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The genus Salvia L. (Lamiaceae: tribe Mentheae) contains about 1000 species. Section Aethiopis in this genus has a distribution in the Mediterranean and central Asia and contains about 34 species in Iran. This study aimed to investigate the chromosome number and meiotic behavior in five species of Salvia sect. Aethiopis. To this end, pollen mother cells were used, and the squash method was employed. The results showed that S. persepolitana and S. spinosa had a chromosome number of 2n=2x=20, while S. sclarea, S. hypoleuca, and S. limbata had a chromosome number of 2n=2x=22. The study of meiotic behavior revealed the presence of abnormalities such as chromosome stickiness, cytomixis, non-synchronous segregation, chromosome bridges, laggard chromosomes, formation of micronuclei in tetrad cells, formation of tripolar cells, and pentapolar with different frequencies in the studied species. The meiotic index was reported as the highest in S. persepolitana and the lowest in S. hypoleuca. Pollen fertility was also affected by meiotic abnormalities, showing a decreasing trend from S. persepolitana to S. spinose. Meiotic abnormalities may have played a role in the evolution of aneuploidy and polyploidy in the Salvia genus.

Intra- and interspecific hybridization in the genus Urochloa is complex due to apomixis and polyploidy. Such barriers can be overcome by crossing apomictic tetraploid plants as pollen donors with artificial tetraploid sexual plants as female parents. Another barrier is the incompatibility between the genomes of the different species used in hybridization. Since the meiotic behavior is a good indication of affinity between genomes in a hybrid, the present study analyzed the meiotic behavior of a sexual polyploid interspecific hybrid of Urochloa from the breeding program at Embrapa Beef Cattle. In addition to the segregational abnormalities associated with polyploidy, cytological studies revealed that, after diakinesis, chromosomes presented an abnormal arrangement in the metaphase plate. In 31.33% of meiocytes, chromosomes were organized into more than one plate, forming up to four metaphase plates. Another abnormality observed in 5.72% of the cells was the lack of convergence of chromosomes to the equatorial plate and consequent abnormal anaphase segregation. These abnormalities led to the formation of several nuclei within the same cell then separated by an irregular cytokinesis pattern, forming tetrads with micronuclei, tetrads with microcytes and polyads. Although the sexual hybrid S44 was selected due to its good agronomic characteristics, such as resistance to pasture spittlebugs, the main insect pest in Urochloa, the abnormal meiotic behavior seriously may compromise the formation of viable gametes and consequent formation of viable seeds. [ABSTRACT FROM AUTHOR]

In view of the scarce cytoembryological knowledge of Lessingianthus and in order to understand the contribution of polyploidy to the evolution of the genus we perform a developmental survey of anthers with the main objective of study if the different ploidy level affect the anther and pollen development in Lessingianthus species and infer the male fertility of diploid and polyploid species. Our results showed that diploid and polyploid species have normal anther development, thus polyploidy did not affect the anther wall development. The following male embryological traits are conserved among the species: tetrasporangiate anthers, four-layered anther wall of dicotyledonous development, with uniseriate persistent epidermis, invasive tapetum, tetrahedral or isobilateral tetrads, and 3-celled pollen grains. Diploid and polyploid species had high male fertility: both presented relatively high meiotic regularity and therefore formed normal viable spores independently of the ploidy level. Lessingianthus argenteus, the only species with high irregular behavior, might be a neopolyploid species. The eight studied species of the genus presented different percentages of meiotic irregularity at the different phases observed. In diploid specimens the irregularities were concentrated in anaphase of meiosis I, whereas in polyploid specimens the irregularities were dispersed through the phases of meiosis II. The main abnormal behavior identified, and therefore the main mechanisms of unreduced microspore formation, were chromosomes out of plate, bridges without fragments and asynchrony of meiosis I and II. These features broadened the male cytoembryological knowledge of the genus, confirming the suggestion that embryological characters related to male gametophyte development are conserved among the studied species. The results contribute to understand the mechanisms of polyploid formation which is an important process during the evolution of the genus. [ABSTRACT FROM AUTHOR]

Lippia alba is a phenotypically variable tropical shrub thought to comprise a young autopolyploid complex. Chromosome numbers in L. alba include 2n = 30, 38, 45, 60, and 90. High levels of chemical and phenotypic variation associated with economic and medicinal importance were reported. However, the genetic background including chromosome composition remains under-explored. Furthermore, the occurrence of at least four ploidal levels in L. alba and the lack of data for polyploid plants in tropical areas also merit further study of L. alba. Here we assessed the chromosome composition using two new satellite repeats (CL98 and CL66) applied as FISH probes to mitotic chromosomes, and we proposed to calculate the degree of homozygosis for CL66 satDNA (named as index h) and to associate it to meiotic instability. The CL98 mapping showed few variations in both number of signals and position. However, the levels of structural homozygosity for a satellite repeat CL66 were very variable. The numbers of CL66-bearing-chromosomes were under-represented in tetraploids relative to diploids implying that CL66 arrays have been lost in tetraploid lineages as a result of increased meiotic instability. High percentage of irregularities was observed in meiotic cells, especially in polyploids. L. alba complex comprised a mixture of homomorphic and heteromorphic chromosomes. Overall, the polyploid complex presents features typical of both young and older stable polyploids. It seems that L. alba genome is still in the process of stabilization. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate genetic stability by determining the meiotic index (MI) and pollen viability in F1RC2 segregating populations, obtained by the crosses between wheat commercial cultivars and synthetic wheat, aimed at introgression/genetic resistance. For MI, three ears were collected per genotype, before anthesis, and they were fixed in Carnoy’s solution. The cytological slides were prepared by crushing the anthers and staining with 1% acetocarmine, and the normal tetrads and the ones with micronuclei were observed under a light microscope. For pollen viability, the ears were collected at the stage of mature pollen grain. The methodological procedure was similar to that of the tetrads, evaluating the pollen grains as viable, with little starch, with two pores, different sizes and non-viable. The pollen grain size was measured by the Axion Vision software. All the segregating populations with MI above 90% and high pollen viability (above 85%) reflected a stable meiotic behavior. About the variation in size, the CIGM90.909/BRS 179 cross showed pollen grains with 58.43 μm and CIGM93.298/BRS Guamirim, 47.15 μm. According to the results, wheat segregating populations were considered meiotically stable and suitable for use in wheat breeding programs and for incorporation of new important genes.

Summary: Allopolyploids have globally higher fitness than their diploid progenitors; however, by comparison, most resynthesized allopolyploids have poor fertility and highly unstable genome. Elucidating the evolutionary processes promoting genome stabilization and fertility is thus essential to comprehend allopolyploid success.Using the Brassica model, we mimicked the speciation process of a nascent allopolyploid species by resynthesizing allotetraploid Brassica napus and systematically selecting for euploid individuals over eight generations in four independent allopolyploidization events with contrasted genetic backgrounds, cytoplasmic donors, and polyploid formation type. We evaluated the evolution of meiotic behavior and fertility and identified rearrangements in S1 to S9 lineages to explore the positive consequences of euploid selection on B. napus genome stability.Recurrent selection of euploid plants for eight generations drastically reduced the percentage of aneuploid progenies as early as the fourth generation, concomitantly with a decrease in number of newly fixed homoeologous rearrangements. The consequences of homoeologous rearrangements on meiotic behavior and seed number depended strongly on the genetic background and cytoplasm donor.The combined use of both self‐fertilization and recurrent euploid selection allowed identification of genomic regions associated with fertility and meiotic behavior, providing complementary evidence to explain B. napus speciation success. [ABSTRACT FROM AUTHOR]

Paspalum notatum is an important forage native to Southern Brazil and one of the most promising fodder species in terms of productivity, quality, resistance and growth speed. The objective of this study was to evaluate the reproductive mode and fertility of hybrid progenies resulting from artificial crosses among artificially duplicated sexual plants, selected intraspecific hybrids of the UFRGS breeding program and apomictic ecotypes of the species. The resulting F1 progenies were represented by 24 plants with high pollen viability (varying from 82.15 to 99.67%) and 1.2:1 segregation for the sexual: apomictic reproduction mode, indicating predominantly sexual hybrids, due to distorted segregation. In the apomictic plants, most chromosomes paired as bivalents in diakinesis. Since the low presence of abnormalities observed in the meiotic chromosome pairing and the high pollen viability of the hybrids, all plants were confirmed as promising parents for future crosses. [ABSTRACT FROM AUTHOR]

The genus Capsicum comprises a large group of hot and sweet peppers, with different morphological varieties and degree of fruits pungency. Due to its active principles is widely used in cooking and in traditional medicine, being sold in large worldwide. In order to provide cytogenetic information which supporting plant breeding programs, this study aimed to analyze the meiotic behavior, chromosome number and pollen viability of the three species of greater economic importance of Capsicum (C. annuum, C. frutescens and C. chinense). Therefore, fruits and flower buds were collected from the Experimental Center of the Universidad Nacional de Colombia, campus Palmira- CEUNP to the corresponding mitotic, meiosis and pollen viability analysis. Plants presented different meiotic abnormalities, where all can disrupt the process of meiosis cell division, creating unbalanced chromosome numbers and varied pollen fertility. Chromosome number variation, checking 2n=2x=24, 2n=2x=26, 2n=4x=48 to 2n=6x=72 chromosomes also occurred. A low degree of non-viable pollen grains was observed for C. frutescens, so these accession should not considered as a parental for plant breeding programs.

Allopolyploidy, which results from the merger and duplication of two divergent genomes, has played a major role in the evolution and diversification of flowering plants. The genomic changes that occur in resynthesized or natural neopolyploids have been extensively studied, but little is known about the effects of the reproductive mode in the initial generations that may precede its successful establishment. To truly reflect the early generations of a nascent polyploid, two resynthesized allotetraploid Brassica napus populations were obtained for the first time by open pollination. In these populations, we detected a much lower level of aneuploidy (third generation) compared with those previously published populations obtained by controlled successive selfing. We specifically studied 33 resynthesized B. napus individuals from our two open pollinated populations, and showed that meiosis was affected in both populations. Their genomes were deeply shuffled after allopolyploidization: up to 8.5 and 3.5% of the C and A subgenomes were deleted in only two generations. The identified deletions occurred mainly at the distal part of the chromosome, and to a significantly greater extent on the C rather than the A subgenome. Using Fluorescent In Situ Hybridization (BAC-FISH), we demonstrated that four of these deletions corresponded to fixed translocations (via homeologous exchanges). We were able to evaluate the size of the structural variations and their impact on the whole genome size, gene content, and allelic diversity. In addition, the evolution of fertility was assessed, to better understand the difficulty encountered by novel polyploid individuals before the putative formation of a novel stable species.

Traditional sugarcane cultivars (Saccharum officinarum) proved highly susceptible to diseases, and this led breeders to progress to interspecific crosses resulting in disease resistance. A backcrossing program to S. officinarum was then required to boost sucrose content. Clonal selection across generations and incorporation of other germplasm into cultivated backgrounds established the (narrow) genetic base of modern cultivars (Saccharum spp.), which have a man-made genome. The genome complexity has inspired several molecular studies that have elucidated aspects of sugarcane genome constitution, architecture, and cytogenetics. However, there is a critical shortage of information on chromosome behavior throughout meiosis in modern cultivars. In this study, we examined the microsporogenesis of a contemporary variety, providing a detailed analysis of the meiotic process and chromosome association at diakinesis, using FISH with centromeric probes. Chromosomal abnormalities were documented by examining high quality preparations of pollen mother cells (700 in total). Approximately 70% of the cells showed abnormalities, such as metaphase chromosomes not lined up at the plate, lagging chromosomes and chromosomal bridges, and tetrad cells with micronuclei. Some dyads with asynchronous behavior were also observed. Due to the hybrid composition of the sugarcane genome, we suggest that bivalent incomplete pairing may occur in the first prophase leading to univalency. The presence of rod bivalents showing the lagging tendency is consistent with a reduction in chiasma frequency. Finally, the presence of chromatin bridges indicates the indirect occurrence of chromosomal inversions, although chromosome fragments were not clearly recognized. Possible reasons for such meiotic abnormalities and the large prevalence of bivalent formation are discussed.

Abstract Sisyrinchium is the largest genus of Iridaceae in the Americas and has the greatest amount of cytological data available. This study aimed at investigating how genomes evolved in this genus. Chromosome number, genome size and altitude from species of sect. Viperella were analyzed in a phylogenetic context. Meiotic and pollen analyses were performed to assess reproductive success of natural populations, especially from those polyploid taxa. Character optimizations revealed that the common ancestor of sect. Viperella was probably diploid (2n = 2x =18) with two subsequent polyplodization events. Total DNA content (2C) varied considerably across the phylogeny with larger genomes detected mainly in polyploid species. Altitude also varied across the phylogeny, however no significant relationship was found between DNA content changes and altitude in our data set. All taxa presented regular meiosis and pollen viability (> 87%), except for S. sp. nov. aff. alatum (22.70%), suggesting a recent hybrid origin. Chromosome number is mostly constant within this section and polyploidy is the only source of modification. Although 2C varied considerably among the 20 taxa investigated, the diversity observed cannot be attributed only to polyploidy events because large variations of DNA content were also observed among diploids.

In this study, original mitotic chromosome counts have been presented for 10 populations belonging to 6 species of Astragalus sect. Onobrychoidei: A. aduncus, A. arguricus, A. cancellatus, A. lilacinus and A. vegetus. All taxa were diploid and possessed 2n = 2x = 16 chromosome number, consistent with the proposed base number of x = 8. In addition, meiotic studies revealed chromosome number of 2n = 2x = 16 for A. aduncus21 and A. brevidens and also 2n = 4x = 32 for A. vegetus99. Although this taxon displayed regular bivalent pairing and chromosome segregation at meiosis, some abnormalities were observed.

Abstract Microsporogenesis studies in Brachiaria have been concentrated in the species B. ruziziensis, B. decumbens and B.brizantha and hybrids because they have great importance as forage. Besides the sexual behavior, B. ruziziensis is among a minority of Brachiaria diploid species (2n = 2 × = 18), while most are tetraploid (2n= 4 × = 36) and apomictic. Brachiaria ruziziensis is used in intra and interspecific crossbreedings. For the success of interspecific hybridization, artificial tetraploidization of B. ruziziensis is necessary. The aim of this study was to compare the microsporogenesis in diploid and synthetic tetraploid B. ruziziensis plants and their respective progenies. The slides were prepared by squash technique and stained with 1% propionic carmine for meiocyte analysis and Alexander's stain for pollen viability. Abnormalities were found in all phases of meiosis in the families of the diploid and tetraploid plants and, in general, the rate was considered low, with the percentage varying according to the genotypes. The diploid family was considered more stable. For both families, there is a tendency to reduce the total frequency of abnormalities in the progenies compared to the mother plants. This response indicates that combinations of random crosses or self-fertilization among plants with the same ploidy level were favorable. For the diploid accessions, the pollen viability index was high, reaching up to 88.3%, whereas the tetraploidized plants presented lower values, reaching a maximum of 61.1%. The results will be of interest to researchers involved in tropical forage breeding or conducting intraspecific crosses, since the occurrence of regular meiosis in progenies ensures the formation of viable pollen grains. Highlights • The diploid plants showed higher pollen viability. • The microsporogenesis of the diploid and tetraploid genotypes of B. ruziziensis evaluated in this study was regular. • The progenies of the diploid and tetraploid plants showed meiotic behavior similar to the respective mother plants. [ABSTRACT FROM AUTHOR]

Traditional sugarcane cultivars (Saccharum officinarum) proved highly susceptible to diseases, and this led breeders to progress to interspecific crosses resulting in disease resistance. A backcrossing program to S. officinarum was then required to boost sucrose content. Clonal selection across generations and incorporation of other germplasm into cultivated backgrounds established the (narrow) genetic base of modern cultivars (Saccharum spp.), which have a man-made genome. The genome complexity has inspired several molecular studies that have elucidated aspects of sugarcane genome constitution, architecture, and cytogenetics. However, there is a critical shortage of information on chromosome behavior throughout meiosis in modern cultivars. In this study, we examined the microsporogenesis of a contemporary variety, providing a detailed analysis of the meiotic process and chromosome association at diakinesis, using FISH with centromeric probes. Chromosomal abnormalities were documented by examining high quality preparations of pollen mother cells (700 in total). Approximately 70% of the cells showed abnormalities, such as metaphase chromosomes not lined up at the plate, lagging chromosomes and chromosomal bridges, and tetrad cells with micronuclei. Some dyads with asynchronous behavior were also observed. Due to the hybrid composition of the sugarcane genome, we suggest that bivalent incomplete pairing may occur in the first prophase leading to univalency. The presence of rod bivalents showing the lagging tendency is consistent with a reduction in chiasma frequency. Finally, the presence of chromatin bridges indicates the indirect occurrence of chromosomal inversions, although chromosome fragments were not clearly recognized. Possible reasons for such meiotic abnormalities and the large prevalence of bivalent formation are discussed. [ABSTRACT FROM AUTHOR]

Forty wild populations belonging to five Asparagus species including the endemic A. altissimus were sampled in an eastwest bioclimatic gradient of North Algeria. More than 250 individuals were taxonomically examined and karyologically investigated. Meiotic behavior was analyzed for each species. New chromosome numbers were consistent with the base number x = 10 for the genus Asparagus, and two cytotypes, diploid and hexaploid, were observed. Four species were found to have 2n = 20 chromosomes, highlighting the prominence of diploidy in North Africa. One polyploid with 2n = 60 is reported here as the first karyological information on the endemic A. altissimus. Karyotype parameters were established and compared for diploid species. New data provided for A. acutifolius and A. albus indicate differences in the number of submetacentric chromosomes and genome size estimated by total chromosome length. A. acutifolius is distinguished by the largest genome, the smallest being that of A. horridus. The hexaploid cytotype consists of very small metacentric chromosomes. All diploid species displayed regular meiotic behavior with mostly bivalent pairing. Abnormalities, including univalents, multivalents, laggards, and bridges, were sometimes observed in A. horridus and A. officinalis. The new cytogenetic information provided in this study is discussed in the biogeographic context of the North African flora. [ABSTRACT FROM AUTHOR]

The genus Capsicum comprises a large group of hot and sweet peppers, with different morphological varieties and degree of fruits pungency. Due to its active principles is widely used in cooking and in traditional medicine, being sold in large worldwide. In order to provide cytogenetic information which supporting plant breeding programs, this study aimed to analyze the meiotic behavior, chromosome number and pollen viability of the three species of greater economic importance of Capsicum (C. annuum, C. frutescens and C. chinense). Therefore, fruits and flower buds were collected from the Experimental Center of the Universidad Nacional de Colombia, campus Palmira-CEUNP to the corresponding mitotic, meiosis and pollen viability analysis. Plants presented different meiotic abnormalities, where all can disrupt the process of meiosis cell division, creating unbalanced chromosome numbers and decreasing pollen fertility. Chromosome number variation, checking 2n=2x=24, 2n=2x=26, 2n=4x=48 to 2n=6x=72 chromosomes, also occurred. A low degree of non-viable pollen grains was observed for C. frutescens genotype, so these accession should not considered as a parental for breeding programs. [ABSTRACT FROM AUTHOR]

Allopolyploidy is a major mode of speciation in flowering plants and particularly in the grass tribe Andropogoneae, which includes sugarcane ( Saccharum officinarum) and relatives. A new species of Saccharum from South America ( S. intermedium) is described here, supported by morphological, molecular and cytogenetic evidence. Previous molecular analyses indicated an allopolyploid origin of the new species through interspecific hybridization between S. angustifolium and S. villosum. The new taxon has intermediate morphology between the two parental species. Cytogenetic analyses of the three species were performed, including chromosome counts, meiotic regularity, and pollen viability and morphology. The new taxon is hexaploid (2 n = 60), while the parental species are triploids (2 n = 30), confirming the ploidy level suggested by the number of paralogues in phylogenetic trees based on low-copy nuclear genes. This represents the first chromosome count for S. intermedium and a new cytotype for S. villosum. Although both parental species are triploids, they surprisingly exhibited regular meiosis and high pollen viability, indicating they are male-fertile, as is the hexaploid new species. Data on geographic distribution and phenology is also presented, aswell as a key for the South American species of Saccharum. [ABSTRACT FROM AUTHOR]

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Euschistus heros (Fabricius, 1798) is one of the most harmful insect pests damaging Brazilian soybean crops and has become a major problem due to its high population density and resistance to insecticides. Currently, there are no data on whether alterations of testicular morphology and chromosomal behavior are associated with the resistance mechanisms related to the action of insecticides. This study integrated analyses of the testicular morphology, meiocyte cell division, and chromosomal structure and behavior in the process of spermatogenesis in E. heros. We compared these features among wild-caught individuals, insecticide-susceptible and -resistant strains. The resistant strain was established through a selection experiment exposing the bugs to insecticides (thiamethoxam + lambda-cyhalothrin) for 15 generations. No differences were detected in the examined features among the three groups of experimental individuals: the testis comprised six lobes, with the fifth lobe thinner than the others; the karyotype was 2n = 14 (12 +XY), with no evident changes in chromosomal breakage, rearrangement or behavior in the meiosis; and abundant spermatozoa were observed in all testicular lobes. Thus, any effects of the long-term (15 generations) experimental selection by exposure to the insecticides were not detected on the male germinal tissue and chromosomes, suggesting the irrelevancy of the examined features to insecticide-resistance mechanisms in E. heros. [ABSTRACT FROM AUTHOR]

Allopolyploidy, which results from the merger and duplication of two divergent genomes, has played a major role in the evolution and diversification of flowering plants. The genomic changes that occur in resynthesized or natural neopolyploids have been extensively studied, but little is known about the effects of the reproductive mode in the initial generations that may precede its successful establishment. To truly reflect the early generations of a nascent polyploid, two resynthesized allotetraploid Brassica napus populations were obtained for the first time by open pollination. In these populations, we detected a much lower level of aneuploidy (third generation) compared with those previously published populations obtained by controlled successive selfing. We specifically studied 33 resynthesized B. napus individuals from our two open pollinated populations, and showed that meiosis was affected in both populations. Their genomes were deeply shuffled after allopolyploidization: up to 8.5 and 3.5% of the C and A subgenomes were deleted in only two generations. The identified deletions occurred mainly at the distal part of the chromosome, and to a significantly greater extent on the C rather than the A subgenome. Using Fluorescent In Situ Hybridization (BAC-FISH), we demonstrated that four of these deletions corresponded to fixed translocations (via homeologous exchanges). We were able to evaluate the size of the structural variations and their impact on the whole genome size, gene content, and allelic diversity. In addition, the evolution of fertility was assessed, to better understand the difficulty encountered by novel polyploid individuals before the putative formation of a novel stable species. [ABSTRACT FROM AUTHOR]

Chromosome number, meiotic behavior, and pollen viability were analyzed in 2 species of genus Solenanthus, S. stamineus (Desf.) Wettst. and S. circinnatus Ledeb, from Iran. This report is the first cytogenetic analysis of these species. All taxa are diploid and possess 2n = 2x = 24 chromosome number, consistent with the proposed base number of x = 12. Although this taxon displayed regular bivalent pairing and chromosome segregation at meiosis, but some abnormalities were observed.

Triticale (X Triticosecale Wittmack) is a good cereal for production of flour and feed. A segregating population of triticale was developed from a male-sterile (MS) plant. To determine whether this new source of male sterility in triticale is appropriate for use in breeding programs the expression of the male sterility phenotype was characterized through spike fertility, meiotic behavior, and pollen. Controlled crosses between male-sterile plants and control varieties male-fertile (MF) of triticale were also conducted, and cytological analyses were performed in the F2 and backcross plants. Plants with male-sterile phenotypes displayed reduced spike fertility when compared to plants with male-fertile phenotypes. Compared to male-fertile plants, male-sterile plants exhibited a lower percentage of normal meiotic cells, a reduced meiotic index and reduced pollen viability. The F2 plants had improved pollen fertility when compared to the male-sterile population; however there were no corresponding improvements in the percentage of normal meiotic cells or in the meiotic index. A single generation of backcrosses resulted in an improved meiotic index and increased pollen viability. However, no changes in the percentage of normal meiotic cells were observed. Meiotic instability, which was shown to be inheritable, was the likely cause of male sterility. Therefore, the use of this population in triticale breeding was considered to be inappropriate because it could promote or contribute to the maintenance of meiotic instability, which is commonly observed in this species.

The aim of the present study was to evaluate the possible effect of environmental factors on meiosis, meiotic index, pollenviability and in vitro germination of pollen from stock plants of the rootstocks Trifoliate, ‘Swingle’, ‘Troyer’, ‘Fepagro C13’, ‘FepagroC37’ and ‘Fepagro C41’ grown in a protected environment in comparison with stock plants grown in the field. The results showed thatvalues for the characteristics analyzed in 2008, 2009 and 2010 were always higher in the field than in the greenhouse conditions. Inthe field, the average of normal meiotic cells was 60.05%, 44.44% and 60.12%, respectively, and in the greenhouse, 52.75%, 30.95%and 52.82%, respectively. Mean pollen viability in the field was 90.28%, 56.23% and 74.74%, and, in the greenhouse, 64.25%, 41.41%and 66.71%, respectively. As temperature oscillations were higher in the greenhouse than in the field, we suggest that this negativelyaffects the reproductive characteristics analyzed.

In this study the original mitotic chromosome counts are presented for 5 Onobrychis species of O. sect. Onobrychis in Iran, 2n = 2x = 14 for O. persica, 2n = 4x = 28 for O. viciifolia, 2n = 4x = 28 for O. altissima, 2n = 2x = 14 for O. shahpurensis and 2n = 2x = 14 for O. sosnovskyi. The basic chromosome numbers of all studied taxa are consistent with the proposed base number of x = 7. In addition, the meiotic chromosome number of 2n = 4x = 28 for O. viciifolia and O. altissima and of 2n = 2x = 14 for O. sosnovskyi and O. persica are reported here. This study is the first report on the chromosome counts of O. persica and O. shahpurensis. All studied taxa displayed regular bivalent pairing and chromosome segregation at meiosis. However, some abnormalities were observed in the taxa are discussed.

In the present paper, the cytogenetic study including meiotic chromosome number and behavior along with pollen viability were performed in 4 populations of Trigonella spruneriana Boiss. This is the first cytogenetic report of the taxon. All populations are diploid and possess 2n = 2x = 16 chromosome number, which is consistent with the proposed basic number of x = 8. In addition, some meiotic irregularities observed in different populations included chromosomes stickiness, B-chromosomes, chromosome bridges resulting from stickiness, the occurrence of laggard chromosomes, formation of micronuclei in tetrad cells and cytomixis. The highest and the lowest percentages of pollen viability were observed in populations SPR 658 and SPR 566, respectively.

Acmella bellidioides es una hierba perenne pequeña, que crece naturalmente en las provincias del nordeste de Argentina, en Brasil, Paraguay y Uruguay. Pertenece a la sección Megaglottis, presenta número cromosómico gamético n = 13 y exhibe un amplio rango de variación morfológica que ha hecho difícil separarla de especies muy cercanas de la misma sección. Acmella bellidioides fue coleccionada en campos abiertos, de suelo arenoso y rocoso y se aplicaron técnicas citogenéticas convencionales para analizar sus cromosomas en mitosis, su comportamiento en la microsporogénesis y para confeccionar su cariotipo. Acmella bellidioides es diploide con 2n = 2x = 26 cromosomas de tamaño pequeño (2,22 - 4,01µm) y 39,25 µm/genoma. Su cariotipo, 12m + 10sm + 4st, es unimodal (A2 = 0,16 / R = 1,80) y levemente asimétrico (A1 = 0,42 / i = 35,88 / r>2 = 0,54 / AI = 3,69) (Categoría 3A de Stebbins). El par 9 (sm) presenta un macrosatélite terminal y constricción secundaria en el brazo corto. La microsporogénesis es normal y produce polen viable (>90%). El comportamiento meiótico es regular. En CMP en diacinesis y metafase I se observan 13 bivalentes. Éste es el primer estudio cariotípico en Acmella. Nuestro registro de 2n = 2x = 26 cromosomas coincide con el número básico x = 13 propuesto para el género y para Megaglottis, la sección más ancestral. Por lo tanto, ésta es la descripción del cariotipo básico de Acmella.Acmella bellidioides is a perennial small herb that naturally grows in north-east Argentina, Brazil, Paraguay and Uruguay. The species belongs to section Megaglottis and it has a chromosome number of n = 13. It exhibits a wide range of morphological variation that has created difficult in distinguishing it from closely related species of this section. Acmella bellidioides was collected in open fields with sandy and stony soils. Classical cytogenetic techniques were applied to analyze chromosomes at mitosis, examine behavior during microsporogenesis, and determine its karyotype. Acmella bellidioides is diploid with 2n = 2x = 26 small size chromosomes (2.22 - 4.01 µm) and 39.25 µm/genome. Its karyotype, 12m + 10sm + 4st is unimodal (A2 = 0.16 / R = 1.80) and slightly asymmetrical (A1 = 0.42 / i = 35.88 / r>2 = 0.54 / AI = 3.69) (3A Stebbins category). Chromosome pair No. 9 (sm) has a terminal macrosatellite in the short arm. Microsporogenesis is normal and produces viable pollen grains (>90%). Meiotic behavior is regular. In PMC at diakinesis and metaphase I, 13 bivalents were observed. This is the first karyotypic study in Acmella. Our record of 2n = 2x = 26 chromosomes agrees with the basic number x = 13 proposed for the genus and for section Megaglottis, regarded as most ancestral. This might be regarded, therefore, as the basic karyotypic description for Acmella.

The meiotic behavior of three tetraploid plants (2n=4x=36) originated from somatic chromosome duplication ofsexually reproducing diploid plants of Brachiaria decumbens was evaluated. All the analyzed plants presented abnormalities relatedto polyploidy, such as irregular chromosome segregation, leading to precocious chromosome migration to the poles and micronucleiduring both meiotic divisions. However, the abnormalities observed did not compromise the meiotic products which were characterizedby regular tetrads and satisfactory pollen fertility varying from 61.36 to 64.86%. Chromosomes paired mostly as bivalents indiakinesis but univalents to tetravalents were also observed. These studies contributed to the choice of compatible fertile sexualgenitors to be crossed to natural tetraploid apomicts in the B. decumbens by identifying abnormalities and verifying pollen fertility.Intraespecific crosses should reduce sterility in the hybrids produced in the breeding program of Brachiaria, a problem observedwith the interspecific hybrids produced so far.

The cytogenetical analysis of the harvestman Holmbergiana weyenberghii (Holmberg) (Eupnoi, Sclerosomatidae, Gagrellinae) from Argentina is reported for the first time. The complement of males is composed of 18 chromosomes. In meiosis there are nine homomorphic bivalents: one large, five medium-sized and three small. The chromosome number of H. weyenberghii is within the range of diploid numbers of the subfamily Gagrellinae Thorell, which shows the lowest chromosome numbers among the sclerosomatids.Se analiza citogenéticamente, por primera vez, una especie de opilión proveniente de Argentina: Holmbergiana weyenberghii (Holmberg) (Eupnoi, Sclerosomatidae, Gagrellinae). Los machos tienen un complemento cromosómico compuesto por 18 cromosomas. En meiosis, hay nueve bivalentes homomórficos: uno mayor, cinco medianos y tres menores. El número cromosómico de H. weyenberghii se encuentra dentro del rango de números diploides de los Gagrellinae Thorell; esta subfamilia presenta los números cromosómicos más bajos de Sclerosomatidae.

Conocer aspectos básicos de la citogenética de las papayas de montaña o papayuelas, especies del género Vasconcellea (Caricaceae) originarias de Ecuador y Colombia, fue el objetivo del trabajo. Botones florales se fijaron en etanol-acético 3:1 por 24h, luego se transfirieron a nueva solución y se almacenaron en frío. Los microsporocitos y los granos de polen se tiñieron con acetocarmín (1%). Se evaluaron las fases de meiosis y la viabilidad de polen para describir el comportamiento cromosómico. Se encontró que: 1) todas las seis especies estudiadas fueron diploides (2n=2x=18); 2) se describió el número cromosómico para V. sphaerocarpa, V. longiflora y V. palandensis (2n=18); 3) el grado de asimetría de los complementos cromosómicos indicó un proceso de evolución; 4) la presencia de numerosos NOR en V. sphaerocarpa está relacionada con los micronucleolos y corroboró el posible origen híbrido; y 5) V. cauliflora (42.98%) y V. cundinamarcensis (47.93%) presentaron la más baja viabilidad polínica.

Conocer aspectos básicos de la citogenética de las papayas de montaña o papayuelas, especies del género Vasconcellea (Caricaceae) originarias de Ecuador y Colombia, fue el objetivo del trabajo. Botones florales se fijaron en etanol-acético 3:1 por 24h, luego se transfirieron a nueva solución y se almacenaron en frío. Los microsporocitos y los granos de polen se tiñieron con acetocarmín (1%). Se evaluaron las fases de meiosis y la viabilidad de polen para describir el comportamiento cromosómico. Se encontró que: 1) todas las seis especies estudiadas fueron diploides (2n=2x=18); 2) se describió el número cromosómico para V. sphaerocarpa, V. longiflora y V. palandensis (2n=18); 3) el grado de asimetría de los complementos cromosómicos indicó un proceso de evolución; 4) la presencia de numerosos NOR en V. sphaerocarpa está relacionada con los micronucleolos y corroboró el posible origen híbrido; y 5) V. cauliflora (42.98%) y V. cundinamarcensis (47.93%) presentaron la más baja viabilidad polínica.This work aims to know basic aspects of cytogenetics of mountain papayas' or 'papayuelas', Vasconcellea species (Caricaceae), originated from Ecuador and Colombia. Flower buds were fixed in 3:1 acetic-alcohol solution for 24 hr, transferred to new solution and stored al low temperature. Both microsporocytes and pollen grains were stained with 1% acetic carmine. Meiosis phases and pollen viability were evaluated to describe chromosome behavior. We found that: 1) all tested species were diploid (2n=2x=18); 2) chromosome number of V. sphaerocarpa, V. longiflora and V. palandensis (2n=18) were by first time reported; 3) asymmetry level of chromosome complements indicated a evolution process in these species; 4) presence of numerous NOR in V. sphaerocarpa associated to micronucleoli corroborated its possible hybrid origin; and 5) V. cauliflora (42.98%) and V. cundinamarcensis (47.93%) presented the low percentage of pollen viability.

Cytogenetic characterization was carried out on 12 accessions from Aster squamatus (Spreng.) Hieron., Pterocaulon polystachyum DC, and Solidago microglossa DC by studying their meiotic behavior and pollen viability. These species are from the Asteraceae family, native to Rio Grande do Sul State, Brazil, and are important for medicinal use. Young inflorescences with four accessions of each species were collected, fixed in ethanol-acetic acid (3:1), and conserved in ethanol 70% until use. The method used was that of squashing the anthers and coloring with acetic orcein 2%. Meiosis was regular in all accessions, presenting chromosomal associations preferentially bivalent, where n=10 was found for Aster squamatus and n=9 for Pterocaulon polystachyum, and Solidago microglossa. The studied accessions presented a Meiotic Index (MI) that varied from 65% to 87% in Aster squamatus, 85% to 92% in Pterocaulon polystachyum, and 64% to 92% in Solidago microglossa, indicating meiotic stability, although irregularities appeared during the cellular division. The pollen viability estimative was high in all studied accessions. These results indicate that the studied species can be included in future studies of genetic breeding.Foi realizada a caracterização citogenética de doze acessos de Aster squamatus, Pterocaulon polystachyum e Solidago microglossa, espécies da família Asteraceae, nativas do Rio Grande do Sul, Brasil, por meio do estudo do comportamento meiótico e da viabilidade polínica, que possuem grande importância para uso medicinal. Inflorescências jovens de quatro acessos de cada espécie foram fixadas em álcool-ácido acético (3:1) e conservadas em álcool 70% até o uso. O método utilizado foi o de esmagamento de anteras e a coloração com orceína acética 2%. A meiose foi regular em todos os acessos, apresentando associações cromossômicas preferencialmente em bivalentes, encontrando-se n=10 para Aster squamatus e n=9 para Pterocaulon polystachyum e Solidago microglossa. Os acessos apresentaram índice meiótico que variou de 65% a 87% em Aster squamatus, de 85% a 92% em Pterocaulon polystachyum e de 64% a 92% para Solidago microglossa, indicando estabilidade meiótica, apesar de o aparecimento de irregularidades durante a divisão celular. A estimativa da viabilidade polínica foi alta para todos os acessos estudados. Esses resultados indicam que as espécies estudadas podem ser incluídas em futuros trabalhos de melhoramento genético.

The Passifloraceae is represented by species of tropical and subtropical origin. The Passiflora is the richest genus with approximately 450 species, 200 of them being native to Brazil. Recent karyological studies have reported the basic chromosome number for the Passiflora genus as x = 6, whereas x = 9, x = 10 and x = 12 were established as secondary basic numbers. High rates of fertility occur in most Passiflora species, since both meiotic index and pollen viability are above 90%. Unusual meiotic behavior has been described in some taxa. Unviable pollen were observed in some diploids species. The genome size varies from 1.83 to 5.36 pg, and significant interspecific variance has been observed. Studies using the FISH methodology have shown that there are two to three rDNA 45S sites and one 5S site in the species analyzed. In this review, information about the above-mentioned studies is presented and discussed in detail.A família Passifloraceae é representada por espécies de origem tropical e subtropical. Passiflora é o gênero mais rico, com aproximadamente 450 espécies, cerca de 200 delas nativas do Brasil. Recentes estudos cariológicos têm relatado o número básico de cromossomos para o gênero Passiflora como sendo x = 6, enquanto x = 9, x = 10 e x = 12 foram considerados números básicos secundários. Altas taxas de fertilidade são observadas na maioria das espécies de Passiflora, uma vez que o índice meiótico e a viabilidade polínica apresentam-se acima de 90%.Comportamento meiótico irregular tem sido descrito para alguns taxas. Grãos de pólen inviáveis foram observados em espécies diplóides. O tamanho do genoma varia de 1,83 a 5,36 pg, e variação interespecífica significativa tem sido observada. Estudos usando a metodologia de hibridização in situ (FISH) tem demonstrado haver de dois a três sites de DNAr 45S e um site de DNAr 5S nas espécies analisadas. Nesta revisão, informações sobre os estudos acima mencionados são apresentados e discutidos em detalhes.

Chromosome numbers and meiotic behavior are presented for the first time for Hypericum caprifoliatum(2n=48), H. cf carinatum (2n=48) and H. polyanthemum (2n= 32) and confirmed the H. perforatum (2n=32) number.Chromosomes are very small (ca. 1 to 2 mm). Meiotic irregularities, such as uni and multivalents, un-oriented chromosomes,bridges and laggards were very frequent in H. caprifoliatum and H. cf carinatum. Meiotic indexes ranged from 44.0 to 73.0%in H. caprifoliatum, 66.0 to 77.0% in H. cf carinatum and was 80.0% for the H. polyanthemum population. Pollen fertilityranged from 42.0 to 88.0% in H. caprifoliatum, 65.0 to 88.0% in H. cf carinatum and was 89.0% for H. polyanthemum.Together with literature and meiotic behavior data, the great variability in pollen size and fertility within and among populationsof H. caprifoliatum and H. cf carinatum could suggest that, as many other Hypericum species, these taxa are apomictic.

Chromosome number, meiotic behavior and pollen viability were evaluated in a collection of 53 Paspalumnicorae Parodi accessions, which are part of a breeding project of the species. All accessions are tetraploid, with 2n=4x=40.Despite the invariable chromosome numbers, there was variation among accessions in the frequencies of different chromosomeconfigurations at diakinesis and metaphase I, such as univalents, trivalents and quadrivalents. Other abnormalities asbridges and laggards were also observed at anaphase and telophase I. Meiotic indexes ranged from 82.00 to 99.50% andpollen viability from 88.99 to 95.06%. As the species is pseudogamous apomictic, fertile pollen is necessary for endospermformation. Results show that all plants are meiotically stable and have enough fertile pollen to be used as male parents incontrolled crosses.

Premise of research. The endangered Pitcairnia encholirioides has limited flowering, a low rate of seed germination, and dominant asexual reproduction. These limitations suggest restrictions in sexual reproduction that could be caused by structural changes during development. Previous results indicated normal development of ovules and female gametophytes. Therefore, to test this hypothesis, anther wall development as well as microsporogenesis and microgametogenesis were analyzed. Methodology. Using cytogenetic and anatomical analysis, the study was undertaken to determine any cellular changes that might affect sexual reproduction of the species. Accordingly, we looked for (1) the presence of cytological changes during the development of anthers and pollen grains and/or (2) any cytogenetic aberration associated with meiosis of the sporogenous cells. Pivotal results. In the samples studied, anther wall development followed the monocotyledonous type, with late proliferation of the middle layer and secretory tapetum. After the establishment of these layers, most anthers showed cytological changes that led to sterile pollen grains. In those anthers that showed fertile development, a thick callose deposition was evident. Then, after dissolution of the callose and release of microspores, the tapetum began to degenerate. However, in sterile anthers, callose deposition was thin, and tapetum degeneration--which began from the establishment of microspore mother cells--was premature. Both of these conditions contributed to the formation of anomalous microspores that did not undergo gametogenesis but did undergo maturation of the pollen wall. In spite of these observations, cytogenetic analyses revealed regular meiosis in both fertile and sterile anthers. Conclusions. Pitcairnia encholirioides bears both sterile and fertile anthers at anthesis, depending on the timing of tapetum degeneration and callose dissolution. Consequently, male sterility could account for the restrictions in sexual reproduction caused by the structural changes noted above. [ABSTRACT FROM AUTHOR]

The genus Passiflora L. consists of approximately 530 widely distributed species, including Passiflora edulis, which has drawn interest because of its commercial and agronomic value. Passiflora cincinnata is another important species owing to its long flowering period and resistance or tolerance to diseases and pests. In the present study, the meiotic segregation and pollen viability of an interspecific hybrid ( P. edulis × P. cincinnata) and its parents were analyzed. The genomic contents were characterized using chromomycin A (CMA)/4′-6′-diamidino-2-phenylindole (DAPI) staining, fluorescent in situ hybridization with 5S/45S ribosomal DNA (rDNA), genomic in situ hybridization (GISH), and inter-simple sequence repeat (ISSR) markers. The results indicated the diploid chromosome number for the parents and interspecific hybrid was 2 n = 18. We also observed regular meiosis, one pair of 5S rDNA sites, and two pairs of 45S rDNA sites that co-localized with two pairs of CMA/DAPI bands. The GISH data revealed three distinct chromosomal groups in the hybrid. The genetic origins of the interspecific hybrid, and its relationship with its parents were also confirmed using ISSR markers. [ABSTRACT FROM AUTHOR]

Chromosome number and meiotic behavior were evaluated in 36 Brazilian accessions of the grass Paspalum (which had never previously been analyzed) to determinate which accessions might be useful in interspecific hybridizations. The analysis showed that one accession of Paspalum coryphaeum was diploid (2n = 2x = 20) and one accession of Paspalum conspersum hexaploid (2n = 6x = 60), the remaining 34 accessions being tetraploid (2n = 4x = 40). The pairing configuration was typical for the ploidy level i.e. in the diploid, chromosomes paired as 10 bivalents, in tetraploids as bi-, tri- and quadrivalents, and in hexaploid as 30 bivalents. A low frequency of meiotic abnormalities (less than 10%) was observed in the diploid, hexaploid and some tetraploid accessions, although the majority of tetraploid accessions showed a high frequency of meiotic irregularities. The use of accessions with a low frequency of meiotic abnormalities in breeding programs is discussed.

Somaclonal variation in plants regenerated by organogenesis from long-term cultured calluses of two diploid staminate genotypes of Asparagus officinalis cv. Argenteuil was characterized by plant phenotype, ploidy, meiotic behavior, pollen viability, fruit and seed set, and AFLP profiles. Phenotypic deviations from the donors were detected in foliage color, flower size, and cladode and flower morphology. Ploidy changes were observed in 37.8% of the 37 regenerants studied. Meiotic alterations in 12 out of 21 regenerants included laggards, dicentric bridges, micronuclei, restitution nuclei and polyads. Of the 408 AFLP markers screened in 43 regenerants and the donors, 2.94% showed polymorphism. High pollen viability was observed in the 22 regenerants analyzed. All crosses between one pistillate plant and 35 regenerants, as well as the controls, produced fruits and seeds; however, no plump seeds resulted in 35.3% of the crosses with regenerants, and no seeds germinated in 12.5% of those with apparently normal seeds. Fruit and seed set was similar in crosses with diploid regenerants with normal meiosis and the controls but was lower in crosses with diploid and polyploid regenerants with abnormal meiosis. Our results show that the regenerated plants exhibited conspicuous somaclonal variation that could be eventually exploited for in vitro selection systems.

O objetivo deste trabalho foi analisar a microsporogênese e a viabilidade dos grãos de pólen em 17 espécies de aráceas coletadas no Rio Grande do Sul, Brasil. Nove espécies foram analisadas quanto à ocorrência de células mãe de pólen (CMP) normais e anormais nas fases de metáfase, anáfase e telófase, tanto da meiose I (M I) como da meiose II (M II); 10 espécies foram estudadas quanto à presença de tétrades com número normal ou anormal de micrósporos e 17 espécies quanto à viabilidade dos grãos de pólen. As CMP anormais apresentaram, tanto em M I quanto em M II, cromossomos fora da placa metafásica ou cromossomos retardatários em anáfase e/ou telófase. As freqüências de CMP normais/anormais encontradas na microsporogênese salientam a grande variação existente entre as espécies. Ressalta-se a ausência de CMP com anomalias na microsporogênese de Monstera deliciosa Adans., assim como em M I de Anthurium scandens (Aubl) Engl. e em M II de Caladium hortulanum Birdsey. O número observado de CMP anômalas, em M I e M II, nas espécies Syngonium podophyllum Schott e Zantedeschia aethiopica Spreng, foi maior que o esperado. A freqüência média de tétrades normais em dez espécies de aráceas, assim como a de grãos de pólen viáveis em 17 espécies, foi significativamente superior à freqüência média de anormais e de inviáveis, respectivamente.The objective of this work was to analyze microsporogenesis and pollen viability in 17 species of the Araceae family collected at Rio Grande do Sul, Brazil. Occurrence of normal and abnormal pollen mother cells (PMC) was analyzed in metaphase, anaphase and telophase, in meiosis I (M I) and meiosis II (M II) of nine species; tetrads with normal or abnormal number of microspores was observed in 10 species, and pollen grain viability, in 17 species. Abnormal PMC presented chromosomes outside the metaphasic plate or laggard chromosomes in anaphase and/or telophase in both M I and M II. The frequencies of normal/abnormal PMC found in microsporogenesis point out to the existence of great variation among the species. It should be emphasized the absence of PMC with abnormalities in Monstera deliciosa Adans. microsporogenesis, as well as in Anthurium scandens (Aubl) Engl. M I and in Caladium hortulanum Birdsey M II. The number of anomalous PMC in Syngonium podophyllum Schott and Zantedeschia aethiopica Spreng in M I and M IIwas higher than expected. Average frequency of normal tetrads in ten araceous species and viable pollen grains in 17 species were significantly superior to the average frequency of abnormal tetrads and unviable pollen grains, respectively.

Despite of economic importance of the genus Paspalum, little or no cytologic information is available for many species. This is the first report about chromosome number and meiotic behavior for P. maritimum. The three accessions collected in Amapá State (North Region of Brazil) were tetraploid (2n=4x=40) with the chromosomes associating predominantly as bivalents. The low frequency of multivalents suggested that they were segmental allotetraploids. All accessions showed a low rate of meiotic irregularities, and as a consequence the pollen fertility was high. The results suggested that these accessions presented potential for use in a hybridization program.Apesar da importância econômica do gênero Paspalum, pouca ou nenhuma informação citológica é encontrada para a maioria das espécies. Esta é a primeira descrição sobre número de cromossomos e comportamento meiótico para P. maritimum. Os três acessos coletados no Estado do Amapá mostraram-se tetraplóides (2n=4x=40) com os cromossomos associando-se predominantemente como bivalentes. A baixa ocorrência de associações multivalentes sugere que estes acessos sejam alotetraplóides segmentais. Todos os acessos mostraram uma baixa frequência de anormalidades meióticas e, como consequência, uma alta fertilidade de pólen, mostrando potencial para serem utilizados em programas de hibridização.

In this study, original mitotic chromosome counts have been presented for 10 populations belonging to 6 species of Astragalus sect. Onobrychoidei: A. aduncus, A. arguricus, A. cancellatus, A. lilacinus and A. vegetus. All taxa were diploid and possessed 2n = 2x = 16 chromosome number, consistent with the proposed base number of x = 8. In addition, meiotic studies revealed chromosome number of 2n = 2x = 16 for A. aduncus21 and A. brevidens and also 2n = 4x = 32 for A. vegetus99. Although this taxon displayed regular bivalent pairing and chromosome segregation at meiosis, some abnormalities were observed. [ABSTRACT FROM AUTHOR]

Interspecific hybrids involving the cultivated C. arabica (2n = 4x = 44, EECC) and two related diploid species (2n = 2x = 22), C. eugenioides (EE) and C. liberica (LL), were produced and analyzed for their relative genome affinity using different complementary approaches, including chromosome association analysis, genomic in situ hybridization (GISH) and pollen fertility. The mean arm pairing frequency ( c) and the relative affinity index ( x) of triploid hybrids with known genome combinations were used as a measure of chromosome homology. Triploid hybrids were highly sterile as a result of meiotic abnormalities (fertility ranged from 1 to 15 %). Nevertheless, all hybrids exhibited a significant occurrence of genome affinities ( x = 0.96 for ECE and 0.81 for ECL). Further analysis using the GISH approach revealed that C. eugenioides was more closely related to C. arabica than to C. liberica, which was in agreement with the ancestral history of the allotetraploid C. arabica. The absence of incompatibility barriers at the stylar level in the flowers of the triploid hybrids indicates the possibility of desirable gene transfer through breeding strategies. [ABSTRACT FROM AUTHOR]

The meiotic behavior of three tetraploid plants (2n=4x=36) originated from somatic chromosome duplication of sexually reproducing diploid plants of Brachiaria decumbens was evaluated. All the analyzed plants presented abnormalities related to polyploidy, such as irregular chromosome segregation, leading to precocious chromosome migration to the poles and micronuclei during both meiotic divisions. However, the abnormalities observed did not compromise the meiotic products which were characterized by regular tetrads and satisfactory pollen fertility varying from 61.36 to 64.86%. Chromosomes paired mostly as bivalents in diakinesis but univalents to tetravalents were also observed. These studies contributed to the choice of compatible fertile sexual genitors to be crossed to natural tetraploid apomicts in the B. decumbens by identifying abnormalities and verifying pollen fertility. Intraespecific crosses should reduce sterility in the hybrids produced in the breeding program of Brachiaria, a problem observed with the interspecific hybrids produced so far. [ABSTRACT FROM AUTHOR]