Amount Of Genetic Variation Research Articles

Genetic Improvement in Plant Architecture, Maturity Duration and Agronomic Traits of Three Traditional Rice Landraces through Gamma Ray-Based Induced Mutagenesis.

Mutation breeding offers a simple, fast and efficient way to rectify major defects without altering their original identity. The present study deployed radiation (gamma rays @ 300Gy)-induced mutation breeding for the improvement and revival of three traditional rice landraces, viz., Samundchini, Vishnubhog and Jhilli. Among the various putative mutants identified in the M2 generation, only three, ten and five rice mutants of Samundchini, Vishnubhog and Jhilli, respectively, were advanced to the M4, M5 and M6 generations, along with their parents and three checks for evaluations based on 13 agro-morphological and 16 grain quality traits. Interestingly, all the mutants of the three landraces showed a reduction in days to 50% flowering and plant height as compared to their parents in all the three generations. The reduction in days to 50% flowering ranges from 4.94% (Vishnubhog Mutant V-67) to 21.40% (Jhilli Mutant J-2-13), whereas the reduction in plant height varies from 11.28% (Vishnubhog Mutant V-45-2, Vishnubhog Mutant V-67) to 37.65% (Jhilli Mutant J-15-1). Furthermore, two, six and three mutants of Samundchini, Vishnubhog and Jhilli have increased their yield potential over their corresponding parents, respectively. Interestingly, Samundchini Mutant S-18-1 (22.45%), Vishnubhog Mutant V-74-6 (36.87%) and Jhilli Mutant J-13-5 (25.96%) showed the highest yield advantages over their parents. Further, a pooled analysis of variance based on a randomized complete block design revealed ample variations among the genotypes for the studied traits. In addition, all the traits consistently showed high to moderate PCV and GCV and a slight difference between them in all three generations indicated the negligible effect of the environment. Moreover, in the association analysis, the traits, viz., fertile spikelets/panicle, panicle length, total tillers/plant, spikelet fertility percent and 100-seed weight showed the usual grain yield/plant, whereas the traits hulling (%) and milling (%) with HRR (%) consistently showed high direct effects and significant positive correlations. The SSR marker-based genome similarity in rice mutants and corresponding parents ranged from 95.60% to 71.70% (Vishnubhog); 95.62% to 89.10% (Samundchini) and 95.62% to 80.40% (Jhilli), indicating the trueness of the mutants. Moreover, the UPGMA algorithm and Gower distance-based dendrogram, neighbour joining tree and PCA scatter diagram assured that mutants were grouped with their respective parents and fell into separate clusters showing high similarity between mutants and parents and dissimilarity among the 24 genotypes. Overall, the information and materials generated from the current study will be very useful and informative for students, researchers and plant breeders. Additionally, our results also showed that irradiation could generate a considerable amount of genetic variability and provide new avenues for crop improvement and diversification.

Comparative investigation of the genetic components of Withania somnifera L. yield and quality traits using multivariate and associations analysis in the Deccan plateau region

The vital herb ashwagandha was farmed for commercial purposes in India. This study aimed to estimate the nature and amount of genetic variation in the 20 attributes in the 29 genotypes of ashwagandha in order to understand the correlations and character contributions to dry root weight/plant and alkaloid content with the selection of potential parents for ashwagandha crop improvement. Twenty-nine ashwagandha genotypes were assessed using a range of genetic metrics, including analysis of variance (ANOVA), genetic variability components, correlation, principal component analysis (PCA), and Mahalanobis D2. The ANOVA confirms a large amount of variability in the genotypes/varieties under study. Out of twenty the four traits, namely fresh leaf weight per plant (X8), dry leaf weight per plant (X9), seed yield per plant (X13), and dry root weight per plant (X16)—indicates the presence of additive gene action in the current study were highly heritable and had a high genetic advance mean value. Starch estimation, main root length, and root diameter were found to be positively and significantly correlated with dry root production per plant and total alkaloid content. The principle component analysis (PCA) results showed that the first four PCA accounted for the bulk (79.56%) of the differences. All genotypes are divided into four clusters based on the distances between and within clusters. Based on the findings mentioned above, it is recommended that genotypes from clusters IV (Poshita, CIMAP-Chetak), cluster II (AKAS-10, AKAS-11, NMITLI-101, and NMITLI-118), and cluster I (AKAS-02, IC-286632, and CIMAP Pratap) be chosen for a different hybridization program. Based on the multidisciplinary investigation, some of the genotypes with desired qualities have been found. They can be employed in upcoming breeding programs to increase alkaloid content and dry root yield.

Prinicipal Component Analysis and Traits Association in Blackgram (Vigna mungo (L.) Hepper)

The present investigation was carried out to assess the genetic variability parameters, correlation and path analysis in the 23 genotypes of Blackgram during Zaid-2021 at the research field, Department of Genetics and Plant Breeding, Naini Agricultural Institute, Sam Higginbottom University of Agriculture, Technology and Sciences, Prayagraj. LBG-645 is identified as high seed yielding per plant at Prayagraj agro-climatic condition. The analysis of variance for all the characters revealed that genotypes were highly significant except harvest index (%). Genotypes were highly significant at 5%, 1% level for all the characters, indicating presence of considerable amount of genetic variability in the parental material tested. The characters with high range estimates of GCV and PCV number of clusters per plant, number of pods per plant. Heritability and genetic advance as % of mean values were high for number of pods per plant. The seed yield per plant exhibited positive significant and correlation with number of pods per plant at genotypic and phenotypic level. At genotypic and phenotypic path coefficient analysis revealed that number of pods per plant had greatest positive direct effect on seed yield per plant. Principal component (PC1) contributed maximum towards variability 22.808% was correlated with Seed Index followed by, plant height and number of seeds per pod. The second principal component (PC2) accounted 21.410% per cent of total variance and it reflected positive loading of days to 50% pod initiation, days to 50% flowering, and pod length whereas; the third principal component (PC3) accounted 15.642% per cent of total variance and positive loading of harvest Index followed by seed Index. Fourth principal component (PC4) contributed 11.325% of variability reflected loadings of days to maturity followed by seed yield per plant. The fifth principal component (PC5) contributed 9.489% variability of seed yield per plant, followed by days to 50% flowering.

Microsatellite and mitochondrial DNA markers unveil the genetic structure of Nellore Palla sheep of India

The present study is carried out to genetically characterise the Nellore Palla sheep and document the genetic divergence among the three varieties of the Nellore sheep breed. Thirty two unrelated individuals from the hometract of Palla, nine each of Brown and Jodipi were sampled for the molecular studies. Fluorscent microsatellite markers were employed to genetically characterise Palla population.The analysis revealed a total of 201 alleles across the 26 loci studied. The mean observed and effective number of alleles per locus was 7.73 and 5.82 respectively. The overall observed and expected heterozygosity across 26 loci was 0.52 and 0.69 respectively. The mean FIS value in the sampled population was 0.24 with a range varying between − 0.24 (MAF209) to 0.77 (INRA063). The mean PIC value and the Shannon’s index value across the 26 loci was 0.643 and 1.49 respectively. The study concluded a considerable amount of genetic diversity with in the Nellore Palla population. The genetic divergence among the three varieties was analysed using 728 bp mitochondrial control region. The analysis for polymorphism and divergence was done with DnaSP software and the results concluded a high polymorphism within the genetic groups. The genetic differentiation estimates revealed no genetic differentiation among the three varieties of Nellore sheep breed. The phylogenetic analysis indicated that all the haplotypes of the three varieties of Nellore were clustering with lineage A except for one haplotype of Palla variety which was clustering with lineage B.

How large and diverse are field populations of fungal plant pathogens? The case of Zymoseptoria tritici.

Pathogen populations differ in the amount of genetic diversity they contain. Populations carrying higher genetic diversity are thought to have a greater evolutionary potential than populations carrying less diversity. We used published studies to estimate the range of values associated with two critical components of genetic diversity, the number of unique pathogen genotypes and the number of spores produced during an epidemic, for the septoria tritici blotch pathogen Zymoseptoria tritici. We found that wheat fields experiencing typical levels of infection are likely to carry between 3.1 and 14.0 million pathogen genotypes per hectare and produce at least 2.1–9.9 trillion pycnidiospores per hectare. Given the experimentally derived mutation rate of 3 × 10−10 substitutions per site per cell division, we estimate that between 27 and 126 million pathogen spores carrying adaptive mutations to counteract fungicides and resistant cultivars will be produced per hectare during a growing season. This suggests that most of the adaptive mutations that have been observed in Z. tritici populations can emerge through local selection from standing genetic variation that already exists within each field. The consequences of these findings for disease management strategies are discussed.

Using gridCoal to assess whether standard population genetic theory holds in the presence of spatio-temporal heterogeneity in population size.

Spatially explicit population genetic models have long been developed, yet have rarely been used to test hypotheses about the spatial distribution of genetic diversity or the genetic divergence between populations. Here, we use spatially explicit coalescence simulations to explore the properties of the island and the two-dimensional stepping stone models under a wide range of scenarios with spatio-temporal variation in deme size. We avoid the simulation of genetic data, using the fact that under the studied models, summary statistics of genetic diversity and divergence can be approximated from coalescence times. We perform the simulations using gridCoal, a flexible spatial wrapper for the software msprime (Kelleher et al., 2016, Theoretical Population Biology, 95, 13) developed herein. In gridCoal, deme sizes can change arbitrarily across space and time, as well as migration rates between individual demes. We identify different factors that can cause a deviation from theoretical expectations, such as the simulation time in comparison to the effective deme size and the spatio-temporal autocorrelation across the grid. Our results highlight that FST , a measure of the strength of population structure, principally depends on recent demography, which makes it robust to temporal variation in deme size. In contrast, the amount of genetic diversity is dependent on the distant past when Ne is large, therefore longer run times are needed to estimate Ne than FST . Finally, we illustrate the use of gridCoal on a real-world example, the range expansion of silver fir (Abies alba Mill.) since the last glacial maximum, using different degrees of spatio-temporal variation in deme size.

Assessment of the Effects of Seed Storage Time on Germination Rate and Performance Evaluation of Ethiopian Faba Bean (Vicia faba L.) Varieties for Yield and Related Traits.

In Ethiopia, faba bean (Vicia faba L.) varieties are important and widely used as a source of food and cash source to large number of subsistence farmers. However, their production and productivity is below the world's average partly because of lack of their sustainable performance in the current scenario of climate change. Therefore, the present study was designed to test the effects of seed storage time and to evaluate the performance of 31 faba bean varieties collected from Holeta, Kulumsa and Sinana agricultural research systems, Ethiopia. The study involved germination test and field experiment that was laid out using randomized complete block design (RCBD) and conducted at multiple test locations. Data were collected on qualitative and quantitative traits and analyzed using SAS version 9.0, and MINITAB® Release 19. Accordingly, most of the varieties showed a promising germination rate regardless of their storage duration suggesting their sustainable performance under suitable storage conditions. Most of the qualitative and quantitative traits showed a wide range of variations revealing their stable performance and better chance for further improvement. Analysis of variance also revealed a highly significant (p < 0.001) variation for several of the traits suggesting maintenance of the original diversity that could be important in further selection breeding. Likewise, high genetic advance coupled with high heritability and genotypic coefficient of variation together with wide range of variations in both PCV and GCV observed in several of the quantitative traits suggest their sustainable performance and significance in further effective selection. Moreover, a promising high yielding varieties such as Dida1, Welki, Hachalu, Ashebeka and Obse have been identified for further use. Clustering grouped the varieties into three clusters implying significant amount of genetic variability among them. Overall, the results generated could be used as a baseline information for improving faba bean production and productivity. However, to exploit more and determine the actual performance of the varieties more markers such as molecular markers (DNA based) are recommended.

SCAR marker development for quick detection of Fusarium oxysporum f. sp. lentis

The Fusarium wilt caused by Fusarium oxysporum f. sp. lentis is recognized as a major seed and soil-borne disease of lentil worldwide. Rapid detection of Fusarium wilt is important for the management of disease at an early stage and thereby preventing the epiphytotic. Forty cultures of Fol were purified after routine isolation from infected seeds from different geographical locations. The amount of genetic diversity was evaluated using PCR amplification with a set of 6 RAPD primers of selective nucleotide primer pairs. The phylogenetic relationship of RAPD marker revealed diversity among the isolates. The RAPD monomorphic bands were cloned and sequenced. The final SCAR marker designed, provides the amplicon size 353bp with Fol isolates. The RAPD derived SCAR marker is the first marker with high sensitivity genomic DNA and species specific for the detection of Fol. This species-specific SCAR marker can be employed for the quick detection of fungus in seed during seed certification or seed health testing for long-term conservation of lentil.

Greater Phage Genotypic Diversity Constrains Arms-Race Coevolution.

Antagonistic coevolution between hosts and parasites, the reciprocal evolution of host resistance and parasite infectivity, has important implications in ecology and evolution. The dynamics of coevolution—notably whether host or parasite has an evolutionary advantage—is greatly affected by the relative amount of genetic variation in host resistance and parasite infectivity traits. While studies have manipulated genetic diversity during coevolution, such as by increasing mutation rates, it is unclear how starting genetic diversity affects host–parasite coevolution. Here, we (co)evolved the bacterium Pseudomonas fluorescens SBW25 and two bacteriophage genotypes of its lytic phage SBW25ɸ2 in isolation (one phage genotype) and together (two phage genotypes). Bacterial populations rapidly evolved phage resistance, and phage reciprocally increased their infectivity in response. When phage populations were evolved with bacteria in isolation, bacterial resistance and phage infectivity increased through time, indicative of arms-race coevolution. In contrast, when both phage genotypes were together, bacteria did not increase their resistance in response to increasing phage infectivity. This was likely due to bacteria being unable to evolve resistance to both phage via the same mutations. These results suggest that increasing initial parasite genotypic diversity can give parasites an evolutionary advantage that arrests long-term coevolution. This study has important implications for the applied use of phage in phage therapy and in understanding host–parasite dynamics in broader ecological and evolutionary theory.

Genomic variations and epigenomic landscape of the Medaka Inbred Kiyosu-Karlsruhe (MIKK) panel

BackgroundThe teleost medaka (Oryzias latipes) is a well-established vertebrate model system, with a long history of genetic research, and multiple high-quality reference genomes available for several inbred strains. Medaka has a high tolerance to inbreeding from the wild, thus allowing one to establish inbred lines from wild founder individuals.ResultsWe exploit this feature to create an inbred panel resource: the Medaka Inbred Kiyosu-Karlsruhe (MIKK) panel. This panel of 80 near-isogenic inbred lines contains a large amount of genetic variation inherited from the original wild population. We use Oxford Nanopore Technologies (ONT) long read data to further investigate the genomic and epigenomic landscapes of a subset of the MIKK panel. Nanopore sequencing allows us to identify a large variety of high-quality structural variants, and we present results and methods using a pan-genome graph representation of 12 individual medaka lines. This graph-based reference MIKK panel genome reveals novel differences between the MIKK panel lines and standard linear reference genomes. We find additional MIKK panel-specific genomic content that would be missing from linear reference alignment approaches. We are also able to identify and quantify the presence of repeat elements in each of the lines. Finally, we investigate line-specific CpG methylation and performed differential DNA methylation analysis across these 12 lines.ConclusionsWe present a detailed analysis of the MIKK panel genomes using long and short read sequence technologies, creating a MIKK panel-specific pan genome reference dataset allowing for investigation of novel variation types that would be elusive using standard approaches.

Statistical significance, selection accuracy, and experimental precision in plant breeding

Genetic selection efficiency is measured by accuracy. Model selection relies on hypothesis testing with effectiveness given by statistical significance (p-value). Estimates of selection accuracy are based on variance parameters and precision. Model selection considers the amount of genetic variability and significance of effects. Questions arise as to which one to use: accuracy or p-value? We show there is a link between the two and both may be used. We derive equations for accuracy in multi-environment trials and determine numbers of repetitions and environments to reach accuracy. We propose a new methodology for accuracy classification based on p-values. This enables a better understanding of the level of accuracy being accepted when certain p-value is used. Accuracy of 90% is associated with p-value of 2%. Use of p-values up to 20% (accuracies above 50%) are acceptable to verify significance of genetic effects. Sample sizes for desired p-values are found via accuracy values.

Review of Sorghum [&amp;lt;i&amp;gt;Sorghum bicolor (L.)&amp;lt;/i&amp;gt; Moench] Genetic Variability Genotypes

Sorghum [<i>Sorghum bicolor (L.)</i> Moench] is a tropical C4 crop that originated in Ethiopia and was domesticated there. It is the fifth most widely grown cereal crop in the world. It is a vital staple crop for more than 500 million people in 30 Sub-Saharan African and Asian nations, although it is mostly farmed as a feed crop in the developed world. In a breeding program, the presence of genetic variety is critical. For sorghum breeding and novel cultivar deployment, the genetic variation present in sorghum germplasm collections is frequently investigated. Effective breeding and genetic conservation may need a well-characterized sorghum genetic resource. The level of trait heritability is linked to the genetic development of breeding populations for yield and its component traits. The amount of genetic variability contained in a population and how it is used determines the success of a crop improvement effort. A breeder's understanding of a crop's genetic diversity usually aids them in selecting desirable parents for breeding programs. As a result, it's critical to examine genetic diversity, heritability, and genetic progress since they provide information that can be used to improve grain yield as well as quality qualities to increase crop production and productivity.

GENETIC VARIABILITY AND REPRODUCTIVE CHARACTERISTICS OF ZEBRAFISH (Cyprinidae Danio rerio) STOCKS

Specimens of cultured zebrafish acquired from different fish farms in Brazil may show genetic variability and alteration in allele frequency due to genetic drift and selective pressure in a captive environment, resulting in the differentiation of productive and reproductive characteristics. The aim of this study was to evaluate the genetic variability and reproductive characteristics of 180 zebrafish specimens from six Brazilian fish farms. A deviation from the Hardy-Weinberg equilibrium was observed in all evaluated stocks. Differentiation among stocks was observed in the amount of genetic variability with respect to observed heterozygosity and the inbreeding coefficient (FIS). Genetic distance between stocks was determined through the Fst index, and the formation of four distinct groups was observed by plotting the dendrogram based on Nei’s genetic distance. Differences were observed among reproductive parameters, such as the average number of eggs per female and hatchability. This second parameter proved to be related to the level of inbreeding of the population, whereas this effect was not observed for spawning frequency. We conclude that zebrafish stocks from the 6 different Brazilian fish farms present significant genetic and phenotypic variability. The genetic structure affects fecundity and should be considered when carrying out work where reproductive rates are evaluated.

Molecular Evolution of Infectious Bronchitis Virus and the Emergence of Variant Viruses Circulating in the United States.

Infectious bronchitis virus (IBV) is a highly infectious and transmissible gammacoronavirus that is nearly impossible to control through biosecurity. Coronaviruses are RNA viruses with an enormous capacity for rapid replication and high rates of mutation, leading to a tremendous amount of genetic diversity. Viral evolution occurs when selection working on genetic diversity leads to new mutations being fixed in the population over time. For IBV, the emergence of variant viruses is likely due to a combination of selection acting on existing genetic diversity, as well as on newly created mutations as the virus replicates, or genetic drift. Immunity against IBV creates a strong selection pressure; however, immunity can also reduce the viral load, decreasing replication and the development of new mutations. Examining the balance between immunity reducing infection, replication, and genetic diversity, and immune pressure selecting for new variants, is extremely difficult at best. Nonetheless, vaccination and immunity do play a role in the emergence of new antigenic variants of IBV. To complicate the situation even more, coronaviruses can undergo recombination, and several studies in the literature report recombination between IBV vaccines and field viruses. However, to our knowledge, unlike genetic drift, recombination alone has not been shown to result in a new antigenic and pathogenic IBV type emerging to cause widespread disease in poultry. Vaccines against IBV that result in an immune population can reduce transmission (basic reproductive number R0 less than 1), making vaccines for IBV the best control strategy available. However, IBV control remains extremely challenging because of the high number of antigenic variants causing disease in poultry and a limited number of vaccines that mostly provide only partial protection against infection and replication of those variants. Currently, there is one major variant IBV circulating in all sectors of US commercial poultry production: DMV/1639/11. This virus was initially detected in 2011, but only began causing significant disease in 2014/2015. Since then, it has affected all three sectors of poultry production (layers, breeders, broilers) and continues to predominate in certain regions of the United States. Additionally, a previously classified variant IBV, which is no longer considered a variant virus, GA08, is highly prevalent. This is attributed to heavy GA08-type IBV vaccine usage because disease caused by the GA08-type virus is rare. Interestingly, the major IBV detected in poultry for several decades, ArkDPI, is no longer among the most detected viruses in the United States. This change corresponds to the shift away from ArkDPI vaccine usage in the broiler sector as GA08 vaccine usage has increased and highlights the role IBV vaccines play in influencing viral populations in commercial chickens.

Molecular Characterization and Population Genetic Structure of Fagopyrum Species Cultivated in Himalayan Regions

Fagopyrum spp. (buckwheat) is a dicotyledonous pseudocereal crop mainly cultivated in the north-western Himalayan regions for its highly nutritional, antioxidant and therapeutic values. In the present investigation, molecular characterization was performed by using ISSR (inter simple sequence repeat) markers on 42 accessions of four buckwheat species (Fagopyrum esculentum, F. sagittatum, F. tataricum and F. kashmirianum). The 12 pre-screened ISSR primers amplified 102 bands, and amongst them 85 bands exhibited polymorphism with an average polymorphism of 82.73%. The results revealed that Shannon’s information indices (I) and Nei’s genetic diversity (H) were low for F. tataricum (I = 0.1028 ± 0.2307; H = 0.0707 ± 0.1617) and high for F. esculentum (I = 0.1715 ± 0.2622; H = 0.1164 ± 0.1796). It was estimated that within the accessions of Fagopyrum species, the species diversity (HT) and mean diversity (HS) were 0.3200 and 0.1041, respectively. Molecular variance partitioning by AMOVA also indicated a significant genetic differentiation accounting for 73% among and 27% within the accessions of Fagopyrum species. Overall, accessions of F. esculentum had the greatest distance from the other accessions of buckwheat species, which includes F. sagittatum, F. tataricum and F. kashmirianum as revealed by FST distance and Nei’s unbiased genetic distance. The dendograms based on UPGMA and PCoA segregated 42 accessions of four buckwheat species into three major groups. This study clearly reveals a considerable amount of genetic diversity at the intra-specific level in F. esculentum, F. sagittatum and F. kashmirianum accessions. The factors responsible for it are diverse geographical conditions, pollinating behavior and cultivation practices adapted in these regions. The study also indicated a close phylogenetic relationship between F. tataricum and F. kashmirianum.

How genetic and environmental variance in personality traits shift across the life span: Evidence from a cross-national twin study.

Decades of research have shown that about half of individual differences in personality traits is heritable. Recent studies have reported that heritability is not fixed, but instead decreases across the life span. However, findings are inconsistent and it is yet unclear whether these trends are because of a waning importance of heritable tendencies, attributable to cumulative experiential influences with age, or because of nonlinear patterns suggesting Gene × Environment interplay. We combined four twin samples (N = 7,026) from Croatia, Finland, Germany, and the United Kingdom, and we examined age trends in genetic and environmental variance in the six HEXACO personality traits: Honesty-Humility, Emotionality, Extraversion, Agreeableness, Conscientiousness, and Openness. The cross-national sample ranges in age from 14 to 90 years, allowing analyses of linear and nonlinear age differences in genetic and environmental components of trait variance, after controlling for gender and national differences. The amount of genetic variance in Extraversion, Agreeableness, and Openness followed a reversed U-shaped pattern across age, showed a declining trend for Honesty-Humility and Conscientiousness, and was stable for Emotionality. For most traits, findings provided evidence for an increasing relative importance of life experiences contributing to personality differences across the life span. The findings are discussed against the background of Gene × Environment transactions and interactions. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Genotyping of Ascaris spp. infecting humans and pigs in Italy, Slovakia and Colombia.

The systematics and taxonomy of Ascaris lumbricoides and Ascaris suum, two of the world's most widespread nematodes, still represent a highly debated scientific issue. Two different transmission scenarios have been described according to endemicity: separated host-specific transmission cycles in endemic regions, and a single pool of infection shared by humans and pigs in non-endemic regions. The swine roundworm A. suum is now recognized as an important cause of human ascariasis also in endemic areas such as China, where cross-infections and hybridization have also been reported, as well as in non-endemic regions like Italy. This study aimed to investigate the molecular epidemiology of human and pig ascariasis in three countries representing different epidemiological scenarios: Italy as a non-endemic country, Colombia as an endemic country, and Slovakia as a non-endemic country, but with a poor socio-economic context linked to some focal populations of Roma settlements. A total of 237 nematodes were analysed: 46 from Colombia (13 from humans, 33 from pigs), 114 from Slovakia (20 from humans, 94 from pigs) and 77 from Italy (17 from humans and 60 from pigs). Genotyping by PCR-RFLP of nuclear (ITS) and sequencing of mitochondrial (cox1) target regions were performed. ITS genotypes were used to estimate the Hardy-Weinberg (HW) equilibrium according to hosts and country of origin. The partial cox1 sequences were used to analyse genetic polymorphisms according to hosts and country of origin, as well as to infer the network of haplotypes, their evolutionary relationships and geographical distribution. 110 quality cox1 sequences were obtained. Haplotype network revealed three main groups corresponding to clade A, B and C. Clade C included most of the human cases from Italy, while those from Slovakia and Colombia were grouped in clade B. Ascaris from Italian and Colombian pigs showed HW equilibrium at the ITS marker, while disequilibrium was found in A. lumbricoides from Slovak pigs, which suggest a high unexpected amount of roundworms of human origin circulating also in pigs. This study updates and extends the current understanding of Ascaris species and genotypes circulating in different epidemiological scenarios, with particular attention to the inclusion of human-derived Ascaris in the phylogenetic cluster C. Despite the evidence of HW equilibrium in the ITS in pig-derived Italian samples, the amount of genetic variation seems to support the existence of two closely related species.

Genetic variability of spiralling whitefly Aleurodicus disperses Russell on Citrus aurantifolia Christm and Ocimum gratissimum L.

The spiralling whitefly, Aleurodicus dispersus Russell (Hemiptera: Aleyrodidae), has a wide range of anatomy, physiology, behaviour, and ecology depending on the host plant. This research looked at the genetic variations between A. dispersus populations on two separate host plants (Citrus aurantifolia and Ocimum gratissimum). The existence of host-related genetic variation in A. dispersus populations was determined using Rapid Amplification of Polymorphic DNA (RAPD) markers. Our findings revealed that the A. dispersus populations on the two host plants had a considerable amount of genetic divergence. The spiralling whiteflies on the adaxial part of Citrus aurantifolia were genetically distinct from those on the abaxial part of the same plants. Various population genetic parameters such as heterozygosity, Nei's genetic gap, and fixation indices (FST) revealed that spiralling whitefly populations vary genetically, which may be attributable to spiralling whitefly populations originating from multiple sources. These findings also have consequences for the invasive pest's quarantine safety strategy.

Genetic imprints of Brosimum alicastrum Sw. in Mexico.

The mechanisms generating the geographical distributions of genetic diversity are a central theme in evolutionary biology. The amount of genetic diversity and its distribution are controlled by several factors, including dispersal abilities, physical barriers, and environmental and climatic changes. We investigated the patterns of genetic diversity and differentiation among populations of the widespread species Brosimum alicastrum in Mexico. Using nuclear DNA microsatellite data, we tested whether the genetic structure of B. alicastrum was associated with the roles of the Trans-Mexican Volcanic Belt and the Isthmus of Tehuantepec as geographical barriers to gene flow and to infer the role of past events in the genetic diversity patterns. We further used a maximum-likelihood population-effects mixed model (MLPE) to identify the main factor affecting population differentiation in B. alicastrum. Our results suggested that Mexican B. alicastrum is well differentiated into three main lineages. Patterns of the genetic structure at a finer scale did not fully correspond to the current geographical barriers to gene flow. According to the MLPE mixed model, isolation by distance is the best model for explaining the genetic differentiation of B. alicastrum in Mexico. We propose that the differentiation patterns might reflect (1) an ancient differentiation that occurred in Central and South America, (2) the effects of past climatic changes, and (3) the functions of some physical barriers to gene flow. This study provides insights into the possible mechanisms underlying the geographic genetic variation of B. alicastrum along a moisture gradient in tropical lowland forests.

Evaluation of growth and yield traits in rice genotypes using multivariate analysis

Rice (Oryza sativa L.) is the first staple crop in terms of production and area of cultivation in Nepal. The amount of genetic variability is important factor in identifying suitable genotypes in rice breeding programs. This study was conducted in Khumaltar, Lalitpur, Nepal during rainy seasons of 2018 and 2019. Forty rice genotypes were planted in Alpha Lattice Design with two replications to determine the genetic diversity among them. The rice genotypes were grouped into 7 clusters based on growth and yield traits. The traits sucnamely plant height, panicle length, number of tillers/plant and grain yield were found highly significant (p < 0.01). Rice genotypes NR 10676-B-1-3-3-3 produced the highest yield (5.65 t/ha), followed by NR10410-89-3-2-1-1 (5.54 t/ha). The highest distance between cluster centroids (83.51) was found in the cluster 2 (Bange Masino, Hansa raj, Indrabeli, NR 11178-B-B-6-1, NR 11368-B-B-17, Pokhreli Jethobudho, Pokhreli Masino), and cluster 4 (IR73008-136-2-2-3, IR74052-95-3-2) indicating genetic dissimilarity among the genotypes which can be utilized in a hybrid breeding programme. Genotypes of cluster 2 had the highest grain yield (4.97 t/ha). The results of this study suggest that genotypes grouped in cluster 2 can be grown for higher grain production in mid-hills of Nepal.