Unreduced Pollen Grains Research Articles

Cytogenetic analysis of interspecific hybridization in oil-tea (Camellia oleifera)

Oil-tea (Camellia oleifera) is an important woody plant species producing edible oil in southern China, which shows complicated cytogenetics and intraspecific polyploidy. In order to explore the ploidy variation in interspecific hybridization of oil-tea Camellia, the ploidy of ‘Huashuo’, ‘Youza 2’ and 18 superior hybrids of ‘Youza 2’ × ‘Huashuo’ were identified by flow cytometry and chromosome counting. C.oleifera variety ‘Huashuo’ was hexaploid (2n = 90), and Camellia yuhsienensis superior plant ‘Youza 2’ was aneuploid based on hexaploid (2n = 91). There are not only hexaploid but also aneuploid in the ‘Huashuo’ × ‘Youza 2’ hybrids. Among the offspring plants, there are 11 plants each with chromosome number of 90, 6 plants each with 91, and 1 plants each with 92. To elucidate the causes of ploidy variation in above findings, the pollen characteristics and chromosomal behavior in meiosis of ‘Huashuo’ were examined by microscopy. The chromosome pairing configuration of meiosis terminal stage of microsporocytes of ‘Huashuo’ was 43 II + 2 IV. In all stages of meiosis, numerous abnormal behaviors were found, such as precocious chromosome migration, free chromosomes, lagging chromosomes and micronucleus. The abnormal rates of metaphase I, anaphase I, metaphase II and anaphase II were 67.5%, 88.1%, 58.4% and 78.9%, respectively. In the tetrad stage, abnormal phenomena such as dyads, triads, hexads and micronucleus were observed, with the frequency of 1.4%, 1.0%, 1.0% and 4.2%, respectively. The pollen diameter of ‘Huashuo’ varied widely (16.92–79.13 μm), suggesting a wide range of ploidy level of pollen grains. From pollen diameter distribution, we concluded that ‘Huashuo’ produced a small number of unreduced pollen grains. These findings are valuable for cytogenetics research and selection strategy of ploidy breeding in C. oleifera.

Male meiosis in 18 species of 07 genera of the tribe Astereae (Asteraceae) from Western Himalaya

Meiotic studies in 18 species belonging to 7 genera of the tribe Astereae from various localities of Western Himalaya have been analyzed. The chromosome number has been reported for the first time in Aster albescens (n = 9) and A. indamellus (n = 9). Further, intraspecific variability has been reported for the first time in A. thomsonii (n = 27), Bellis perennis (n = 5) and Myriactis nepalensis (n = 18). In India, the chromosome numbers are reported for first time in Aster himalaicus (n = 9), Brachyactis roylei (n = 9), Erigeron bellidioides (n = 9) and E. borealis (n = 9). B-chromosomes have been reported for the first time in Erigeron acer (n = 9 + 1 − 2B). Besides, most of the populations show laggards, chromosome stickiness and cytomixis from early prophase to telophase-II, leading to the formation of aneuploid cells or meiocytes with doubled chromosome number. Such meiotic abnormalities produce unreduced pollen grains and adversely affect pollen viability.

Genetic potential and cytoembryological characteristics of Beta vulgaris L. lines of apozigotic reproduction

Purpose. To investigate the possibility of transferring elements of apozigotic reproduction (adventitious embryo) to combinational-valuable CMS lines; to carry out screening of breeding materials of the Verkhniatska Research Breeding Station for apomictic reproduction. Methods. Cytoembryological methods of embryogenesis, microsporogenesis.Results. It was found that the bulk of pollen grains of all the breeding materials under study belonged to the type b. In addition, they were characterized by a high variability of pollen grains (12.0 to 26.0 microns) that indicated the instability of the breeding materials. The line Sf (I2S1I11) had genotypes with the pollen type c. The type of pollen indicates the presence of unreduced pollen grains and it is a marker of the presence of unreduced parthenogenesis, which relates to regular apomixis. Most of the anomalies in embryological development were recorded in accessions F1 CMS 2-1 No. 120, 123 (8–10%), and F2 CMS 25 No. 105, 102 (6.0–7.3%). The following anomalies of the embryo were detected: the location of the embryo in the pectoral part, the medial position of the embryo, coenocytes. The SF line of I2S1I11 No. 3314 was characterized by the largest number of apomictic embryo clusters (55%). The presence of coenocytes was detected.Conclusions. The possibility of transferring the adventitious embryo from the donor [Sf line (I2S1I11)] to the combinational-valuable MS lines was studied. It has been established that the line F2 MS 25 shows a greater tendency to form apomictic germs (7.3–14.9%), compared with F1CMS 2-1 (5.0–12.5%). The analyzed CMS lines of the Verkhniatska RBS were characterized by certain instability under the cytoembryological test.

Cytogenetic study of the genus Anchusa L. (Boraginaceae) in Iran

AbstractAnchusa L., with four species, is one of the weedy species of Boraginaceae in Iran. These species are distributed in different habitats. Species delimitation is mainly based on corolla lobes, corolla tube condition and fruit shape. In this study chromosome number and meiotic behavior of 10 populations of Anchusa taxa have been considered. Due to the large number of studied populations of A. italica we have considered the intra-specific variation in this species. Statistical multivariate methods were done by use of PAST software ver. 5. 2012. Although all populations showed the chromosome number 2n = 4x = 32, population of A. arvensis subsp. orientalis showed the presence of n = 8 (2n = 2x = 16). This is the first meiotic study for Anchusa. Variation in meiosis stages such as synozytic knot was observed. Meiotic irregularities such as cytomyxis, stickiness, anaphase bridge, laggard chromosomes, micronucleus, triad and unreduced pollen grains were observed.

Impact of cytomixis on the microspogenesis and formation of unreduced pollen grains in monocots

Aim. Despite significant progress in the investigation of cytomixis its functional role and effect on the course of meiosis as well as mechanisms of 2n pollen grains formation is still not completely clear. We have studied the destination of cytomictic chromatin as well the mechanisms of unreduced microspores formation in species of monocots with spontaneous cytomixis. Methods. Light and fluorescent microscopy. Results. The cytomictic chromatin forms additional meiotic chromosomes in the recipient microsporocytes. Many of these meiotic chromosomes undergo rearrangement and fragmentation but retain their bivalent organization. Conclusions. Cytogenetic anomalies of microsporogenesis caused by activation of cytomixis in prophase may reflect meiosis stabilization mechanisms by assimilation and adaptation or diminution and reutilization of the introduced DNA. The main mechanism of polyploidization of microsporocytes and pollen grains in studied monocots is the restitution of the first meiotic division via the formation of a meta-anaphase 1 block.Keywords: cytomixis, microsporogenesis, additional (recipient) chromosomes, meta-anaphase 1 block, Lilium croceum Chaix., Allium cepa L., Allium fistulosum L.

Cytogenetic variations in eight species of Saussurea DC. (Asteraceae, Cardueae) from Northwest Himalaya

The genus Saussurea comprises many species with highly medicinal, religious or other economical values. The chromosome number in the genus ranges from 2n = 24 to 108, based on x = 12, 13, 16, or 17, but the primary base number is still not clear. The present meiotic study cover 8 species (14 populations) of Saussurea from the Northwest Himalayas, and add new or varied cytotypes, as an attempt to solve the enigmatic cytogenetic variations in the genus. The chromosome numbers in Saussurea auriculata (n = 16) is new to the world, while S. costus (n = 17), S. jacea (n = 17) and S. roylei (n = 17) reveal the varied cytotypes at world level. Besides, S. taraxicifolia (n = 16) is a first ever report for Indian populations. The meiotic studies on different populations reveal a substantial amount of meiotic abnormalities in the form of chromosome stickiness, un-oriented bivalents, cytomixis, laggards, etc. leading to the meiocytes with less (aneuploidy) or more (polyploidy) chromosome numbers. These abnormalities may produce unreduced pollen grains and adversely affect pollen viability. The high number of these meiotic abnormalities may be responsible for the chromosome number variation in the genus.

Anomalous Chromosomal Behaviour and Chromosomal Data in Some Members of Subclass Gamopetalae from District Hamirpur (H. P.), India

The present study pertains to the cytomorphology of 19 species belonging to nine families of the subclass Gamopetalae from Hamirpur district (H. P.). Out of these, 5 species are new or varied chromosomes reports. Campanula benthamii (2n=2x=28) and Leucas hyssopifolia (2n=2x=22) are the first ever chromosome counts for the species. Spilanthes acmella (2n=6x=78) and Borreria articularis (2n=4x=52) are varied cytotypes. Meanwhile, the B chromosome is reported for the first time in Leucas lanata (2n=22+0-1B). Almost all of the accessions (with disparity in percentage) show laggards, chromosome stickiness and cytomixis from early prophase to telophase-II, leading to the formation of aneuploid cells or meiocytes with double the normal chromosome number. Such meiotic abnormalities produce unreduced pollen grains and reduce pollen viability.

The rising world of flow cytometric analysis of pollen grains.

Key terms flow cytometry; genome size; plant sciences; pollen grains; pulse analysis FLOW cytometry is nowadays recognized as a vital tool in plant sciences, with more and more applications in both basic and applied research (1). Due to the unique characteristics of plant material, i.e., complex three-dimensional tissues with the presence of rigid cell walls, specific methods had to be developed to produce suspensions of single particles of interest (2). These particles of interest include, nuclei, mitochondria, chloroplasts, and chromosomes, with most of the applications being focused around the estimation of nuclear DNA content (either in absolute or relative amounts), leading to increasing impacts in the fields of plant breeding and population biology. One of the few single particles produced by plants is the pollen grain. Still, most works focused on studying pollen grains have involved the extraction of nuclei or sperm cells, rather than using the intact pollen. This is mostly due to the autofluorescence and/or specific staining of the pollen exine, and to the particle size limitations of some flow cytometers (3). To add to this, isolation of high-quality nuclei from pollen grains is often difficult, at least in comparison with somatic tissues. Together, these difficulties have led to a very minute number of publications involving flow cytometric analysis of pollen grains in the last 25 years.

Meiotic studies in some species of tribe Cichorieae (Asteraceae) from Western Himalayas.

The present paper deals with meiotic studies in 15 species belonging to 6 genera of the tribe Cichorieae from various localities of Western Himalayas. The chromosome number has been reported for the first time in Hieracium crocatum (2n = 10) and Lactuca lessertiana (2n = 2x = 16). Further, intraspecific variability has been reported for the first time in H. umbellatum (2n = 2x = 10 and 2n = 6x = 54), Tragopogon dubius (2n = 2x = 14 and 2n = 4x = 28), and T. gracilis (2n = 2x = 14). The chromosome report of 2n = 2x = 10 in Youngia tenuifolia is made for the first time in India. Maximum numbers of the populations show laggards, chromosome stickiness, and cytomixis from early prophase to telophase-II, leading to the formation of aneuploid cells or meiocytes with double chromosome number. Such meiotic abnormalities produce unreduced pollen grains and the reduced pollen viability.

Cytomorphological investigations in Oxyria digyna Hill. from the Kashmir Himalaya, India

In the present paper, detailed cytomorphological investigations in Oxyria digyna Hill. from Kashmir Himalaya-India have been reported for the first time. All the of 14 investigated populations of O. digyna are diploid based on x = 7. Out of these in two populations 0-2B chromosomes have been recorded for the first time while 6 populations differed significantly in their meiotic characteristics. Meiotic abnormalities during male meiosis observed include inter PMC chromatin transfer (cytomixis). Non-synchronous disjunction of some bivalents, laggards and bridges at anaphases and telophases. Consequent to these meiotic anomalies, microsporogenesis in meiocytes is abnormal resulting in to dyads, triads and polyads with or without micronuclei. The overall effect is seen in reduced pollen fertility. Unreduced pollen grains were observed in some populations, which differed significantly in their size compared to the normal (reduced) pollen grains. It is observed that a smaller frequency of pollen grains differed morphologically in Aharbal and Yosmarg populations. The remaining eight populations showed regular meiotic course, normal microsporogenesis and high percentage of pollen fertility (95.09-99.09%).

Correlation between geography and cytogenetic diversity in Pomegranate (Punica granatum L.) cultivars in Iran

Pomegranate (Punica granatum L.) is an important horticultural plant with several cultivated forms planted in different regions of Iran. Due to its economic importance, studies have been carried out to illustrate the genetic diversity at the chromosomal and molecular levels in different pomegranate cultivars growing in this region. This study analyzed chromosome pairing and B-chromosomes of 21 pomegranate cultivars and tried to investigate the effects of geographical parameters like altitude and longitude as well as elevation and the mean annual rainfall on cytogenetic diversity of these taxa. An ANOVA test revealed the presence of a significant difference for chiasmata and chromosome pairing among the cultivars, indicating their genetic differences. A positive significant correlation was observed between total chiasma frequency and terminal chiasmata, intercalary chiasmata and the mean number of quadrivalents. A significant positive correlation was observed between annual rainfall and the mean number of rod bivalents, while a significant negative correlation was found for the number of ring bivalents. Altitude did not show any correlation with the cytogenetic characters studied, but showed a significant negative correlation with the number of univalents. Longitude showed significant positive correlation with the number of ring bivalents and a negative correlation with the number of univalents and intercalary chiasmata. PCA analysis showed that both geographical and cytological features contribute greatly in the diversity observed in the pomegranate cultivars. The occurrence of multipolar cells and unreduced pollen grains were observed in some of the cultivars.

New Chromosome Number Reports in <i>Cousinia</i> Species (Compositae)

The cytological study of several populations in 4 species of Cousinia tenuifolia, C. tabrisiana, C. urumiensis and C. microcephala showed the occurrence of 2n=2x=26 chromosome number in all the species studied, information which is new to science. The species formed mainly bivalents and univalents in the metaphase of meiosis I, but in some populations quadrivalents were also formed due to heterozygote translocations. A wide range of meiotic abnormalities were observed including laggard chromosome formation, chromosomes stickiness and tripolar cell formation, leading to the formation of unreduced pollen grains. The occurrence of 0-2 B-chromosomes was observed in most of the species and populations studied. Karyotype analysis showed that the chromosomes are metacentric (m) and submetacentric (sm), varying in size from 0.55 to 1.79 μm. The ANOVA test showed significant difference in total chromosome length, size of the long arm and short arm of the chromosomes as well as arm ratio of the chromosome pair numbers 1–4 and 8, indicating the role of both quantitative and structural changes of chromosome in cytological diversity of Cousinia species.

Cytogenetic Analysis of Mehr Cotton Cultivar and Its Crossing Progenies: A Search for Unreduced Pollen Grains

Cytogenetic Analysis of Mehr Cotton Cultivar and Its Crossing Progenies: A Search for Unreduced Pollen Grains

Population Diversity and Polyploidy Incidence in 3 <i>Silene</i> Species. A Cytological Approach

Cytological studies were performed in 20 populations of 3 Silene species of the section Auriculatae L., Silene gynodiocia Ghazanfar, S. crispans Litw., S. indeprensa Schischk. The populations studied had 2n=2x=24, 2n=4x=48 and 2n=8x=96 chromosome number, showing 2 polyploidy levels for S. indeprensa and S. gynodiocia. The chromosomes were mostly metacentric and submetacentric but 1 pair of teloentric chromosome was observed in the octaploid Dargaz population of S. indeprensa. The ANOVA test showed no significant difference among populations of S. indeprensa and populations of S. gynodiocia for size of the chromosomes, mean chromosome length, A1 and A2 indices as well as TF value. This indicates that no significant chromatin loss or gain has occurred in the process of karyotype differentiation in these populations, and in the case of octaploid and tetraploid populations, still the mean value of chromosomes are maintained. However, the species differed significantly for CV value, indicating that during species diversification a change has occurred in the size of chromosomes within a karyotype due to structural changes of the chromosomes. Meiosis analysis showed that the chromosomes mainly form bivalents and univalents in the metaphase of meiosis I, although some amounts of quadrivalents were observed in all populations including diploids due to heterozygote translocations. T-test analysis showed significant difference in the relative values of total and terminal chiasmata as well as a number of ring bivalents between the populations having 2n=24 and 2n=48 chromosome number indicating that with an increase in polyploidy level, significant change has occurred in the number of genes controlling chiasma frequency. The occurrence of unreduced pollen grains indicates the role of this phenomenon in polyploidy incidence in the species studied.

Meiotic Chromosome Numbers in 9 Iranian Species of Oryzopsis (Poaceae)

Meiotic studies were performed in 9 Oryzopsis species of O. pubiflora, O. lateralis, O. holciformis, O. barbellata, O. munroi, O. microcarpa, O. sphacelata, O. virescense and O. molinioides showing the presence of 2n=2x=24 in all nine species studied. The species studied were diploid and had 12 chromosome number, and in O. microcarpa, O. sphacelata, O. molinioides and O. virescense chromosomes are new count. B-chromosomes 0–2 were observed in all species studied, which were smaller than A-chromosomes and did not pair with them. T-test analysis between the cells with B-chromosomes and those devoid of Bs showed significant difference in chiasma frequency and distribution as well as in chromosomes pairing only in O. munroi, with significant reduction in meiotic values in the presence of B-chromosomes. The occurrence of large pollen grains (possibly unreduced pollen grains) was observed along with small (normal) pollen grains in these species. Significant difference observed in chiasma frequency and distribution among species studied may be of use in species delimitation. Moreover species relationships obtained based on cytological data partly supports taxonomic treatment of the genus.

Cytomixis and Unreduced Pollen Grain Formation in Alopecurus L. and Catbrosa Beauv. (Poaceae)

Meiotic studies were performed on the populations of four Alepecurus L. species and varieties as well as five populations of two Catabrosa species. Alopecurus textilis showed 2n=8x=56 chromosome number, the varieties of A. myosuroides var. myosuroides and A. myosuroides var. breviaristatus showed 2n=2x=14 and A. arundinaceus possessed 2n=6x=42. Catabrosa aquatica and C. capusii showed 2n=4x=20 chromosome number. The chromosome numbers of A. textilis, A. myosuroides var. myosuroides and A. myosuroides var. breviaristatus and C. capusii are new to science, while hexaploid level is new for A. arundinaceus. Tetraploid and octaploid species of Alopecurus and Catabrosa studied formed bivalents in metaphase of meiosis-I, which is considered a diplontic behavior for polyploid species. Grouping of the species by clustering methods based on relative cytogenetical characteristics showed good separation between Alopecurus and Catabrosa species indicating the cytogenetic distinctness of these two grass genera. Cytomixis and chromosome migration occurred in most of the species and populations studied forming aneuploid and polyploid meiocytes. Unreduced pollen grains were formed possibly as a result of cytomixis in the species studied.

Chromosome Pairing and Chiasma Formation in Some Olive (Olea europaea L.) Cultivars of Iran

Cytogenetic characteristics of 11 olive cultivars were studied considering their chromosome pairing and segregation. The cultivars studied possessed 2n=4x=46 chromosome number and formed only bivalents in metaphase of meiosis-I. The cultivars differed significantly in their chiasma frequency and distribution as well as chromosome pairing indicating partly their genetic distinctness. Meiotic abnormalities including laggard chromosomes and chromosome stickiness occurred in the cultivars studied. B-chromosomes, cytomixis and unreduced pollen grains were observed in some of the cultivars. Clustering and ordination of the olive cultivars based on cytogenetic characteristics showed distinctness of these cultivars. B-chromosomes and unreduced pollen grain formation are new in olive cytogenetics.

Controlled Pollination with Sorted Reduced and Unreduced Pollen Grains Reveals Unreduced Embryo Sac Formation in Diospyros kaki Thunb. ‘Fujiwaragosho’

This study investigated ploidy levels of endosperm and embryos in seeds of the hexaploid (2n = 6x = 90) Diospyros kaki ‘Fujiwaragosho’ to determine the possible origin of unusual ploidy levels observed in seedlings of this cultivar. Female flowers of ‘Fujiwaragosho’ were pollinated with sorted reduced (3x) and unreduced (6x) pollen grains of ‘Zenjimaru’ in 2004 and 2005. Embryo rescue culture was conducted with normally developing seeds that were excised from immature fruit harvested in August. Ploidy levels of the endosperm and plantlets from the embryos in the seeds were determined by flow cytometry. In some cases, chromosomes of root tip cells of the plantlets were also counted to determine ploidy levels of the embryos. It appeared that seeds obtained with reduced pollen pollination contained a normal hexaploid embryo and nonaploid (9x) endosperm, while those obtained with unreduced pollen pollination mostly contained a dodecaploid (12x) embryo and octadecaploid (18x) endosperm. These results indicated unreduced embryo sac formation in ‘Fujiwaragosho’. We discuss the possible cause of the occurrence of only nonaploid and octadecaploid endosperm, respectively, with reduced and unreduced pollen pollinations.

Cytogenetic study of some populations of Foeniculum vulgare (Umbelliferae) in Iran

AbstractChromosome pairing, chiasma frequency and distribution as well as chromosome segregation were analyzed in 13 populations of Foeniculum vulgare. All populations possessed n = 11 (2n = 2x = 22) chromosome number forming mainly bivalents with some amount of quadrivalents possibly due to the occurrence of heterozygote translocations. Cytomixis and desynapsis occurred in all populations leading to the formation of unreduced pollen grains. Cluster analysis of meiotic data showed distinctness of the populations in their meiotic behavior.

Meiotic Studies of Some Stipa (Poaceae) Species and Populations in Iran

Meiotic studies were performed on 11 populations of 8 Stipa species concerning polyploidy level, chiasma frequency and distribution, chromosomes association and segregation. All the species and populations studied possessed n=22 (2n=4x=44) chromosome number. The chromosome numbers of 3 species are reported for the first time. The populations and species studied differed significantly in their meiotic characteristics. Meiotic abnormalities observed included laggard chromosome formation, stickiness and cytomixis. Cytomixis led to the formation of aneuploid meiocytes. Unreduced pollen grains were observed in 2 species, which differed significantly in their size compared to the normal (reduced) pollen grains.