Amount Of Genetic Variation Research Articles

Genetic relationships among some old walnuts (Juglans regia L.) genotypes in Iran and selection of superior genotypes

Abstract Walnut (Juglans regia L.) is one of the oldest and most economically important edible nut species due to its high nutritional value. Iran is known as one of the most important centres of the origin and diversity of walnuts worldwide. This research was carried out to determine the genetic relationships of some old walnut genotypes in Iran in order to select superior genotypes and better conserve them. The results of morphological evaluation of the fruits showed that the highest coefficients of variation were related to nut weight, kernel weight, percentage kernel, thickness and weight of the shell, and thickness and weight of the packing tissue in both years. The average morphological traits among the studied genotypes were different, such that the highest nut weights in the first and second years were 15.59 and 14.79 g and the corresponding lowest values were 7.37 and 7.79 g, respectively. The highest and lowest kernel weights were observed in the first years to be 8.09 and 3.80 g and in the second years were 6.94 and 2.65 g, respectively. The highest kernel percentages in the first and second years were 64.97 and 59.79% and the lowest percentages were 39.52 and 27.80% in the first and second years, respectively. Molecular evaluation results showed that the 16 start codon of target (SCoT) primers amplified a total of 166 bands with an average of 10.44 bands per primer. The number of polymorphic bands was changed from 2 to 19 in primers SCoT-19 and SCoT-15. The average polymorphism information content value was 0.30 and the highest amount of this index (0.36) was observed in SCoT-14 and SCoT-19 primers. The results of principal component analysis and analysis of molecular variance indicated the presence of relatively high diversity within the investigated genotypes. The amount of genetic diversity within the investigated regions was 84% and that between areas was 16%. Based on the obtained results, it was concluded that SCoT markers could provide helpful information on the genetic relationships among walnut genotypes, which can be used in future walnut breeding and conservation programmes.

A new species of Hylarana Tschudi, 1838 (Amphibia: Anura: Ranidae) from the Nicobar Islands, India

The island of Great Nicobar is known to support high degree of herpetofaunal diversity and endemism due to insular isolation. Among them, the population of Hylarana chalconota on this island was assessed to determine its taxonomic status and affinities using morphological, acoustic, and molecular data. Molecular phylogeny based on 16S rRNA showed a considerable amount of genetic divergence with 9.19–16.45% from congeners of the Hylarana chalconota complex. We describe this population as a new species, noting its unique morphological characteristics and phylogenetic position.

Study of Genetic Diversity of Aromatic Rice Genotypes Using Random Amplified Polymorphic DNA Markers

The study of genetic variation in aromatic rice is necessary for enhancing and preserving its genetic makeup. In this study, we amplified four Random Amplified Polymorphic DNA (RAPD) markers from the genomes of 11 different aromatic rice genotypes in order to evaluate the genetic variation and relatedness in aromatic rice. The genotypes were collected from different sources- five of which were obtained from the Bangladesh Rice Research Institute, one from the Bangladesh Institute of Nuclear Agriculture, and the remaining five were local genotypes. In RAPD profiling, twenty-seven of the thirty-six bands that were generated by the four primers were polymorphic, resulting in an estimated average polymorphism of 47.22 percent. The average value of the polymorphic information content was 0.309 with a range from 0.165 to 0.456, indicating that the primers were effective to detect genetic diversity between the genotypes. The genetic diversity and Shannon information index across all of the genotypes and primers were 0.176 and 0.260, respectively, which indicated that there was a certain amount of genetic variation in the studied aromatic rice genotypes. Kalizira and Binadhan-9 genotypes had the smallest genetic distance (0.057), while it was the highest (0.406) between the BRRI dhan 34 and BRRI dhan 50. The genotype pairs BRRI dhan 38 vs BRRI dhan 34, BRRI dhan 38 and Kalizira, and Zirakatari and Kalizira had also a higher level (0.365) of genetic distances. The genotypes were grouped into two main clusters in the UPGMA dendrogram. Cluster I included five genotypes: BRRI dhan 34, Basmoti, Atashail, Kalizira, and Binadhan-9. Cluster II included remaining six genotypes: BR5, BRRI dhan 38, BRRI dhan 50, Uknimodhu, BRRI dhan 37, and Zirakatari. Documentation of the genetic variation and relatedness among the aromatic rice genotypes under this investigation could be useful for future research into the development of aromatic rice and related fields. J Bangladesh Agril Univ 22(3): 277-284, 2024

Assessment of Genetic Diversity of Brinjal (Solanum melongena L.) in the coastal region of Karaikal, India

Genetic divergence among 25 brinjal genotypes for 13 characters was evaluated in a breeding programme aimed at improving yield potential by using Mahalanobis D2 statistics. The genotypes were grouped into six clusters suggesting considerable amount of genetic diversity in the study material. The cluster I had constituted maximum of 17 genotypes followed by cluster II which had three genotypes and cluster IV with two genotypes. The cluster III, cluster V and cluster VI each had one genotype. The intra-cluster D2 value ranged from 0.00 to 61.67 and the inter-cluster D2 value ranged from 89.49 to 343.51. The maximum intra-cluster distance of 61.67 was exhibited by the cluster I followed by cluster IV and cluster III, V, VI. The inter cluster distance was found to be high between cluster II and IV followed by cluster IV and V, cluster II and VI and cluster II and V. The contribution of different characters towards divergence indicated that, fruit yield per plant contributed the maximum percentage of 79.00 towards genetic divergence followed by individual fruit weight (8.00 percent) and number of fruits per cluster (3.00 percent). Thus, it indicated that the genotypes from cluster IV (fruit yield per plant), cluster VI (individual fruit weight) and cluster IV (number of fruits cluster-1) could be selected for crop improvement in brinjal as they recorded higher cluster mean values for traits contributing maximum towards genetic divergence.

Applicability of SCoT markers in unraveling genetic variation and population structure among sugar beet (Beta vulgaris L.) germplasm.

Sugar beet (Beta vulgaris L.) holds significant importance as a crop globally cultivated for sugar production. The genetic diversity present in sugar beet accessions plays a crucial role in crop improvement programs. During the present study, we collected 96 sugar beet accessions from different regions and extracted DNA from their leaves. Genomic DNA was amplified using SCoT primers, and the resulting fragments were separated by gel electrophoresis. The data were analyzed using various genetic diversity indices, and constructed a population STRUCTURE, applied the unweighted pair-group method with arithmetic mean (UPGMA), and conducted Principle Coordinate Analysis (PCoA). The results revealed a high level of genetic diversity among the sugar beet accessions, with 265 bands produced by the 10 SCoT primers used. The percentage of polymorphic bands was 97.60%, indicating substantial genetic variation. The study uncovered significant genetic variation, leading to higher values for overall gene diversity (0.21), genetic distance (0.517), number of effective alleles (1.36), Shannon's information index (0.33), and polymorphism information contents (0.239). The analysis of molecular variance suggested a considerable amount of genetic variation, with 89% existing within the population. Using STRUCTURE and UPGMA analysis, the sugar beet germplasm was divided into two major populations. Structure analysis partitioned the germplasm based on the origin and domestication history of sugar beet, resulting in neighboring countries clustering together. The utilization of SCoT markers unveiled a noteworthy degree of genetic variation within the sugar beet germplasm in this study. These findings can be used in future breeding programs with the objective of enhancing both sugar beet yield and quality.

Haplotype-resolved genome assembly of the diploid Rosa chinensis provides insight into the mechanisms underlying key ornamental traits

Roses are consistently ranked at the forefront in cut flower production. Increasing demands of market and changing climate conditions have resulted in the need to further improve the diversity and quality of traits. However, frequent hybridization leads to highly heterozygous nature, including the allelic variants. Therefore, the absence of comprehensive genomic information leads to them making it challenging to molecular breeding. Here, two haplotype-resolved chromosome genomes for Rosa chinensis ‘Chilong Hanzhu’ (2n = 14) which is high heterozygous diploid old Chinese rose are generated. An amount of genetic variation (1,605,616 SNPs, 209,575 indels) is identified. 13,971 allelic genes show differential expression patterns between two haplotypes. Importantly, these differences hold valuable insights into regulatory mechanisms of traits. RcMYB114b can influence cyanidin-3-glucoside accumulation and the allelic variation in its promoter leads to differences in promoter activity, which as a factor control petal color. Moreover, gene family expansion may contribute to the abundance of terpenes in floral scents. Additionally, RcANT1, RcDA1, RcAG1 and RcSVP1 genes are involved in regulation of petal number and size under heat stress treatment. This study provides a foundation for molecular breeding to improve important characteristics of roses.

Evaluation of Genetic Divergence in Chickpea (Cicer arietinum L.) Germplasm

A field experiment was carried out to assess the nature and magnitude of genetic divergence in forty genotypes of desi chickpea using Mahalanobis’s D2 Statistics. High magnitude of heritability (bs) was recorded for plant height, days to 50% flowering, biological yield, harvest index, number of pods per plant, seed yield per plot, 100 seed weight and seed yield per plant. High heritability coupled with high genetic advance was observed for seed yield per plant, seed yield per plot, number of pods per plant, 100 seed weight, harvest index, biological yield and plant height suggesting that, the role of additive gene effect and possibilities of achieving high genetic progress through selection. The forty chickpea genotypes were grouped into seven clusters suggesting considerable amount of genetic diversity in the material. The cluster III has a total of 10 genotypes, followed by cluster II with nine, cluster VI with seven, cluster IV and V with four, and cluster I and VII with three genotypes, respectively. The intra-cluster D2 value ranged from 148.25 to 491.49 while, inter-cluster D2value ranged from 386.99 to 2141.49. The maximum intra cluster distance was found in cluster I followed by cluster VII and VI, indicating that cross combinations may occur through hybridization between genotypes from the same clusters. The highest inter-cluster distance was observed between cluster I and V (2141.49), followed by cluster I and IV (1590.64), cluster II and V (1271.17) and cluster I and VII (1184.91) suggesting that the genetic architecture of the genotypes in one cluster differ entirely from those included in other clusters. These lines may be utilized in further breeding programe for the exploitation of hybrid vigour and suggesting wide diversity between them and crossings between genetically diverse lines will result in heterotic segregants, genotypes in these clusters could be employed as parents in a hybridization program to develop desirable plant types. Among the ten traits studied, maximum contribution was made by harvest index (21.28 %) followed by number of pods per plant (19.36%), biological yield (15.13%), plant height (14.87%), days to 50% flowering (12.18%) and seed yield per plant (8.08%). The genotypes ICC15921, ICC15903, K1058 and ICC15926, ICC15226, ICC7549, ICC15855 were identified as genetically diverse parents, which can be utilized for future crop improvement programe in chickpea. The aforementioned findings show that these genotypes contain the greatest genetic diversity and are useful for creating a large number of segregants through a crossing program.

The Effects of De Novo Mutation on Gene Expression and the Consequences for Fitness in Chlamydomonas reinhardtii.

Mutation is the ultimate source of genetic variation, the bedrock of evolution. Yet, predicting the consequences of new mutations remains a challenge in biology. Gene expression provides a potential link between a genotype and its phenotype. But the variation in gene expression created by de novo mutation and the fitness consequences of mutational changes to expression remain relatively unexplored. Here, we investigate the effects of >2,600 de novo mutations on gene expression across the transcriptome of 28 mutation accumulation lines derived from 2 independent wild-type genotypes of the green algae Chlamydomonas reinhardtii. We observed that the amount of genetic variance in gene expression created by mutation (Vm) was similar to the variance that mutation generates in typical polygenic phenotypic traits and approximately 15-fold the variance seen in the limited species where Vm in gene expression has been estimated. Despite the clear effect of mutation on expression, we did not observe a simple additive effect of mutation on expression change, with no linear correlation between the total expression change and mutation count of individual MA lines. We therefore inferred the distribution of expression effects of new mutations to connect the number of mutations to the number of differentially expressed genes (DEGs). Our inferred DEE is highly L-shaped with 95% of mutations causing 0-1 DEG while the remaining 5% are spread over a long tail of large effect mutations that cause multiple genes to change expression. The distribution is consistent with many cis-acting mutation targets that affect the expression of only 1 gene and a large target of trans-acting targets that have the potential to affect tens or hundreds of genes. Further evidence for cis-acting mutations can be seen in the overabundance of mutations in or near differentially expressed genes. Supporting evidence for trans-acting mutations comes from a 15:1 ratio of DEGs to mutations and the clusters of DEGs in the co-expression network, indicative of shared regulatory architecture. Lastly, we show that there is a negative correlation with the extent of expression divergence from the ancestor and fitness, providing direct evidence of the deleterious effects of perturbing gene expression.

Studies on genetic variability and heritability in bulb onion (Allium cepa L.) in the South-Eastern plains of Bihar, India

The study was conducted at Vegetable Research Farm, Department of Horticulture, Bihar Agricultural University, Sabour, Bhagalpur during Rabi season 2021-22 with the objective to study genetic variability in onion (Allium cepa L.) for yield and yield attributing traits. The experimental material consisted of 15 onion genotypes from different locations in India. Experimental trial was laid out in a RBD with three replications. Analysis of variance was done by the method suggested by Panse and Sukhatme (1967). The observations were recorded on five randomly selected plants of all genotypes for plant height, number of leaves, leaf length, leaf width, pseudostem length, neck thickness, polar diameter, equatorial diameter, and average bulb weight. Analysis of variance indicated significant differences among the genotypes for all the characters under study which implied a considerable amount of genetic variability in the genotypes included in the study. The highest average weight of onion bulb was recorded in genotype LC-1 (62.13g) which was statistically at par with LC-2 (58.53g), Patna Red (57.80g), Bhima Shakti (57.28 g) and Agrifound Light Red (56.87g). High PCV and GCV were recorded for pseudostem length and neck thickness. Moderate GCV and PCV were found in leaf width, average bulb weight, plant height, leaf length, equatorial diameter and bulb size index. High heritability along with high genetic advance as percentage of mean was exhibited by all the morphological traits. The genotypes LC-1, LC-2, Patna Red and Bhima Shakti were identified as promising ones for the yield and yield contributing traits.

Genetic divergence for crop improvement in Sesame (Sesamum indicum L.)

Genetic divergence in 92 accessions of sesame was evaluated by using Mahalanobis D2 statistics to identify the potential parents in the hybridization programme. The genotypes were grouped into twelve clusters suggesting a considerable amount of genetic diversity in the material. The traits viz., number of primary branches per plant, number of capsules per plant and seed yield per plant contributed maximum towards the divergence and emphasis should be given for these traits for improving yield potential in sesame.

Untapped Genetic Resources for Breeding Acidic Soil-Adapted Chickpea (Cicer arietinum L.) Cultivars

Globally, more than half of potentially arable land is acidic, and aluminum (Al) is the primary factor limiting plant growth and crop productivity on acidic soils worldwide. The development and utilization of Al-tolerant crops is a sustainable approach to enhancing crop production on acidic soils. For this purpose, screening available genetic resources under Al-stressed conditions is a crucial initial step. Hence, the present study aimed to evaluate the Al tolerance of 264 Ethiopian chickpea landraces under hydroponic conditions without Al (control) and with 120 µM Al (Al treatment). Significant (p < 0.001) variations were detected among the genotypes for all studied traits under control (0 µM Al) and 120 µM Al concentration. The relative growth values for the 120 µM Al/0 µM Al ratio was also significant, indicating the presence of a considerable amount of genetic variation in Ethiopian chickpea landraces in terms of Al tolerance. Based on relative root growth (RRG) as an Al-tolerance parameter, the genotypes were grouped into five distinct (p < 0.001) classes. The highest RRG value (1.59) was obtained for genotype ETC_209008, followed by ETC_41184 and ETC_212589, while ETC_208995 had the lowest RRG value of 0.27. Of the total landraces screened, 35% had higher RRG values than the tolerant genotype ETC_WL_1_2016 used as a reference, indicating the presence of adequate genotypes capable of outperforming the reference genotype on acidic soils. The genotypes identified in the present study may serve as sources of novel alleles in genes regulating Al tolerance in chickpea that can be utilized in breeding programs to improve the crop’s adaptation to acidic soils, thus contributing to smallholder farmers’ increased nutritional and food security.

Dissecting genomic regions and underlying sheath blight resistance traits in rice (Oryza sativa L.) using a genome-wide association study.

The productivity of rice is greatly affected by the infection of the plant pathogenic fungus Rhizoctonia solani, which causes a significant grain yield reduction globally. There exist a limited number of rice accessions that are available to develop sheath blight resistance (ShB). Our objective was to identify a good source of the ShB resistance, understand the heritability, and trait interactions, and identify the genomic regions for ShB resistance traits by genome-wide association studies (GWAS). In the present study, a set of 330 traditional landraces and improved rice varieties were evaluated for ShB resistance and created a core panel of 192 accessions used in the GWAS. This panel provides a more considerable amount of genetic variance and found a significant phenotypic variation among the panel of rice accessions for all the agro-morphological and disease-resistance traits over the seasons. The infection rate of ShB and disease reaction were calculated as percent disease index (PDI) and area under the disease progress curve (AUDPC). The correlation analysis showed a significant positive association between PDIs and AUPDC and a negative association between PDI and plant height, flag leaf length, and grain yield. The panel was genotyped with 133 SSR microsatellite markers, resulting in a genome coverage of 314.83 Mb, and the average distance between markers is 2.53 Mb. By employing GLM and MLM (Q + K) models, 30 marker-trait associations (MTAs) were identified with targeted traits over the seasons. Among these QTLs, eight were found to be novel and located on 2, 4, 8, 10, and 12 chromosomes, which explained the phenotypic variation ranging from 5% to 15%. With the GWAS approach, six candidate genes were identified. Os05t0566400, Os08t0155900, and Os09t0567300 were found to be associated with defense mechanisms against ShB. These findings provided insights into the novel donors of IC283139, IC 277248, Sivappuchithirai Kar, and Bowalia. The promising genomic regions on 10 of 12 chromosomes associated with ShB would be useful in developing rice varieties with durable disease resistance.

Hybrid Vigour and Combining Ability in Biofortified Maize (Zea mays L.)

The study was conducted during winter season of 2020–2021 and rainy season of 2021 at Maize Research Station, Sardarkrushinagar Dantiwada Agricultural University, Bhiloda, Gujarat, India. The aim of the study was to assess magnitude of heterosis and combining ability of forty-five single cross hybrids developed by half-diallel mating design involving ten parents and two standard checks. The field experiment was laid out in randomized block design with three replications. The heterosis, combining ability and components of genetic variance were studied for diverse thirteen characters. The analysis of variance revealed that mean square values of genotypes were significant for all the characters which indicated the existence of considerable amount of genetic variation in genotypes for all the characters. Among single crosses, IMR-76×IMR-58 exhibited maximum mean and desired SCA effect and standard heterosis for β-carotene and IMR-53×IMR-72 for kernel yield. The general and specific combining ability variances observed highly significant for all traits except days to tasseling (only additive gene action), anthesis-silking interval and shelling percentage (only non-additive gene action). The σ2A/σ2D ratio indicated that preponderance of non-additive gene action for the inheritance of these characters suggesting due weightage should be given to heterosis breeding for genetic improvement of these traits. The crosses namely IMR-52×IMR-72 and IMR-51×IMR-58 presented significant heterosis for days to maturity, grain yield, iron and β-carotene content.

Multivariate Analysis in Wheat (Triticum aestivum L.) for Yield and Attributing Traits under Soil Salinity and Alkalinity in Haryana

Salt-affected soils could be used by improving and developing salt-tolerant genotypes depending upon the amount of genetic variation and salt stress response of adapted and donor sources of wheat. Salt stress affects 20% of global cultivable land and is increasing continuously owing to the change in climate and anthropogenic activities. Globally, saline soils cover 3.1% i.e. 397 mha of the total land area and around 6.74 mha area of India is affected due to salinity. Salinity stress negatively affects the growth and development of wheat leading to low grain yield and quality. A station varietal trial was conducted to identify salt-tolerant genotypes, wherein 24 genotypes including 4 checks, namely, KRL 19, WH 157, KRL 210 and KRL 283 were evaluated in 6 replications in 4.0 m x 1.20 m in RBD under natural saline patch (pH 8.5, ECe 4.2 dsm-1) at Research area of Wheat and Barley Section, Department of Genetics and Plant Breeding and Department of Soil Science (pH 8.5, ECe 4.5 dsm-1), CCS HAU, Hisar during Rabi 2021-22. Observations were recorded for germination (%), days to heading, days to maturity, plant height (cm), tillers per meter row, 1000-grain weight (g), grain yield per plot (g/plot) and hectoliter weight (kg/hl). High positive correlation has been observed for 1000-GW (g) with GY/P (g/plot), PH (cm) with hectoliter weight (kg/hl). Non-significant correlation was observed between days to heading and germination with plant height and hectoliter weight. Clustering of genotypes based on Ward’s Euclidean method was done so that identical genotypes may grouped together; 24 genotypes were grouped into three distinct clusters. Hectolitre weight (kg/hl) expressed as point of dissection of studied traits as GY/P (g/plot), 1000-GW (g), DM and PH (cm) falls at one side and germination (%), DH and T/meter row lies at another side. Entries, namely, WH 1313 (59.6 q/ha), WH 1306 (54.9 q/ha) and WH 1309 (52.9 q/ha) performed better and found significantly superior to the best check WH 157 (43.5+8.2 q/ha) at Department of Genetics and Plant Breeding. P 13582 (61.6 q/ha), P 13650 (62.1 q/ha) performed better and found significantly superior to best check KRL 283 (46.4+13.7 q/ha) at Department of Soil Sciences. Identification of wheat genotypes based on simultaneous selection among contributing traits will improve grain yield. Stable and promising genotypes may be included in breeding program aimed to develop salt tolerant varieties at state and national level to ensure nutritional food security.

Gene action and combining ability for yield and other quantitative traits under timely and late sown conditions in chickpea (Cicer arietinum L.)

An investigation was carried out to understand the nature and magnitude of gene action in 28 F1 hybrids of chickpea (Cicer arietinum L.) under timely (E1) and late sown (E2) conditions. The analysis of variance revealed a considerable amount of genetic variability among the materials under study in both environments. The significant difference of general combining ability (GCA) and specific combining ability (SCA) variances indicated that both additive and non-additive gene action played an important role in the genetic control of all the traits under both E1 and E2 conditions. The study identified CSJ-515 and HC-5 as the best combiners for seed yield and it contributing traits under both environments, whereas Avrodhi in timely sown and CSJD-884 and RSG 963 under late sown conditions. Significantly higher specific combining ability, heterosis, and heterobeltiosis were recorded in the crosses, CSJD 884 x RSG 963, CSJD 884 x RSG 973, CSJD 884 x Avrodhi, RSG 963 x CSJ 515 in both the environment, while CSJD 884 x RSG 963 and RSG 973 x Avrodhi in late sown conditions. The identified F1 hybrids may be suitable for the improvement of grain yield in chickpeas for specific environments.

Assessing the Genetic Variability of Sweet Chestnut Varieties from the Tuscan Apennine Mountains (Italy)

Castanea sativa Mill. is a valuable species with historical and economic importance in Europe, particularly in the Mediterranean area. In Italy, chestnut cultivation has been developed for centuries, leading to the recognition of more than 300 varieties. Nevertheless, a profusion of local names has been assigned by growers, causing the occurrence of synonyms and homonyms across the country. This research focused on genetic characterization and identification using 21 single sequence repeats (SSRs) for four chestnut varieties (i.e., Pastinese, Nerattino, Carpinese, and Rossola) commonly used for flour production in the Tuscan Apennine Mountains (Pistoia Province). A comprehensive number of 55 accessions identified by local growers as belonging to the four varieties were analyzed, in addition to a few “Marrone” accessions as outgroups. The 21 microsatellites were highly informative, detecting 98 alleles and displaying an average polymorphism information content (PIC) equal to 0.582. In addition, a considerable amount of genetic diversity was revealed, as shown by the heterozygosity levels (He = 0.634 and Ho = 0.475). The STRUCTURE analysis provided clear distinctions among the different varieties, splitting them into four separate groups. This result was also confirmed by UPGMA dendrogram and principal co-ordinates analysis (PCoA). However, one accession (Carp_5), previously identified as Carpinese, showed an allelic profile attributable to Pastinese, suggesting that farmers might have performed mislabeling or grafting propagation errors. Thus, our results confirm the use of SSRs to allocate the accessions of different varieties, uncovering possible synonyms and homonyms. Specifically, in the context of the Pistoiese mountain region, this tool can favor the traceability of processed products, such as flour, enhancing the quality and economic value of the local market. Lastly, our findings have revealed a considerable genetic variability within the Tuscan chestnut varieties whose preservation is mandatory to face climate change challenges through sustainable forest management practices.

Experimental evolution of evolutionary potential in fluctuating environments.

Variation is the raw material for evolution. Evolutionary potential is determined by the amount of genetic variation, but evolution can also alter the visibility of genetic variation to natural selection. Fluctuating environments are suggested to maintain genetic variation but they can also affect environmental variance, and thus, the visibility of genetic variation to natural selection. However, experimental studies testing these ideas are relatively scarce. In order to determine differences in evolutionary potential we quantified variance attributable to population, genotype and environment for populations of the bacterium Serratia marcescens. These populations had been experimentally evolved in constant and two fluctuating environments. We found that strains that evolved in fluctuating environments exhibited larger environmental variation suggesting that adaptation to fluctuations has decreased the visibility of genetic variation to selection.

Genetic diversity analysis in sesame (Sesamum indicum L.)

In the present investigation, 70 genotypes of sesame were characterized for 12 morphological and 14 quantitative characters and subjected to genetic divergence (UPGMA hierarchial clustering) analysis. It revealed that a considerable amount of genetic variability was exhibited for majority of the morphological traits except for locule number per capsule, capsule number per leaf axil and capsule shape. In divergence analysis for both morphological and quantitative characters, 70 genotypes were grouped into seven clusters at the genetic distance of 0.5 using Ward’s minimum variance method and Gower’s method of genetic distance. Selection of the genotypes present in different clusters having more genetic distance, preferably belonging to different geographical origin may result in more heterotic effects in the hybridization programme. Good recombinants can be obtained by mating between clusters I and VII for genotypes viz., GJT-5, RT-46 with TMV-3, VRI-3, Paiyur 1 as they have maximum genetic distance between them. Most of the characters recorded high mean values in cluster VII. Hence, for improvement of these traits, the genotypes present in cluster VII could be exploited as parents. Keywords: Sesame, Diversity, Cluster, UPGMA

Genetic Diversity and Population Structure in Solanum nigrum Based on Single-Nucleotide Polymorphism (SNP) Markers

Solanum nigrum is a noxious weed in agricultural ecosystem that limits many crops’ production. The aim of the present study was to understand the level of genetic diversity and population structure of S. nigrum in China. A specific-locus amplified fragment (SLAF) sequencing method was conducted to detect single-nucleotide polymorphisms (SNPs) in the genomes of S. nigrum from 66 populations in China. A total of 616,533 high-quality SNPs were identified from 189,840 SLAFs, with an average sequencing depth of 10.59× fold and a Q30 value of 93% and a GC content of 42.78%. It showed a considerable amount of genetic diversity and genetic variability of S. nigrum among samples. The genetic differentiation of S. nigrum indicated that there was a low level of genetic differentiation (Fst < 0.1000) among geographical populations. A cluster analysis showed that populations of S. nigrum were divided into two subgroups, with some samples from adjacent position roughly clustered together, which showed some correlation between geographic origins. A population structure analysis suggested the 66 S. nigrum samples could have originated from three different genetic clusters. The Xinjiang site was the only location where all genetic clusters were found, which suggested these populations were genetically diverse. These results showed that there was a high degree of genetic diversity and low difference among the different geographical populations of S. nigrum. The results from the genetic structure of the SNP markers indicated that wide genetic variability exists among the population of S. nigrum in China, which may contribute to the adaptation and infestation of this weed species.

A Comparative Study on Nutritional and Biochemical Characterization of Banana Cultivars of Assam, India

An experiment was conducted in the Department of Horticulture, Assam Agricultural University, Jorhat to evaluate the huge diversity among the different banana germplasm in the state of Assam. The experiment comprised of 24 banana (Musa spp.) genotypes, of which the fruits were collected for precise biochemical characterization of the variations present in the collection. This analysis had created a database of the biochemical characterization of the fruits of different indigenous banana genotypes of Assam from which, it can be concluded that, there exists great genotype diversity among the Musa germplasm of Assam considering the fruit biochemical aspects and considerable amount of genetic variations are present even among the closely related genotypes within the same genomic group.