Winter wheat yield improvement by genetic gain across different provinces in China

The replacement of winter wheat varieties has contributed significantly to yield improvement worldwide,with remarkable progress in China.Drawing on two sets of data,production yield from the National Bureau of Statistics of China and experimental yield from literature,this study aims to(1)illustrate the increasing patterns of production yield among different provinces from 1978 to 2018 in China,(2)explore the genetic gain in yield and yield relevant traits through the variety replacement based on experimental yield from 1937 to 2016 in China,and(3)compare the yield gap between experimental yield and production yield.The results show that both the production and experimental yields significantly increased along with the variety replacement.The national annual yield increase ratio for the production yield was 1.67%from 1978 to 2018,varying from 0.96%in Sichuan Province to 2.78%in Hebei Province;such ratio for the experimental yield was 1.13%from 1937 to 2016.The yield gap between experimental and production yields decreased from the 1970s to the 2010s.This study reveals significant increases in some yield components consequent to variety replacement,including thousand-grain weight,kernel number per spike,and grain number per square meter;however,no change is shown in spike number per square meter.The biomass and harvest index consistently and significantly increased,whereas the plant height decreased significantly.

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.

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.

Impact of Genetic Diversity of Uropathogenic Escherichia coli and Klebsiella pneumoniae Strains on the Dissemination of Extended Spectrum Beta-Lactam Resistance Genes in Côte d’Ivoire

The increase and spread of bacterial resistance to extended-spectrum beta-lactam antibiotics are reported in many infections and are a real public health problem worldwide. Drug pressure is a factor that favors the emergence of a population of better adapted bacteria. However, there is no literature highlighting the genetic diversity and evolutionary structure of E. coli and K. pneumoniae in an environment with high selection pressure in Côte d’Ivoire. The objective of this study was to evaluate the genetic diversity of E. coli and K. pneumoniae strains circulating at the HKB Hospital in Abobo and at the Daloa Regional Hospital and its impact on the dissemination of extended spectrum beta-lactam resistance genes. A total of 39 strains isolated from the urinary tract of infected patients, including 30 strains of E. coli and 9 strains of K. pneumoniae were studied. A total of 39 strains isolated from the urinary tract of infected patients, including 30 strains of E. coli and 9 strains of K. pneumoniae were studied. From genomic DNA extracts, ESBL resistance genes were amplified by PCR and sequenced, in addition to genetic typing by ERIC-PCR. The data obtained were submitted to genetic and bioinformatics analyses. The results have shown a genetic diversity important in E. coli and K. pneumoniae with diversity indexs (SID) ranging from 0.5 to 0.77. The genetic structure of the bacterial species studied has shown a clonal distribution of strains with clones expressing TEM-9 and CTX-M-15 variants. Also, this clonal structure was correlated with the spread of resistance genes in E. coli and K. pneumoniae. The spread of resistant clones is a factor that might limit the fight against antibiotic resistance.

Investigating the genetic diversity of several varieties of Iranian tomato (Solanum lycopersicum) using RAPD and ISSR molecular markers

Background:Numerous studies have demonstrated the existence of approximately 7,500 genetic tomato varieties worldwide.Hence,it is crucial to assess the genetic diversity among tomato cultivars.This study aimed to investigate the genetic diversity of selected Iranian tomato cultivars(Solanum lycopersicum)using RAPD and ISSR molecular markers.Method:Ten RAPD primers and ten ISSR primers were employed to assess the genetic diversity among 10 tomato cultivars:Matin,RFT 112,Hirad,Golsar,Raha,Hengam,Hedah,Fasa,JS12,and Emerald.Data analysis involved the UPGMA algorithm and NTYSYSpc software.Results:RAPD analysis revealed close genetic proximity between Fasa and JS12,as well as between Raha and Hadieh.Conversely,the RFT 112,Hengam,Hirad,and Emerald cultivars exhibited significant genetic diversity within this group.ISSR primer analysis identified Hengam as the most diverse variety,while Matin,Emerald,and Vibrid,as well as Raha and JS12,displayed genetic similarities with minimal observed diversity.Furthermore,the overall analysis of the cultivars using RAPD and ISSR markers indicated that Hengam exhibited the highest diversity among all the varieties.Notably,Raha and JS12 demonstrated limited diversity in this analysis.Conclusion:This research demonstrates substantial genetic diversity among the investigated tomato varieties,with Hengam displaying the highest diversity within this group.Furthermore,ISSR markers proved more effective in determining genetic diversity in tomato plants.

Genetic gain and inbreeding from simulation of different genomic mating schemes for pig improvement

Background Genomic selection involves choosing as parents those elite individuals with the higher genomic estimated breeding values(GEBV)to accelerate the speed of genetic improvement in domestic animals.But after multi-generation selection,the rate of inbreeding and the occurrence of homozygous harmful alleles might increase,which would reduce performance and genetic diversity.To mitigate the above problems,we can utilize genomic mating(GM)based upon optimal mate allocation to construct the best genotypic combinations in the next generation.In this study,we used stochastic simulation to investigate the impact of various factors on the efficiencies of GM to optimize pairing combinations after genomic selection of candidates in a pig population.These factors included:the algorithm used to derive inbreeding coefficients;the trait heritability(0.1,0.3 or 0.5);the kind of GM scheme(focused average GEBV or inbreeding);the approach for computing the genomic relationship matrix(by SNP or runs of homozygosity(ROH)).The outcomes were compared to three traditional mating schemes(random,positive assortative or negative assortative matings).In addition,the performance of the GM approach was tested on real datasets obtained from a Large White pig breeding population.Results Genomic mating outperforms other approaches in limiting the inbreeding accumulation for the same expected genetic gain.The use of ROH-based genealogical relatedness in GM achieved faster genetic gains than using relatedness based on individual SNPs.The GROH-based GM schemes with the maximum genetic gain resulted in 0.9%-2.6%higher rates of genetic gainΔG,and 13%-83.3%lowerΔF than positive assortative mating regardless of heritability.The rates of inbreeding were always the fastest with positive assortative mating.Results from a purebred Large White pig population,confirmed that GM with ROH-based GRM was more efficient than traditional mating schemes.Conclusion Compared with traditional mating schemes,genomic mating can not only achieve sustainable genetic progress but also effectively control the rates of inbreeding accumulation in the population.Our findings demonstrated that breeders should consider using genomic mating for genetic improvement of pigs.

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.

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.

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.

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.

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.

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.

Population Genetic Diversity in Chinese Pomegranate (Punica granatum L.) Cultivars Revealed by Fluorescent-AFLP Markers

Eighty-five pomegranate （Punica granatum L.） cultivars from six geographical populations located at Shandong, Anhui, Shaanxi, Henan, Yunnan, and Xinjiang Provinces were studied for its population genetic diversity by means of fluorescent-AFLP markers. The results indicated that 135-185 polymorphic loci were amplified by eight pairs of primers at species level. An average of 158.25 polymorphic loci was amplified for each primer combination. The polymorphism percentage ranged from 62.5% to 86.11%, and the average polymorphism percentage was 73.26%. This indicated that there was plentiful genetic diversity in pomegranate cultivars. The genetic diversity at the species level was higher than that at the population level. The order of the genetic diversity was Henan population 〉 Xinjiang population 〉 Shaanxi population 〉 Anhui population 〉 Shandong population 〉 Yunnan population. Variance analysis showed that there was significant difference between populations in genetic diversity. The genetic differentiation coefficient between populations （Gsr） was 0.2018, which indicated that gene differentiation was mainly within the population, and between populations, it accounted for 20.18% of the total variation. Gene flow （Nm） between the populations measured was 1.9027 based on the genetic differentiation coefficient between populations, indicating that there was mild gene flow between populations. The UPGMA cluster analysis showed that most accessions from the same population were clustered together, but there was partly gene exchange. All genetic parameters indicated that there was plentiful genetic diversity in pomegranate cultivars in China, of which Henan population was significantly higher than the other populations, and it had wide application foreground in pomegranate breeding in China.

Assessment of Genetic Diversity of Yunnan,Tibetan,and Xinjiang Wheat Using SSR Markers

A total of 206 SSR （Simple Sequence Repeats） primer pairs were used to detect genetic diversity in 52 accessions of three unique wheat varieties of western China. A total of 488, 472, and 308 allelic variants were detected in 31 Yunnan, 15 Tibetan and 6 Xinjiang wheat accessions with an average of PIC values 0.2764, 0.3082, and 0.1944, respectively. Substantial differences in allelic polymorphisms were detected by SSR markers in all the 21 chromosomes, the 7 homoeologous groups, and the three genomes （A, B, and D） in Yunnan, Tibetan, and Xinjiang wheat. The highest and lowest allelic polymorphisms in all the 21 chromosomes were observed in 3B and 1D chromosomes, respectively. The lowest and highest allelic polymorphisms among the seven homoeologous groups was observed in 6 and 3 homoeologous groups, respectively. Among the three genomes, B genome showed the highest, A the intermediate, and D the lowest allelic polymorphism. The genetic distance （GD） indexes within Yunnan, Tibetan, and Xinjiang wheat, and between different wheat types were calculated. The GD value was found to be much higher within Yunnan and Tibetan wheat than within Xinjiang wheat, but the GD value between Yunnan and Tibetan wheat was lower than those between Yunnan and Xinjiang wheat, and between Tibetan and Xinjiang wheat. The cluster analysis indicated a closer relationship between Yunnan and Tibetan wheat than that between Yunnan and Xinjiang wheat or between Tibetan and Xinjiang wheat.

Comparative Assessment of Genetic Diversity of Peanut (Arachis hypogaea L.)Genotypes with Various Levels of Resistance to Bacterial Wilt Through SSR and AFLP Analyses

Bacterial wilt （BW） caused by Ralstonia solanacearum is an important constraint to peanut （Arachis hypogaea L.） production in several Asian and African countries, and planting BW-resistant cultivars is the most feasible method for controlling the disease. Although several BW-resistant peanut germplasm accessions have been identified, the genetic diversity among these has not been properly investigated, which has impeded efficient utilization. In this study, the genetic relationships of 31 peanut genotypes with various levels of resistance to BW were assessed based on SSR and AFLP analyses. Twenty-nine of 78 SSR primers and 32 of 126 AFLP primer combinations employed in this study were polymorphic amongst the peanut genotypes tested. The SSR primers amplified 91 polymorphic loci in total with an average of 3.14 alleles per primer, and the AFLP primers amplified 72 polymorphic loci in total with an average of 2.25 alleles per primer. Four SSR primers （14H06, 7G02, 3A8, 16C6） and one AFLP primer （P1M62） were found to be most efficient in detecting diversity. The genetic distance between pairs of genotypes ranged from 0.12 to 0.94 with an average of 0.53 in the SSR data and from 0.06 to 0.57 with an average of 0.25 in the AFLP data. The SSR-based estimates of the genetic distance were generally larger than that based on the AFLP data. The genotypes belonging to subsp, fastigiata possessed wider diversity than that of subsp, hypogaea. The clustering of genotypes based on the SSR and AFLP data were similar but the SSR clustering was more consistent with morphological classification ofA. hypogaea. Optimum diverse genotypes of both subsp, hypogaea and subsp.fastigiata can be recommended based on this analysis for developing mapping populations and breeding for high yielding and resistant cultivars.

RAPD analysis of genetic diversity of nine strains of Auricularia auricular cultivated in Heilongjiang Province

Polymorphism of nine strains （CF05, CF09, 29, 916, AU9, Chang10, Chang7, 8808 and AU. Japanese） of A. auricular cultivated in Heilongjiang Province were analyzed by RAPD （Random Amplication polymorphic DNA）. Thirteen primers were selected from forty PCR primers with 10bp long random primer. The results showed that nine strains of A. auricular have a high level of genetic diversity and the percentage of DNA polymorphic was 96.05. The genotypes of 9 strains of Auricularia auricular were identified by the fingerprints from primer 27 and primer 46 by RAPD analysis. The results are helpful for quickly identifying strains of A. auricular in its early breeding time, and also provides a powerful theoretic basis to differentiate strains （Auricularia auricular） whose morphology is very similar in breeding programs of edible fungus.

RAPD Analysis for Genetic Diversity of Nineteen Common and Tartary Buckwheat Varieties

[Objective]The study aimed to carry out RAPD analysis of genetic diversity of common and tartary buckwheat varieties.[Method] The genetic diversity of 19 common and tartary buckwheat varieties including the tested varieties in Guizhou region during 1999-2010 and their parents were studied using 7 primers by means of random amplified polymorphic DNA（RAPD）.[Result]A total of 149 DNA bands were obtained.In which,141 bands were polymorphic,accounting for 94.89%.Polymorphism analysis and cluster analysis showed that all varieties had their own special bands different from each other.The varieties native to Weining were close to each other,and other common buckwheat varieties were obviously different from each other.The interspecific genetic variation was the greatest;the intraspecific genetic variation of common buckwheat varieties was greater than that of tartary buckwheat varieties.[Conclusion]The RAPD fingerprints of the 19 buckwheat varieties were established in present study.

Comparison of Genetic Diversity Between Local Cultivated Aromatic and Non-aromatic Rice in Yunnan Province

[ Objective] The genetic diversity of the local cultivated aromatic rice and non-aromatic rice in Yunnan Province were compared to provide further genetic resources for breeding practice. [Method] Genetic diversity of 10 aromatic rice and 45 non-aromatic rice were analyzed by 64 SSR primers covered on 12 rice chromosomes. [ Result] Per locus 5.44 and 7.98 alleles in average were detected, ranging from 2 to 12 and from 2 to 17 in aromatic and non-aromatic rice, respectively. Average genetic multiplicity index（Hs） was 0.46 and 0.67 respectively. The average polymorphism information content （PIC） was 0.43 and 0.58 in aromatic and non-aromatic rice respectively. [ Conclusion] The results indicated that genetic diversity was higher in non-aromatic rice than in aromatic rice.

Study on Genetic Diversity of Agronomic Traits and Genetic Relationships among Core Collections of Bitter Gourd

[Objective] This study aimed to investigate the genetic diversity of agronomic traits and genetic relationships among core collections of bitter gourd.[Method] Total 141 germplasms of bitter gourd were selected,and the genetic diversity of 13 agronomic traits was analyzed.In addition,total 46 core collections of bitter gourd were employed,and their genetic relationships were analyzed based on the phenotypic values and genotypic values of 5 agronomic traits,respectively.[Result] The genetic diversity analysis of agronomic traits showed that the genetic diversity indexes of the 4 qualitative traits of bitter gourd germplasms ranged from 0.46 to 1.34;the distribution of the 9 quantitative traits data was more dispersed with average coefficient of variation of 20.02%.The genetic relationship analysis showed that based on the phenotypic values and genotypic values of the 5 quantitative traits,the genetic distances among the 46 core collections of bitter gourd were different.Based on the genotypic values,the genetic distances among the 46 bitter gourd core collections ranged from 0.84 to 10.71.The 46 germplasms were divided into 17 groups with the rescaled distance of 8.5,which further classified the relationships among different germplasms.[Conclusion] This study will lay a solid foundation for the effective utilization of core collections and new variety breeding in bitter gourd.

EST-SSR Marker-based Genetic Diversity Analysis of Rhododendron simsii Germplasm in Guifeng Mountain

Rhododendron simsii（Ericaeae：Rhododendron） has high ornamental value and ecological value.In this study,7 pairs of novel EST-SSR markers were developed from the genomic sequence of R.simsii,and they were used to investigate the genetic diversity of 32 natural R.simsii samples from Guifeng Mountain,Hubei Province.Results showed that a total of 31 polymorphic bands were amplified with allele number per locus of 4.43.Mean values of heterozygosity（Ho） and expected heterozygosity（He） were 0.679 58 and 0.723 14,respectively.This research will not only enrich the existing SSR database,but also lay a foundation for subsequent studies about molecular marker-assisted breeding,genetic diversity analysis,genetic structure analysis and phylogenetic analysis.