Genome-wide SNP markers provided insights into the reproductive strategy and genetic diversity of the green tide causative species Ulva prolifera in China

Ulva prolifera is the causative species of the annually occurring large-scale green tides in China since 2007.Its specific biological features on reproductivity strategies,as well as intra-species genetic diversity,are still largely unknown,especially at the genome level,despite their importance in understanding the formation and outbreak of massive green tides.In the present study,the restriction site-associated DNA genotyping approach(2b-RAD)was adopted to identify the genome-wide single-nucleotide polymorphisms(SNPs)of 54 individual thalli including samples collected from Subei Shoal in 2019 and Qingdao coast from 2019 to 2021.SNPs genotype results revealed that most of the thalli in 2019 and 2020 were haploid gametophytes,while only half of the thalli were gametophytes in 2021,indicating flexibility in the reproductive strategies for the formation of the green tides among different years and the dominance of asexual and vegetative reproductive mode for the floating period.Besides,population analysis was conducted,and it revealed a very low genetic diversity among samples from Subei Shoal and the Qingdao coast in the same year and a higher divergence among samples in different years.The results showed the efficiency of 2b-RAD in the exploration of SNPs in U.prolifera and provided the first genome-wide scale evidence for the origin of the large-scale green tides on the Qingdao coast.This study improved our understanding of the reproductive strategy and genetic diversity of the green tide causative species and will help further reveal the biological causes of the green tide in China.

Epidemiological Surveillance: Genetic Diversity of Rotavirus Group A in the Pearl River Delta, Guangdong, China in 2019

Objective This study aimed to understand the epidemic status and phylogenetic relationships of rotavirus group A(RVA)in the Pearl River Delta region of Guangdong Province,China.Methods This study included individuals aged 28 days–85 years.A total of 706 stool samples from patients with acute gastroenteritis collected between January 2019 and January 2020 were analyzed for 17 causative pathogens,including RVA,using a Gastrointestinal Pathogen Panel,followed by genotyping,virus isolation,and complete sequencing to assess the genetic diversity of RVA.Results The overall RVA infection rate was 14.59%(103/706),with an irregular epidemiological pattern.The proportion of co-infection with RVA and other pathogens was 39.81%(41/103).Acute gastroenteritis is highly prevalent in young children aged 0–1 year,and RVA is the key pathogen circulating in patients 6–10 months of age with diarrhea.G9P[8](58.25%,60/103)was found to be the predominant genotype in the RVA strains,and the 41 RVA-positive strains that were successfully sequenced belonged to three different RVA genotypes in the phylogenetic analysis.Recombination analysis showed that gene reassortment events,selection pressure,codon usage bias,gene polymorphism,and post-translational modifications(PTMs)occurred in the G9P[8]and G3P[8]strains.Conclusion This study provides molecular evidence of RVA prevalence in the Pearl River Delta region of China,further enriching the existing information on its genetics and evolutionary characteristics and suggesting the emergence of genetic diversity.Strengthening the surveillance of genotypic changes and gene reassortment in RVA strains is essential for further research and a better understanding of strain variations for further vaccine development.

Genetic diversity of the S-type small subunit ribosomal RNA gene of Plasmodium knowlesi isolates from Sabah,Malaysian Borneo and Peninsular Malaysia

Objective:To determine the genetic diversity of Plasmodium(P.)knowlesi isolates from Sabah,Malaysian Borneo and Peninsular Malaysia,targeting the S-type SSU rRNA gene and including aspects of natural selection and haplotype.Methods:Thirty-nine blood samples infected with P.knowlesi were collected in Sabah,Malaysian Borneo and Peninsular Malaysia.The S-type SSU rRNA gene was amplified using polymerase chain reaction,cloned into a vector,and sequenced.The natural selection and haplotype of the S-type SSU rRNA gene sequences were determined using DnaSP v6 and illustrated using NETWORK v10.This study's 39 S-type SSU rRNA sequences and eight sequences from the Genbank database were subjected to phylogenetic analysis using MEGA 11.Results:Overall,the phylogenetic analysis showed no evidence of a geographical cluster of P.knowlesi isolates from different areas in Malaysia based on the S-type SSU rRNA gene sequences.The S-type SSU rRNA gene sequences were relatively conserved and with a purifying effect.Haplotype sharing of the S-type SSU rRNA gene was observed between the P.knowlesi isolates in Sabah,Malaysian Borneo,but not between Sabah,Malaysian Borneo and Peninsular Malaysia.Conclusions:This study suggests that the S-type SSU rRNA gene of P.knowlesi isolates in Sabah,Malaysian Borneo,and Peninsular Malaysia has fewer polymorphic sites,representing the conservation of the gene.These features make the S-type SSU rRNA gene suitable for comparative studies,such as determining the evolutionary relationships and common ancestry among P.knowlesi species.

Genetic Diversity of Jute Mallow (Corchorus spp.) Accessions Based on ISSR Markers

Jute mallow is a nutritious leafy vegetable. The leaves are rich in proteins, vitamins and essential amino acids. Molecular characterization of Jute mallow with focus on improvement of leaf yield is scarcely reported. In the present study, inter sequence simple repeats (ISSR) molecular markers were employed to assess genetic diversity and relationships of 83 accessions of Jute mallow from different parts of Africa and Asia conserved at the World Vegetable Center East and Southern Africa. A total of 89 bands were amplified by 8 ISSR primers. Number of polymorphic bands per primer ranged from 2 to 6 with an average of 2.75 bands per primer. Polymorphic information content (PIC) values ranged from 0.390 to 0.760 with average of 0.53. Average Nei’s gene diversity (h) and Shannon’s information index (I) were 0.335 and 0.494 respectively. The highest pairwise genetic distance was 0.431 observed in a population from East Africa accessions. PC1 and PC2 axis explained 21.69% and 11.66% of the total variation respectively. UPGMA cluster analysis grouped the accessions into six main clusters at genetic similarity coefficient of 0.53 as standard value for classification. These results have important implications for jute mallow breeding and conservation.

Genetic diversity and occult hepatitis B infection in Africa: A comprehensive review

BACKGROUND Occult hepatitis B infection(OBI)is a globally prevalent infection,with its frequency being influenced by the prevalence of hepatitis B virus(HBV)infection in a particular geographic region,including Africa.OBI can be transmitted th-rough blood transfusions and organ transplants and has been linked to the development of hepatocellular carcinoma(HCC).The associated HBV genotype influences the infection.AIM To highlight the genetic diversity and prevalence of OBI in Africa.METHODS This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and involved a comprehensive search on PubMed,Google Scholar,Science Direct,and African Journals Online for published studies on the prevalence and genetic diversity of OBI in Africa.RESULTS The synthesis included 83 articles,revealing that the prevalence of OBI varied between countries and population groups,with the highest prevalence being 90.9%in patients with hepatitis C virus infection and 38%in blood donors,indicating an increased risk of HBV transmission through blood transfusions.Cases of OBI reactivation have been reported following chemotherapy.Genotype D is the predominant,followed by genotypes A and E.CONCLUSION This review highlights the prevalence of OBI in Africa,which varies across countries and population groups.The study also demonstrates that genotype D is the most prevalent.

Genetic Diversity in Cowpea (Vigna unguiculata (L.) Walp) under Two Growing Conditions*

This study explores the use of genetic variability for advancing the genetic improvement of Cowpea (Vigna unguiculata (L.) Walp), particularly in response to insect infestation stress. Over a period spanning 2015 to 2017, forty accessions of cowpeas were evaluated to determine their variability under both insecticide spray and no insecticide spray conditions at the Teachings and Research Farms, Federal University of Agriculture, Abeokuta. The experimental design was a randomized complete block design in three replicates. The accessions were evaluated for plant height, leaf length, leaf width, number of days of 50% flowering, number of pods per plant, pod length, number of seeds per plant, 100-seed weight, and seed yield. Data collected were subjected to principal component and single linkage cluster analyses. Principal axis I (PCA1) accounted for 39% and 35% under insecticide spray and no insecticide spray respectively to the total variation in the accessions. Plant height with a factor score of 0.38, leaf length (0.41), number of leaves (0.37), and 100-seed, weight (0.30) was related to PCAI under insecticide spray while leaf width (0.32). Pod length (0.37) and number of seeds/plant (0.38) were significant to PCA1 under no insecticide spray. Notably, accessions such as SAMPEA6, SAMPEA10, IFE-Brown, and IFE-BPE exhibited consistent performance across both conditions, while others displayed condition-specific attributes. For instance, NGB1063, NGB1152, and NGB1093 demonstrated distinct traits under insecticide spray, while NGB1146 and NGB1124 exhibited notable characteristics under no insecticide spray conditions. Therefore, identifying these forty accessions with desirable traits hold promise for future genetic improvement efforts of cowpea cultivation in Nigeria and beyond.

Core collection construction of tea plant germplasm in Anhui Province based on genetic diversity analysis using simple sequence repeat markers

The tea plant[Camellia sinensis(L.)O.Kuntze]is an industrial crop in China.The Anhui Province has a long history of tea cultivation and has a large resource of tea germplasm with abundant genetic diversity.To reduce the cost of conservation and utilization of germplasm resources,a core collection needs to be constructed.To this end,573 representative tea accessions were collected from six major tea-producing areas in Anhui Province.Based on 60 pairs of simple sequence repeat(SSR)markers,phylogenetic relationships,population structure and principal coordinate analysis(PCoA)were conducted.Phylogenetic analysis indicated that the 573 tea individuals clustered into five groups were related to geographical location and were consistent with the results of the PCoA.Finally,we constructed a core collection consisting of 115 tea individuals,accounting for 20%of the whole collection.The 115 core collections were considered to have a 90.9%retention rate for the observed number of alleles(Na),and Shannon’s information index(I)of the core and whole collections were highly consistent.Of these,39 individuals were preserved in the Huangshan area,accounting for 33.9%of the core collection,while only 10 individuals were reserved in the Jinzhai County,accounting for 8.9%of the core set.PCoA of the accessions in the tea plant core collection exhibited a pattern nearly identical to that of the accessions in the entire collection,further supporting the broad representation of the core germplasm in Anhui Province.The results demonstrated that the core collection could represent the genetic diversity of the original collection.Our present work is valuable for the high-efficiency conservation and utilization of tea plant germplasms in Anhui Province.

Analysis of genetic diversity and prediction of Larix species distribution in the Qinghai–Tibet Plateau,China

Larix resources in the Qinghai-Tibet Plateau have important ecological and economic values.However,the lack of genetic diversity background and related research hinders the development of conservation strategies.In this study,genetic diversity and distribution of fi ve Larix species were investigated.Using 19 polymorphic microsatellite markers to study 272 representative individuals from 13 populations,the results show low genetic diversity at the population level,with variation explained mainly by diff erentiation among populations.The Larix populations were classifi ed into two clades,one formed by eight populations,including three of the species in this study,L.kongboensis,L.speciosa,and L.potaninii var.australis.The other clade consists of fi ve populations,including the other two species in this study,L.griffi thii and L.himalaica.Genetic distance of the species was aff ected by geographical isolation and genetic diversity was mainly aff ected by altitude.The area suitable for Larix spp.decreased during the Last Glacial Maximum compared to the current distribution according to the niche model,but should increase in future climate scenarios(2050s),expanding westward along the Himalayas.These results provide an important scientifi c basis for the development of conservation strategies and further the sustainable utilization of Larix resources in the Qinghai-Tibet Plateau.

Analysis of genetic diversity and population structure in sweetpotato using SSR markers

Sweetpotato, Ipomoea batatas(L.) Lam., is an important food crop worldwide. Large scale evaluation of sweetpotato germplasm for genetic diversity is necessary to determine the genetic relationships between them and effectively use them in the genetic improvement. In this study, the genetic diversity of 617 sweetpotato accessions, including 376landraces and 162 bred varieties from China and 79 introduced varieties from 11 other countries, was assessed using 30 simple sequence repeat(SSR) primer pairs with high polymorphism. Based on the population structure analysis,these sweetpotato accessions were divided into three groups, Group 1, Group 2 and Group 3, which included 228, 136and 253 accessions, respectively. Consistent results were obtained by phylogenic analysis and principal coordinate analysis(PCoA). Of the three groups, Group 2 showed the highest level of genetic diversity and its accessions were mainly distributed in low-latitude regions. The accessions from South China exhibited the highest level of genetic diversity, which supports the hypothesis that Fujian and Guangdong were the first regions where sweetpotato was introduced to China. Analysis of molecular variance(AMOVA) indicated significant genetic differentiations between the different groups, but low levels of genetic differentiation existed between the different origins and accession types.These results provide valuable information for the better utilization of these accessions in sweetpotato breeding.

Full-length transcriptome sequence and SSR marker development for genetic diversity research in yellowfin seabream Acanthopagrus latus

Yellowfin seabream Acanthopagrus latus is an important economic fish in Chinese coastal areas.Given its narrow distribution and overfishing,the genetic diversity of yellowfin seabream has been restricted for artificial breeding and reproduction.We performed full-length transcriptome sequencing and assembly of the genome of yellowfin seabream.A total of 68086 unigenes were obtained,with an N50 of 3391 bp on average length of 2933 bp.A total number of 50593 expressed sequence tags linked to simple sequence repeats(EST-SSR)were identified,among them dinucleotide repeats(40.6%)and AC/GT motifs(38.5%)were the most frequent.Of the 190 EST-SSRs for which PCR primer pairs were designed,150 primer pairs successfully amplified target loci and 15 SSRs showed high polymorphism.The alleles per locus ranged 6-50 on average of 25.3.The expected and observed heterozygosity varied from 0.632 to 0.969 and from 0.519 to 0.953,respectively.The polymorphic index content(PIC)values of each locus ranged 0.587-0.966 on average of 0.851.Among six yellowfin seabream population samples preliminarily tested for genetic diversity and differentiation,the Fangchenggang(FCG)population in Guangxi Province had the highest mean observed heterozygosity(H_(o))value(0.786),whereas the Zhangzhou(ZZ)population in Fujian Province had the lowest(0.678).The pairwise fixation index(Fst)values indicated significant population differentiation among six yellowfin seabream populations.This study provided evidence for the usefulness of the transcriptomic resource information and EST-SSR markers for natural resource conservation,population genetics,and breeding studies of yellowfin seabream in South China.

Pre-Breeding Genetic Diversity Assessment of Tomato(Solanum lycopersicum L.)Cultivars Based on Molecular,Morphological and Physicochemical Parameters

Appropriate knowledge of the parental cultivars is a pre-requisite for a successful breeding program.This study characterized fruit yield,quality attributes,and molecular variations of ten tomato cultivars during three consecutive generations under greenhouse conditions.Peto 86,Castle Rock,and Red Star cultivars showed the highest fruit yield(kg/plant),total phenolic compounds(TPC),and sap acidity.Principal component analysis categorized the evaluated fruit yield into three groups based on their quality attributes.A robust positive correlation appeared among traits inside each group.A positive correlation was likewise noticed between the first and the second groups.However,a negative correlation was detected between the first,the second and the third group.Molecular profiling,using seven inter-simple sequence repeat(ISSR)primers,produced 60 loci,including 49 polymorphic loci.The molecular analysis also pinpointed the highest genetic similarity(0.92)between P73 and Moneymaker,while the lowest genetic similarity(0.46)was observed between Castle Rock and Moneymaker.The cultivars P73 and Moneymaker showed the lowest genetic distance(2.24),while the highest genetic distance(5.92)was observed between Super Marmand and Peto86,on the one hand,and between Castle Rock and Moneymaker,on the other hand.The chemical analysis of fruit sap indicated the highest levels of TPC,total flavonoids,anthocyanin,ascorbic acid and total soluble solids in Peto 86 and Castle Rock cultivars.Phylogeny analysis of tomato cultivars based on morphological and molecular attributes indicated four distinct clades.Peto 86,Castle Rock,and Red star cultivars can be recommended for the tomato hybridization breeding programs in the future,with other tomato cultivars as potentially high-yielding parents.

Genetic Diversity,Population Structure,and Genome-Wide Association Study of Seven Agronomic Traits in 273 Diverse Upload Cotton Accessions

Upland cotton(Gossypium hirsutum)is the most important plant producing natural fibers for the textile industry.In this study,we first investigated the phenotypic variation of seven agronomic traits of 273 diverse cotton accessions in the years 2017 and 2018,which were from 18 geographical regions.We found large variations among the traits in different geographical regions and only half of the traits in either years 2017 or 2018 followed a normal distribution.We then genotyped the collection with 81,612 high quality SNPs.Phylogenetic tree and population structure revealed a diverse genetic structure of the core collection,and geographical diversification was an important factor,but account for part of the variances of genetic diversification.We then performed genome-wide association study for the seven traits in the years 2017 and 2018,and the average values of each trait in the two years,respectively.We identified a total of 19 significant marker-trait associations and found that Pollen Ole e 1 allergen/extension could be the candidate gene associated with the fall-off cotton bolls from the last three branches.In addition,large variations were observed for the heritability of traits in the years 2017 and 2018.These results provide new potential candidate genes for further functional validation,which could be useful for genetic improvement and breeding of new cotton cultivars with better agronomic performances.

Genetic Diversity of Ustilaginoidea virens in Heilongjiang Province

In recent years, the occurrence of rice false smut has become increasingly serious and the area of damage has expanded year by year, so the false smut has become one of the diseases which have seriously affected rice yield and quality in Heilongjiang Province. However, the genetic diversity research on false smut in Heilongjiang Province was relatively weak. In the current investigation, seven polymorphic SSR markers were taken to analyze the genetic diversity among 89 strains of the pathogens of rice false smut collected from five main rice growing areas in Heilongjiang Province, China. The results showed that the amplified bands of each pair of primers were between 2 and 7. A total of 43 bands were obtained, and each primer was expanded for 4.8 bands. The genetic similarity coefficient(GSC) between strains by using SSR molecular marker analysis showed that the GSC of the strain of Ustilaginoidea virens was 0.613-0.955, with an average of 0.741. According to the results cluster analysis, when the genetic distance was 0.73, 89 strains were divided into three groups, and five strains of rice smut strains were distributed in three populations, and strains in Harbin City were mainly distributed in group Ⅲ. In Mudanjiang City, the strains were mainly distributed in groups Ⅰ and Ⅲ, and the strains in Suihua City were mainly distributed in groups Ⅰ and Ⅱ, and the strains in Jiamusi City were evenly distributed in groups Ⅰ, Ⅱ and Ⅲ, and the strains in Qiqihar City were mainly distributed in groups Ⅱ and Ⅲ. The results showed that the genetic background of Ustilaginoidea virens in Heilongjiang Province was relatively low in complexity, and the overall inheritance of the strain was relatively stable.

Insight into Genetic Diversity of Cultivated Lima Bean (Phaseolus lunatus L.) in Benin

Lima bean is a tropical and subtropical legume from the genus Phaseolus which is cultivated for its importance in food and in medicine, but which remains a Neglected and Underutilized Crop in Benin. Understanding the genetic diversity of a species’ genetic resources is useful for the establishment of appropriate conservation strategies and breeding programs and for sustainable use. We use 6 out of ten SSR markers to analyze the diversity and population structure of 28 Lima bean landraces collected in Benin. A total of 28 alleles with an average of 4.16 alleles per SSR were amplified. The Polymorphic Information Content value ranged from 0.079 to 0.680 with an average of 0.408. The analysis of population structure revealed three subpopulations. PCoA revealed three well-separated clusters among the analyzed accessions in accordance with the population structure results and the clustering based on the Neighbor-Joining tree. AMOVA showed highly significant (p = 0.001) diversity among and within populations. Hence, 32% of the genetic variation was distributed among the population and 68% was distributed within populations. A high PhiP value (0.321) was found between the three sub-subpopulations indicating a high genetic differentiation between these sub-subpopulations. By exhibiting the highest average number of alleles, Shannon-Weaver information and Shannon-Weaver diversity indices, and the highest mean number of private alleles, subpopulation 1 is the main gene pool of the analyzed collection. The present study is an important starting point for the establishment of appropriate conservation strategies and breeding programs for Lima bean genetic resources.

Adaptive genetic diversity of dominant species contributes to species co-existence and community assembly

The synthesis of evolutionary biology and community ecology aims to understand how genetic variation within one species can shape community properties and how the ecological properties of a community can drive the evolution of a species.A rarely explored aspect is whether the interaction of genetic variation and community properties depends on the species'ecological role.Here we investigated the interactions among environmental factors,species diversity,and the within-species genetic diversity of species with different ecological roles.Using high-throughput DNA sequencing,we genotyped a canopydominant tree species,Parashorea chinensis,and an understory-abundant species,Pittosporopsis kerrii,from fifteen plots in Xishuangbanna tropical seasonal rainforest and estimated their adaptive,neutral and total genetic diversity;we also surveyed species diversity and assayed key soil nutrients.Structural equation modelling revealed that soil nitrogen availability created an opposing effect in species diversity and adaptive genetic diversity of the canopy-dominant Pa.chinensis.The increased adaptive genetic diversity of Pa.chinensis led to greater species diversity by promoting co-existence.Increased species diversity reduced the adaptive genetic diversity of the dominant understory species,Pi.kerrii,which was promoted by the adaptive genetic diversity of the canopy-dominant Pa.chinensis.However,such relationships were absent when neutral genetic diversity or total genetic diversity were used in the model.Our results demonstrated the important ecological interaction between adaptive genetic diversity and species diversity,but the pattern of the interaction depends on the identity of the species.Our results highlight the significant ecological role of dominant species in competitive interactions and regulation of community structure.

Microsatellite analysis of genetic diversity and population structure of Chinese mitten crab (Eriocheir sinensis)

Chinese mitten crab （Eriocheir sinensis） has higher commercial value as food source than any other species of Eriocheir in China. To evaluate the germplasm resources and characterize the genetic diversity and population structure of the crabs in different water systems, two stocks and two farming populations were assessed with 25 polymorphic microsallite loci available in public GenBank. Basic statistics showed that the average observed heterozygosity （Ho） amongst populations ranged from 0.5789 to 0.6824. However, a remarkable presence of inbreeding and heterozygote deficiencies were observed. To analyze population structure, pairwise FST coefficients explained only -10.3% variability from the subdivision of mitten crab populations, the remaining variability stems from the subdivision within subpopulations. Although the four populations had slight differentiation, different allelic frequencies resulted in distinct population structures. Two stocks and one farming population were clustered together to the phylogenetic branch of Yangtze crab, with an approximate membership of 95%. Whereas, another farming population was clustered singly to the phylogenetic branch of the Liaohe crab, with a membership of 97.1%. The tests for individual admixture showed that Yangtze crab had probably been contaminated with individuals from other water systems. Genetic relationships between populations also supported the conclusion that Yangtze crab and Liaohe crab had different gene pools in spite of the origins of the same species.

AFLP analysis revealed differences in genetic diversity of four natural populations of Manila clam (Ruditapes philippinarum) in China

The amplified fragment length polymorphism （AFLP） technology was used to analyze the genetic diversities in four natural populations of Manila clam （ Ruditapes philippinarum）, distributed in four sea areas of China, i.e. , the Bohai Sea, the Huanghai Sea, the East China Sea and the South China Sea. Two hundred and sixty-four AFLP loci were analysed in 195 individuals and revealed high levels of genetic diversity. The percentage of polymorphic loci ranged from 92.13% to 96.06% and the Shannon＇ s information index was from 0.256 8 to 0. 275 6. By analyzing molecular variance （ AMOVA）, it was found that there were high levels of genetic differentiation between populations of Qingdao and the other three sea areas. Cluster analysis by Nei＇ s pairwise distances grouped specimens by geographical origin, except the population of Qingdao. A conclusion can be drawn that there are high genetic diversities in the four natural populations of Manila clam in China and some distinct differences existed among and between the four populations. The results also indicated that human cultivation activities will have great influence on the genetic structure of the population of Qingdao.

Genetic diversity and differentiation of mud crab Scylla serrata populations from southeastern China

The genetic diversity and differentiation of 6 mud crab Scylla serrata populations from southeastern China are investigated using allozyme electrophoresis. The mean number of alleles per locus population is 1.3 ± 0.1; the percentage of polymorphic loci per population is 27.3; the observed heterozygosity ranges from (0.195±0.083) to ( 0.241±0.090) and the expected heterozygosity ranges from ( 0.105±0.043 ) to ( 0.131±0.047 ). The coefficient of gene differentiation among populations is low (Fst =0.032), indicating that only 3.2 % of the total genetic diversity comes from inter-population, while the remaining 96.8 % comes from intra-population differences. The genetic distance among populations is 0.000-0.008 (the average is 0.002). Gene flow among the populations is large (Nm = 7.56).Genetic structure is very similar among 6 Scylla serrata populations.

Genetic Diversity and Relationship of Weedy Rice in Taizhou City, Jiangsu Province, China

Microsatellite markers and morphological characteristics were used to explore the genetic diversity and possible origin of weedy rice in Taizhou City, Jiangsu Province, China. Fifty-two weedy rice (Oryza sativa L.) accessions were compared with two wild rice, four hybrid rice and five cultivars using 22 simple sequence repeat (SSR) primer pairs. A total of 107 fragments were amplified, averaging 5.6 alleles per primer pair. The polymorphic index content (PIC) values ranged from 0.3077 to 0.7951, averaging at 0.5870. The average genetic distance of all samples ranged from 0.02 to 0.46 with an average of 0.262. The genetic distance among Taizhou weedy rice ranged from 0.03 to 0.44 with an average of 0.224. Cluster analysis showed that all the weedy rice accessions from Taizhou City were indica, and could be subdivided into different genotypes. The majority (86%) of weedy rice was most closely related to hybrid rice. The Taizhou weedy rice accessions were morphologically similar, but still could be delineated into indica or japonica group by some morphological traits. It is suggested that the levels of genetic and morphological diversities of weedy rice in Taizhou City are low and these weedy rice plants originated from the segregating progenies of hybrid rice that had naturally introgressed with cultivated rice.

Comparative Analysis of Genetic Diversity in Landraces of Waxy Maize from Yunnan and Guizhou Using SSR Markers

Waxy maize landraces are abundant inYunnan and Guizhou of China. Genetic diversity of waxy maize landraces from Yunnan and Guizhou were analyzed using SSR markers. We screened 38 landraces with 50 primers that generated 3 to 6 polymorphic bands, with an average of 4.13 bands. Shannon＇s information indices for genetic diversity of the 14 waxy maize landraces from Yunnan varied from 4.9571 to 42.1138 and averaged 26.5252; Shannon＇s information indices for genetic diversity of the 24 waxy maize landraces from Guizhou varied from 22.0066 to 40.6320 and averaged 32.3156. For the 14 waxy maize landraces from Yunnan, the within-landrace genetic diversity accounted for 45.40% and the among-landrace genetic diversity accounted for 54.60% of the total genetic diversity observed. For the 24 waxy maize landraces from Guizhou, the within-landrace genetic diversity accounted for 50.76% and the among-landrace genetic diversity accounted for 49.24% of the total observed. Some individual landraces possessed as much as 96.86% of the total genetic diversity occurring among landraces within origins. Differentiation between geographic origins accounted for only 3.14% of the total genetic diversity. Both Yunnan and Guizhou would be the diversity centers and the original centers of waxy maize.