Intergeneric Somatic Hybrid Plants Between Citrus and Poncirus trifoliata and Evaluation of Their Root Rot Resistance

Protoplasts of Page tangelo (Citrus reticulata Blanco×C. paradisi Macf.) cell suspension culture were electrically fused with mesophyll protoplasts isolated from trifoliate orange (Poncirus trifoliata (L.) Raf.). More than 150 plantlets regenerated after 4-5 months of culture. The regenerated plants were trifoliate with well developed root systems. Root_tip chromosome counting of more than 20 randomly selected plants revealed that they were all tetraploids (2n=4x=36). RAPD analysis of 7 randomly selected plants verified their hybridity. Inoculation of citrus Phytophthora parasitica Dastar toxin on leaves of somatic hybrids and both parental genotypes showed that Page tangelo was moderately susceptible, and trifoliate orange was highly resistant while the somatic hybrids were resistant. The potential of this somatic hybrid as rootstock is also discussed.

Genetic diversity analysis of Penicillium marneffei isolated from AIDS patients in Guangdong, China using randomly amplified polymorphic DNA

Background Penicillium mameffei （P. marneffe~） is an emerging pathogenic fungus that can cause invasive mycosis in patients with AIDS. The epidemiological features of P. marneffeiinfection in AIDS patients in Guangdong province remain unclear so far. This study aimed to investigate the genetic diversity within a population of 163 P. mameffei isolates obtained from AIDS patients and search for the dominant clinical strains in Guanqdong province.

Genetic Diversity Caused by Environmental Stress in Natural Populations of Niupidujuan as Revealed by RAPD Technique

Multiplex environmental factors are generally expected to have significant effects on genetic diversity of plant populations.In this study,randomly amplified polymorphic DNA（RAPD） technique was used to reveal the genetic diversity in the same species of four populations collected from Niupidujuan（Rhododendron chrysanthum） at different altitudes,an endangered species,endemic to Northeast China.Initially,twenty informative and reproducible primers were chosen for final RAPD analysis.A total of 152 clear bands were obtained,including 143 polymorphic ones.With the help of POPGENE software,the poly rate was calculated to be 94.07% and the evenness of amplified bands for every primer was 6.8.Additionally,the mean observed number of alleles was 1.7265 with an effective number of 1.3608.An examination of the gene indicated a diversity of 0.2162 with an information diversity index of 0.3313.For these data,the clustering blurred analysis was performed with the aid of NTSYS-pc software to define the Nei＇s gene diversity and the Shannon information diversity index of the four plant populations.The relationships between the genetic diversity indexes on the one hand and the geographic and climatic factors on the other hand were estimated by the Pearson correlation with SPSS 11.0 software.The results of the correlation analysis show that there were significant（P〈0.05） or highly significant（P〈0.01） correlations between each of the genetic diversity indexes and the different temperature which were mainly caused by the altitude different populations located.These data highlight the importance of native populations in shaping the spatial genetic structure in Niupidujuan.

Genetic diversity and differentiation of pedunculate ( Quercus robur ) and sessile ( Q. petraea ) oaks

This study was conducted to determine the parent-off spring genetic structure of the pedunculate oak(Quercus robur L.),sessile oak(Q.petraea[Matt.]Liebl.)and their hybrids.Forty half-sib Quercus families and their maternal trees originating from one tree stand in southern Lithuania were analyzed using SSR and RAPD markers.Based on a preliminary study of leaf morphological traits,the individuals separated into six groups.The studied halfsib oak families were also compared for allelic diversity,including group variations;genotypic structure;genetic diversity;and the degree of genetic subdivision and diff erentiation.The level of genetic variation and subdivision was lower in the hybrid families than in the families of the parental species.Genotypic analysis of the half-sibling off spring showed the asymmetric nature of interspecifi c hybridization processes of pedunculate and sessile oaks in mixed stands.

RAPD Technique Used to Determine the Purity of Hybrid Hot Pepper Seeds

Two hybrid hot pepper varieties Xiangyan 5 and Xiangyan 10, and their parents were analyzed the polymerase chain reaction with MJ /PT 200 Peltrier Themal Cycler and DS 800 White-ultravilot Transilluminator to set up a RAPD system adaptable to the purity determination of the hy-brid seeds. Among the 39 random primers, 2 and 4 primers were found to be used effectively in Xiangyan 5 and Xiangyan 10 respectively.

Molecular characterization of Acidithiobacillus ferrooxidans strains isolated from different environments by three PCR-based methods

PCR-based DNA fingerprinting, REP-PCR(repetitive element PCR), RAPD(randomly amplified polymorphic DNA) and16 S r DNA sequence analyses were used to characterize 23 Acidithiobacillus ferrooxidans strains isolated from different environments.(GTG)5 and BOXA1 R primer were selected for REP-PCR. Twenty arbitrary primers were used for RAPD to acquire DNA profiles from A. ferrooxidans. Both RAPD and REP-PCR produce complex banding patterns and show good discriminatory ability in differentiating closely related strains of A. ferrooxidans. The strains are clustered into 4 or 5 major groups and reveal genomic diversity using(GTG)5-PCR, BOX-PCR and RAPD analysis. Phylogenetic tree based on 16 S r DNA sequences of 23 strains and related strains shows that they are clustered into two distinct groups. Twelve strains are highly related to a new Acidithiobacillus named Acidithiobacillus ferrivorans. The results indicate that PCR-based methods are effective in revealing genetic diversity among A. ferrooxidans.

Genetic Diversity and Pathogenicity Variation in Rhizoctonia solani Isolates from Rice in Sichuan Province, China

Fifty-five representative samples of Rhizoctonia solani isolates, which were collected and isolated from five different ecological regions in Sichuan Province, China, were purified and analyzed for the pathogenicity and molecular genetic variation. The hyphal fusion test revealed that almost all the isolates belonged to the AG-IIA group except the isolate D42. In addition, some of the isolates were ＇bridging isolates＇, which could fuse with several groups simultaneously. The pathogenicity analysis on in vitro leaves confirmed a significant pathogenicity variation in the tested isolates. The 55 isolates were then classified into 8 groups by further RAPD （randomly amplified polymorphic DNA） cluster analysis at the similarity coefficient of 0.941. The results suggest that under the certain ecological conditions in Sichuan Province, China, most of the R. solanistrains were genetically stable, but a few changed drastically.

Application of Molecular Marker Technology in the Study of Forest Tree Species

Due to its unique advantages, molecular marker technology is widely applied in the research of forest tree species. This paper reviewed the application of molecular marker technology in tree species resource diversity, germplasm identification, genetic map construction, gene mapping and marker-assisted selection (MAS) breeding. In addition, it elaborated the great significance of molecular marker technology to promote the sustainable development of forestry production in China.

Genetic differentiation of Arthrobacter population from heavy metal-contaminated environment

Six samples containing extremely high concen-tration of Pb,Zn,and Cd were obtained from the layers of 5−10 cm and 25−30 cm three tailing piles,with ages of about 10,20 and more than 80 years,respectively.Then,48 bacterial strains were obtained from these samples,and sub-sequently their phylogenetic positions were determined by analysis on the partial sequence of 16S rRNA gene(fragment length ranging from 474 to 708 bp).These isolates were members of the Arthrobacter genus,phylogenetically close to A.keyseri and A.ureafaciens,with sequence ranging from 99.1%to 100%.Furthermore,genetic variation between sub-populations from different samples was revealed by analysis on their randomly amplified polymorphic DNA profile.Nei genetic distance showed that the greatest differentiation occurred between subpopulation A and C.Notably,either genetic distance between subpopulations from the layers of 5−10 cm and 25−30 cm of each tailing pile or between same layers of different tailing pile increased with the history of tailings.Moreover,correlation analysis showed that soluble Pb has a significantly negative relationship with Nei’gene diversity of subpopulation.It was assumed that soluble Pb may be respon-sible for the reduced genetic diversity of the Arthrobacter popu-lation.Our data provided evidence that genetic differentiation of microbial populations was consistent with the changes of environmental factors,particularly heavy metals.

Genetic structure and differentiation of Psathyrostachys huashanica populations detected with RAPD markers

Psathyrostachys huashanica Keng is a perennial grass and belongs to genus Psathyrostachys under Triticeae.sathyrostachys is found in the center of Middle Asia and the Caucasus Mountain,while P.huashanica,a species endemic to China,is only located in Mt.Hua in the Shaanxi province,China.At present,the population of this species is decreasing,and reaching the edge of extinction.Due to the limitation in distribution and the importance as breeding material for germplasm storage,it has been considered as first class among the national protected rare plants.For this reason,the present study is significant in probing plant flora,origin and evolu-tion of Triticeae,and crop breeding.Randomly amplified polymorphic DNA(RAPD)markers were used to analyze the genetic structure and differentiation of P.huashanica popula-tions sampled in three valleys(Huangpu,Xian,and Huashan Valleys)in Mt.Hua.One hundred and twenty-two RAPD fragments were obtained in all 266 individuals with 20 prim-ers with a mean of 6.1(2-10)fragments per primer.The percentage of polymorphic loci(PPB)was 60.66%in Huangpu Valley,90.98%in Xian Valley,95.08%in Huashan Valley,and the total PPB was 95.08%,which indicated a highly genetic variability of P.huashanica.The Shannon’s Information index and GST were 0.3306 and 0.3263,respectively,indicating that there were more genetic variations within the subpopulations than those among the subpopulations.The gene flow among the subpopulations of P.huashanica(Nm=1.0322)was much less than that of the common ane-mophytes(Nm=5.24).Mean genetic distance is 0.1571(range:0.0022-0.2901).The highest value of genetic distance was found between the subpopulation(hp1)of Huangpu Valley and the highest altitude subpopulation(h8)of Huashan Valley.Correlation analysis detected significant correlation between genetic distance and vertical distance of altitude.Clustering analysis and principal coordinate analysis revealed the genetic differentiation among the populations of P.huashanica.Differentiation mainly occurred between the higher altitude subpopulations and the lower altitude sub-populations,suggesting that altitude might be the major factor that restricted the gene flow between different altitude subpopulations and resulted in differentiation of subpopulations.