An AFLP-based survey of genetic diversity and relationships of major farmed cultivars and geographically isolated wild populations of <Emphasis Type="Italic">Saccharina japonica</Emphasis> (Phaeophyta) along the northwest coasts of the Pacific

The genetic diversity and relationships of six representative cultivars and six geographically isolated wild populations of Saccharina japonica along the northwest coasts of the Pacific Ocean were investigated using AFLP markers. A total of 547 bands were generated across all samples by ten primer combinations. At the cultivar or population level, the percentage of polymorphic loci (P), gene diversity (H), and Shannon’s information index (I) was highest in Dalian population (P 59.05%; H 0.2057; I 0.3062) and lowest in Lianjiang cultivar (P 9.87%; H 0.0331; I 0.0497). At the species level, P, H, and I were 85.01%, 0.1948, and 0.3096, respectively. Unique bands were detected in all the six wild populations, with Dalian being the most. In comparison, only Yanza cultivar possessed one unique band. The G _ST value was 0.6226 and the gene flow (N _m ) was 0.1515, indicating strong genetic differentiation among cultivars and populations. Two UMPGA dendrograms were constructed based on the Dice similarity coefficients among individuals and on genetic distances among cultivars and populations, which generally revealed three major clades corresponding to three countries. Analysis of molecular variance revealed that a larger proportion (60.21%) of the total genetic variation was attributable to differences among cultivars and populations. The Mantel test suggested that genetic differentiation was positively correlated with geographic distance (r = 0.7962, P = 0.011) in the six wild populations, agreeing with the isolation by distance model. On the whole, low to moderate genetic diversity within cultivars and populations (except Dalian population) and high genetic differentiation among cultivars and populations were detected.     

A Study of Conservation Genetics in Cupressus chengiana,an Endangered Endemic of China,Using ISSR Markers

ISSR markers were used to analyze the genetic diversity and genetic structure of eight natural populations of Cupressus chengiana in China. ISSR analysis using 10 primers was carried out on 92 different samples. At the species level, 136 polymorphic loci were detected. The percentage of polymorphic bands (PPB) was 99%. Genetic diversity (H _e) was 0.3120, effective number of alleles (A _e) was 1.5236, and Shannon’s information index (I) was 0.4740. At the population level, PPB = 48%, A _e=1.2774, H _e=0.1631, and I=0.2452. Genetic differentiation (G _st) detected by Nei’s genetic diversity analysis suggested 48% occurred among populations. The partitioning of molecular variance by AMOVA analysis indicated significant genetic differentiation within populations (54%) and among populations (46%; P < 0.0003). The average number of individuals exchanged between populations per generation (N _m ) was 0.5436. Samples from the same population clustered in the same population-specific cluster, and two groups of Sichuan and Gansu populations were distinguishable. A significantly positive correlation between genetic and geographic distance was detected (r=0.6701). Human impacts were considered one of the main factors to cause the rarity of C. chengiana, and conservation strategies are suggested based on the genetic characters and field investigation, e.g., protection of wild populations, reestablishment of germplasm bank, and reintroduction of more genetic diversity.     

Genetic variation and phylogeographic history of <Emphasis Type="Italic">Picea likiangensis</Emphasis> revealed by RAPD markers

Repeated cycles of retreat and recolonization during the Quaternary ice ages are thought to have greatly influenced current species distributions and their genetic diversity. It remains unclear how this climatic oscillation has affected the distribution of genetic diversity between populations of wind-pollinated conifers in the Qinghai-Tibetan region. In this study, we investigated the within-species genetic diversity and phylogenetic relationships of Picea likiangensis, a dominant forest species in this region using polymorphic DNA (RAPD) markers. Our results suggest that this species has high overall genetic diversity, with 85.42% of loci being polymorphic and an average expected heterozygosity (H _E) of 0.239. However, there were relatively low levels of polymorphism at population levels and the differences between populations were not significant, with percentages of polymorphic bands (PPB) ranging from 46.88 to 69.76%, Nei’s gene diversity (H _E) from 0.179 to 0.289 and Shannon’s indices (Hpop) from 0.267 to 0.421. In accordance with our proposed hypothesis, a high level of genetic differentiation among populations was detected based on Nei’s genetic diversity (G _ST = 0.256) and AMOVA analysis (Phi _st = 0.236). Gene flow between populations was found to be limited (Nm = 1.4532) and far lower than reported for other conifer species with wide distribution ranges from other regions. No clusters corresponding to three morphological varieties found in the south, north and west, respectively, were detected in either UPGMA or PCO analyses. Our results suggest that this species may have had different refugia during the glacial stages in the southern region and that the northern variety may have multiple origins from these different refugia.     

A Study of Genetic Structure of Stephania yunnanensis (Menispermaceae) by DALP

Genetic diversity and genetic structure within and among ten populations of Stephania yunnanensis H. S. Lo and three populations of S. epigaea H. S. Lo from Yunnan province were evaluated by direct amplification of length polymorphism (DALP) markers. Five primer groups were screened, and a total of 287 DNA fragments were amplified, among which 266 were polymorphic, averaging 53.2 polymorphic bands per primer group in S. yunnanensis. The percentage of polymorphic bands of S. yunnanensis was 92.68% at the species level and 61.92% within the ten populations sampled. At the species level, the observed number of alleles (N _a) was 1.9268 and the effective number of alleles (N _e) was 1.5933; Nei’s gene diversity (H) was 0.3414; Shannon’s information index (I) was 0.5057. At the population level, N _a = 1.6192, N _e = 1.4001, H = 0.2298, and I = 0.3401. Total gene diversity of S. yunnanensis was 0.3419. Gene diversity within population was 0.2298, coefficient of gene differentiation was 0.3278, and estimated gene flow was 1.0254. The results indicated that the genetic differentiation was relatively higher among populations of S. yunnanensis. DALP markers were an informative and useful method for assaying genetic diversity and authenticating species of Stephania. These data could provide basic molecular evidence for establishing a reasonable strategy for protecting and exploiting the resource of S. yunnanensis.     

Microsatellite markers isolated in olive ( Olea europaea L.) are suitable for individual fingerprinting and reveal polymorphism within ancient cultivars

We have isolated and sequenced 52 microsatellites or simple sequence repeats (SSRs) from nearly 60 positive clones obtained from two ’Frantoio’ olive genomic libraries enriched in (AC/GT) and (AG/CT) repeats, respectively. The repeat-containing fragments obtained from genomic DNA restricted with Tsp509I were separated using a biotinylated probe bound to streptavidin-coated paramagnetic beads. Fragments were then cloned into lambda ZAPII vector and sequenced. Thirty of the 36 primer pairs which gave correct re-amplification in the source genome were used to assay the polymorphism of 12 olive cultivars, namely four well-known cultivars (’Coratina’, ’Frantoio’, ’Leccino’, ’Pendolino’) and eight ancient cultivars grown locally near Lake Garda (’Casaliva’, ’Favarol’, ’Fort’, ’Grignan’, ’Less’, ’Raza’, ’Rossanel’, ’Trep’). The local cultivars were each re- presented by two to four long-lived individuals. The analysis was carried out using ³³P-labelled primers and 6% polyacrylamide sequencing gels. All except two microsatellites showed polymorphism, the number of alleles varying from 1 to 5. The average genetic diversity (H) was 0.55. The power of discrimination (PD) was 0.60. All cultivars, including the local ones, were easily separated from each other. Variations in the SSR pattern were observed among individual plants of the same cultivar in four out of the eight local cultivars analysed. Several primer pairs (17%) amplified more than one locus. Received: 23 March 2001 / Accepted 17 May 2001     

Assessment of genetic diversity of pigeonpea cultivars using RAPD analysis

In our present study assessment of genetic diversity and identification of pigeonpea cultivars has been done by employing 76 random amplified polymorphic DNA (RAPD) primers. Out of 796 amplified products, 587 showed polymorphism (73.7 %) and an average of 10.47 bands were amplified per primer. Cluster analysis based on Jaccard’s similarity coefficient using UPGMA grouped all the cultivars into three clusters. The cluster I consists of 7 cultivars, cluster II of 11 cultivars in 4 sub-clusters and cluster III 4 cultivars. Two cultivars were not included in any cluster. The clustering was strongly supported by high bootstrap values. Furthermore, high values of the average heterozygosity (H_av) and marker index (MI) also indicated the efficiency of RAPD as a marker system.     

Gas exchange,chlorophyll fluorescence,and osmotic adjustment in two mango cultivars under drought stress

The responses of photosynthetic gas exchange, chlorophyll fluorescence, content of pigments, main osmolytes, and malondialdehyde (MDA) to water-withholding for 15 days and re-hydration in seedlings of two mango cultivars (Mangifera indica L. var. “Choke Anand’ and var. “Khieo Sawoei”) under 50% sunlight and full sunlight were investigated. For both cultivars, the water-witholding resulted in progressively decreases in leaf relative water content, net photosynthesis (P _n), stomatal conductance (g _s), and increases in the conversion of xanthophyll cycle pigments estimated by an index of leaf spectral reflectance (ΔPRI), carotenoid to chlorophyll ratio, non-photochemical quenching (NPQ), the contents of malondialdehyde (MDA) and compatible solutes (total soluble sugar and proline). The effect of the water stress was more pronounced in full sunlight than 50% sunlight. The maximum photochemistry efficiency measured at dawn was fairly constant during the period of the treatment for both cultivars under both light regimes. The water stress caused less pronounced inhibition of photosynthesis in “Choke Anand” than in “Khieo Sawoei” cultivar under both light regimes. After re-hydration, the recovery was relatively quicker in “Choke Anand” than in “Khieo Sawoei” cultivar. Both cultivars in both 50% and full sunlight showed complete recovery in photochemistry after 5 days of re-watering but photosynthesis did not show a complete recovery as indicated by gas exchange rates. As the results of lower NPQ, ΔPRI and osmotic adjustment in the cultivar “Khieo Sawoei” compared to the cultivar “Choke Anand”, the former cultivar was less tolerant to drought than the latter. Our study further showed that partial shading (e.g., 50% of sunlight) significantly alleviated the harmful effect of drought stress on mango cultivars but in fact stomata of seedlings grown in partial shade was more responsive to water deficit than in full light.     

Differences in the Induction of Defence Responses in Resistant and Susceptible Muskmelon Plants Infected with Colletotrichum lagenarium

Defence reactions occurring in resistant (cv. Gankezaomi) and susceptible (cv. Ganmibao) muskmelon leaves were investigated after inoculating with Colletotrichum lagenarium. Lesion restriction in resistant cultivars was associated with the accumulation of hydrogen peroxide (H₂O₂). The activity of antioxidants catalase (CAT) and peroxidase (POD) significantly increased in both cultivars after inoculation, while levels of both CAT and POD activity were significantly higher in the resistant cultivar. Ascorbate peroxidase (APX) increased in both cultivars after inoculation, and level of APX activity was significantly higher in the resistant cultivar. Glutathione reductase (GR) activity significantly increased in both cultivars following inoculation, but was higher in the resistant cultivar, resulting in higher levels of ascorbic acid (AsA) and reduced glutathione (GSH). Phenylalanine ammonia lyase (PAL) significantly increased in inoculated leaves of both cultivars, resulting in higher levels of total phenolic compounds and flavonoids. The pathogenesis‐related proteins chitinase (CHT) and β‐1, 3‐glucanase (GLU) significantly increased following inoculation with higher activity in the resistant cultivar. These findings show that resistance of muskmelon plants against C. lagenarium is associated with the rapid accumulation of H₂O₂, resulting in altered cellular redox status, accumulation of pathogenesis‐related proteins, activation of phenylpropanoid pathway to accumulation of phenolic compounds and flavonoids.     

The activity of antioxidative enzymes,contents of H<Subscript>2</Subscript>O<Subscript>2</Subscript> and of ascorbate in tomato leaves of cultivars more or less sensitive to infection with <Emphasis Type="Italic">Botrytis cinerea</Emphasis>

The aim of the present studies was to compare H₂O₂ and ascorbate contents as well as peroxidase (PO) and catalase (CAT) activities in leaves of less susceptible cultivar Perkoz and more susceptible Corindo after B. cinerea infection. Increase in H₂O₂ contents in both Perkoz and Corindo cytosol was observed, however, it appeared earlier in the less susceptible cultivar. The increase in PO activity in the cytosol fraction was observed 48 hours after infection in both cultivars but it was greater in the less susceptible Perkoz. No significant differences between the tested cultivars were observed in ascorbate peroxidase (APX) activity and in reduced and oxidated ascorbate contents. PO activity was thoroughly analyzed in the apoplast fraction. It was measured with syringaldazine (S), tetramethylbenzidine (TMB) and ferulic acid (FA)—substrates characteristic of isoenzymes involved in lignification and stiffening of a cell wall. Increase in PO activity with these substrates was observed earlier in cultivar Perkoz than in cultivar Corindo. Similarly, increase in PO activity with NADH appeared significantly earlier in cultivar Perkoz. Apoplastic PO was separated with DEAE Sepharose and two fractions binding and non-binding were obtained. Binding PO fraction was significantly more active especially with S, TMB and NADH after B. cinerea infection. The increase in the enzyme activity was mostly observed in cultivar Perkoz. Binding PO was separated by electrophoresis on acrylamide gel and revealed six enzymatic forms from which three were much more active after infection in cultivar Perkoz. The obtained results suggest that cell wall strengthening mediated by apoplast PO is a key factor responsible for different resistance of tomato cultivars Perkoz and Corindo to B. cinerea infection.     

Genetic Variation in the Endangered Endemic Species Cycas fairylakea (Cycadaceae) in China and Implications for Conservation

Cycas fairylakea is an endangered endemic species in China. Genetic diversity within and among four natural populations of this species in China was investigated using amplified fragments length polymorphism (AFLP). A moderate to low level of intraspecific genetic diversity was detected in this species (at population level: P = 39.57 %, H₀ = 0.244; at species level: P = 60.22%, H₀ = 0.356). The among-population component accounted for, respectively, 25.7 and 31.5% of the genetic variation, according to AMOVA and Shannon’s index, indicating most of the genetic variation was found between individuals within populations. All four populations have opposite pyramid age structure, and few coning individuals, which is still decreasing. Possibly because of habitat degradation and environmental pollution, plant diseases and insect pests in the populations were extremely serious, suggesting that the main factors threatening the survival of C. fairylakea populations were not genetic variation, but human activities and the breeding system of this species.     

Genetic diversity of Sinojackia dolichocarpa (Styracaceae), a species endangered and endemic to China,detected by inter-simple sequence repeat (ISSR)

Sinojackia dolichocarpa, a species endangered and endemic to China, is distributed only in the regional area of Shimen and Sangzhi in Hunan Province. Inter-simple sequence repeat (ISSR) markers were used to investigate the genetic diversity within and among the four natural populations of S. dolichocarpa. Leaf samples were collected from 84 individuals. Thirteen ISSR primers selected from 80 primers gave rise to 137 discernible DNA bands of which 100 (72.99%) were polymorphic. On average each primer gave rise to 10.5 bands including 7.7 bands with polymorphic profile. At the species level, high genetic diversity was detected (PPB: 72.99%; H_E: 0.2255; Ho: 0.3453). However, relatively low genetic diversity existed within populations. Population in Maozhuhe (MZH) exhibits the greatest level of variability (PPB: 40.38%, H_E: 0.1566, Ho: 0.2330), whereas the population in Jingguanmen (JGM) finds its own variability at the lowest level (PPB: 30.66%; H_E: 0.1078; Ho: 0.1601). A high level of genetic differentiation among populations was revealed by Nei's gene diversity statistics (45.30%), Shannon's information measure (45.24%) and analysis of molecular variance (AMOVA) (52.88%). The main factors responsible for the high level of differentiation among populations are probably related to the selfing reproductive system and the isolation of populations. The strong genetic differentiation among populations indicates that the management for the conservation of genetic variability in S. dolichocarpa should aim to preserve every population.     

AFLP Analysis of Genetic Diversity of the Endangered Species Sinopodophyllum hexandrum in the Tibetan Region of Sichuan Province,China

Amplified fragment length polymorphism (AFLP) markers were used to estimate the genetic diversity of seven wild populations of Sinopodophyllum hexandrum (Royle) Ying from the Tibetan region of Sichuan Province, China. Six primer combinations generated a total of 428 discernible DNA fragments, of which 111 were polymorphic. The percentage of polymorphic bands (PPB) was 25.93 at the species level, and PPB within population ranged from 4.91 to 12.38%. Genetic diversity (H _E) within populations varied from 0.01 to 0.04, averaging 0.05 at the species level. As revealed by the results of AMOVA analysis, 58.8% of the genetic differentiation occurred between populations, and 41.2% within populations. The genetic differentiation was, perhaps, due to the limited gene flow (N _m=0.43) of the species. The correlation coefficient (r) between genetic and geographical distance using Mantel's test for all populations was 0.698 (P=0.014). The UPGMA cluster analysis revealed a similar result in that the genetic distances among the populations show, to a certain extent, a spatial pattern corresponding to their geographic locations. On the basis of the genetic and ecological information, we propose some appropriate strategies for conserving the endangered S. hexandrum in this region.     

Genetic diversity of Astragalus nitidiflorus, a critically endangered endemic of SE Spain,and implications for its conservation

Inter-simple sequence repeats (ISSR) markers were used to assess the genetic diversity and population structure in five populations of Astragalus nitidiflorus, a critically endangered species endemic to southeast Spain. Eight primers amplified 78 bands with 40 (51.3%) being polymorphic. Statistical results indicated a low genetic diversity at the population and species level, with percentages of polymorphic bands (PPB) ranging from 28.2 to 37.2% (an average of 31.8%), and means of gene diversity (H_E) of 0.129 and 0.171 respectively. The Shannon’s index (SI) ranged from 0.160 to 0.214 at the population level and was 0.260 at the species level. A low level of genetic differentiation among populations was detected, based on the Shannon’s information index (0.297), the coefficient of genetic differentiation between populations (G_ST = 0.2418) and AMOVA analysis (Φ_ST = 0.255). The estimated gene flow (Nm) was 0.789. The high genetic connectivity found among populations of A. nitidiflorus is an evidence of a recent habitat fragmentation. In addition, a bottleneck event in the past has been revealed, with a subsequent reduction of population size and a loss of genetic variation. Based on these results, the conservation strategy of A. nitidiflorus was proposed.     

Genetic Relationships of Ornamental Cultivars of Ginkgo biloba Analyzed by AFLP Techniques

Eight primer combinations that produced clear and a large number of polymorphic bands were screened from 64 EcoR I/Mse I primer combinations (Mse I fluorescent labeled). The genetic relationships of 21 ornamental cultivars of Ginkgo biloba L. from the United States of America, Holland, Japan, France, and China were analyzed. These primer combinations produced a total of 1 119 bands, 229 specific loci (including 54 absent bands, and 175 monomorphic bands). Among them, 983 polymorphic bands (PPB), accounting for 88%, were detected. The percentage of identification per primer combination was as high as 100%. The average PPB of 14 foreign cultivars was 35.86% and the average PPB of seven domestic cultivars was 31.51%. Genetic similarity coefficient (SC) among all cultivars varied from 0.4899 to 0.8499, and all cultivars were divided into the four clusters when SC was set at 0.7300. The cultivars from the same origin did not fall into the same group. The cultivars from France and China were classified into three groups. According to the comprehensive analyses based on specific loci, similarity coefficient, and clustering results, eight cultivars ‘Fastigiata’, ‘Tit’, ‘Tubifolia’, ‘Daeryinxing’, ‘Variegata’, ‘Horizontalis, ‘Pendula’, and ‘Yiyuanyeziyinxing’ were considered to be important germplasms of ornamental cultivars of Ginkgo biloba.     

Determination of the population genetic structure of the invasive weed <Emphasis Type="Italic">Ageratina adenophora</Emphasis> using ISSR-PCR markers

A genetic analysis of nuclear DNA was performed by inter-simple sequence repeat-polymerase chain reaction (ISSR-PCR) technique on 32 populations of Ageratina adenophora, an invasive triploid weed in China. Among the 100 ISSR markers detected, 12 showed genetic variation both within and among the populations. Among the 446 amplified bands, 93.5% were found polymorphic. Most individuals (99%) displayed a unique ISSR fingerprint pattern, which yielded a high level of polymorphism (P _o = 93.5%) and genetic diversity (Nei’s H _T = 0.2354). The estimates of population variation, based on ISSR-PCR, were high, as measured by the analysis of molecular variance (AMOVA, F _ST = 0.3140), the Wright’s F-statistics (G _ST = 0.3453), and the Shannon’s information index (H _sp = 0.3716). AMOVA revealed 68.6% genetic variation within the populations and 91.2% within the provinces. The Mantel test showed that genetic distance was significantly correlated with geographic distance. Published in Russian in Fiziologiya Rastenii, 2009, Vol. 56, No. 3, pp. 453–459. This text was submitted by the authors in English.     

S-genotyping of old apple cultivars from the Carpathian basin: methodological, breeding and evolutionary aspects

Apple exhibits self-incompatibility controlled by the multiallelic S-locus. Twenty-three old apple cultivars were S-genotyped using three different approaches (allele-specific polymerase chain reaction (PCR) + cleaved amplified polymorphic sequences (CAPS), consensus PCR + sequencing and consensus PCR + CAPS) to compare the robustness and reliability of these techniques and characterise genotypes from the Carpathian basin that might be useful in resistance breeding. Best results were obtained using the ASPF3 and ASPR3S consensus primer pair that detected 96% of all alleles carried by the 23 cultivars tested. Flow cytometry analysis was also needed to control the completeness of the genotypes as was seen in case of a tetraploid cultivar with only three assigned S-alleles. The genetic disparity between the old Carpathian basin and modern apple cultivars was indicated by differences in allele frequency data (S ₉, S ₂₄ and S ₂₆) as well as single nucleotide polymorphisms in S ₁, S ₂, S ₇ S ₂₄ and S ₂₆ and indels in S ₂₀ and S ₂₆ alleles. An alignment of partial genomic sequences indicated trans-specific and trans-generic evolution of S-ribonuclease alleles in the Maloideae subfamily (S ₂₆ and S ₂₈) and a possibly recent introgression event (S ₁) between Malus × domestica and Malus sylvestris. These data suggest that the genome of old cultivars from the Carpathian basin was enriched by several Malus taxa and are free from the consequences of modern breeding. These cultivars may contribute to the widening of the genetic basis of cultivated apple and prevent genetic erosion in future commercial cultivars.     

Drought-induced oxidative damage and antioxidant responses in peanut (<Emphasis Type="Italic">Arachis</Emphasis><Emphasis Type="Italic">hypogaea</Emphasis> L.) seedlings

Two cultivars of peanut (Arachis hypogaea L.) which were designated as resistant (Florispan) and sensitive (Gazipasa) according to their growth retardation under drought stress conditions were compared for their oxidative damage and antioxidant responses. Sixteen days-old peanut seedlings were subjected to PEG-6000 solutions of two different osmotic potentials; −0.4 and −0.8 MPa, and various growth parameters, photosystem II activity, changes in malondialdehyde (MDA), hydrogen peroxide (H₂O₂) and proline levels, activities of ascorbate peroxidase (APX), catalase (CAT), peroxidase (POX) and gluthatione reductase (GR) enzymes were determined. Both cultivars exhibited water deficit at −0.8 MPa osmotic potential of PEG-6000 and H₂O₂ levels significantly increased during exposure to −0.4 MPa osmotic potential. However, H₂O₂ levels were under control in both cultivars at exposure to −0.8 MPa osmotic potential. Significant proline accumulation was observed in the tissues of cv. Florispan at −0.8 MPa osmotic potential, whereas proline accumulation did not appear to be an essential part of the protection mechanism against drought in cv. Gazipasa. No significant variation in chlorophyll fluorescence values were detected in neither of the cultivars. Enzyme activity measurements revealed that Gazipasa copes well with lesser magnitudes of drought stress by increasing the activity of mainly APX, and during harsh stress conditions, only APX maintains its activity in the tissues. In cultivar Florispan, GR activity appears to take role in lesser magnitudes of drought stress, whereas CAT and APX activities appear to be very crucial antioxidative defenses during intense stress conditions. The results indicate that, the level of proline and activities of the enzymes CAT and APX are important mechanisms for the maintenance of drought tolerance in peanut plants.     

Isolation and characterization of 11 microsatellite loci from Camellia sinensis in Taiwan using PCR-based isolation of microsatellite arrays (PIMA)

We report 11 novel microsatellite primer pairs for the wild tea, Camellia sinensis (L.) O. Kuntze forma formosensis Kitamura. These simple sequence repeat markers were tested in 24 samples collected from wild tea populations, and in cultivars and C. japonica. The number of alleles ranged from 4 to18. The expected (H _E) and observed (H _O) heterozygosity were 0.687–0.946 and 0.042–0.792, respectively. All loci were significantly deviated from Hardy-Weinberg expectations due to the heterozygote deficiency, indicating a dramatic loss of genetic polymorphisms in the rare species. Significant LD was discovered in most loci. These primers may provide a tool for understanding demography and population structure in wild tea.     

AFLP analysis of nephthytis (Syngonium podophyllum Schott) selected from somaclonal variants

This study analyzed genetic differences of 19 cultivars selected from somaclonal variants of Syngonium podophyllum Schott along with their parents as well as seven additional Syngonium species and six other aroids using amplified fragment length polymorphism (AFLP) markers generated by 12 primer sets. Among the 19 somaclonal cultivars, ‘Pink Allusion’ was selected from ‘White Butterfly’. Tissue culture of ‘Pink Allusion’ through organogenesis resulted in the development of 13 additional cultivars. Self-pollination of ‘Pink Allusion’ obtained a cultivar, ‘Regina Red Allusion’, and tissue culture propagation of ‘Regina Red Allusion’ led to the release of five other cultivars. The 12 primer sets generated a total of 1,583 scorable fragments from all accessions, of which 1,284 were polymorphic (81.9%). The percentages of polymorphic fragments within ‘White Butterfly’ and ‘Regina Red Allusion’ groups, however, were only 1.2% and 0.4%, respectively. Jaccard's similarity coefficients among somaclonal cultivars derived from ‘White Butterfly’ and ‘Regina Red Allusion’, on average, were 0.98 and 0.99, respectively. Seven out of the 15 cultivars from the ‘White Butterfly’ group and three out of six from the ‘Regina Red Allusion’ group were clearly distinguished by AFLP analysis as unique fragments were associated with respective cultivars. The unsuccessful attempt to distinguish the remaining eight cultivars from the ‘White Butterfly’ group and three from the ‘Regina Red Allusion’ group was not attributed to experimental errors or the number of primer sets used; rather it is hypothesized to be caused by DNA methylation and/or some rare mutations. This study also calls for increased genetic diversity of cultivated Syngonium as they are largely derived from somaclonal variants.     

UV-irradiation mutation of tetraspores of Gracilariopsis lemaneiformis and screening of thermotolerant strains

The rhodophyte Gracilariopsis lemaneiformis is one of the most economically important marine algae in China. In order to extend the cultivation period and enlarge the cultivation area, mutagenic breeding was used in this study for screening strains with thermal tolerance. The tetraspores were mutated by UV irradiation, and then thermotolerant strains were screened by exposing developing tetraspores to a range of higher temperatures. Two heat-tolerant mutants, MT-17 and MT-18, were obtained and physiologically compared with cultivar 981 and the wild strains. The results demonstrated that the two mutants grew at significantly higher rates than wild strains and similar to that of cultivar 981 both in the laboratory and the sea. The malondialdehyde contents in MT-17 and MT-18 were all significantly lower than the wild-type after 3-day heat stress, and that in MT-18 was lower than cultivar 981. The superoxide dismutase activities of MT-17 and MT-18 were significantly higher than the wild-type, and those of MT-18 and cultivar 981 were at the same level all through the treatment. The heat shock protein 70 gene expressions of two mutants was higher than the wild-type and that of MT-18 remained at the same level as that of cultivar 981 after 4 h heat shock. All these indicate that the two mutants were more tolerant to high temperature than the wild-type. RSAP (restriction site amplified polymorphism) analysis indicated the genetic background of the two mutants may be changed. The mutagenesis and selection process may help to develop heat-tolerant G. lemaneiformis cultivars in the future.