Sterile Triploids Research Articles

Characterization of piRNAs in Diploid and Triploid Pacific Oyster Gonads: Exploring Their Potential Roles in Triploid Sterility.

PIWI-interacting RNAs (piRNAs) are crucial for silencing transposable elements, germ cell development, and gametogenesis. Triploid Pacific oysters (Crassostrea gigas) are vital in the oyster aquaculture industry due to reduced fertility and rapid growth. This study integrates piRNA and mRNA expression analyses to elucidate their potential contributions to the sterility of triploid C. gigas. Bioinformatics analysis reveals a distinct U-bias at the 5' terminal of oyster piRNAs. The abundance of piRNA clusters is reduced in triploid gonads compared to diploid gonads, particularly in sterile gonads, with a significant decrease in piRNA numbers. A specific piRNA cluster is annotated with the PPP4R1 gene, which is downregulated in infertile female triploids and exhibits a negative correlation with three piRNAs within the cluster. Differential expression analysis identified 46 and 88 piRNAs in female and male comparison groups, respectively. In female sterile triploids, the expression of three target genes of differentially expressed piRNAs associated with cell division showed downregulation, suggesting the potential roles of piRNAs in the regulation of cell division-related genes, contributing to the gonad arrest observed in female triploid oysters. In male triploid oysters, piRNAs potentially interact with the target genes associated with spermatogenesis, including TSSK4, SPAG17, and CCDC81. This study provides a concise overview of piRNAs expression in oyster gonads, offering insights into the regulatory role of piRNAs in triploid sterility.

Kazakhstan Has an Unexpected Diversity of Medicinal Plants of the Genus Acorus (Acoraceae) and Could Be a Cradle of the Triploid Species A. calamus.

The Acorus calamus group, or sweet flag, includes important medicinal plants and is classified into three species: A. americanus (diploid), A. verus (tetraploid), and A. calamus (sterile triploid of hybrid origin). Members of the group are famous as components of traditional Indian medicine, and early researchers suggested the origin of the sweet flag in tropical Asia. Subsequent research led to an idea of the origin of the triploid A. calamus in the Amur River basin in temperate Asia, because this was the only region where both diploids and tetraploids were known to co-occur and be capable of sexual reproduction. Contrary to this hypothesis, triploids are currently very rare in the Amur basin. Here, we provide the first evidence that all three species occur in Kazakhstan. The new records extend earlier data on the range of A. verus for c. 1800 km. Along the valley of the Irtysh River in Kazakhstan and the adjacent Omsk Oblast of Russia, A. verus is recorded in the south, A. americanus in the north, and A. calamus is common in between. We propose the Irtysh River valley as another candidate for a cradle of the triploid species A. calamus. It is possible that the range of at least one parent species (A. americanus) has contracted through competition with its triploid derivative species, for which the Irtysh River floods provide a tool for downstream range expansion. We refine our earlier data and show that the two parent species have non-overlapping ranges of variation in a quantitative metric of leaf aerenchyma structure.

APIS: an updated parentage assignment software managing triploids induced from diploid parents.

In aquaculture, sterile triploids are commonly used for production as sterility gives them potential gains in growth, yields, and quality. However, they cannot be reproduced, and DNA parentage assignment to their diploid or tetraploid parents is required to estimate breeding values for triploid phenotypes. No publicly available software has the ability to assign triploids to their parents. Here, we updated the R package APIS to support triploids induced from diploid parents. First, we created new exclusion and likelihood tables that account for the double allelic contribution of the dam and the recombination that can occur during female meiosis. As the effective recombination rate of each marker with the centromere is usually unknown, we set it at 0.5 and found that this value maximizes the assignment rate even for markers with high or low recombination rates. The number of markers needed for a high true assignment rate did not strongly depend on the proportion of missing parental genotypes. The assignment power was however affected by the quality of the markers (minor allele frequency, call rate). Altogether, 96-192 SNPs were required to have a high parentage assignment rate in a real rainbow trout dataset of 1,232 triploid progenies from 288 parents. The likelihood approach was more efficient than exclusion when the power of the marker set was limiting. When more markers were used, exclusion was more advantageous, with sensitivity reaching unity, very low false discovery rate (<0.01), and excellent specificity (0.96-0.99). Thus, APIS provides an efficient solution to assign triploids to their diploid parents.

Genome-wide identification and expression analysis of Dmrt gene family and their role in gonad development of Pacific oyster (Crassostrea gigas).

Doublesex and Mab-3-related transcription factor (Dmrt) is a type of transcription factor with a zinc-finger DM structural domain, which plays a significant role in sex determination and differentiation in animals. Although Dmrt has been reported in many vertebrates and invertebrates, it has rarely been studied in bivalves. In this study, a total of three members of the Dmrt gene family were identified and characterized in Crassostrea gigas, and all these CgDmrt genes contained a conserved DM domain. Analysis of the phylogenetic tree and gene structure revealed that Dmrt genes clustered on one branch may have similar functions in bivalves. Expression profiling of CgDmrt mRNA in different tissues and stages of gonad development indicated that CgDmrt3 exhibited sexually dimorphic expression and played an important role in the development of the male gonad in C. gigas. Furthermore, analysis of CgDmrt mRNA expression between fertile triploids and sterile triploids showed that CgDmrt3 may be involved in sperm production. Collectively, the systematic analysis of the CgDmrt genes will provide potential insights into the function of these genes in gonadal development.

Effects of Polyploidization on Locomotor and Flight Activity, and Body Size of Males in Japanese Bumblebee, Bombus ignitus

Polyploid animals are seen in the wild in only a few groups such as planaria, weevils, ants, wasps, and bees. The sex of bumblebees is determined by the single-locus complementary sex determination (sl-CSD) system resulting in females emerging from fertilized eggs and males (normal males, haploid) emerging from unfertilized eggs. However, diploid males (polyploids) emerged from fertilized eggs when the sex-determining locus become homozygous caused by inbreeding due to population contraction. To examine the effects of polyploidization on behavioral characteristics in bumblebee males, Bombus ignitus, haploid and diploid males were compared in locomotor activity, ease of staying inside the hive, and flight activity in a laboratory experiment. The results showed that diploid males had higher locomotor activity levels, were less likely to stay inside the hive, and had lower flight activity levels than haploid males. The reduced flight activity levels may lead to lower mating rates in the field. Furthermore, the body size of diploid males was smaller than that of haploid males. Diploid males of bumblebees have a low reproductive and produce diploid sperms to emerge sterile triploids, thus creating a considerable genetic load on the population. The behavioral and morphological characteristics of diploid males may unintentionally serve as a mechanism to prevent the emergence of sterile triploids.

Origin, genetic structure and evolutionary potential of the natural hybrid Ranunculus circinatus × R. fluitans

Understanding the genetic variability of hybrids provides information on their current and future evolutionary role. In this paper, we focus on the interspecific hybrid Ranunculus circinatus × R. fluitans that forms spontaneously within the group Ranuculus L. sect. Batrachium DC. (Ranunculaceae Juss.). Genome-wide DNA fingerprinting using amplified fragment length polymorphisms (AFLP) was employed to determine the genetic variation among 36 riverine populations of the hybrid and their parental species. The results demonstrate a strong genetic structure of R. circinatus × R. fluitans within Poland (Central Europe), which is attributed to independent hybridization events, sterility of hybrid individuals, vegetative propagation, and isolation through geographical distance within populations. The hybrid R. circinatus × R. fluitans is a sterile triploid, but, as we have shown in this study, it may participate in subsequent hybridization events, resulting in a ploidy change that can lead to spontaneous fertility recovery. The ability to produce unreduced female gametes of the hybrid R. circinatus × R. fluitans and the parental species R. fluitans is an important evolutionary mechanism in Ranunculus sect. Batrachium that could give rise to new taxa.

Variability of Reproduction Pathways in the Central-European Populations of Hawthorns with Emphasis on Triploids.

The role of apomeiosis, parthenogenesis, and pseudogamy in the asexual reproduction of some plant groups has not been fully elucidated in relation to species diversification. Quantitative analyses of seed origin may help in gaining better understanding of intercytotypic interactions. Asexual reproduction associated with polyploidy and frequent hybridization plays a crucial role in the evolutionary history of the genus Crataegus in North America. In Europe, the genus represents a taxonomically complex and very difficult species group not often studied using a modern biosystematic approach. We investigated the reproduction pathways in mixed-cytotype populations of selected taxa of Crataegus in eastern Slovakia, Central Europe. The investigated accessions were characterized by seed production data and the ploidy level of mature plants as well as the embryo and endosperm tissues of their seeds determined via flow cytometry. Diploid and polyploid hawthorns reproduce successfully; they also produce high numbers of seeds. An exception is represented by an almost sterile triploid. Diploids reproduce sexually. Polyploids shift to asexual reproduction, but pseudogamy seems to be essential for regular seed development. In rare cases, fertilization of unreduced gametes occurs, which offers opportunity for the establishment of new polyploid cytotypes between diploid sexuals and polyploid asexuals. Opposite to sexual diploids, triploids are obligate, and tetraploids almost obligate apomicts. Apomixis is considered to help stabilize individual weakly differentiated polyploid microspecies. Pseudogamy is a common feature and usually leads to unbalanced maternal to paternal contribution in the endosperm of triploid accessions. Parental contribution to endosperm gene dosage is somehow relaxed in triploids. Our Crataegus plant system resembles reproduction in the diploids and polyploids of North American hawthorns. Our data provide support for the hypothesis that polyploidization, shifts in reproduction modes, and hybridization shape the genus diversity also in Central Europe.

Triploidization of rainbow trout affects proteins related to ovary development and reproductive activity

Rainbow trout are characterized by high amenability to chromosome manipulations during early development to produce androgens, gynogens, or sterile triploids, which are relevant in aquaculture. An understanding of the mechanisms affecting oogenesis and those resulting in diminished gonadal development in triploids is an important area of scientific study. Therefore, the aim of this study was to compare the ovary proteome from triploid (3 N) and diploid (2 N) rainbow trout females using tandem mass tag (TMT) peptide labelling coupled with liquid chromatography–mass spectrometry (LC–MS/MS) to identify differentially expressed proteins (DEPs) between 2 N and 3 N. The potential biological role of DEPs was also explored using comparative functional gene set enrichment to designate the potential protein markers of 3 N sterility. We identified a total of 3899 DEPs (q < 0.05), including 956 downregulated and 2943 upregulated proteins in 3 N ovaries compared to 2 N ovaries. The identified clusters for downregulated proteins in 3 N included lipid metabolic process, hormone biosynthesis, transport and exocytosis, cell junction organization and sperm-egg recognition, which can result in (i) the disruption of lipid, steroid hormone and vitellogenesis processes, (ii) impaired amino acid uptake, (iii) defects in cell–cell junctions reflecting tissue abnormalities and aberrant gonadal morphology, and (iv) impaired functions related to maintaining the proper structure of the vitelline envelope, oocyte formation and fertilization competence. With respect to upregulated proteins in 3 N ovaries, RNA processing, cell cycle, cytoskeleton organization and regulation of metabolic process were the primary clusters, which may reflect (i) the disturbance to RNA processing responsible for impairment of ovary development in triploid rainbow trout, (ii) disruption of spindle formation, incorrect chromosome alignment and segregation during meiotic division, (iii) increase in regulatory mechanism of apoptosis, which in consequence can provoke abnormal gonadal development and sterility, and (iv) enhanced ubiquitin–proteasome system governing aberrant gonadal morphology in 3 N females and oocyte maturation. The obtained results provide an accurate portrait of molecular changes in rainbow trout ovaries in response to triploidization and may contribute to a better understanding of the mechanisms responsible for impaired oogenesis in rainbow trout triploid females, which in turn leads to their sterility. Data are available via ProteomeXchange with identifier PXD034492.

Heat shock treatments for polyploid induction in Clarias gariepinus: Different time after fertilization and treatment duration

Manipulation chromosome through heat shock treatment is safe method and can be applied to mass production in order to fulfil demand in animal food industry. The aim of the study was to evaluate how heat shock affected fertilized eggs after 4 minutes (triploid) and 40 minutes (tetraploid) of fertilization. After heat treatment of Clarias gariepinus fish eggs, the rate of abnormality of fertilized eggs were also determined. Heat shock treatments were 39°C, 40°C, and 41°C for 4 minutes, with times of 4 minutes after fertilization and 40 minutes after fertilization, with three repetitions of each treatment. The results showed that heat shock after 4 minutes of fertilization significantly affected the rate of slow embryonic development starting from the cleavage stage of 8 cell up to hatching compared to treatment 40 minutes after fertilization. The treatment with a shocking temperature of 41°C after 4 minutes of fertilization resulted in the highest percentage rate of abnormalities, 45.67%. Thus, this study revealed that tetraploid development was superior to triploid development due to higher egg abnormalities in triploid. Tetraploids are preferable as broodstocks to produce sterile triploids and can enlarge rapidly.

Investigation of the role of endogenous miRNAs in determining sterility in triploid Pacific oysters (Crassostrea gigas)

Triploid oysters generate fewer gametes than diploid oysters and exhibit varying degrees of gonad development. The expression of related genes, such as those involved in gametogenesis and energy metabolism, may influence reproductive potential. In addition, microRNAs (miRNAs) are important regulators of gene expression. However, the contribution of miRNAs has not yet been assessed in sterile triploid Pacific oysters (Crassostrea gigas). We therefore obtained extensive miRNA and gene expression data to identify potentially critical miRNA-mRNA interactions that are linked to sterility in triploid C. gigas. Here, we found miR-263-x to be significantly downregulated in the gonads of sterile females. The upregulated target genes were associated with lipid droplet formation, which revealed the likely involvement of nutrient accumulation during gonadal development as regulated by miR-263-x in female sterile triploids. In males, the upregulated miRNAs (miR-1992-y and miR-2001-x) were shown to regulate spermatogenesis-related gene expression, including flagellar formation, and cell proliferation and migration. Our results suggest that energy redistribution regulated by miRNAs may be critical for gonad development in females, indicating that sterile triploids undergo a significant reduction in gamete number and show an increased accumulation of nutrients in the gonads. Our findings further indicate that decreased expression of genes related to spermatogenesis regulated by miRNAs is important in gonadal dysgenesis in sterile triploids. These results shed light on the epigenetic regulatory mechanisms governing sterility in triploid bivalves.

Once more unto the breach, dear friends: Resolving the origins and relationships of the Pellaea wrightiana hybrid complex.

The taxonomic status of Wright's cliff brake fern, Pellaea wrightiana, has been in dispute ever since it was first described by Hooker in 1858. Previously published evidence suggested that this "taxon" may represent a polyploid complex rather than a single discrete species, a hypothesis tested here using a multifaceted analytical approach. Data derived from cytogenetics, spore analyses, leaf morphometrics, enzyme electrophoresis, and phylogenetic analyses of plastid and nuclear DNA sequences are used to elucidate the origin, relationships, and taxonomic circumscription of P. wrightiana. Plants traditionally assigned to this taxon represent three distinct polyploids. The most widespread, P. wrightiana, is a fertile allotetraploid that arose through hybridization between two divergent diploid species, P. truncata and P. ternifolia. Sterile triploids commonly identified as P. wrightiana, were found to be backcross hybrids between this fertile tetraploid and diploid P. truncata. Relatively common across Arizona and New Mexico, they are here assigned to P. ×wagneri hyb. nov. In addition, occasional sterile tetraploid plants assigned to P. wrightiana are shown here to be hybrids between the fertile allotetraploid and the tetraploid P. ternifolia subsp. arizonica. These tetraploid hybrids originated independently in two regions of parental sympatry (southern Arizona and west Texas) and are here assigned to P. ×gooddingii hyb. nov. Weaving together data from a diversity of taxonomic approaches, we show that plants identified as P. wrightiana represent three morphologically distinguishable polyploids that have arisen through repeated hybridization events involving the divergent sexual taxa P. ternifolia and P. truncata.

Transcription Analysis for Core Networks of lncRNAs-mRNAs: Implication for Potential Role in Sterility of Crassostrea gigas.

Simple SummaryThis study reveals the expression profiles of lncRNA in the gonads of the Pacific oyster Crassostrea gigas. The potential function of lncRNAs was predicted in the case of antisense and cis-regulatory mechanisms based on their physical positions and their coexpression relationships in the case of trans regulation. Sterility-related DEGs and DELs were chosen for subsequent analysis, demonstrating that trans-regulatory lncRNAs might play a vital role in the gametogenesis of C. gigas. We constructed core networks of lncRNAs–mRNAs for triploid sterile females and hermaphrodites based on pathway results, in which 28 lncRNAs and their 54 trans-regulatory genes were detected. Among 28 sterility-specific lncRNAs, MSTRG.79882.3 and MSTRG.79882.4 for triploid sterile females and MSTRG.33704.1, MSTRG.63844.1, and MSTRG.5675.1 for hermaphrodites play the most significant role.Long noncoding RNA (lncRNA), a type of non-protein-coding transcript, is emerging as a crucial regulator of gene expression. However, few roles of lncRNA in the reproductive process of the Pacific oyster (Crassostrea gigas) have been defined, especially in the regulatory mechanism of sterile triploids gametogenesis. To uncover the potential role of lncRNA, the gonads of diploids, sterile triploids, and partially sterile triploids underwent RNA sequencing. A total of 9618 reliable lncRNAs were identified. The target relationship between lncRNA and mRNA was predicted based on cis, trans, and antisense regulation with bioinformatic software. We chose differentially expressed lncRNAs and mRNAs when sterile triploids were compared to partially sterile triploids and diploids for subsequent functional enrichment analysis. Findings revealed that trans-regulatory lncRNAs might play a significant role in the gametogenesis of C. gigas. Combining pathway results, we constructed core networks of lncRNAs–mRNAs for triploid sterile females and hermaphrodites. Fifty-four genes related to cell division, germline-cell maintenance, and glycogen metabolism were found to be associated with sterility. A total of 28 candidate lncRNAs were predicted to trans-regulate these genes. We speculated that MSTRG.79882.3 and MSTRG.79882.4 for triploid sterile females and MSTRG.33704.1, MSTRG.63844.1, and MSTRG.5675.1 for hermaphrodites were highly important as they were predicted to regulate more sterility-specific genes than others. Our work collectively identified sterility-related lncRNAs and implicated the potential mechanism of lncRNA-mediated regulation in the gametogenesis of sterile triploid oysters.

A comparison of triploid and diploid Atlantic salmon (Salmo salar) performance and welfare under commercial farming conditions in Norway

ABSTRACT Avoiding genetic interactions between wild and farmed Atlantic salmon is regarded as one of the major requirements for a sustainable salmon aquaculture industry. For this reason, farming functional sterile triploids has been suggested as a possible solution. However, knowledge about how triploids cope under commercial conditions is lacking. In the present study, we compared the performance of diploid and triploid Atlantic salmon among four Norwegian aquaculture companies. Diploid and triploid groups of the same genetic line were farmed in western, mid, and northern Norway under commercial conditions from seawater transfer until slaughter.Overall, triploid salmon exhibited reduced survival, higher incidence of emaciated fish, and scored, on average, a lower quality rating during primary processing. The results highlight the need for further research on how to improve the welfare and performance of triploid salmon in commercial aquaculture operations.

Integration of miRNA-mRNA co-expression network reveals potential regulation of miRNAs in hypothalamus from sterile triploid crucian carp

The sterile triploid crucian carp (TC) has growth superiority which is generated from crossing between diploid red crucian carp (Carassius carassius red var. ♀) (RC) and tetraploid hybrid linage [derived from RC (♀) × common carp (Cyprinus carpio, ♂) (CC)]. Hypothalamus is an important control center for hormone releasing participating in gonadal development. In the present study, the microRNA (miRNA) alternations in the hypothalamus from RC, CC and TC were analyzed. A total of 143 known miRNAs and 519 novel miRNAs were identified from the hypothalamus. Thereinto, miR-7a, miR-128 and miR-9-3p were the most abundant miRNAs accounting for 13.37%, 12.01% and 11.15% of all the miRNA reads, respectively. A total of 109, 208 and 228 differentially expressed miRNAs (DEMs) were identified from RC vs TC, CC vs TC and CC vs RC, respectively. For these DEMs, 46 miRNA-mRNA pairs were identified by miRNA target prediction. In addition, using weighted gene co-expression network analysis (WGCNA), 17 modules of co-expressed miRNAs and mRNA were constructed and yellow module had the highest correlation with the sterile triploid. A total of 107 novel miRNAs, 29 conserved miRNAs and 1343 genes were contained in yellow module and metabolic processes, biosynthetic processes, chromosome organization, cytoskeleton organization, gene expression and axis specification were enriched GO terms in this module. The top three hub miRNAs were let-7a, miR-100 and miR-122 which were correlated with 1086, 1172 and 1222 genes, respectively. These results indicated that the hub miRNAs and their regulated gene network play a central role in controlling endocrine secretion and gamete maturation. In addition, the abnormal expression of these miRNAs contributes to the sterility of TC. The present evidence provides insights into the miRNA and gene constructed network of sterility in triploid fish.

Triploidy affects postprandial ammonia excretion but not specific dynamic action in 1+ brook charr, Salvelinus fontinalis

The use of sterile triploids in aquaculture is currently limited because of reduced performance in situations of aerobic stress such as high temperature, hypoxia, and exhaustive exercise. Many studies have therefore attempted to find underlying metabolic differences between triploids and their diploid counterparts to improve triploid rearing protocols. This study investigated the effects of triploidy on postprandial metabolism (and therefore also pre-feeding standard metabolic rate; SMR) in 1+ (193 ± 5 g; mean ± SE) diploid and triploid brook charr, Salvelinus fontinalis. Oxygen uptake and total ammonia nitrogen (TAN) excretion were measured at 14–15 °C for previously fasted (for eight days) fish from 48 h before to 48 h after being sham-fed or fed a single ration of 0.4% of their body mass. While there were no ploidy-related differences in SMR or any of the measured SDA parameters, triploids had significantly higher net TAN excretion (by 36%) than diploids. Such a difference in protein metabolism could affect triploid growth and survival when simultaneously faced with suboptimal conditions, though further studies are warranted.

Morphological characterization of diploid and triploidAcorus calamus(Acoraceae) from southern Western Siberia, parthenocarpy in sterile plants and occurrence of aneuploidy

AbstractFinding morphological differences between cytotypes that are stable throughout their geographical range is important for understanding evolution of polyploid complexes. The ancient monocot lineage Acorus includes two groups, of which A. calamus s.l., an important medicinal plant, is a polyploid complex with a centre of diversity in Asia. European plants are sterile triploids introduced by humans. An early study suggested that plants from temperate Asia are tetraploids, but subsequent work revealed diploids and triploids rather than tetraploids in Asiatic Russia; however, cytotype diversity in Western Siberia is insufficiently known. We document the occurrence of diploids and triploids in Western Siberia. Triploids that do not differ in genome size from European Acorus are abundant in the valley of the river Ob where the ability for extensive vegetative propagation provides ecological advantages. An isolated population of aneuploid triploids with 33 chromosomes is found outside the Ob valley. Flow cytometry provides an efficient tool for identification of aneuploid plants in Acorus. All triploids are sterile, but their flowers develop uniform parthenocarpic fruits. Fruits of diploids usually vary in size within a spadix depending on the number of developing seeds. In contrast to North America, where the native diploid plants differ from the introduced triploids by the absence of a secondary midrib of the ensiform leaf blade, Siberian diploids are similar to triploids in possessing a secondary midrib. We confirm that diploids differ from triploids in the size of air lacunae in leaves, which is determined by cell number rather than cell size in septa of aerenchyma. A combination of spathe width and spadix length measured after the male stage of anthesis shows different (slightly overlapping) patterns of variation between diploids and triploids in our material.

Expression pattern of Piwi-like gene implies the potential role in germline development in the Pacific oyster Crossosrea gigas

Piwi is necessary for germ cell development in a diverse range of organisms and homologues have been commonly used to identify primordial germ cells (PGCs) during embryogenesis. Here, we isolated full-length cDNA of Piwi ortholog in the Pacific oyster Crassostrea gigas and characterized its expression patterns (Cg-Piwi-like) along with analyzing the expression alternation in the gonad of diploids compared with those sterile triploids. qPCR showed that the transcript of Cg-Piwi-like was mainly restricted to the gonad in diploids with ovarian tissues of triploids showing the highest expression. in situ hybridization revealed that Cg-Piwi-like was found in both female and male gonad where the strongest expression was shown in the germ cells at early stages with no signal in somatic cells. Whole-mount in situ hybridization suggested Cg-Piwi-like was maternally deposited and the localization of Cg-Piwi-like mRNA in mesodermal cells might be the putative PGCs in C. gigas. These results suggest that Cg-Piwi-like was involved in germ line formation, differentiation, and maintenance of germ cells in C. gigas. The obtained findings provide valuable evidences to further facilitate identification of the putative PGCs in the Pacific oyster using Cg-Piwi-like as a molecular marker.

Telomere Dynamics in the Diploid and Triploid Rainbow Trout (Oncorhynchus mykiss) Assessed by Q-FISH Analysis.

Changes of telomere length with age were assessed in diploid and triploid rainbow trout (Oncorhynchus mykiss) females in the cross-sectional study using Q-FISH technique. Triploid trout as sterile do not invest an energy in gametogenesis and continue to grow, whereas fertile diploid individuals suffer from declines in growth and survival during sexual maturation. However, triploid and diploid specimens exhibited similar patterns of telomere dynamics. Telomere length in the embryos, larvae and one-year-old juveniles did not change significantly. In the second year after hatching, subadults exhibited substantially shortened telomeres, while significant increase of the telomere length was reported in the three-year-old adults. On the other hand, correlation between telomere length and body size was observed in the triploid, but not in the diploid rainbow trout. Telomere shortening observed in two-year-old subadults may have been associated with the premature period of the fast growth in rainbow trout. Similar pattern of the telomere dynamics reported in the fertile diploids and sterile triploids indicated processes related to reproduction did not affect telomere dynamics in this species. Unexpected increase of the telomere length reported during the third year of life confirmed that in rainbow trout telomeric DNA shortens and lengthens, depending on the developmental stage.

Ploidy, Fertility, and Phenotypes of F1 Hybrids between Tetraploid Highbush Blueberry Cultivars and Diploid Vaccinium elliottii

A progeny of 55 blueberry seedlings produced by pollinating 4301 flowers of tetraploid highbush blueberry cultivars with pollen from 19 different diploid Vaccinium elliottii plants was studied to determine hybridity and ploidy. Of the 21 seedlings whose phenotypes were intermediate between parental types, indicating hybridity, 18 were triploid and three were tetraploid. Pollen of the triploids, when viewed at ×250, was almost all shrunken and aborted, although some triploid hybrids produced a few large, plump microspores in dyads or monads. Triploids produced no seed when pollinated with pollen from 4x highbush or 2x V. elliottii or when open-pollinated outside the greenhouse in the presence of fertile diploid and tetraploid blueberries. Tetraploid hybrids produced large populations of vigorous seedlings when intercrossed. Both triploid and tetraploid F1 hybrids were intermediate between the parents in leaf size and flower size. The triploids produced no berries; the tetraploids were intermediate between the parents in berry size but averaged lower in Brix and berry firmness than either parent. Seven additional F1 hybrids from reciprocal crosses were obtained by pollinating 2309 flowers of 2x V. elliottii with pollen from tetraploid highbush cultivars. Although five V. elliottii clones served as female parents in these crosses, only one produced any seedlings. Six of the seven hybrids flowered and were fertile tetraploids; one was a sterile triploid.

Polyploidy as a Management Strategy for Invasive Species

Most invasive species are prolific seed-producing landscape ornamental plants that have been introduced to non-native habitats with limited or no natural controls on their reproduction and spread. Techniques for converting prolific seed-producing landscape ornamentals into sterile or nearly sterile forms are available. Oryzalin and colchicine have been used to double chromosomes, resulting in autotetraploids with reduced fertility and potential parent plants of sterile triploids. Guard cell measurements and flow cytometry have been used to determine ploidy conversion and identify polyploids. Complete sterility has been achieved in three species of shower trees (Cassia sp.), and up to a 95% reduction in seed production has been achieved in royal poinciana (Delonix regia) and african tulip tree (Spathodea campanulata). Monkey pod (Albizia saman) crosses have produced triploid progeny to evaluate for sterility.