ABSTRACT
BACKGROUND: Procambarus clarkii produces high-quality, delicious meat that is high in protein, low in fat, and rich in calcium and phosphorus. It has become an important aquatic resource in China. Our objectives are (i) to analyze the level of genetic diversity of P. clarkii populations; (ii) to explore the genetic differentiation (Gst); and (iii) to propose appropriate strategies for the conservation. RESULTS: In this study, Shannon's index (I) and Nei's gene diversity index (H) for P. clarkii were high (I = 0.3462 and H = 0.2325 on average and I = 0.6264, H = 0.4377 at the species level) based on the SSR markers. The expected heterozygosity value of 17 microsatellite loci in 25 crayfish populations was 0.9317, the observed heterozygosity value was 0.9121, and the observed number of alleles per locus was 2.000; and the effective number of alleles per locus was 1.8075. Among the P. clarkii populations, the inbreeding coefficient within populations (Fis) was 0.2315, overall inbreeding coefficient (Fit) was 0.4438, genetic differentiation coefficient among populations (Fst) was 0.3145 and gene differentiation (Gst) was 0.4785 based on SSR analyses. The cluster analysis results obtained by unweighted pair-group method with arithmetic mean (UPGMA) analysis, principal coordinate analysis (PCoA) and STRUCTURE analysis were similar. A mantel test showed that the isolation-by-distance pattern was not significant. CONCLUSIONS: The high Gst among P. clarkii populations is attributed to genetic drift and geographic isolation. The results indicated that more P. clarkii populations should be collected when formulating conservation and aquaculture strategies.
Subject(s)
Animals , Genetic Variation , Microsatellite Repeats , Astacoidea/genetics , Phylogeny , China , Polymerase Chain Reaction , Aquaculture , Aquatic Environment , Wetlands , Genetic Carrier ScreeningABSTRACT
Objective::Sixty-nine germplasm samples of Picria felterrae collected from the main producing areas in Guangxi were subject to genetic diversity and genetic relationship analyses using the simple seguence repeat(SSR) molecular marker technology and good germplasm genes associated with the content of picfeltarraenins were screened so as to provide references for germplasm resource evaluation, phylogenetic analysis, and molecular mark assisted breeding of that species. Method::20 pairs of randomly selected primers were amplified based on the transcriptome sequencing technology. The genetic diversity of and genetic relationship between the 69 samples were analyzed using the genetic polymorphic information for each marker locus, and one-variable linear regression and multiple stepwise regression analyses were performed to screen molecular markers associated with the content of picfeltarraenins. Result::The amplification using the 20 pairs of SSR primers produced 76 alleles, 3.8 alleles for each locus on average, higher than effective alleles (1.969 2), and the rare allele rate was 38.2%, suggesting that the alleles distributed unequally. The polymorphism rates of alleles varied between 0-59%, with an average of 38.24%, showing a great difference among loci. The polymorphic information content (PIC) varied between 0-0.621 1, with an average of 0.378 0.Shannon polymorphic information index varied between 0-1.240 1, with an average of 0.759.Nei's gene diversity index (Nei) varied between 0-0.682 3, with an average of 0.440 9.P21 had the highest level accompanied with the lowest P7 for the above three indexes, and significant genetic diversity differences were identified among the loci. For all loci, the mean observed heterozygosity was 0.382 4, lower than the average expected heterozygosity of 0.442 5, suggesting the loss of heterozygosity, the average genetic differentiation coefficient (Fst) was 0.365 9 and the average gene flow Nm was 0.433 2, suggesting a high genetic divergence and a low gene flow. The results of one-variable linear regression and multiple stepwise regression showed that there were 5 loci related to each of the picfeltarraenin IA and IB, and only 1 loci was associated with the content of both. Conclusion::There were significant differences in the genetic diversity of 20 SSR marker sites, and the 69 germplasm samples were greatly genetically differentiated and had low gene flow. From the selected 20 SSR markers 9 marker loci associated with the content of picfeltarraenin IA and IB were selected. The results can be used as a reference for phylogenetic analysis and selective breeding of Picria felterrae.
ABSTRACT
Aim: Alternaria blight caused by Alternaria lini is one of the major diseases of linseed which severely affects the yield and productivity. Here, we utilizes F2 mapping population derived from a resistant (JRF-4) and a susceptible (Chambal) genotypes of linseed and SSRs to identify the markers associated with Alternaria blight resistance using bulk segregant analysis approach. Methodology: A population consisting of 154 F2 individuals was developed from the cross between JRF-4 (resistant) and Chambal (susceptible). All 154 F2 individuals were screened with 100 polymorphic SSRs to identify extreme phenotype. Two bulk of extremes phenotypes (disease resistant and disease susceptible) from F2 mapping population were used for the bulked segregant analysis. The SSR primers that distinguished the parental lines were used to amplify the DNA from two bulks and banding pattern was observed to identify the SSRs that can differentiate the resistant and susceptible phenotypes bulk for Alternaria blight. Markers validation was carried out by amplifying DNA from individual plants of each bulk. Results: Out of 100, only 10 markers showed polymorphism among the bulks and of which only three markers viz., LUSc 898_3_12, Lu 2472 and Lu 3078 were able to differentiate the disease resistant and susceptible individuals from F2 population. Further, single marker linear regression approach was used to validate the association of selected polymorphic markers with the disease. The markers LUSc 898_3_12 and Lu 2472 showed significant regression which confirmed their linkage with Alternaria blight resistance. Interpretation: The two markers having significant regression can be used for diseases resistance breeding during marker assisted selection.
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In order to develop genomic-SSR markers for species of Saxifraga genus, a mixed plant genomic DNA sample was sequenced based on high-throughput Illumina MiSeq platform. According to genomic sequencing data, SSR loci were identified with MISA software, and then primers were designed with Primer 3 software. A total of 120 pairs of primers were randomly synthesized and amplified in genomic DNA of a few plant samples. Those primers who have yielded polymorphic bands and were considered easy to amplify were identified. After that, transferability of these primers was evaluated, and phylogenetic relationship of 25 species of Saxifraga genus was analyzed with UPGMA (unweighted pair group method analysis). In our results, 587 256 sequences containing SSRs were identified from a total of 1 881 979 combined read pairs obtained in genomic sequencing. Primers were designated to amplify SSRs containing two to six nucleotide repeat units, screened in a small portion of species. Finally, 17 pairs of primers which have produced abundant of polymorphic bands with little problem were amplified in 25 species of Saxifraga genus. A total of 2 687 polymorphic bands were obtained, the average polymorphic rate was 158 bands per pairs of primers. The transferability rate was ranging from 88.0% to 100% across 25 species of Saxifraga. In phylogenetic analysis, the clustering of 25 species based on 17 pairs of SSR primers was different from morphological classification. Our analysis has provided molecular data for genetic relationship of Saxifraga genus, and the transferable and polymorphic SSRs have provided information for genetic diversity research.
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ABSTRACT Mungbean (Vigna radiata (L.) Wilczek) also known as green gram is an important source of protein in the category of food legumes. In the present study, SSR marker is used to analyze the genetic diversity amongst 23 genotypes of mungbean. Out of a total of 10 primers used for SSR analysis revealed generation of 15 alleles. The number of alleles per locus ranged from one (CEDG006, CEDG010, CEDG050, CEDG088, CEDG092 and CEDG232) to three (CEDG 214), with an average of 1.5 allele per primer. The index for expected heterozygosity was 0.29 ranging from 0.15 to 0.49 revealed a deficit in heterozygosity. The size of amplification products varied in case of each primer and the range was found to be 100 bp to 190 bp. 13 out of 15 alleles were found polymorphic. The average PIC value of SSR marker was found to be 0.205. The value of Jaccard's similarity coefficient had ranged from 0.28-1.00 with an average value of 0.64. The dendrogram constructed on SSR molecular marker data through UPGMA method and PCA using average linkage, had enabled grouping of the genotypes into three main clusters. Clustering pattern based on SSR marker data clearly indicated the narrow genetic base of mungbean genotypes that emphasizes the need to explore and exploit more number of germplasm from additional source to study genetic variation in mungbean for genetic improvement. The results indicated the marked usefulness of SSR in the assessment of genetic diversity in mungbean crop.
ABSTRACT
A triploid (2n = 3x = 36) rice plant was obtained by screening a twin seedling population in which each seed germinated to two or three sprouts that were then crossed with diploid plants. One diploid plant was chosen among the various F1 progenies and developed into an F2 population via self-pollination. Compared with the control variety Shanyou 63, this F2 population had a stable agronomical performance in field trials, as confirmed by the F-test. The stability of the F2 population was further substantiated by molecular analysis with simple sequence repeat markers. Specifically, of 160 markers assayed, 37 (covering all 12 chromosomes) were polymorphic between the parental lines. Testing the F1 hybrid individually with these markers showed that each PCR product had only a single band instead of two bands from each parent. The bands were identical to either maternal (23 markers) or paternal (eight markers) bands or distinct from both parents (six markers). The amplified bands of all 60 randomly selected F2 plants were uniform and identical to those of the F1 hybrid. These results suggest that the F1 plant is a non-segregating hybrid and that a stable F2 population was obtained. This novel system provides an efficient means for shortening the cycle of hybrid rice seed production.