Hg^2＋对金银莲花根和叶片的伤害

研究了汞离子胁迫下金银莲花〔Ｎｙｍｐｈｏｉｄｅｓｉｎｄｉｃａ（Ｌ．）Ｋｕｎｔｚｅ〕根受害情况、根部过氧化物酶活性和新叶叶绿素含量的变化。根部受害程度随汞离子浓度升高和处理时间的延长而加重。低浓度Ｈｇ２＋短时间处理后根过氧化物酶活性升高,而高浓度Ｈｇ２＋长时间处理后根过氧化物酶活性下降,且随着Ｈｇ２＋浓度的升高或处理时间的延长过氧化物酶活性均呈下降趋势。新叶叶绿素含量对Ｈｇ２＋胁迫的反应与根过氧化物酶活性的变化相似。     

Development of microsatellite markers for mango (Mangifera indica L.)

Microsatellite markers for mango (Mangifera indica L.) were developed using a genomic library enriched for (GA)_n and (GT)_n dinucleotide repeats. A subset of 41 positive clones was sequenced and primers were designed. Twenty‐eight primer pairs produced polymorphic amplification products for a diversity sample including 15 mango cultivars and two accessions from the related species Mangifera laurina and Mangifera applanata. Nineteen simple sequence repeat (SSR) loci with clear scorable patterns were chosen to study diversity in the mango germplasm bank of Guadalupe (FWI). The number of alleles ranged from three to 13 with observed levels of heterozygosity ranging from 0.059 to 0.857.     

Analysis of diversity and relationships among mango cultivars using Start Codon Targeted (SCoT) markers

Genetic variation and relationships among 47 mango germplasm and 3 relative species from Guangxi province in China, were analyzed using Start Codon Targeted (SCoT) markers. Using 33 selected SCoT primers 273 bands were generated with an average of 8.27 bands per primer among the 50 accessions, of which 208 (76.19%) were polymorphic. Genetic relationships estimated using the SM similarity coefficient generated values between different pairs of accessions that varied from 0.531 to 0.923 with an average of 0.782. These coefficients were utilized to construct a dendrogram using the UPGMA. All 50 accessions were basically classified into six clusters and correspond well with their recorded pedigrees. The results will provide much more useful information for the management of germplasm and will also be useful to improve the current breeding strategies. The results also demonstrate that the SCoT marker system is useful for identification and genetic diversity analysis of mango cultivars.     

Competitive Performance of Nymphoides Peltata (Gmel.) O. Kuntze Growing in Microcosm

Two experiments were conducted to investigate the effects of competition on growth and performance of Nymphoides peltata (Gmel.) O. Kuntze in microcosm. Part of the research on growth and biomass allocation of N. peltata in response to competition had been reported early (Wu, Z. & D. Yu, 2004, Hydrobiologia 527: 241–250). This paper focuses on the morphological variations of N. peltata under competitive pressure. First, competition between N. peltata and Zizania latifolia (Griseb.) Turcz. ex Stapf. was assigned with the densities of N. peltata to Z. latifolia ratios of 4:0, 4:2, 4:4 and 4:8. Water surface coverage, surface area per leaf blade and number of leaves per plant of N. peltata all declined significantly with increasing density of competitor. Similar results were also found for petiole length and density of branching. However, the variations of planting density did not significantly affect the number of ramets per plant and the stolon length of N. peltata. Second, competitions between N. peltata and emerged Z. latifolia, floating-leaved Trapa bispinosa Roxb. and submerged Myriophyllum spicatum L. were also studied simultaneously. The results showed that significant difference was only found for the water surface coverage of N. peltata. No other significant differences were found for the number of ramets per plant, number of leaves per plant, density of branching, surface area per leaf blade, petiole length, and stolon length of N. peltata. Our studies indicate that N. peltata presents morphological variations when it is growing with Z. latifolia, such that the growth of above-ground parts decrease (i.e., leaf number, petiole length, branching density) and the growth of below-ground parts remains stable (i.e., stolons length). However, N. peltata does not show apparent differences in morphology when it is growing with T. bispinosa or M. spicatum. Accordingly, we conclude that the growth of N. peltata may be apparently inhibited by the presence of Z. latifolia, while T. bispinosa and M. spicatum may have little impact on the growth and performance of N. peltata.     

Microsatellite markers reveal high genetic diversity in date palm (<Emphasis Type="Italic">Phoenix dactylifera</Emphasis> L.) germplasm from Sudan

Genetic diversity in date palm germplasm from Sudan representing 37 female and 23 male accessions was investigated using 16 loci of microsatellite (SSR) primers. Eight female accessions from Morocco were included as reference material. The tested SSR markers showed a high level of polymorphism. A total of 343 alleles were detected at the 16 loci. The number of alleles per marker ranged from 14 to 44 with an average of 21.4 per locus. A high level of expected heterozygosity was observed among Sudan cultivars (0.841), Morocco cultivars (0.820) and male accessions (0.799). The results indicate that the genetic groups of the Sudan cultivars and/or males do not follow a clear geographic pattern. However, the morocco group showed significant differentiation in relation to the Sudan groups, as measured by F (ST) values and genetic distances. The effect of the methods of pollination and cultivar selection on the genetic structure was clearly detected by the weak clustering association that was observed for the majority of accessions originating from Sudan and Morocco as well. This suggests the need for further investigation on the genetic diversity of Sudanese date palm germplasm. A deeper insight will be revealed by a detailed analysis of populations originating from different geographic locations.     

Mapping and genome organization of microsatellite sequences in rice (Oryza sativa L.)

In order to enhance the resolution of an existing genetic map of rice, and to obtain a comprehensive picture of marker utility and genomic distribution of microsatellites in this important grain species, rice DNA sequences containing simple sequence repeats (SSRs) were extracted from several small-insert genomic libraries and from the database. One hundred and eighty eight new microsatellite markers were developed and evaluated for allelic diversity. The new simple sequence length polymorphisms (SSLPs) were incorporated into the existing map previously containing 124 SSR loci. The 312 microsatellite markers reported here provide whole-genome coverage with an average density of one SSLP per 6 cM. In this study, 26 SSLP markers were identified in published sequences of known genes, 65 were developed based on partial cDNA sequences available in GenBank, and 97 were isolated from genomic libraries. Microsatellite markers with different SSR motifs are relatively uniformly distributed along rice chromosomes regardless of whether they were derived from genomic clones or cDNA sequences. However, the distribution of polymorphism detected by these markers varies between different regions of the genome. Received: 5 May 1999 / Accepted: 16 August 1999     

黄顶菊的大孢子发生、雌配子体与胚胎发育

用常规石蜡制片对黄顶菊(Flaveria bidentis(L.) Kuntze)大孢子发生、雌配子体和胚胎的发育过程进行了观察.黄顶菊雌蕊柱头二裂,2心皮,1室,单胚珠,基生胎座,单珠被,薄珠心,倒生胚珠,具发达的珠被绒毡层.珠心表皮下分化出孢原细胞,孢原细胞直接发育为大孢子母细胞,大孢子母细胞减数分裂形成直列四分体...     

Genetic diversity and population structure of the Asian green mussel Perna viridis in South China Sea based on microsatellite markers

The green mussel, Perna viridis is ecologically and economically important in the coastal region of the South China Sea. Determining its population genetic structure at this fine geographic scale will help sustainable management of natural stocks. In this study, we examined the genetic diversity and population genetic structure of P. viridis from four locations in the South China Sea (n = 45–48) using nine microsatellite loci. The results showed moderate levels of genetic diversity in all four samples (mean A = 13.222–14.000, mean A_e = 7.092–7.571, mean A_r = 12.894–13.746, mean H_o = 0.596–0.656, mean H_e = 0.690–0.733) and a large effective population size estimate for the pooled sample (total N_e estimates = infinity, 95% CI = 1869.0-infinity). We did not detect any sign of recent bottleneck events in P. viridis populations in the South China Sea. The conventional and a model-based analysis reveal low, non-significant genetic divergence among the four samples (F_ST = − 0.001–0.005, P > 0.05/6). The results obtained from this study can provide valuable genetic information for the conservation and fishery management of P. viridis by retaining the high N_e estimates.     

黄顶菊小孢子发生与雄配子体发育的研究

利用常规石蜡切片技术,观察了黄顶菊小孢子发生及雄配子体发育过程.结果表明:(1)花药具4个花粉囊,花药肇发育为基本型,由4层细胞构成一表皮、药室内壁、中层和绒毡层,绒毡层属于变形型,其细胞为双核;(2)从孢原细胞出现到二细胞花粉粒形成,同一花药四个花粉囊的发育不同步;(3)孢原细胞为单孢原起源;小孢子母细胞减数分裂为连续型,形成的四分体为四而体型排列;(4)成熟花粉粒为二细胞型,三个萌发孔,花粉外壁具有明显的刺,偶尔观察到巨大花粉;(5)小孢子母细胞时期,花药壁中层毗邻绒毡层的一面产生外绒毡层膜,包被绒毡层和小孢子母细胞.     

Evaluation of the genetic diversity of Laiwu pigs using twenty-seven microsatellite markers

The Laiwu pig, an indigenous pig breed known for extremely high intramuscular fat content, is a well-preserved ancient breed due to long-term natural and artificial selections. In this study, using 27 microsatellite markers jointly recommended by the International Society of Animal Genetics (ISAG) and the Food and Agriculture Organization (FAO), we investigated the genetic diversity of the Laiwu pig breed. The genetic diversity of Laiwu pigs is dramatically low, with the observed heterozygosity ranging from 0.067 to 0.767. Among the 27 microsatellite markers, 10 were high polymorphic loci, 10 were moderate polymorphic loci, six were low polymorphic loci, and no polymorphism was detected at one locus (IGFI). Further analyses with the 10 high polymorphic loci and five moderate polymorphic loci revealed that the Laiwu pig breed was inbred and heterozygous deficient to some extent, but not severely, and that the Laiwu pigs were relatively pure, with almost no hybridization with other breeds. Two subgroups of the current 13 Laiwu pig pedigrees were identified. These results suggest that the Laiwu pig breed has a low diversity and a conservation program must be developed to preserve the “Laiwu pig” gene pool.     

Isolation of polymorphic microsatellite markers from <Emphasis Type="Italic">Przewalskia tangutica</Emphasis> (Solanaceae)

Microsatellite-containing regions were isolated and characterized in Przewalskia tangutica Maxim (Solanaceae), an endemic and endangered species to the Qinghai-Tibetan Plateau of China. An enrichment protocol yielded 200 positive clones. We designed primers to amplify 29 unique microsatellites, 12 of which amplified cleanly and were polymorphic. A survey of 17 individuals showed that these loci are highly variable with the number of alleles ranging from 3 to 12, and expected heterozygosity ranged from 0.2929 to 0.4947. Those markers will be useful for studies of population structure and intraspecific variation in P. tangutica.     

The Effects of Competition on Growth and Biomass Allocation in Nymphoides peltata (Gmel.) O. Kuntze Growing in Microcosm

Two experiments were designed to investigate the effects of competition on growth and biomass allocation in Nymphoides peltata. First, competition between N. peltata and Zizania latifolia was assigned with the densities of N. peltata to Z. latifolia ratios of 4:0, 4:2, 4:4 and 4:8. The increase of density of Z. latifolia resulted in apparent decrease of total biomass, relative growth rate (RGR), leaf area ratio (LAR) and mean leaf area per plant of N. peltata. N. peltata allocated above-ground biomass to shoots and roots and decreased the ratios of above-ground to below-ground biomass (A _b/B _b) with increasing density of Z. latifolia. Second, competitions between N. peltata and emerged Z. latifolia, floating-leavedTrapa bispinosa and submerged Myriophyllum spicatum were studied in the mean time. Total biomass, A _b/B _b and mean leaf area per plant of N. peltata were higher when competing with floating-leaved T. bispinosa than in N. peltata growing in the community with submerged M. spicatum and emerged Z. latifolia. There were no significant differences in RGR, net assimilation rate (NAR) and LAR of N. peltata when growing with each of the competitor species. Our studies indicate that the growth of N. peltata is strongly inhibited by the presence of Z. latifolia, and N. peltata can show certain competitive advantages over T. bispinosa and M. spicatum.     

Complex population genetic structure in the endemic Canary Island pine revealed using chloroplast microsatellite markers

The Canary archipelago, located on the northwestern Atlantic coast of Africa, is comprised of seven islands aligned from east to west, plus seven minor islets. All the islands were formed by volcanic eruptions and their geological history is well documented providing a historical framework to study colonization events. The Canary Island pine (Pinus canariensis C. Sm.), nowadays restricted to the westernmost Canary Islands (Gran Canaria, Tenerife, La Gomera, La Palma and El Hierro), is considered an old (Lower Cretaceous) relic from an ancient Mediterranean evolutionary centre. Twenty seven chloroplast haplotypes were found in Canary Island pine but only one of them was common to all populations. The distribution of haplotypic variation in P. canariensis suggested the colonization of western Canary Islands from a single continental source located close to the Mediterranean Basin. Present-day populations of Canary Island pine retain levels of genetic diversity equivalent to those found in Mediterranean continental pine species, Pinus pinaster and Pinus halepensis. A hierarchical analysis of variance (AMOVA) showed high differentiation among populations within islands (approximately 19%) but no differentiation among islands. Simple differentiation models such as isolation by distance or stepping-stone colonization from older to younger islands were rejected based on product-moment correlations between pairwise genetic distances and both geographic distances and population-age divergences. However, the distribution of cpSSR diversity within the islands of Tenerife and Gran Canaria pointed towards the importance of the role played by regional Pliocene and Quaternary volcanic activity and long-distance gene flow in shaping the population genetic structure of the Canary Island pine. Therefore, conservation strategies at the population level are strongly recommended for this species.Communicated by D.B. NealeA. Gómez and S.C. González-Martínez as joint authors     

Micropropagation of tea (Camellia sinensis (L.) O. Kuntze) using Thidiazuron

The effect of thidiazuron (TDZ) on the micropropagation of Camellia sinensis (China hybrid) was compared with that of benzylaminopurine (BAP) using nodal segments from in vitro raised seedlings. Extremely low concentrations of TDZ (1pM–100nM) alone were effective in inducing shoot bud proliferation and maintaining high rates of shoot multiplication on hormone-free media. On the other hand, higher concentrations of BAP (1–10M) and its continued presence were required to initiate and sustain shoot proliferation. While wider ranges of BAP combined favourably with auxins like NAA or IBA, only specific combinations of TDZ and NAA were effective for shoot proliferation. TDZ treated explants yielded healthy shoots, with sturdy leaves, even during the initial stages of growth, whereas, the effect of BAP was cumulative over subcultures in attaining a high proliferative rate.     

Isolation and characterization of microsatellite loci in Ostryopsis davidiana (Betulaceae)

Ostryopsis (Betulaceae) is a samll genus endemic to China with only two species. Both of them play an important role in restoring the local ecosystems. The distribution of genetic diversity between and within populations in each species are important to further utilize the wild genetic resources and explore the interspecific divergence. In this study, we developed 10 microsatellite loci from O. davidiana by the combining biotin capture method for the first time. A total of 27 microsatellite sequences were recovered through screening the library and 10 of them are polymorphic. The number of alleles per locus in 18 sampled individuals ranged from 3 to 6, expected heterozygosity and observed heterozygosity ranged from 0.2958 to 0.4767 and from 0.1591 to 0.2997, respectively. In addition, all markers have been crossly checked in the other congeneric species. These microsatellite markers would together provide a useful tool for investigating the genetic diversity and structure of both species and speciation mechanism between them.     

Isolation and characterization of microsatellite markers for Achyranthes bidentata (Amaranthaceae) using next-generation sequencing platform

Achyranthes bidentata Blume (Amaranthaceae) is a perennial herb that is widely distributed in India, Java, China, and Japan. The natural resources of A. bidentata in its geo-authentic product area have rapidly declined in recent years because of the over-collection of its roots. To devise adequate conservation and management strategies for this species, its genetic diversity and population structure should be characterized. Roche 454 pyrosequencing combined with magnetic bead enrichment was used to develop microsatellite markers for A. bidentata. A total of 903 microsatellite loci were identified from 42,004 individual sequence reads. One hundred microsatellite loci were selected to test the primer amplification efficiency across 16 individuals from two A. bidentata populations. Of these tested markers, 8 yielded polymorphic amplification products, 29 yielded single alleles. For polymorphic primer pairs, the number of alleles per locus ranged from 2 to 4, with an average of 2.75. The observed and expected heterozygosities ranged from 0.353 to 0.671 and 0.250 to 0.938, respectively. The inbreeding coefficient varied from −0.692 to 0.627. This set of markers will provide useful tools for examining genetic diversity and population structure, and aid in better understanding of the conservation of A. bidentata.     

Genetic diversity and population structure of Korean wild soybean (Glycine soja Sieb. and Zucc.) inferred from microsatellite markers

Korea is considered one of the centers of genetic diversity for cultivated as well as wild soybeans. Natural habitats of wild soybeans are distributed across the Korean mainland and the islands surrounding the Korean peninsula. In this study, the genetic diversity of 100 mainland Korean wild soybean accessions was evaluated by using 42 simple sequence repeat markers covering 17 soybean chromosomes. All analyzed loci were polymorphic and a total of 114 alleles were found. The observed average genetic diversity was low (0.4). The results showed that the 100 selected accessions did not exactly follow the geographical distribution. These results were further confirmed by the phylogeny inferred from five morphological characteristics (i.e., leaf shape, leaf area, plant shape, seed area, and 100-seed weight). Together, the genetic and morphological evaluations suggested conclusively that the selected population did not follow the geographical distribution pattern. The present study could provide useful information for the ex situ conservation and exploitation of wild soybean accessions in soybean improvement stratagems, and will aid in further understanding about the phylogeography of the species in the Korean center of diversity.     

Genetic diversity analysis by microsatellite markers in four captive populations of the sika deer (Cervus nippon)

The Chinese sika deer (Cervus nippon) is a rare and vulnerable animal in China for medical use. In this study, the genetic diversity and population genetic structure of 113 Chinese sika deer from 4 populations (Linyi Farm, LF; Linyi Park, LP, Yangzhou Farm, YF; Yangzhou Zoo, YZ) were investigated with 14 microsatellite loci. Eighty-three alleles were detected at the 14 loci in all populations. The expected heterozygosity ranged from 0.257 to 0.863 and the observed heterozygosity from 0.226 to 0.821. The polymorphism information content at different loci ranged from 0.217 to 0.825. The results of the HWE (Hardy–Weinberg equilibrium) tests indicated that only four loci (CEH-5, BL42, Mber70, and CEH-2) were in HWE (P > 0.01). The mean number of alleles per population ranged from 3.21 to 5.64, observed and expected heterozygosities ranged from 0.568 to 0.685, respectively. Positive inbreeding coefficient (F_IS) values were found in every population. F_ST values ranged from 0.101 in the LF to 0.155 in the YZ. The genetic identity ranged from 0.1236 to 0.1645. The genetic distance ranged from 0.4746 to 0.6025. The results of this study indicate moderate genetic variation and polymorphism across the loci. Appropriate breeding strategies should be designed for deer in captivity.     

Genetic diversity estimation and core collection construction of Sinojackia huangmeiensis based on novel microsatellite markers

Sinojackia huangmeiensis is a critically endangered tree species in the Styracaceae endemic to China. To create tools to better evaluate the genetic diversity of this species, we used a modified genomic library enrichment method, the PETUER (Probe Extension and TEACl Universal EnRichment) method, to develop genetic markers. The resulting 18 microsatellite loci had high polymorphism with 3–12 alleles per locus and showed negligible stutter. Observed (H_O) heterozygosities were 0.057–0.724, and polymorphism information content (PIC) was 0.109–0.794. No significant linkage disequilibrium between pairs of loci was found. All 123 individuals found in the National Natural Reserve of Longgan Lake was genotyped at the 18 loci and used to estimate a UPGMA dendrogram. Using an iterative clustering method, a set of 18 individuals was established as a core collection to represent genetic diversity and would be useful to facilitate the conservation for S. huangmeiensis. In addition, we tested the 18 loci for cross-species amplification in three other Sinojackia species and the closely related Changiostyrax dolichocarpa. These polymorphic loci will be valuable for future population genetic and phylogenetic studies of S. huangmeiensis and congeneric species, as well as in closely related Styracaceae.