Compiling molecular evidence from a tetraploid rose genome into a near-saturated map for the identification of pigment-related genes

With their high economic value and cultural significance,modern roses are one of the most important ornamental plants.Because of their complicated genetic background and tetraploid nature,the creation of high-density genetic maps of roses has been a challenge that has slowed the pace of molecular breeding for modern roses.The current construction of tetraploid genetic maps based on existing diploid rose genomes could lead to inaccurate marker information and genotyping results.Therefore,we generated the first high-quality tetraploid genome of Rosa chinensis‘Yunzheng Xiawei.'Utilizing Illumina,PacBio,and Hi-C sequencing technologies,we assembled a genome of 858.59 Mb with 14pseudo-chromosomes.Mode of inheritance analysis using PolyOrigin indicated that modern roses show both quadrivalent and bivalent pairing.Based on this reference genome,high-density genetic maps were constructed using MSTmap with nearly saturated markers.Quantitative trait locus(QTL)analysis was conducted using WinQTLCart and R/qtl for flavonoids and carotenoids,and 11 QTL clusters were identified.By combining the genome annotation,phylogenetic analyses,and gene expression analyses,we were able to identify several key genes related to flavonoid and carotenoid biosynthesis.This study provides the basis for further genetic analyses of highly heterozygous tetraploid roses and could facilitate the progress of marker-assisted selection in modern roses.

Breeding and Seed Reproduction Techniques of a New Tetraploid Common Buckwheat Variety‘Pintianqiao 3’

[Objectives]This study was conducted to actively carry out the breeding of new tetraploid common buckwheat varieties and its supporting breeding techniques.[Methods]Pintianqiao 3 is a new tetraploid common buckwheat variety developed by College of Agriculture of Shanxi Agricultural University and Agricultural Genetic Resources Center of Shanxi Agricultural University,using‘Pintianqiao 1’as the parent,through mutation treatment with 0.2%colchicine aqueous solution,grain selection,plant selection,isolation and identification,variety comparison,regional test and field investigation.The variety has chromosomes 2n=4X=32,and shows a spring sowing period of 101 d and a summer sowing period of 80 d,large flowers and seeds(with a 1000-grain weight of 41.4 g),and good resistance to lodging.[Results]From 2021 to 2022,Pintianqiao 3 participated in the independent joint regional test of common buckwheat varieties in Shanxi Province,and the average yield in 10 test positions was 1.8 kg,equivalent to 1800 kg/hm^(2),which was 8.4%higher than the control.It passed the field investigation conducted by Shanxi provincial expert group for identification of non-major crop varieties in Dongyang and Kelan experimental sites on September 2-3,2022.On January 4,2024,it passed the preliminary examination of Shanxi Provincial Crop Variety Approval Committee.The seed reproduction technique of Pintianqiao 3 including land selection,preparation before sowing,sowing,field management and timely harvesting has been developed.[Conclusions]This study provides technical support for the demonstration and popularization of this new variety.

四倍体胡柚与鸡尾葡萄柚有性杂交创制三倍体新种质

【目的】柑橘三倍体具有无核或少核的特点,通过4x×2x杂交方式创制三倍体种质,以弥补鸡尾葡萄柚种子多、抗寒性差的缺点。【方法】以四倍体(双二倍体)胡柚为母本与二倍体鸡尾葡萄柚杂交,果实成熟后对种子大小进行分类并进行组织培养,采用流式细胞仪、SSR分子标记鉴定再生子代的倍性及遗传组成。【结果】共授粉40朵花,坐果19个,坐果率为47.5%。获得的230粒种子中,大种子占56粒,再生49株,2株为三倍体(占大种子再生后代的4.08%);小种子117粒,再生69株,35株为三倍体(占小种子再生后代的50.72%);败育种子57粒,再生4株,2株为三倍体。经SSR分子标记鉴定,39株三倍体子代均为双亲杂交后代,同时鉴定出1株杂种四倍体后代。【结论】创制了一批异源三倍体和四倍体新种质,为选育抗寒、无核的杂种葡萄柚新品种奠定了种质基础。

Construction and Analysis of Asexual Mutant Population of Tetraploid Potato Longshu 7 Induced by EMS

[Objective] This study was conducted to detect the variation induction ability of ethyl methanesulfonate （EMS）, to construct a mutant population. [Method] 0.6%, 1.2% and 2.4% EMS solutions were used for inducing 2 400 stem segments of test-tube plantlets of tetraploid potato Longshu 7, and an asexual mutant population including leaf, plant type, stem, stolon, glandular hair traits was constructed. [Result] Twenty two mutation types, i.e. etiolated plantlet, albino plantlet, leaf-color gradient, etiolated vein, wrapped bud, lobed leaf, crinkled leaf, deformed compound leaf, cluster, branch, top enlargement, top bifurcation, succulent, stolon distortion, stolon shift, early tuberization, hair stolon, stem enlargement, vine stem, foliage stem, glandular hair and whorled leaf types were observed in total. There were 52 mutant single plants in total, with a mutation rate of 21.67‰. [Conclusion] The glandular hair, clustered short-stem, branched stem and early tuberization types of mutants have higher application value, and are anticipated to be used in potato functional genome research, gene improvement and germplasm innovation.

Study on Relation between Endogenous Phytohormones and Ovule Abortion in Tetraploid Robinia pseudoacacia

This study was conducted to investigate ovule abortion of tetraploid Robinia pseudoacacia and its reasons. It was found that in the ovule development period of tetraploid R. pseudoacacia from 15 d after coronal opening, the levels of growth-promoting endogenous hormones in abortive ovules were lower than those in normal ovules, and the level of a growth-inhibiting hormone was always higher than those in normal ovules, indicating that ovule abortion of tetraploid R. pseudoacacia might be related to abnormal endogenous phytohormones in ovules. This study laid a foundation for further study on highly sterile phenomenon of tetraploid R. pseudoacacia seeds.

紫花苜蓿CNGC基因家族全基因组鉴定及干旱胁迫下的调控模式分析

环核苷酸门控通道蛋白(cyclic nucleotide-gated channel proteins,CNGC)在Ca^(2+)信号转导过程中发挥着重要作用。利用生物信息学和分子生物学的研究方法对四倍体紫花苜蓿(Medicago sativa‘Xinjiangdaye’)CNGC基因家族成员进行全基因组鉴定和干旱胁迫下的调控模式分析。结果表明:新疆大叶苜蓿基因组中共包含67个MsCNGC基因,不均匀地分布在30条染色体上,分属5个亚家族,共包含20个Motif,其启动子区域存在多种响应逆境胁迫的作用元件。新疆大叶苜蓿叶片中共表达了28个MsCNGC基因,有26个在干旱胁迫下不均匀上调,其中MsCNGC 59表达量最高且在干旱胁迫下上调倍数最大。MsCNGCs含有29~120个磷酸化位点,能被LRR蛋白激酶磷酸化,MsLRRs与MsCNGCs基因表达之间呈显著的正相关关系。此外,Ca^(2+)信号转导相关基因MsCaM、MsCML和MsCDPK表达量在干旱胁迫下显著上调。综上,四倍体紫花苜蓿MsCNGCs对干旱胁迫的响应包括转录调控和蛋白质的磷酸化调控,在干旱胁迫下能通过参与Ca^(2+)信号转导途径提高紫花苜蓿的抗旱性。

Research on Pollen Grains of Tetraploid Lines and Diploid Control Line of Chrysanthemum cinerariifolium (Trev.) Vis.

[Objective] The aim was to study characters of pollen grains of tetraploid lines and diploid control line of Chrysanthemum cinerariifolium (Trev.) Vis.,morphological characters,fertility of pollen grain and germination percentage of seeds. [Method] Pollen grains were prepared by sulphuric acid-acetyl oxide decomposition method. The lengths of polar axis and equatorial axis of pollen grains were determined with general optical microscope. The morphology of pollen grains was observed with SEM (scanning electron microscope) and the typical visual fields of 2 500× (or 2 000×),7 000× were taken pictures. [Result] Comparing with the diploid control line,the pollen grains of five tetraploid lines which were tested were different from the diploid line in morphology,sculpture,etc.. 4 of the 5 tested samples were significant larger than the diploid line in size and one was similar to the diploid line. [Conclusion] This research provided references for breeding tetraploid improved varieties of Chrysanthemum cinerariifolium (Trev.) Vis. with good fertility and high germination percentage.

红掌特伦萨四倍体的离体诱导及其鉴定

为了研究红掌四倍体的离体诱导和鉴定技术体系,为其倍性育种和杂交育种奠定基础,以特伦萨愈伤组织为试验材料,采用0.5、1.0、2.0、4.0 g·L^(-1)的秋水仙素分别处理2、4、6、8 h,之后转入培养基MS+6-BA 2.0 mg·L^(-1)+NAA 0.5 mg·L^(-1)进行愈伤组织的生长和丛生芽分化,75 d后将丛生芽转入培养基1/2 MS+NAA 0.2 mg·L^(-1)诱导生根,待丛生芽生根后统计愈伤组织块存活率、再生植株数,并对再生植株进行染色体倍性鉴定和核型分析。结果表明,随着秋水仙素浓度的增加,红掌愈伤组织块存活率呈下降趋势,但愈伤组织块上诱导的再生植株数无显著变化;在0.5~2.0 g·L^(-1)的秋水仙素浓度范围内,红掌疑似四倍体的诱导率随着处理浓度与时间的增加而增加,2.0 g·L^(-1)秋水仙素处理6与8 h时,诱导率达8.50%与8.77%;特伦萨和疑似四倍体红掌的基因组分别为3.73和7.01 Gb;染色体压片倍性鉴定结果证明了疑似四倍体的倍性为四倍体。红掌二倍体的核型公式为2n=2x=30=8 st+16 sm+6 m,四倍体的核型公式为2n=4x=60=8 st+32 sm+20 m;与红掌二倍体植株相比,四倍体植株叶片变厚、气孔变大、保卫细胞密度变小,佛焰苞直径变大,单个花序花期变长,差异均达显著水平。综上,采用2.0 g·L^(-1)秋水仙素处理6 h可培育红掌四倍体植株,此四倍体可作为红掌倍性育种和杂交育种的重要种质资源。

四倍体部分性水泡状胎块2例临床病理分析并文献复习

目的探讨四倍体部分性水泡状胎块(PHM)临床特征、病理形态学特点、发病机制及临床管理方式。方法收集2例四倍体PHM,分析其临床特征、病理形态学、免疫组织化学表型及分子遗传学机制,并复习相关文献。结果2例女性患者年龄分别28岁和30岁,孕早期流产。例1超声示妊囊内未见胚芽,妊囊周围探及散在多个无回声区;例2超声示妊囊内见一细小胚芽,未见心管搏动。例1肉眼观察见水泡状绒毛,最大径0.1~0.3 cm;例2肉眼观察未见水泡状绒毛。2例镜下观察均有绒毛大小不一、轮廓不规则,绒毛不同程度水肿伴中央水池形成,滋养细胞轻度增生,细胞异型性不明显,绒毛间质细胞增生、可见核碎屑及滋养层细胞包涵体,未见绒毛间质纤维化,未见有核红细胞及胚胎成分,其中例1绒毛滋养层细胞基底膜下可见线性矿物质沉积,例2绒毛间质可见黏液样背景。免疫组织化学表型均为p57阳性,阳性率分别为10%~40%、10%~50%;Ki-67阳性率较高,分别为60%~80%和60%~90%。短串联重复序列(STR)基因分型均为四倍体PHM,父本与母本等位基因比例为3∶1,父本等位基因来自2个精子,其中1个精子卵内复制。性染色体FISH检测为XXYY、XXXX。2例行清宫术后分别随访1年、10个月均未发生持续性妊娠滋养细胞疾病。结论四倍体PHM比较少见,临床病理特征不典型,确诊依赖于STR基因分型。

Comparison Between a Tetraploid Turnip and Its Diploid Progenitor(Brassica rapa L.):The Adaptation to Salinity Stress

Polyploidy is pursued in plant breeding programs due mainly to its ability to yield larger vegetative or reproductive organs. In controlled growth chamber experiments, a tetraploid turnip （cv. Aijiaohuang, 4n） and its diploid progenitor （cv. Aijiaohuang, 2n） were evaluated for their tolerance to salinity stress via investigations on a group of physiological parameters. The results indicate that the tetraploid turnip exhibit better adaptation to a high concentration salt medium （200 mmol L-1）, as evidenced by a less-affected germination rate and a healthier morphological appearance at the seedling stage. Furthermore, an extension of salinity stress up to a certain period of time at the 5-7-leaf stage shows differences between the tetraploid turnip and its diploid progenitor. The former had a higher K＋/Na＋ ratio in the roots, higher glutathione concentration and antioxidant activities in the leaves, and smaller reductions in photosynthetic capacity in terms of leaf chlorophyll content. Studies on the differences between an autopolyploid and its respective relative, from which the autopolyploid originated, in terms of their tolerance to salinity and/or other abiotic stresses, have remained rather limited. The comparison is interesting due to a homogenous genetic background.

Mapping QTL underlying tuber starch content and plant maturity in tetraploid potato

Tuber starch content and plant maturity are two important agronomic traits of potato. To investigate the complex genetic basis of these traits in the cultivated potato, as well as the relationship between them, we developed a linkage map in a tetraploid population of 192 clones derived from the cross Longshu 8 × Zaodabai and mapped quantitative trait loci(QTL) for tuber starch content and plant maturity using data collected in three diverse environments over two years. We detected eleven QTL for tuber starch content distributed on seven chromosomes, of which four, on chromosomes I, II, and VIII, were expressed in at least three environments. For plant maturity, we identified six QTL on chromosomes II, IV,V, VII, and XI, one of which, on chromosome V, showed LOD peaks ranging from 45.2 to 62.5 cM and explained 21.6%–26.6% of phenotypic variation was expressed in five of the six environments. Because the reproducible QTL for plant maturity and tuber starch content mapped to different chromosomes and neither overlapping QTL, nor any genetic interaction between QTL were detected, we infer that tuber starch content and plant maturity are controlled by independent genetic loci. This inference supports the prospect of breeding potato for both early maturity and high starch content.

Analysis of three types of triterpenoids in tetraploid white birches(Betula platyphylla Suk.) and selection of plus trees

Betulin, oleanolic acid, and betulinic acid are naturally occurring pentacyclic triterpenoids that have significant medicinal value. Considerable amounts of these triterpenoids are available in the outer bark of white birch. In this study, we used ultrasound-assisted extraction （UAE） to extract triterpenoids from birch bark rapidly and with high efficiency. Using high performance liquid chro- matography （HPLC）, three types of triterpenoids were separated and detected. We examined the differences among triterpenoids extracted from diploid versus tetra- ploid white birch. Then, we used factor analysis to screen out tetraploid white birches with comprehensively excel- lent performance. The results indicate that the optimum conditions for extraction include the use of ethanol as an extraction solvent, a solid-to-liquid ratio of 0.1 g/10 ml, ultrasonic power set at 100 W, a temperature of 60 ℃ and an extraction time of 15 min. A reversed-phase C18 col- umn （4.6 mm × 250 mm × 5 μm） with a column tem- perature of 30 ℃ and the mobile phase composed of A （acetonitrile） and B （0.1% aqueous phosphoric acid, v/v） at a flow rate of 0.5 ml/min were used, and the detection wavelength was 195 nm. No significant difference wasobserved between diploid and tetraploid white birch in terms of the content of three types of triterpenoids （at a confidence level of 0.05）. As triterpenoid content, height, and DBH （diameter at breast height） are strongly interre- lated, we used factor analysis to evaluate all individuals, and we screened out six plus trees with excellent com- prehensive characters.

Effects of different supplements on tetraploid black locust (Robinia pseudoacacia L.) silage

Preparation of silage is a common method to preserve green forage. It plays an important role in improving forage utilization, solving the problem of forage provision and meeting the nutritional needs of livestock in winter and spring. The effects of various supplements on tetraploid black locust （Robinia pseudoacacia L.） silage were studied by analyzing its color, odor, texture, pH value, the composition and amount of organic acids, the ammonia-N/total-N ratio, crude protein, neutral detergent fibers and acid detergent fibers. Our results show that the silage quality of wilted tetraploid R. pseudoacacia preserved alone is acceptable, while adding brown sugar and Yishengkang to tetraploid R. pseudoacacia foliage improved its quality. The treatments consisting of the tet- raploid R. pseudoacacia mixed with 33% and 50% corn stalk achieved the best silage quality in terms ofpH value （p 〈 0.01）, amount of lactic acid （p 〈 0.01）, the ammonia-N/total-N ratio （p 〈 0.01） and the fermentation quality. These treatments also resulted in a high content of crude protein and lower amounts of acid detergent fibers. The treatment consisting of the tetraploid R. pseudoacacia mixed with 20% corn stalk was also good in the quality of its fermentation.

High density genetic map and quantitative trait loci(QTLs)associated with petal number and flower diameter identified in tetraploid rose

Rose is one of the most important ornamental and economic plants in the world.Modern rose cultivars are primarily tetraploid,and during meiosis,they may exhibit double reduction or preferential chromosome pairing.Therefore,the construction of a high density genetic map of tetraploid rose is both challenging and instructive.In this study,a tetraploid rose population was used to conduct a genetic analysis using genome sequencing.A total of 17382 single nucleotide polymorphism(SNP)markers were selected from 2308042 detected SNPs.Combined with 440 previously developed simple sequence repeats(SSR)and amplified fragment length polymorphism(AFLP)markers,a marker dosage of 6885 high quality markers was successfully assigned by GATK software in the tetraploid model.These markers were used in the construction of a high density genetic map,containing the expected seven linkage groups with 6842 markers,a total map length of 1158.9 c M,and an average inter-marker distance of 0.18 c M.Quantitative trait locus(QTL)analysis was subsequently performed to characterize the genetic architecture of petal number and flower diameter.One major QTL(qpnum-3-1)was detected for petal number in three consecutive years,which explained 20.18–22.11%of the variation in petal number.Four QTLs were detected for flower diameter;the main locus,qfdia-2-2,was identified in two consecutive years.Our results will benefit the molecular marker-assisted breeding of modern rose cultivars.In addition,this study provides a guide for the genetic and QTL analysis of autotetraploid plants using sequencing-based genotyping methods.

Agronomic characterization and genetic analysis of the supernume-r ary spikelet in tetraploid wheat(Triticum turgidum L.)

The supernumerary spikelets（SS）characters of tetraploid wheat（Triticum turgidum L.）resulting in more spikelets and kernels per spike,thus enhancing sink capacity may contribute to potential wheat yield improvement.In order to investigate the effect of different SS types on agronomic characters and understand the genetic base of SS phenotype in tetraploid wheat,near isogenic lines（NILs）,bh-50 with normal spikelets（NS）,bh-51 with four-rowed spikelets（FRS）,bh-52 with short-ramified spikelets（SRS）,and bh-53 with long-ramified spikelets（LRS）in a Triticum durum cv.ZY1286 genetic background were developed by continuous backcrossing.Agronomic characters showed that the SS phenotype lines,bh-51,bh-52and bh-53 have significant increase in the number of spikelets and grains per spike compared with the NS phenotype line bh-50（P〈0.05）,and bh-53 line showed much more increase than those of bh-51 and bh-52.However,bh-53 had the lowest grain weight and the longest spike development stage than those of other spike phenotypes.These results indicated that the different SS types have different effects on the agronomic and spike characters.Genetic analysis through bh-50/bh-51and bh-51/bh-53 F2 populations showed that a recessive major gene controlled the spike architecture to transform from NS to FRS,and a dominant major gene determined the change of spike phenotype from FRS to RS.DNA sequences of Tt BH/WFZP ortholog on chromosome 2AS revealed that a single nucleotide polymorphism（SNP）substitution happened in the open reading frame（ORF）region of all the SS tetraploid wheat accessions,which may lead to the generation of lateral meristems between glume and lemma during the immature spike development.While the fates of the lateral meristems,developing into lateral spikelets or branched spikelets,may be determined by another major gene.Our results presented here may advance our understanding and knowledge of the genes and genetic pathways determining the spike architecture development in wheat.

Expression of the Gene Encoding the Tetraploid of Carboxyl-terminal Peptide of β-hCG Containing Thirtyseven Amino Acid Residues in E.coli

This study was carried out to investigate the possible enhancement of im- munogenicity of the carboxyl-terminal peptide of β-hCG which is made up of 37 amino acid residues (109-145) and contains the specific epitope (antigenic determinant) of hCG. Materials &. Methods hCGβ-CTP37 tetraploid cDNA was constructed by linking four hCGβ-CTP37 cDNAs together. The product was then subcloned into the E. coli expres- sion vector pQE60 to construct the expression vector pQE60/ (hCGβ-CTP37)4. Recom- binant (hCGβ-CTP37)4 was expressed in E. colt-X-blue. Results Western blot analysis showed that the tetraploid of hCGβ-CTP37 had an ap- parent molecular weight of 20 kD and had relatively stronger anti-hCG antibody-bind- ing activity compared with the diploid from. Conclusion The tetraploid of hCGβ-CTP37 may be a more potent immunogen for raising anti-hCG vaccines for fertility regulation or suppression of tumor.

Analysis of Seed Phenotypic and Metabolic Characteristics of Diploid and Tetraploid Tartary Buckwheat

Polyploid plants grow well,are stress tolerant,and are rich in nutrients and bioactive compounds.Thus,they are useful for improving crop quality and yield.In this study,we compared the seed characteristics and metabolite profiles of diploid and tetraploid tartary buckwheat,which was developed via an artificially induced chromosome doubling event.The length,width,area,and thousand-grain weight were greater for the tetraploid seeds than for the diploid seeds.However,the germination rate decreased for the tetraploid seeds.Additionally,there was a gap between the shell and kernel of the tetraploid seeds.Moreover,the water absorption rate was higher for the tetraploid than for the diploid seeds.Chromosome doubling increased the seed total flavonoid content and deepened the seed color.A principal component analysis of the ultrahigh-pressure liquid chromatography-high resolution mass spectrometry data revealed the clear separation between the diploid and tetraploid samples.An orthogonal partial least squares-discriminant analysis and other multivariate statistical analyses identified 83 differentially abundant compounds,with most of the flavonoid metabolites more abundant in the tetraploid than in the diploid seeds.Research on tartary buckwheat polyploidy may result in enhanced germplasm resources and may clarify the mechanism underlying the biosynthesis of bioactive compounds.

Transcript and Sequence Analysis of S-RNases in Self-Compatible Tetraploid Chinese Cherry (Prunus pseudocerasus L.)

Chinese cherry （Prunus pseudocerasus L.） is an allotetraploid species and exhibits natural self-compatibility.However,the full-length cDNA sequences,functional analysis and the transcripts of S-RNase alleles in Chinese cherry cultivars are not known.In the two cultivars Taixiaohongying and Laiyang Short Cherry with S1S2S3S4 genotypes,two S-RNases were transcribed in Northern blotting,and the two full-length cDNAs of S-RNase were cloned and analyzed.As the result,the transcribed S-RNases were S1-RNase and S2-RNase.The two complete cDNA sequences of S1-RNase and S2-RNase were registered as EU073938 and EU073939,respectively,and had characteristic structure of rosaceous S-RNases based on their sequences indicating that they had normal function for S-RNase in the style.The S3-RNase and S4-RNase were not transcribed in the style and were nonfunctional for S-RNase,so S3m and S4m could be used to represent the nonfunctional S3-RNase and S4-RNase.The phylogenetic analysis implied that the S-RNases of Prunus,including Chinese cherry,had lower intra-specific similarity and diverged earlier than the divergence of species in Prunus.

Cytogenetic Mechanism for the Aneuploidy and Mosaicism Foundin Tetraploid Pacific Oyster Crassostrea gigas （Thunberg）

Chromosome constitution was investigated in adult tetraploid Pacific oyster produced by blocking the first polar body oftriploid eggs which were fertilized with haploid sperms. A high incidence of aneuploid and heteroploid mosaics were found amongthe offspring. Of 20 individuals identified, only 9 （45%） were eutetraploid which contained 40 chromosomes; 2 （10%） were ane-uploid （hypotetraploid）, which contained 39 and 38 chromosomes, respectively; and 9 （45%） were heteroploid mosaics. One mosaicwas consisted of cells containing 40 and 39 chromosomes, respectiovely （1：1 in cell number）, while the other 8 were consisted ofcells containing chromosomes varying between tetraploid and triploid. It was also interesting to note that 3 mosaics even containedsome diploid cells with 20 chromosomes. A certain number of cells of 2 tetraploids and 8 mosaics spread with 32-37 well-scatteredand some clumped chromosomes at metaphase. The percentage of aneuploid cells with chromosomes varying between triploid andtetraploid correlated significantly with that of heteroploid mosaics cells with clumping chromosomes （P〈0.05）. Our findings sug-gested that reversion existed in both tetraploid and triploid oyster and chromosome clumping may underline the chromosome elimi-nation in tetraploid oyster. It seems that the reversing cells, at least some of them, continuously eliminate their chromosomes until themost stable diploid state is established.

Tetraploid induced by physical and chemical methods in Jinjiang oyster（Crassostrea rivularis）

In order to induce tetraploid into Jinjiang oyster (Crassostrea rivularis), embryos were treated with physical (cold or heat shock) and chemical (chlorpromazinum or traditional Chinese medicine)methods in the first 3 min before the cleavage of zygotes or at the onset of the first cleavage of one or two eggs. Measurements show that the induction rates of tetraploid in the embryos inspected are 28%, 30%, 28. 4% and 35. 8% for heat-shock (39℃, 3 min),cold-shock (10℃, 3min),chlorpromazinum (0. 375 mg/dm3, 10 min) and traditional Chinese medicine (50 g/dm3 )extract (57 cm3, 10 min),respectively. The tetraploid induction rate in the larvae treated with traditional Chinese medicine is 32. 5%.It is evident that the induction rate of tetraploid in embryos insected at an early stage is the most remarkable when treated. with traditional Chinese medicine.