ABSTRACT
Abstract The present study aimed to assess population structure and phylogenetic relationships of nine subspecies of Brassica rapa L. represented with thirty-five accessions cover a wide range of species distribution area using isozyme analysis in order to select more diverse accessions as supplementary resources that can be utilized for improvement of B. napus. Enzyme analysis resulted in detecting 14 putative polymorphic loci with 27 alleles. Mean allele frequency 0.04 (rare alleles) was observed in Cat4A and Cat4B in sub species Oleifera accession CR 2204/79 and in subspecies trilocularis accessions CR 2215/88 and CR 2244/88. The highest genetic diversity measures were observed in subspecies dichotoma, accession CR 1585/96 (the highest average of observed (H0) and expected heterozygosity (He), and number of alleles per locus (Ae)). These observations make this accession valuable genetic resource to be included in breeding programs for the improvement of oilseed B. napus. The average fixation index (F) is significantly higher than zero for the analysis accessions indicating a significant deficiency of heteozygosity. The divergence among subspecies indicated very great genetic differentiation (FST = 0.8972) which means that about 90% of genetic diversity is distributed among subspecies, while 10% of the diversity is distributed within subspecies. This coincides with low value of gene flow (Nm = 0.0287). B. rapa ssp. oleifera (turnip rape) and B. rapa ssp. trilocularis (sarson) were grouped under one cluster which coincides with the morphological classification.
Resumo O presente estudo teve como objetivo avaliar a estrutura populacional e as relações filogenéticas de nove subespécies de Brassica rapa L. representadas com 35 acessos, cobrindo uma ampla gama de áreas de distribuição de espécies usando análise isoenzimática, a fim de selecionar acessos mais diversos como recursos suplementares que podem ser utilizados para melhoria de B. napus. A análise enzimática resultou na detecção de 14 loci polimórficos putativos com 27 alelos. A frequência média de 0,04 alelo (alelos raros) foi observada em Cat4A e Cat4B, nas subespécies Oleifera CR 2204/79 e nas subespécies trilocularis CR 2215/88 e CR 2244/88. As maiores medidas de diversidade genética foram observadas na subespécie dicotômica CR 1585/96 (a média mais alta observada (H0) e heterozigosidade esperada (He) e número de alelos por locus (Ae). Essas observações tornam esse acesso um valioso recurso genético a ser incluído em programas de melhoramento de oleaginosas B. napus. O índice médio de fixação (F) é significativamente maior que 0 para os acessos à análise, indicando uma deficiência significativa de heterozigose. A divergência entre as subespécies indicou uma grande diferenciação genética (FST = 0,8972), o que significa que cerca de 90% da diversidade genética é distribuída entre as subespécies, enquanto 10% da diversidade é distribuída nas subespécies. Isso coincide com o baixo valor do fluxo gênico (Nm = 0,0287). B. rapa ssp. oleifera (nabo) e B. rapa ssp. trilocularis (sarson) foram agrupados conforme a classificação morfológica.
Subject(s)
Brassica napus , Brassica rapa/genetics , Phylogeny , Genetic Variation/genetics , Plant Breeding , Isoenzymes/geneticsABSTRACT
Abstract The present study aimed to assess population structure and phylogenetic relationships of nine subspecies of Brassica rapa L. represented with thirty-five accessions cover a wide range of species distribution area using isozyme analysis in order to select more diverse accessions as supplementary resources that can be utilized for improvement of B. napus. Enzyme analysis resulted in detecting 14 putative polymorphic loci with 27 alleles. Mean allele frequency 0.04 (rare alleles) was observed in Cat4A and Cat4B in sub species Oleifera accession CR 2204/79 and in subspecies trilocularis accessions CR 2215/88 and CR 2244/88. The highest genetic diversity measures were observed in subspecies dichotoma, accession CR 1585/96 (the highest average of observed (H0) and expected heterozygosity (He), and number of alleles per locus (Ae)). These observations make this accession valuable genetic resource to be included in breeding programs for the improvement of oilseed B. napus. The average fixation index (F) is significantly higher than zero for the analysis accessions indicating a significant deficiency of heteozygosity. The divergence among subspecies indicated very great genetic differentiation (FST = 0.8972) which means that about 90% of genetic diversity is distributed among subspecies, while 10% of the diversity is distributed within subspecies. This coincides with low value of gene flow (Nm = 0.0287). B. rapa ssp. oleifera (turnip rape) and B. rapa ssp. trilocularis (sarson) were grouped under one cluster which coincides with the morphological classification.
Resumo O presente estudo teve como objetivo avaliar a estrutura populacional e as relações filogenéticas de nove subespécies de Brassica rapa L. representadas com 35 acessos, cobrindo uma ampla gama de áreas de distribuição de espécies usando análise isoenzimática, a fim de selecionar acessos mais diversos como recursos suplementares que podem ser utilizados para melhoria de B. napus. A análise enzimática resultou na detecção de 14 loci polimórficos putativos com 27 alelos. A frequência média de 0,04 alelo (alelos raros) foi observada em Cat4A e Cat4B, nas subespécies Oleifera CR 2204/79 e nas subespécies trilocularis CR 2215/88 e CR 2244/88. As maiores medidas de diversidade genética foram observadas na subespécie dicotômica CR 1585/96 (a média mais alta observada (H0) e heterozigosidade esperada (He) e número de alelos por locus (Ae). Essas observações tornam esse acesso um valioso recurso genético a ser incluído em programas de melhoramento de oleaginosas B. napus. O índice médio de fixação (F) é significativamente maior que 0 para os acessos à análise, indicando uma deficiência significativa de heterozigose. A divergência entre as subespécies indicou uma grande diferenciação genética (FST = 0,8972), o que significa que cerca de 90% da diversidade genética é distribuída entre as subespécies, enquanto 10% da diversidade é distribuída nas subespécies. Isso coincide com o baixo valor do fluxo gênico (Nm = 0,0287). B. rapa ssp. oleifera (nabo) e B. rapa ssp. trilocularis (sarson) foram agrupados conforme a classificação morfológica.
ABSTRACT
Background & objectives: Although having immense clinical relevance, yet only a few studies have been targeted to understand the chikungunya virus (CHIKV) susceptibility and growth in Aedes aegypti populations from India. This study was undertaken to investigate CHIKV susceptibility and growth kinetics in Ae. aegypti along with genetic heterogeneity of Ae. aegypti populations. Methods: Dose dependent CHIKV susceptibility and growth kinetic studies for three CHIKV strains reported from India were carried out in Ae. aegypti mosquito populations. The phenotypic variation and genetic heterogeneity in five Ae. aegypti populations were investigated using multivariate morphometrics and allozyme variation studies. Results: The dissemination and growth kinetics studies of the three CHIKV strains showed no selective advantage for a particular strain of CHIKV in Ae. aegypti. At 100 per cent infection rate, five geographic Ae. aegypti populations showed differences in dissemination to three CHIKV strains. Morphometric studies revealed phenotypic variation in all the studied populations. The allelic frequencies, F statistics, and Nei’s genetic identity values showed that genetic differences between the populations were small, but significant. Interpretation & conclusions: The results obtained in this study suggest that genetic background of the vector strongly influences the CHIKV susceptibility in Ae. aegypti.
ABSTRACT
This paper gives a model of a structured population with respect to an autosomal locus with two alleles. The population reproduces in discrete and non-overlapping generations. The population is assumed to be in equilibrium in that exactly the same distribution of genotypic proportions is reproduced in each generation. The population is subdivided into 'localities' which are characterized by the local gene frequencies. Within each locality the genotypic proportions may depart from Hardy-Weinberg proportions and the same fixation index applies to all localities. The system departs from reality by assuming that the frequency of the first allele follows the beta distribution. However, this enables a convenient way to derive the mating frequencies of parents so that equilibrium is maintained. Wright's F-statistics are applied to characterize the population as a whole. The system is extended to permit an arbitrary level of outbreeding.