Genetic diversity and phylogenetic relationships in cowpea revealed by chloroplast DNA analysis
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2017-12-20
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O feijão-frade (Vigna unguiculata L. Walp) pertence à família Fabaceae e é originário de África. É uma leguminosa de grão de grande valor nutritivo, capaz de tolerar diferentes stresses, tais como secura, temperaturas elevadas e stresses do solo, tais como, a baixa fertilidade, solos ácidos, básicos e pouco drenados. O estudo da diversidade genética é uma área de pesquisa importante porque só uma avaliação tão completa quanto possível desta variabilidade permite a utilização do germoplasma no melhoramento de plantas. A diversidade genética pode ser avaliada através de carateres morfológicos e de marcadores moleculares. Existe um crescente interesse no uso do ADN cloroplastidial em estudos de populações, uma vez que a conservação dos genes neste genoma permite desenhar primers universais, o que facilita estudos filogenéticos de populações de indivíduos relativamente afastados. Neste trabalho, uma colecção de landraces de feijão-frade do Sul da Europa foi caraterizada por parâmetros morfológicos e agronómicos. A diversidade e relações genéticas existentes nestas landraces comparativamente com acessos de outras partes do mundo, e com outras espécies de Vigna foram estudadas também através de marcadores microssatélites cloroplastidiais (cpSSRs). Ao nível das caraterísticas qualitativas avaliadas nas landraces do Sul da Europa, os hábitos de crescimento ereto e semi-ereto foram os mais frequentes (44% e 42%, respetivamente); a folha terminal de forma sub-sagitada foi o tipo preponderante (44%); as duas cores de flor observadas foram branca (72%) e roxa (28%); e as sementes tinham, maioritariamente, cor creme (94%) com hilo preto (58%) e forma de rim (69%). Relativamente às caraterísticas quantitativas verificou-se ser o peso total das sementes a caraterística com maior coeficiente de variação (62,54 %) e o tamanho da vagem a caraterística com menor coeficiente de variação (15,29 %). O peso de 100 sementes apresentou um elevado valor de heritabilidade (h2 = 0,98). A análise de agrupamentos, efetuada através do método Ward com base em 10 caraterísticas morfo-agronómicas, repartiu as landraces desta coleção por três grupos distintos, não se tendo observado nenhuma relação entre as landraces em cada um dos grupos e a sua origem geográfica. A análise em componentes principais (PCA) mostrou que os primeiros três componentes principais explicam 82,1 % da variação total. Um conjunto de 10 pares de primers foi utilizado para analisar a diversidade genética de 108 acessos de Vigna unguiculata compreendendo as subespécies alba, pubescens, tenuis e unguiculata (var. spontanea e var. unguiculata, cultigrupo unguiculata e cultigrupo sesquipedalis) e ainda 5 acessos de outras espécies de Vigna (V. racemosa, V. radiata e V. mungo), incluindo maioritariamente acessos cultivados mas também silvestres. Oito dos 10 loci (ccmp3, ccmp7, VgcpSSR1, VgcpSSR10, VgcpSSR12, VgcpSSR14, ccSSR4, cSSR7) revelaram-se polimórficos ao nível das várias espécies estudadas. O conjunto dos 34 diferentes alelos detetados combinaram-se em 10 haplótipos diferentes, oito dos quais únicos. O haplótipo mais frequente (90.3%), putativamente ancestral, incluiu acessos cultivados de V. unguiculata ssp. unguiculata cultigrupo unguiculata e V. unguiculata ssp. unguiculata cultigrupo sesquipedalis, e acessos silvestres de V. unguiculata ssp. unguiculata var. spontanea e V. unguiculata ssp. tenuis. O presente estudo permitiu mostrar a grande diversidade ainda existente no feijãofrade em Portugal e outros países do Sul da Europa, apesar do baixo polimorfismo detetado no seu genoma cloroplastidial. Verificou-se ainda a existência de haplótipos partilhados por material cultivado e silvestre. A grande variabilidade detetada na coleção de feijão-frade agora estudada e a partilha de haplótipos revela-se de grande importância para programas de melhoramento desta espécie
Cowpea (Vigna unguiculata L. Walp) belongs to the family Fabaceae and is native to Africa. It is a nutritious grain legume, able to tolerate different stresses, such as drought, high temperatures and tolerates most soil stresses, such as low fertility, acidic, basic and poorly drained soils. The study of genetic diversity is an important research area because only an evaluation as complete as possible of this variability allows the use of germplasm in plant breeding. Genetic diversity can be evaluated using morphological traits and molecular markers. There is a growing interest in the use of cloroplastidial DNA in studies of populations, because with the conservation of the gene in this genome, allows to design universal primers, which facilitates phylogenetic studies of populations of relatively remote individuals. In this study, a collection of cowpea landraces from Southern Europe was characterized by morphological and agronomic traits. The diversity and genetic relationships in this landraces comparatively with accessions from other parts of the world, and with other species of Vigna, were also studied through chloroplast microsatellite markers (cpSSRs). At the level of the qualitative traits evaluated in the landraces of Southern Europe, the erect and semi-erect growth habits were the most frequent (44% and 42%, respectively); subhastate shape (44%) was the most occurring terminal leaflet type; the two flower colours observed were white (72%) and purple (28%); and seeds had, mostly, cream colour (94%) with black hilum (58%) and kidney shape (69%). In relation to the quantitative characteristics, was verified that the total seed weight was the characteristic with the highest coefficient of variation (62.54%) and the pod length with the lowest coefficient of variation (15.29%). The 100 seeds weight presented a high value of heritability (h2 = 0.98). The cluster analysis performed using the Ward method based on 10 morphological and agronomic characteristics, divided the landraces of this collection in three distinct groups, and was not observed relationships between the landraces in each group and their geographical origin. Principal component analysis (PCA) showed that the first three major components accounted for 82.1% of the total variance. A set of 10 pairs of primers were used to analyse the genetic diversity of 108 accessions of Vigna unguiculata including alba, pubescens, tenuis and unguiculata subspecies (var. spontanea and var. unguiculata, cultigroup unguiculata and cultigroup sesquipedalis) and 5 accessions of other species of Vigna (V. racemosa, V. radiata and V. mungo), including mostly cultivated, but also wild. Eight of the 10 loci (ccmp3, ccmp7, VgcpSSR1, VgcpSSR10, VgcpSSR12, VgcpSSR14, ccSSR4, cSSR7) were polymorphic at the level of the various species studied. The set of 34 different detected alleles were combined into 10 different haplotypes, eight of which were unique. The most frequent haplotype (90.3%), putatively ancestral, included cultivated accessions of V. unguiculata ssp. unguiculata cultigroup unguiculata and V. unguiculata ssp. unguiculata cultigroup sesquipedalis, and wild species of V. unguiculata ssp. unguiculata var. spontanea and V. unguiculata ssp. tenuis. The present study allowed to show the great diversity still existing in cowpea in Portugal and other Southern Europe countries, despite the low polymorphism detected in its chloroplastidial genome. It was verified the existence of haplotypes shared by cultivated and wild material. The great variability detected in this collection of cowpea studied and the sharing of haplotypes is of great importance for breeding programs of this species.
Cowpea (Vigna unguiculata L. Walp) belongs to the family Fabaceae and is native to Africa. It is a nutritious grain legume, able to tolerate different stresses, such as drought, high temperatures and tolerates most soil stresses, such as low fertility, acidic, basic and poorly drained soils. The study of genetic diversity is an important research area because only an evaluation as complete as possible of this variability allows the use of germplasm in plant breeding. Genetic diversity can be evaluated using morphological traits and molecular markers. There is a growing interest in the use of cloroplastidial DNA in studies of populations, because with the conservation of the gene in this genome, allows to design universal primers, which facilitates phylogenetic studies of populations of relatively remote individuals. In this study, a collection of cowpea landraces from Southern Europe was characterized by morphological and agronomic traits. The diversity and genetic relationships in this landraces comparatively with accessions from other parts of the world, and with other species of Vigna, were also studied through chloroplast microsatellite markers (cpSSRs). At the level of the qualitative traits evaluated in the landraces of Southern Europe, the erect and semi-erect growth habits were the most frequent (44% and 42%, respectively); subhastate shape (44%) was the most occurring terminal leaflet type; the two flower colours observed were white (72%) and purple (28%); and seeds had, mostly, cream colour (94%) with black hilum (58%) and kidney shape (69%). In relation to the quantitative characteristics, was verified that the total seed weight was the characteristic with the highest coefficient of variation (62.54%) and the pod length with the lowest coefficient of variation (15.29%). The 100 seeds weight presented a high value of heritability (h2 = 0.98). The cluster analysis performed using the Ward method based on 10 morphological and agronomic characteristics, divided the landraces of this collection in three distinct groups, and was not observed relationships between the landraces in each group and their geographical origin. Principal component analysis (PCA) showed that the first three major components accounted for 82.1% of the total variance. A set of 10 pairs of primers were used to analyse the genetic diversity of 108 accessions of Vigna unguiculata including alba, pubescens, tenuis and unguiculata subspecies (var. spontanea and var. unguiculata, cultigroup unguiculata and cultigroup sesquipedalis) and 5 accessions of other species of Vigna (V. racemosa, V. radiata and V. mungo), including mostly cultivated, but also wild. Eight of the 10 loci (ccmp3, ccmp7, VgcpSSR1, VgcpSSR10, VgcpSSR12, VgcpSSR14, ccSSR4, cSSR7) were polymorphic at the level of the various species studied. The set of 34 different detected alleles were combined into 10 different haplotypes, eight of which were unique. The most frequent haplotype (90.3%), putatively ancestral, included cultivated accessions of V. unguiculata ssp. unguiculata cultigroup unguiculata and V. unguiculata ssp. unguiculata cultigroup sesquipedalis, and wild species of V. unguiculata ssp. unguiculata var. spontanea and V. unguiculata ssp. tenuis. The present study allowed to show the great diversity still existing in cowpea in Portugal and other Southern Europe countries, despite the low polymorphism detected in its chloroplastidial genome. It was verified the existence of haplotypes shared by cultivated and wild material. The great variability detected in this collection of cowpea studied and the sharing of haplotypes is of great importance for breeding programs of this species.
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Vigna unguiculata L. Walp , landraces , caraterísticas morfológicas e agronómicas , marcadores moleculares , cpSSRs