Preliminary Study on Induction and Identification of Polyploidy of Shandong Salvia miltiorrhiza Buds Treated by Colchicine

[Objective] The aim was to study the feasibility of using colchicine to induce polyploidy from the buds of Shandong Salvia miltiorrhiza.[Method] The buds of Shandong Salvia miltiorrhiza were induced by colchicine.[Result] When the concentration of colchicine supplemented in culture medium was 12 mg/L,the induction rate of polyploidy was the highest（36.6%）,but its survival rate was only 16.7%.When the concentration of colchicine was 8 mg/L,the induction rate of polyploidy was 15.9%,and its survival rate was up to 40.0%.Polyploidy plant of Shandong Salvia miltiorrhiza was strong and had thick,large and dark leaves,and long stomata on the lower epidermis of leaves had small density.[Conclusion] Colchicine could induce buds effectively,and the polyploidy breeding material of Salvia miltiorrhiza was obtained,which laid a foundation for shortening breeding process.

The coexistence of hermaphroditic and dioecious plants is associated with polyploidy and gender dimorphism in Dasiphora fruticosa

Dasiphora fruticosa comprises male,female and hermaphrodite plants,which are distributed sympatrically in some populations on the Qinghai-Tibet Plateau.To explore what governs the coexistence of these three sexual phenotypes,we investigated the DNA contents,pollen and ovule production,pollen deposition,and performed hand-pollination in both hermaphroditic and dioecious individuals of D.fruticosa.Flow cytometry confirmed that the DNA content of males and females were almost twice as much as that of the hermaphrodites.Male and female flowers produced more pollen grains and ovules than hermaphroditic flowers.Hand-pollinated treatments showed that unisexual flowers were sterile in one sexual function and bisexual flowers were fertile for both functions,but no sterile seeds were produced between unisexual and bisexual flowers.Our findings imply that polyploidy is related to gender dimorphism,and both are likely to play a strong role in the coexistence of two cryptic biological species of D.fruticosa(low ploidy hermaphroditic species and high ploidy dioecious species)in the Qinghai-Tibet Plateau.

<i>In Vitro</i>Induction of Polyploidy in <i>Citrus reticulata</i>Blanco

Possibility of polyploidy induction by colchicine in “Balady” mandarins was investigated in vitro. Seeds were immersed in different concentrations of colchicine solutions (0.01%, 0.05%, 0.1% and 0.2%) for different durations (12, 24 and 48 hr), then cultured in vitro on MS medium at half strength. Seed survival percentage decreased by increasing colchicine concentration and duration of treatment showing the lowest percentage at 0.2% for 48 hr. The highest DNA content was recorded at 0.2% for 24 hr. Stomata No. per unit area was decreased by colchicine treatments;moreover stomata length and width were studied. The results indicated that colchicine treatment at 0.1% for 48 hr had the highest tetraploid induction efficiency percentage.

Induced Polyploidy as a Tool for Increasing Tea(Camellia sinensis L.) Production

Tea （Camellia sinensis L.） represents different ploidy levels. In the present paper, we reviewed the recent data on the diploid, aneuploid and polyploid formed their origin and chemically induced polyploidy and predicted it role in teagenetic improvement for better yield. Different polidy levels had different effects on tea physiology. Tetraploid and triploid had more vigour and hardness due to increased size of cells, while triploid could have even more vigours due to increased size of cells and sterilities. Chemically induced polyploidy had been found an important tool for improving plant physiology and production, therefore, induced polyploids should be produced to overcome the problem of low yield and limited rainfall in tea growing areas.

Science Letters:Two ancient rounds of polyploidy in rice genome

An ancient genome duplication (PPP1) that predates divergence of the cereals has recently been recognized. We report here another potentially older large-scale duplication (PPP2) event that predates monocot-dicot divergence in the genome of rice (Oryza sativa L.), as inferred from the age distribution of pairs of duplicate genes based on recent genome data for rice. Our results suggest that paleopolyploidy was widespread and played an important role in the evolution of rice.

Improving Growth Performance of Jatropha curcas by Inducing Polyploidy through Colchicine Treatment

This study was planned to assess genetic variation in Jatropha curcas as affected by colchichine treatments. During the experiment, seeds of Jatropha curcas were collected from mature and healthy Jatropha plants and were soaked in different concentrations of colchicines. The second treatment was that of time of soaking (seeds were soaked in different concentrations for different time durations). The results clearly revealed that by increasing the concentration of colchicine treatment, parameters like stomatal density, and size of the guard cells were reduced.

Reply to Zwaenepoel et al.: Meeting the Challenges of Detecting Polyploidy Events from Transcriptomic Data

Dear Editor,Transcriptomic data have been widely employed to infer whole genome duplications (WGDs, or paleopolyploidy)(Jiao et al., 2011;Barker et al., 2016;Huang et al., 2016), through the use of large numbers of recognized paralogs with associated gene tree and Ks distributions, with the ability to date such polyploidy events.

Plant polyploidy and evolution

Polyploidy refers to two or more complete sets of chromosomes that are combined within a nucleus,and includes both autopolyploidy and allopolyploidy(Otto 2007).Polyploidy is a recurring theme in the evolutionary history of plants and it has been considered an important mechanism for speciation and also for adaptability to changing environments(Shimizu-Inatsugi et al.2017).In nature,about one-third of flowering plants are polyploids,and a great majority of them are allopolyploids.There are many cultivated allopolyploid species,such as cotton,Brassica and potato,the possible evolutionary history of which can be inferred with high certainty.

Cellular polyploidy in organ homeostasis and regeneration

Polyploid cells,which contain more than one set of chromosome pairs,are very common in nature.Polyploidy can provide cells with several potential benefits over their diploid counterparts,including an increase in cell size,contributing to organ growth and tissue homeostasis,and improving cellular robustness via increased tolerance to genomic stress and apoptotic signals.Here,we focus on why polyploidy in the cell occurs and which stress responses and molecular signals trigger cells to become polyploid.Moreover,we discuss its crucial roles in cell growth and tissue regeneration in the heart,liver,and other tissues.

Cotton genome: challenge into the polyploidy

Cottons are the most important fiber crops in the world.The cotton genus Gossypium has 52 species,including seven allotetraploid species and 45 diploids.Four species were domesticated and remain as crops under cultivation today:the New World allopolyploid species G.hirsutum and G.barbadense(2n=52),and the Old World diploid species G.arboreum and G.herbaceum(2n=26).The primary cultivated species is Upland cotton(G.hirsutum L.),which accounts for more than 90%of global cotton fiber production.

Origin and evolution of a new tetraploid mangrove species in an intertidal zone

Polyploidy is a major factor in the evolution of plants,yet we know little about the origin and evolution of polyploidy in intertidal species.This study aimed to identify the evolutionary transitions in three truemangrove species of the genus Acanthus distributed in the Indo-West Pacific region.For this purpose,we took an integrative approach that combined data on morphology,cytology,climatic niche,phylogeny,and biogeography of 493 samples from 42 geographic sites.Our results show that the Acanthus ilicifolius lineage distributed east of the Thai-Malay Peninsula possesses a tetraploid karyotype,which is morphologically distinct from that of the lineage on the west side.The haplotype networks and phylogenetic trees for the chloroplast genome and eight nuclear genes reveal that the tetraploid species has two sub-genomes,one each from A.ilicifolius and A.ebracteatus,the paternal and maternal parents,respectively.Population structure analysis also supports the hybrid speciation history of the new tetraploid species.The two sub-genomes of the tetraploid species diverged from their diploid progenitors during the Pleistocene.Environmental niche models revealed that the tetraploid species not only occupied the near-entire niche space of the diploids,but also expanded into novel environments.Our findings suggest that A.ilicifolius species distributed on the east side of the Thai-Malay Peninsula should be regarded as a new species,A.tetraploideus,which originated from hybridization between A.ilicifolius and A.ebracteatus,followed by chromosome doubling.This is the first report of a true-mangrove allopolyploid species that can reproduce sexually and clonally reproduction,which explains the long-term adaptive potential of the species.

Drought stress tolerance analysis of Populus ussuriensis clones with different ploidies

The selection of drought-tolerant plants is an important aspect of plant breeding.We studied physiological and biochemical mechanisms of different ploidies of Populus ussuriensis Kom.that relate to drought stress tolerance.We used a 5%(v/v)polyethylene glycol(PEG-6000)solution to simulate drought stress.We recorded leaf phenotypes including color,dry area and curl degree.We evaluated sequential variations in some drought stress tolerance-related physiological and biochemical indices and compared these among diploid clones(CK),triploid clones(T12)and tetraploid clones(F20).T12 leaves exhibited slightly more drought stress damage than CK and F20 leaves.CK leaves suffered the most severe drought stress damage.The physiological and biochemical indices of the different ploidies differed significantly 12 days after drought stress treatment.The activities of superoxide dismutase,peroxidase,catalase and proline in the triploid(T12)leaves were the highest.The relative electric conductivity and malondialdehyde content of T12 leaves were the lowest.The index values of F20 were between those ofthe diploid and triploid.In consideration of these results,the drought resistance of the three different ploidies of P.ussuriensis can be ranked as T12>F20>CK.We speculate that the gene expression patterns of polyploid clones of poplar will change after genome doubling and that some of the drought stress tolerance-related physiological and biochemical indices will be improved,resulting in greater drought tolerance of polyploid clones.

Morphological, cytological and molecular analyses of a synthetic hexaploid derived from an interspecific hybrid between Gossypium hirsutum and Gossypium anomalum

Gossypium anomalum represents an inestimable source of genes that could potentially be transferred into the gene pool of cultivated cotton. To resolve interspecific hybrid sterility problems, we previously treated triploid hybrids derived from a cross between Gossypium hirsutum and G. anomalum with 0.15% colchicine and obtained a putative fertile hexaploid. In this study, we performed morphological, molecular and cytological analyses to assess the hybridity and doubled status of putative interspecific hybrid plants. Most of the morphological characteristics of the putative hexaploid plants were intermediate between G. hirsutum and G.anomalum. Analysis of mitotic metaphase plates revealed 78 chromosomes, confirming the doubled hybrid status of the hexaploid. Genome-wide molecular analysis with different genome-derived SSR markers revealed a high level of polymorphism(96.6%) between G. hirsutum and G. anomalum. The marker transferability rate from other species to G. anomalum was as high as 98.0%. The high percentage of polymorphic markers with additive banding profiles in the hexaploid indicates the hybridity of the hexaploid on a genome-wide level. A-genome-derived markers were more powerful for distinguishing the genomic differences between G. hirsutum and G. anomalum than D-genome-derived markers. This study demonstrates the hybridity and chromosomally doubled status of the(G. anomalum × G. hirsutum)2hexaploid using morphological, cytological and molecular marker methods. The informative SSR markers screened in the study will be useful marker resources for tracking the flow of G. anomalum genetic material among progenies that may be produced by future backcrosses to G. hirsutum.

Adaptive responses drive the success of polyploid yellowcresses(Rorippa,Brassicaceae)in the Hengduan Mountains,a temperate biodiversity hotspot

Polyploids contribute substantially to plant evolution and biodiversity;however,the mechanisms by which they succeed are still unclear.According to the polyploid adaptation hypothesis,successful polyploids spread by repeated adaptive responses to new environments.Here,we tested this hypothesis using two tetraploid yellowcresses(Rorippa),the endemic Rorippa elata and the widespread Rorippa palustris,in the temperate biodiversity hotspot of the Hengduan Mountains.Speciation modes were resolved by phylogenetic modeling using 12 low-copy nuclear loci.Phylogeographical patterns were then examined using haplotypes phased from four plastid and ITS markers,coupled with historical niche reconstruction by ecological niche modeling.We inferred the time of hybrid origins for both species as the mid-Pleistocene,with shared glacial refugia within the southern Hengduan Mountains.Phylogeographic and ecological niche reconstruction indicated recurrent northward colonization by both species after speciation,possibly tracking denuded habitats created by glacial retreat during interglacial periods.Common garden experiment involving perennial R.elata conducted over two years revealed significant changes in fitness-related traits across source latitudes or altitudes,including latitudinal increases in survival rate and compactness of plant architecture,suggesting gradual adaptation during range expansion.These findings support the polyploid adaptation hypothesis and suggest that the spread of polyploids was aided by adaptive responses to environmental changes during the Pleistocene.Our results thus provide insight into the evolutionary success of polyploids in high-altitude environments.

Asymmetric evolution and domestication in allotetraploid cotton (Gossypium hirsutum L.)

Polyploidy plays a major role in genome evolution,which corresponds to environmental changes over millions of years.The mechanisms of genome evolution,particularly during the process of domestication,are of broad interest in the fields of plant science and crop breeding.Upland cotton is derived from the hybridization and polyploidization of its ancient A and D diploid ancestors.As a result,cotton is a model for polyploid genome evolution and crop domestication.To explore the genomic mysteries of allopolyploid cotton,we investigated asymmetric evolution and domestication in the A and D subgenomes.Interestingly,more structural rearrangements have been characterized in the A subgenome than in the D subgenome.Correspondingly,more transposable elements,a greater number of lost and disrupted genes,and faster evolution have been identified in the A subgenome.In contrast,the centromeric retroelement(RT-domain related) sequence of tetraploid cotton derived from the D subgenome progenitor was found to have invaded the A subgenome centromeres after allotetrapolyploid formation.Although there is no genome-wide expression bias between the subgenomes,as with expression-level alterations,gene expression bias of homoeologous gene pairs is widespread and varies from tissue to tissue.Further,there are more positively selected genes for fiber yield and quality in the A subgenome and more for stress tolerance in the D subgenome,indicating asymmetric domestication.This review highlights the asymmetric subgenomic evolution and domestication of allotetraploid cotton,providing valuable genomic resources for cotton research and enhancing our understanding of the basis of many other allopolyploids.

Divergence in homoeolog expression of the grain length-associated gene GASR7 during wheat allohexaploidization

Hexaploid wheat has triplicated homoeologs for most of the genes that are located in subgenomes A, B, and D. GASR7, a member of the Snakin/GASA gene family, has been associated with grain length development in wheat. However, little is known about divergence of its homoeolog expression in wheat polyploids. We studied the expression patterns of the GASR7 homoeologs in immature seeds in a synthetic hexaploid wheat line whose kernels are slender like those of its maternal parent(Triticum turgidum, AABB, PI 94655) in contrast to the round seed shape of its paternal progenitor(Aegilops tauschii, DD, AS2404). We found that the B homoeolog of GASR7 was the main contributor to the total expression level of this gene in both the maternal tetraploid progenitor and the hexaploid progeny, whereas the expression levels of the A and D homoeologs were much lower. To understand possible mechanisms regulating different GASR7 homoeologs, we firstly analyzed the promoter sequences of three homoeologous genes and found that all of them contained gibberellic acid(GA) response elements, with the TaG ASR7 B promoter(pT aG ASR7B) uniquely characterized by an additional predicted transcriptional enhancer. This was confirmed by the GA treatment of spikes where all three homoeologs were induced, with a much stronger response for TaG ASR7 B. McrB C enzyme assays showed that the methylation status at pT aG ASR7 D was increased during allohexaploidization, consistent with the repressed expression of TaG ASR7 D. For pT aG ASR7 A, the distribution of repetitive sequence-derived 24-nucleotide(nt) small interfering RNAs(siR NAs) were found which suggests possible epigenetic regulation because 24-nt siR NAs are known to mediate RNA-dependent DNA methylation. Our results thus indicate that both genetic and epigenetic mechanisms may be involved in the divergence of GASR7 homoeolog expression in polyploid wheat.

Glycosmis longipetala F.J.Mou & D.X.Zhang,a new species of Rutaceae from China

Glycosmis longipetala F. J. Mou ＆ D. X. Zhang is described from Guangxi and Yunnan provinces in southwestern China. The new species is similar to G. cochinchinensis （Lour.） Pierre ex Engl. by its simple leaves, but distinguishable in having long-elliptic or oblanceolate （vs. ovate） leaves, long-ovoid to ellipsoid （vs. ovoid） floral buds, ovaries with many tubercles （vs. smooth） and glabrous （vs. pubescent） stamens. The pollen grains of the new species are 23.9±3.09 （20.8-27.0）×22.0±1.80 （20.4-24.4）μm in size with reticulate exine ornamentation in equatorial area and foveolate in polar area. The chromosome number of the new species is 2n=72.

Production of autotetraploid plants by in vitro chromosome engineering in Allium hirtifolium

Persian shallot has been propagated vegetatively through daughter bulbs and has a narrow genetic base.In the present study,to create genetic diversity in terms of ploidy level,the effects of in vitro polyploidization were investigated on morphological,physiological and phytochemical traits.Different colchicine treatments(0,0.3%,0.5% and 0.7% concentrations)for 24,36 and 48 h and oryzalin treatments(0,0.001%,0.002% and 0.004% concentrations)for 4,6 and 8 h were used.A sterile basal plate of bulbs was used for the induction of polyploidy in liquid and solid media.After obtaining plantlets,root tip chromosomes were counted for the determination of ploidy levels.Flow cytometry was performed to confirm the chromosome counting results.The regenerated diploid and tetraploid plantlets were transferred to ex vitro conditions.Colchicine and oryzalin were both successful in inducing polyploids and the polyploids induced were tetraploids and mixoploids.The highest induction of polyploidy was obtained in solid media using 0.5%(w/v)colchicine for 36 h(35.0% polyploidy induction)and in 0.001%(w/v)Oryzalin for 8 h(45.5% polyploidy induction).Differences in plantlet height and weight,bulblet weight,density,stomatal width and length,and chlorophyll content were observed between tetraploid and diploid plants.Chromosome duplication,as a result of tetraploid induction,significantly influenced the antioxidant content and enzyme activities.The results showed that total phenolic content,allicin,and antioxidant capacity were significantly higher in the tetraploid plantlets than that in the diploid plantlets.SRAP loci polymorphisms indicated that the 12 autotetraploid plants(with high allicin content)had different genotypes from the parental diploid plant.Besides,in vitro polyploidy induction not only duplicated chromosomes but also altered the DNA sequence in Allium hirtifolium.In vitro induction of tetraploids in A.hirtifolium can be a reliable way to obtain suitable plant material for breeding programs to generate new genotypic variations.

Tolerance of New Introgressive Hybrid and Backcross Forms Pathogenic Micromitisms (<i>Verticillium dahliae</i>Kleb and Fusarium oxysporum f.sp. vasinfectum)

The article is based on the use of experimental polyploidy method, with the introduction of new introgressive hybrid forms combining several species genotype with pathogenic Verticillium dahliae Kleb. and the effects of mycotoxins separated from the Fusarium oxysporum f.sp. vasinfectum micromicette on the yield of plant seeds. New artificial complex hypertension forms based on experimental polyploidy Verticillium dahliae Kleb. and Fusarium oxysporum f.sp. vasinfectum combine the potential of resistance to mycotoxins separated from microcrystals, making a tremendous contribution to the selection of new varieties and to the effectiveness of selection as a result of the use of genetic selective research as genetic-selective genetic-selector studies.

Karyotype Analysis of <i>Ocimum basilicum</i>in South-Eastern Nigeria

Ocimum basilicum is widely distributed in the tropical and subtropical regions of the world, with greatest variability in Africa and India. It is valued in many countries for its culinary, medicinal, industrial and religious importance. Although cytogenetic entries on the plant have been made in other geographical locations of the world, in Nigeria, such entries, prior to this report, have been limited if not completely unavailable. In this analysis, axillary buds, obtained from growing plants, were used to conduct mitotic study. Results from this study showed chromosome counts of 2n = 48 and 60, thus bringing to light the existence of chromosome number variation and the possibility of polyploidy at different levels in the plant species in this agro-ecological zone. This research has, therefore, established that at least there are two cytotypes in the population of Ocimum basilicum growing in the humid forest vegetation zone of Nigeria. Analysis of the two cytotypes revealed asymmetrical karyotypes, indicative of advancement in the evolutionary trend of the plant species.