Genetic difference of Chinese horseshoe crab(Tachypleus tridentatus) in southeast coast of China based on mitochondrial COI gene analysis

Population genetic structure and historical demography of Chinese horseshoe crab (T.tridentatus)along southeast coast of China were inferred from the sequence data of mitochondrial cytochrome c oxidase subunit Ⅰ (COI) fragment.The sequence analysis for 964 bp COI fragment was conducted in 28 individuals collected from five localities:Ninghai in Zhejiang Province,Meizhou and Zhangpu in Fujian Province,Beihai of Guangxi Zhuang Autonomous Region and Danzhou of Hainan Province.Sequence variation was relatively low with a total of seven transitions observed.In all localities,Haplotype H3 was the dominant type observed among eight haplotypes defined previously,and was at the center of radiation in Median-Joining network.The prolonged star-like network suggests a signature of population expansions.The level of diversity was low in total,with haplotype diversity ( Hd) being equal to 0.765 and nucleotide diversity (π) being equal to 0.00118,respectively.The genetic structure analysis revealed the significant genetic difference between Ninghai and Danzhou populations.Both mismatch distribution analysis and Fu's Fs test provided consistent inference of historic population expansion.The low genetic diversity of horseshoe crab observed along China coast indicated that urgent measures should be taken to protect this rare marine animal.

Analysis of Genetic Difference Between Species in Lupins by AFLP

The genetic difference between species in 18 lupins (Lupinus L .) varieties including L. angus-tifolius L., L . albus L., L. pilosus Murr. was analyzed using AFLP. A total of 462 bands were observed, a-mong of which, 442 (95.7%) were polymorphic, with an average of 110.5 polymorphic bands for each AFLP primer combination. The average genetic diversity index was 0.781 in this study. The genetic difference between species was higher than that of between varieties, the average identification percentage of four AFLP primer combinations was 100% and 84.7% between species and between varieties, respectively. The cluster analysis indicated that 3 species were distinctly distinguished on the dendrogram using UPGMA method.

Analysis of Genetic Differences among Monokaryon Strains of Flammulina velutipes Using SCoT and ISSR Markers

[Objective]This study aimed to analyze genetic differences among Flammulina velutipes monokaryon strains.[Method]Twenty F1monokaryon strains（W1-W20）of F.velutipes were separated with conventional dilution method.Fifteen SCoT primers and nine ISSR primers were screened.According to amplification results,genetic similarity coefficients among various strains were calculated using NTsys 2.10e analysis software for cluster analysis.[Result]Six primers could be use to amplify clear polymorphic bands.To be specific,a total of 327 clear DNA fragments were amplified,including 287 polymorphic bands,accounting for 87.77%of the total number of bands amplified.Based on SCoT analysis,the genetic identity（GI）among 20 strains ranged from 0.187 5 to 0.937 5;to be specific,GI between W2 and W3 and that between W11 and W12 reached the maximum of 0.9375;GI between W15 and W18 was the minimum of 0.187 5.Based on ISSR analysis,GI among 20 strains ranged from 0.250 0 to 1.000 0;to be specific,GI between W3,W4 and W9,GI between W15 and W17,and that between W16 and W19 reached the maximum of 1.000;GI between W14 and W18 was the minimum of 0.250 0.Such low genetic identity fully demonstrated great genetic differences among F.velutipes monokaryons.According to results of cluster analysis,at a similarity level of 0.55,20 F.velutipes monokaryons were significantly divided into three groups using SCoT markers;at a similarity level of 0.66,20 F.velutipes monokaryons were divided into three groups using ISSR markers.Specifically,W11,W18 and W20 were invariably divided into one group;W15 and W17 were divided into one subgroup.[Conclusion]In this study,two type of markers were used for analysis of genetic diversity among F.velutipes monokaryon strains,which provided scientific and practical basis for screening high-quality monokaryon parents of F.velutipes.

Genetic Differences of Mitten Crabs Based on RFLP Analysis on Mitochondrial Cytochrome Oxidase Subunit I(COI) Gene

The genetic differences of 15 mitten crab populations from 6 river systems in China's Mainland and 1 population from Russia were studied based on RFLP analysis of mitochondrial cytochrome oxidase subunit I （CO I）. The results showed that Tas I-RFLP pattern could be used as a genetic marker to distinguish Eriocheir hepuensis from Eriocheir sinensis, Eriocheirjaponica and Eriocheir leptognathus; genetic distances among 13 populations of Eriocheir sinensis range from 0 to 0.015, indicating that they were different geographic strains; the subspecies status of Eriocheir sinensis and Eriocheir hepuensis （population from Nanliujiang） were considered owning to their genetic distances of 0.02-0.044, indicating that genetic divergence between them was low; Eriocheir leptognathus （population from Nanpaihe, Tianjin） was the most distant taxon with genetic distances value of 0.147-0.195, which could be defined as genetic distances between species in genus Eriocheir.

Differences of EST-SSR and genomic-SSR markers in assessing genetic diversity in poplar

We analyzed the genetic differences of 16 poplar clones between genomic-SSR and EST-SSR markers. The statistical results show that the average number of alleles detected by genomic-SSR was 4.1, Shannon＇s index 1.0646, observed heterozygos- ity 0.4427 and expected heterozygosity 0.5523, while for the EST-SSR, the average number of alleles was 2.8, Shannon＇s index 0.6985, observed heterozygosity 0.2330 and expected heterozygosity 0.4684. Cluster analysis indicated that the EST-SSR capacity of genotypic identification was more precise than that of genomic-SSR. These resuks reveal that EST-SSR and genomic-SSR have statistically significant genetic differences in polymorphism detection and genotypic identification. These differences could provide a theoretical basis for the rational use of SSR markers in species diversity and other related research.

Analysis of genetic effects and heritabilities for amylose content of indica rice in different environments

An understanding of the genetic effects of em-bryo genes for rice quality traits is of impor-tance for rice quality improvement. Analysisof embryo, endosperm, cytoplasmic, and ma-ternal genetic effects and genotype×environ-

Effects of Mutation and Hybridization on Breeding of Super High Yield Wheat Varieties

In order to develop high quality wheat varieties with super high yield, a theory which improved the genetic difference between parents by performing radi- ation mutation on them to enhance heterosis was proposed. The dry seeds treated and planted last year were radiated frequently by X- ray from 2003 to 2004. Then the dry seeds were radiated by high energy X ray combined with nuclear magnetic resonance from 2005 to 2007. We have treated the dry seeds repeatedly for 3 years and gained a variety of aberrant plants. These mutants were used as parents that were hybridized with the best plants in field. It was shown that a lot of mutant plants appeared in the f＇llial generations. After that, we selected big grains and super big grains among them. The result showed that, middle stem plants with big grains and low stem plants with big grains appeared. This phenomenon might be due to the breakthrough of linkage relationship between big grain trait and high stem trait. With the technique practice and materials, the new thoughts and methods were provided for induction and utilization of heterosis of wheat, which created a va- riety of seed selection and breeding materials for breeding super wheat varieties.

Breeding of Super-large-grain Wheat Germplasms

[Objectives]This study was conducted to breed high-yielding wheat varieties. [Methods] A new breeding technology of "Artificial mutagenesis to increase genetic differences between parents and to enhance heterosis" was put forward. Longnan 71 a and Longnan 71 a mutants bred by this technology were crossed with other mutants and normal materials. [Results] In the Wudu experimental field of Longnan City, the traits of super-large grain appeared in the obverse and inverse cross with Longnan 71 a as parents. The trait of super-large grain was dominantly inherited. The traits of various combinations in the Fgeneration were segregated. In the Fgeneration, one super-large-grain low-stalk line and other lines with specific traits were selected. In the Fgeneration, two super-large-grain low-stalk large-ear lines were selected. These three super-large-grain low-stalk wheat lines had reduced plant height and good lodging resistance, and possessed two high-yielding characters among the three factors of yield, so they were expected to be further bred into high-yielding wheat varieties. One line with the largest grain length of 10.3 mm was selected in the Fgeneration. After two years of breeding, in 2022, the largest grain length was measured to be 10.6 mm, and the average 1 000-grain weight and the largest 1 000-grain weight were 75.8 and 100 g, respectively. [Conclusions] This study is about the major progress in artificial cultivation of super-large-grain wheat and has considerable practical value.