apresentam-se no Capítulo 3. Foram obtidos um total de 570
marcadores, dos quais 541 (95,03%) se revelaram polimórficos. Os valores dos índices de similaridade variaram entre 0,239 para as variedades comerciais versus genótipos
silvestres, e 0,143 para as variedades locais versus genótipos silvestres. As relações
filogenéticas distribuíram as aveleiras por três grupos, mostrando uma clara separação
dos genótipos silvestres das variedades locais e comerciais.
No Capítulo 4 apresentam-se os resultados da análise com microssatélites (SSRs)
nucleares, para a avaliação das relações filogenéticas. O nível de polimorfismo
encontrado foi elevado, conforme o indicado pela heterozigocidade média esperada
(0,74), pela heterozigocidade média observada (0,71) e pelo conteúdo de informação de
polimorfismo (0,78). O dendrograma mostrou uma clara separação dos genótipos
silvestres, variedades locais e variedades comerciais. Os resultados reforçam a hipótese
de que os genótipos silvestres constituem um ‘hotspot’ de diversidade e fornecem pistas
sobre a origem de algumas variedades locais.
Os resultados obtidos para a identificação dos alelos S encontram-se no Capítulo 5.
Para este estudo foram utilizadas variedades locais de aveleira que foram polinizadas no
campo, com pólen de genótipos cujos alelos S são conhecidos. Três variedades locais
revelaram ter o alelo S2, duas apresentaram o alelo S5, e quatro, um dos quatro alelos S3, S5, S10, S18. Uma variedade local foi compatível com todos os 17 alelos S testados, e em duas foi possível identificar dois alelos, S5 e S9.
A variabilidade fenotípica e a composição nutricional dos frutos apresentam-se no
Capítulo 6. Nas variedades locais observou-se o valor médio mais elevado para o peso do fruto, peso do miolo e teor em óleo, tendo as variedades comerciais apresentado os
valores médios mais baixos. Os genótipos silvestres revelaram o teor médio mais alto em proteína e os valores médios mais baixos para o teor em aminoácidos essenciais. As
variedades comerciais demonstraram os valores médios mais elevados para o teor em
aminoácidos essenciais e para os minerais fósforo e ferro. Os valores médios mais altos
de potássio, cálcio e boro foram encontrados nas variedades locais, enquanto os genótipos silvestres apresentaram as médias mais elevados em magnésio, zinco, manganésio e sódio. Uma análise baseada em componentes principais e outra hierarquizada permitiram identificar os genótipos mais interessantes (oito variedades locais) relativamente aos caracteres morfológicos e à composição nutricional.
No Capítulo 7 apresentam-se as conclusões gerais e as perspetivas futuras
Os resultados obtidos neste trabalho podem contribuir para a definição dos
melhores polinizadores para o planeamento de novos pomares e desenvolvimento de
novas variedades. A diversidade genética encontrada nos genótipos silvestres e nas
variedades locais pode fornecer informações relevantes para a conservação da
diversidade genética ainda existente. O elevado teor em óleo e o reduzido teor em ácido
linoleico podem permitir a seleção de progenitores para programas de melhoramento com o objetivo de aumentar a estabilidade do óleo e o valor nutricional dos frutos.
Hazelnut (Corylus avellana L.), belongs to the family Betulaceae and to the order Fagales. This species is native from Europe and Eastern Asia, and is cultivated for more than 5,000 years. During the last centuries, most of the cultivars were selected from local wild populations. Hazelnut is found at north and center of Portugal. Since the 90s, the production of hazelnut has declined, and could allow the lost of landraces. The evaluation of genetic diversity in wild genotypes and local populations is highly important for the use and management of the existent collections. With the aim of evaluating the genetic diversity and understanding the phylogenetic relationships among the Portuguese hazelnut landraces and reference cultivars, it were studied 58 genotypes, including landraces, wild genotypes and reference cultivars, at the morphological, molecular and biochemical levels. In Chapter 1 is presented a review of the origin and domestication of hazelnut, molecular markers, self-incompatibility alleles (S-alleles) and nutritional composition of the fruit. The evaluation of genetic diversity at the cloroplastidial DNA (cpDNA) level by microsatellites (cpSSRs), is presented in Chapter 2. Four out of ten studied loci were polymorphic. In total, 11 haplotypes were detected, and haplotype A was the most frequent in both landraces and reference cultivars. In the wild genotypes were found four exclusive haplotypes (H, I, J and L). This diversity could indicate the North of Portugal as a potential refugium during the last glacial period. The genetic diversity and the phylogenetic relationships, evaluated by inter-simple sequence repeat (ISSR) and amplified fragment length polymorphism (AFLP) markers are presented in Chapter 3. A total of 570 markers was obtained, and 541 (95.03%) revealed to be polymorphic. The similarity indexes ranged from 0.239 for reference cultivars versus wild genotypes, and 0.143 for landraces versus wild genotypes. The phylogenetic relationships distributed the hazelnuts into three groups, showing a clear separation among wild genotypes, landraces and reference cultivars. In Chapter 4 were presented the results achieved with the nuclear microsatellite (SSR) markers for the evaluation of the phylogenetic relationships. The level of polymorphism was high as verified by the mean values of expected heterozygosity (0.74), observed heterozygosity (0.71), and polymorphism information content (0.78). The dendrogram showed a clear separation of the wild genotypes, landraces and reference cultivars. These results reinforce the hypothesis that wild genotypes constitute a hotspot of diversity and provided us clues about the origin of some landraces. The results about the identification of S-alleles are presented in Chapter 5. In this study were used hazelnut landraces that were pollinated in the field with pollens from genotypes with known S-alleles. Three landraces revealed to have the S2 allele, two presented the S5 allele, and four showed one of following alleles S3, S5, S10, or S18. One landrace was compatible with the 17 S-alleles tested, and in two landraces was possible to identify two alleles, S5 and S9. The phenotypic variability and nutritional composition of the fruits are presented in Chapter 6. The landraces showed the highest average for the nut and kernel weight and oil content, while the reference cultivars presented the lowest mean values. The wild genotypes presented the highest amount of protein, and the lowest values in essential amino acids. The reference cultivars demonstrated the highest mean values for essential amino acids and for the minerals phosphorus and iron. The highest average values of potassium, calcium and boron were found in the landraces, whereas the wild genotypes presented the highest averages in magnesium, zinc, manganese, and sodium. An analysis based on the principal components and a dendrogram allowed the identification of the most interesting genotypes (eight landraces) concerning the morphological traits and the nutritional composition. In Chapter 7 are presented the general conclusions and future perspectives. The results obtained in this work, could contribute for the definition of the best pollinators for the planning of new orchards and development of new cultivars. The genetic diversity found on wild genotypes and landraces may provide relevant information for the conservation of the genetic diversity that still remains. The high oil content and the reduced amount of linoleic acid could allow the selection of progenitors for breeding programs with the goal of increasing the kernel oil stability and the nutritional value of the fruits.
Hazelnut (Corylus avellana L.), belongs to the family Betulaceae and to the order Fagales. This species is native from Europe and Eastern Asia, and is cultivated for more than 5,000 years. During the last centuries, most of the cultivars were selected from local wild populations. Hazelnut is found at north and center of Portugal. Since the 90s, the production of hazelnut has declined, and could allow the lost of landraces. The evaluation of genetic diversity in wild genotypes and local populations is highly important for the use and management of the existent collections. With the aim of evaluating the genetic diversity and understanding the phylogenetic relationships among the Portuguese hazelnut landraces and reference cultivars, it were studied 58 genotypes, including landraces, wild genotypes and reference cultivars, at the morphological, molecular and biochemical levels. In Chapter 1 is presented a review of the origin and domestication of hazelnut, molecular markers, self-incompatibility alleles (S-alleles) and nutritional composition of the fruit. The evaluation of genetic diversity at the cloroplastidial DNA (cpDNA) level by microsatellites (cpSSRs), is presented in Chapter 2. Four out of ten studied loci were polymorphic. In total, 11 haplotypes were detected, and haplotype A was the most frequent in both landraces and reference cultivars. In the wild genotypes were found four exclusive haplotypes (H, I, J and L). This diversity could indicate the North of Portugal as a potential refugium during the last glacial period. The genetic diversity and the phylogenetic relationships, evaluated by inter-simple sequence repeat (ISSR) and amplified fragment length polymorphism (AFLP) markers are presented in Chapter 3. A total of 570 markers was obtained, and 541 (95.03%) revealed to be polymorphic. The similarity indexes ranged from 0.239 for reference cultivars versus wild genotypes, and 0.143 for landraces versus wild genotypes. The phylogenetic relationships distributed the hazelnuts into three groups, showing a clear separation among wild genotypes, landraces and reference cultivars. In Chapter 4 were presented the results achieved with the nuclear microsatellite (SSR) markers for the evaluation of the phylogenetic relationships. The level of polymorphism was high as verified by the mean values of expected heterozygosity (0.74), observed heterozygosity (0.71), and polymorphism information content (0.78). The dendrogram showed a clear separation of the wild genotypes, landraces and reference cultivars. These results reinforce the hypothesis that wild genotypes constitute a hotspot of diversity and provided us clues about the origin of some landraces. The results about the identification of S-alleles are presented in Chapter 5. In this study were used hazelnut landraces that were pollinated in the field with pollens from genotypes with known S-alleles. Three landraces revealed to have the S2 allele, two presented the S5 allele, and four showed one of following alleles S3, S5, S10, or S18. One landrace was compatible with the 17 S-alleles tested, and in two landraces was possible to identify two alleles, S5 and S9. The phenotypic variability and nutritional composition of the fruits are presented in Chapter 6. The landraces showed the highest average for the nut and kernel weight and oil content, while the reference cultivars presented the lowest mean values. The wild genotypes presented the highest amount of protein, and the lowest values in essential amino acids. The reference cultivars demonstrated the highest mean values for essential amino acids and for the minerals phosphorus and iron. The highest average values of potassium, calcium and boron were found in the landraces, whereas the wild genotypes presented the highest averages in magnesium, zinc, manganese, and sodium. An analysis based on the principal components and a dendrogram allowed the identification of the most interesting genotypes (eight landraces) concerning the morphological traits and the nutritional composition. In Chapter 7 are presented the general conclusions and future perspectives. The results obtained in this work, could contribute for the definition of the best pollinators for the planning of new orchards and development of new cultivars. The genetic diversity found on wild genotypes and landraces may provide relevant information for the conservation of the genetic diversity that still remains. The high oil content and the reduced amount of linoleic acid could allow the selection of progenitors for breeding programs with the goal of increasing the kernel oil stability and the nutritional value of the fruits.
Descrição
Tese de Doutoramento em Genética Molecular Comparativa e Tecnológica
Palavras-chave
Corylus avellana , Variação genética , Microssatélites , Melhoramento de plantas