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HIGHLIGHTS Callogenesis was induced from watermelon anthers The auxin 2,4-D at 2.0 and 5.0 μM concentrations induced callus formation. Anthers' responses to the pre-treatment at 4 °C varied according to the watermelon genotype.
Abstract Callus induction is one of the pathways required for haploid plant regeneration through anther culture. Pollen viability, as well as the effect of growth regulators and cold pretreatment on anthers of two watermelon lines (Smile and Sugar Baby) to induce callus formation were herein evaluated. Pollen viability was estimated through the staining technique using 2% acetic carmine. Male flower buds were collected and disinfested to allow removal anthers. These anthers were placed on Murashige and Skoog medium, which was supplemented with 2,4-dichlorophenoxyacetic (2,4-D) at 0.0, 0.5, 1.0, 2.0 or 5.0 μM or with 6-benzylaminopurine at 0.0, 0.5, 1.0, 1.5, or 2.0 μM, in combination with 2.0 μM of 2,4-dichlorophenoxyacetic. Anthers were pretreated at 4 °C, for two days and then placed in vitro. Both watermelon lines provided high pollen viability rates (from 93 to 98%). The 2.0 and 5.0 μM concentrations of 2,4-D stimulated higher friable callus formation. The optimal concentration of 2,4-D was estimated at 3.78 μM and 4.17 μM, which had callus induction rates of 64% and 52%, respectively. The combination of 2.0 μM of 2,4-D and 6-benzylaminopurine did not lead to increased anther response to callus induction. The pre-treatment applied to flower buds at 4 °C enabled callus induction and the anther response to callus induction was genotype-dependent.
Subject(s)
Plant Growth Regulators , Pollen , Citrullus , GenotypeABSTRACT
Stevia rebaudiana (Bertoni) Bertoni (2n=2x=22) (Asteraceae family) is a species of economic value due to the presence of steviol glycosides in leaves -mainly stevioside and rebaudioside A- which are non-caloric sugars. In 2013, a collection of plants (genotypes) from four contrasting environments was established in Tucuman, Argentina, for evaluation under local conditions and, eventually, breeding purposes. As a first step, pollen viability and meiosis was studied in a sample of 56 plants. The percentage of pollen viability varied from medium (69.4%) to high (99.6%) in 52 of them, but from low (36.5%) to relatively low (51.5%) in the remaining four. The latter four plants also presented pollen grains of heterogeneous size, which were classified as n (normal, the most frequent size in the sample),
Stevia rebaudiana (Bertoni) Bertoni (2n=2x=22) (familia Asteraceae) es una especie de valor economico debido a la presencia de glucosidos de esteviol en sus hojas, principalmente esteviosido y rebaudiosido A, que son azucares no caloricos. En 2013, se establecio una coleccion de plantas (genotipos) provenientes de cuatro ambientes contrastantes en Tucuman, Argentina, para su evaluacion en condiciones locales y, eventualmente, con fines de mejoramiento genetico. Como primer paso, se estudio la viabilidad del polen y la meiosis en una muestra de 56 plantas. El porcentaje de viabilidad del polen fue de medio (69,4%) a alto (99,6%) en 52 de ellas, pero de bajo (36,5%) a relativamente bajo (51,2%) en las cuatro restantes. Las ultimas cuatro plantas tambien presentaron granos de polen de tamano heterogeneo, que se clasificaron como n (normal, el tamano mas frecuente en la muestra),
ABSTRACT
Abstract Evolutionary analyses have been widely used for evaluation of genetic diversity of natural populations and correlate these data to the fitness of the species, especially in the case of threatened species. Calydorea crocoides occurs in a restricted area at altitudes from 800 to 1500 m in southern Brazil and is considered endangered. A study assessing genetic diversity, cytogenetic features and ecological niche was performed aiming to characterize C. crocoides by multidisciplinary approaches. Molecular data highlighted that most of the total variation (76%; p < 0.001) was found within populations and the parameters of genetic diversity were high at the species level (PPB = 98.97%; I = 0.4319; h = 0.2821). Gene flow (Nm) was estimated in 0.97 individuals per generation. Cytogenetically, C. crocoides presents a bimodal karyotype and low asymmetry. DAPI banding pattern was uniform, but the CMA-signal evidenced a pericentric inversion in the population ESC688. The species presents high pollen viability and two different morphologies of pollen grains. Our data showed high levels of polymorphism maintained in this species that could ensure conservationist practices in which the main goal is to preserve the evolutionary potential of the species through the maintenance of genetic diversity.
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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.
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Objective To study the reproductive biology of Chinese herbal medicine Polygonatum cyrtonema Hua. Methods The flowering habit of P. cyrtonema was observed and recorded regularly. The pollen viability at different flowering periods was detected by TTC. The stigma activity at different flowering periods was measured by the benzidine-hydrogen peroxide method. The hybridization index was estimated and pollen-ovule ratio was calculated. The breeding system of P. cyrtonema was determined by six different artificial pollination treatments. Results The flower buds of P. cyrtonema appeared at April 5. They bloomed at April 10 and fruited early in May, flowering about 30–40 days. The pollen began to have viability since the anthers were not cracked, and loss viability after flowers withered. The pollen viability at the bloom day was about 73.06%±5.19%. The stigmas began to have activity before flowers opening and lost it when the flowers began to decline. The hybridization index was 4, so the breeding system of P. cyrtonema Hua was partly self-compatible and xenogamy needing pollinator according to Dafni's standard.The pollen-ovule ratio was 1799.20±445.54,therefore the breeding system of P.cyrtonema Hua was facultative xenogamy according to Cruden's standard. The results of artificial pollination experiments showed that P. cyrtonema Hua had three breeding methods,including apomixis,selfing and outcrossing.The fruit setting rate of P. cyrtonema Hua was greatly influenced by external conditions such as strong wind and rain.Generally,P.cyrtonema Hua had a low fruit-set percentage because of obvious flower and fruit dropping. The natural fruit setting rate was only 17.46%. Conclusion The coexistence of apomixes, sexual and asexual reproduction in P. cyrtonema are the survival strategy adapting to different habitat types.
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Objective To study the reproductive biology of Chinese herbal medicine Polygonatum cyrtonema Hua. Methods The flowering habit of P. cyrtonema was observed and recorded regularly. The pollen viability at different flowering periods was detected by TTC. The stigma activity at different flowering periods was measured by the benzidine-hydrogen peroxide method. The hybridization index was estimated and pollen-ovule ratio was calculated. The breeding system of P. cyrtonema was determined by six different artificial pollination treatments. Results The flower buds of P. cyrtonema appeared at April 5. They bloomed at April 10 and fruited early in May, flowering about 30–40 days. The pollen began to have viability since the anthers were not cracked, and loss viability after flowers withered. The pollen viability at the bloom day was about 73.06%±5.19%. The stigmas began to have activity before flowers opening and lost it when the flowers began to decline. The hybridization index was 4, so the breeding system of P. cyrtonema Hua was partly self-compatible and xenogamy needing pollinator according to Dafni's standard.The pollen-ovule ratio was 1799.20±445.54,therefore the breeding system of P.cyrtonema Hua was facultative xenogamy according to Cruden's standard. The results of artificial pollination experiments showed that P. cyrtonema Hua had three breeding methods,including apomixis,selfing and outcrossing.The fruit setting rate of P. cyrtonema Hua was greatly influenced by external conditions such as strong wind and rain.Generally,P.cyrtonema Hua had a low fruit-set percentage because of obvious flower and fruit dropping. The natural fruit setting rate was only 17.46%. Conclusion The coexistence of apomixes, sexual and asexual reproduction in P. cyrtonema are the survival strategy adapting to different habitat types.
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Objective: To observe the morphology, measure the activity of pollen of Senna obtusifolia, determine the optimum conditions for pollen germination, induce the formation of callus from its anthers as well as identify its ploidy levels, and thus to lay a basis for its haploid breeding. Methods: Microscopic observation of the anther squashed method was used to reveal the morphology of pollen; The pollen activity was investigated using I2-KI staining and the size of the flower buds with the highest pollen activity was determined; Liquid culture and microscopic observation were performed to determine the optimum culture medium, pH value, and temperature for pollen germination; Microscopic observation of the acetocarmine-stained pollen was performed to determine microspore development stages; The optimum conditions for callus formation were studied by in vitro anther culture; The phenol fuchsin staining was improved for the identification of callus ploidy levels. Results: Pollen of S. obtusifolia is ellipsoid with three germinal furrows, and mostly two germination holes showed germination; The highest pollen activity was found in buds with vertical diameters about 1.0-1.1 cm; The optimum culture medium for pollen germination was determined to be 10% sucrose + 1% boric acid, with maximum germination cultured for 1-3 h at 25 ℃; The uni-nucleate microspore stage was in buds with vertical diameters about 0.9-1.1 cm; Calluses were successfully obtained by culturing the uni-nucleate stage anthers in an inducing medium MS + 1.0 mg/L 6-BA + 2.0 mg/L NAA + 3% sucrose + 0.6% agar and callus enrichment culture was done in MS + 1.0 mg/L 6-BA + 1.0 mg/L IAA + 1.0 mg/L 2,4-D + 1.0 mg/LGA3 + 3% sucrose; There was ploidy separation in callus, with the haploid and diploid cells coexisted. Conclusion: The optimum culture medium for pollen germination is 10% sucrose + 1% boric acid; The optimum anthers for in vitro culture is within flower buds with a vertical diameter of 0.9-1.1 cm; The chimeric calluses obtained from anthers of S. obtusifolia lay a solid foundation for the further induction of haploid plants from its pollen for breeding.
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RESUMO A análise histoquímica dos grãos de pólen através do uso de corantes permite a determinação de sua viabilidade polínica. O objetivo deste estudo foi comparar a eficiência dos corantes orceína acética 2% e reativo de Alexander modificado, para estimar a viabilidade polínica de vinte acessos de araçazeiro (Psidium cattleianum Sabine) – uma árvore de frutos muito apreciados que também é utilizada para fins medicinais. Botões florais na pré-antese foram coletados e fixados em etanol:ácido acético (3:1) por 24 horas, após os botões foram transferidos para etanol 70% e mantidos sob refrigeração. A técnica de esmagamento das anteras foi utilizada no preparo das lâminas. Para cada acesso foram preparadas 2 lâminas por corante e analisados 500 grãos de pólen por lâmina. A viabilidade polínica foi estimada através da porcentagem de grãos de pólen viáveis. De modo geral, observou-se que os grãos de pólen corados com orceína acética 2% apresentaram viabilidade alta, acima de 98,1%, e os acessos não diferiram entre si. A viabilidade polínica através da coloração com a solução de Alexander variou de 43% (acesso Silveira Martins 1) a 97% (acesso Candelária 1), mostrando que provavelmente exista variabilidade genética entre os acessos. Em apenas dois acessos não houve diferença significativa entre os valores de viabilidade encontrados através dos dois corantes testados. Conclui-se então que a orceína acética 2% superestimou a viabilidade polínica de P. cattleianum e que o reativo de Alexander é o mais preciso, devido a sua dupla coloração (verde de malaquita + fucsina ácida). Assim, indica-se o reativo de Alexander para análise de estimativa da viabilidade polínica de genótipos de araçá envolvidos em um programa de melhoramento genético.
ABSTRACT The histochemical analysis of pollen grains through the use of stains makes it possible to determine their pollen viability. The purpose of this study was to compare the efficiency of 2% acetic orcein and Alexander’s stain modified, in estimating the pollen viability of twenty strawberry guava accessions (Psidium cattleianum Sabine) – a valued fruit tree which is used for medicinal purposes. Pre-anthesis flower buds were collected and fixed in ethanol:acetic acid (3:1 v/v) for 24 hours at room temperature, subsequently they were stored in 70% ethanol under refrigeration. The anther squash technique was performed for slide preparation. In each accession two slides per stain and 500 pollen grains were analyzed. The pollen viability was estimated according to the percentage of viable pollen grains. Overall, it was observed that pollen grains stained with 2% acetic orcein evinced a high viability, higher than 98,1%, and the accessions did not differ. The pollen viability estimated with Alexander’s stain varied from 43% (accession of Silveira Martins 1) to 97% (accession of Candelária 1), indicating that there is probably genetic variability among the accessions. There was no significant difference among the levels of viability found by means of the two stains in only two accessions. In conclusion, 2% acetic orcein overestimated the pollen viability of P. cattleianum, whereas the Alexander’s stain is in turn more accurate due to its two stains (green malachite and fuchsine). Thus, it is indicated Alexander’s stain for analysis estimation of pollen viability of strawberry guava genotypes involved in a genetic improvement program.
Subject(s)
Staining and Labeling/methods , Feasibility Studies , Psidium/classification , Plants, Medicinal/classification , Coloring Agents/classificationABSTRACT
T.arjuna and T.tomentosa come under multipurpose tree category and are of immense economic importance besides being the primary food plants of Tasar silkworm Antheraea mylitta D. Blooming occurs from second week of May in T.arjuna and last week of May in T.tomentosa. Number of flowers per raceme range between 41 in accession 235 to 58 in accession 702 of T.arjuna and 53 (acc.531) to 73 (acc.501) of T. tomentosa. Fruit set per cent ranged between 2.0 in accessions 235 and 236 to 4.00 in accession 533 of T.arjuna. Per cent fruit set was 3.0 to 3.2 in accessions 501 and 531, respectively of T.tomentosa under open pollination condition. There was no fruit set in un - pollinated and covered racemes. Days required for fruit initiation in T.arjuna x T.arjuna combination varied between 12 to 14 days and fruit set was 1.8 to 2.5 percent. In T.arjuna x T.tomentosa combinations initiation of fruit set took 10 (acc.701 x acc.501) to 14 (acc.533 x acc.531) days and fruit set was 1.5 to 2.4 per cent. Present studies indicate that inter-specific hybridization is possible in T.arjuna and T.tomentosa. New hybrid varieties can be developed through inter-specific hybridization having higher yield in comparison to the existing genotypes.
ABSTRACT
The experiment comprised of six genotypes viz., NAC-01-10, NAC-02-10, NAC-03-10, NAC-04-10, NAC-05-10, NAC-06-10 selected for petal colour and number of layers of petals to estimate pollen viability, in-vitro pollen germination, stigma receptivity and crossed seed set percentage to find out the crossing ability of genotypes. The present experiment was laid out at the experimental field of Horticulture Section, College of Agriculture, Nagpur, during 2010-11. Pollen viability of six genotypes of annual chrysanthemum showed a range of 69.69% to 86.66% viability, Percentage of germination on the day of anthesis ranged from 22.72% (NAC-06-10) to 66.66% (NAC-01-10). First day pollen pollinated on first day stigma showed 100% stigma receptivity in all six genotypes and the crossed seed set ranged from 61.60% (NAC-04-10 × NAC-05-10) to 92.00% (NAC-01-10 × NAC-04-10) among direct crosses whereas, the percentage ranged from 42.00% (NAC-04-10 × NAC-02-10) to 90.00% (NAC-05-10 × NAC-01-10) among the reciprocal crosses. All the six genotypes are highly suitable for their use as parents in crossing program.
ABSTRACT
Terminalia arjuna is a deciduous tree widely distributed in tropical semi-evergreen and moist deciduous forests. Flowers of T. arjuna have ten stamens, which remain inside the bud and anthesis is carried out at different times of the day. Pollen grains are yellow in colour, medium and spherical, aperture is tri zonocolporate and exine is smooth. The pollen: ovule ratio is about 15,400 : 1. Optimum germination was seen in BBM + 12.5% sucrose. After 16 hr of anthesis, the pollen grains lost their viability and there was no fruit set. The current findings will be useful in studying pollen – pistil interactions, gene flow and heterozygosity of the T. arjuna populations.
ABSTRACT
The genus Heteropterys is one of the major genera in Malpighiaceae. However, few cytological and palynological studies were reported. The present work described for the first time the chromosome number, heterochromatin pattern, meiotic behavior, pollen viability and palynological aspects of Heteropterys ubellata, a very spread species. One large Brazilian population was evaluated using conventional techniques for meiotic studies and acetolyse to access the pollen morphology. The species showed 2n = 20 chromosomes, normal meiotic development and viable pollens. Great blocks of heterochromatin were observed around the centromers. DAPI staining was positive for centroeric heterochroatin, hile CMA3 ark as observed just at terinal regions of one pair of hoologues chromosomes. This result and the presence of one chromosome pair attached to the nucleoli during the pachytene and diakinesis suggested the presence of only one pair of NORs. Palynological analysis revealed that pollen grains are apolar, 6 porate and with colpoids associated to all pores. The pollen content was positive for the starch test, and the exine was rugulate with little psilate regions.
O gênero Heteropterys é um dos maiores gêneros entre as Malpighiaceae. Entretanto, poucos estudos citológicos e palinológicos foram relatados. O presente trabalho descreveu pela primeira vez o número cromossômico, o padrão heterocromático, o comportamento meiótico, a viabilidade polínica e aspectos palinológicos de Heteropterys umbellata, uma espécie muito disseminada. Uma grande população brasileira foi estudada utilizando técnicas convencionais para o estudo de cromossomos meióticos e acetólise para acessar a morfologia polínica. A espécie apresentou 2n = 20 cromossomos, desenvolvimento meiótico normal e pólens viáveis. Grandes blocos de heterocromatina foram observados ao redor dos cen-trômeros. A coloração com DAPI foi positiva para a hetero-cromatina centromérica, enquanto marcas com CMA3 foram observadas somente em um sítio terminal de um par de cromossomos homólogos. Este resultado e a presença de um par de cromossomos associados a um nucléolo durante o paquíteno e diacinese sugerem a presença de somente um par de RONs. A análise palinológica revelou que os grãos de pólen são apolar, com 6 poros e colpóides associados a todos eles. O conteúdo polínico foi positivo para o teste de amido e a exina mostrou-se rugulada com poucas regiões psiladas.
Subject(s)
Chromosomes, Plant/genetics , Heterochromatin/genetics , Malpighiaceae/cytology , Brazil , Chromosome Banding , Karyotyping , Malpighiaceae/classification , Malpighiaceae/geneticsABSTRACT
Passiflora genus, Passifloraceae family, has more than 500 species and 120 of them are native species of Brazil. All species produce fruits that are used as food, medicine and decoration. Floral buttons of five species were collected and fixed in a mixture of ethanol and acetic acid (3:1). The slides were prepared by squashing and staining with 1% propionic carmine. Results showed that during microsporogenesis there were few irregularities, mostly frequently related to chromosome irregular segregation as: precocious migration to poles in metaphase I and II, non-oriented bivalent chromosomes at metaphase I and II, and laggard chromosomes in anaphase I and II, forming micronuclei in telophases I and II and tetrad with microcyte. Another observed irregularity is related to the organization of spindle fibers in meiosis II as they organize themselves in T and V shapes and in sequential spindle. However, in the V-shaped spindle configuration, there was fusion between two nuclei that were close, forming triads instead of tetrads. Irregular chromosome segregation, abnormal spindles and irregularities in the cytokinesis process were responsible for the formation of monads, dyads, triads and polyads. However, the pollen grain viability was not harmed, presenting an 83.98% to 98.59% fertility variation.
O gênero Passiflora, família Passifloraceae, apresentam mais de 500 espécies, havendo no Brasil aproximadamente 120 espécies nativas. Todas as espécies produzem frutos que são utilizados como produtos alimentícios, medicinais e ornamentais. Botões florais de cinco espécies foram coletados e fixados em etanol/acido acético (3:1). As lâminas foram preparadas utilizando a técnica de esmagamento e coradas com carmim propiônico a 1%. Como resultado, observou-se que durante a microsporogênese poucas irregularidades foram encontradas, as mais frequentes estão relacionadas à segregação irregular dos cromossomos, tais como: migração precoce para os pólos em metáfase I e II, bivalente não orientado em metáfase I e II, e cromossomos retardatários em anáfase I e II, levando a formação de micronúcleos em telófases I e II, e micrócito em tétrades. Outra irregularidade observada esta relacionada a organização das fibras dos fusos em meiose II, que se organizam na forma em T, em V e fuso sequencial. Na configuração de fuso na forma de V ocorreu fusão entre dois núcleos que estavam próximos, formando tríade ao invés de tétrade. A segregação irregular dos cromossomos, a formação de fusos anormais e as irregularidades no processo de citocinese foram responsáveis pela formação de mônades, díades, tríades e políades como produtos final da meiose. Porém, a viabilidade dos grãos de pólen não foi comprometida, apresentado uma variação de 83,98% a 98,59% de fertilidade.
Subject(s)
Cytokinesis , Meiosis , Passiflora , PollenABSTRACT
Ocimum basilicum, cv. Maria Bonita (Lamiaceae), conhecido como manjericão, é espécie que apresenta propriedades aromáticas, condimentares e medicinais, por ser rico emóleos essenciais. É muito usado nas indústrias farmacêuticas e de alimentos em geral. O objetivo deste trabalho foi estudar as propriedades do pólen e estigma do manjericão (cultivar Maria Bonita) identificando procedimentos simples que possam contribuir para programas de melhoramento. Para análise da disponibilidade, viabilidade do pólen e receptividade de estigma, botões florais foram coletados de hora em hora ao longo do dia, e lâminas eram montadas e coradas, para observação em microscópio óptico. Foi verificado que o manjericão apresenta antese diurna, assincrônica e com a maioria das flores se abrindo entre 10:00 e 11:00 horas. Quanto ao estudo do pólen foi verificado que a viabilidade manteve-se elevada ao longo do dia e a conservação por até 90 dias demonstrou bons níveis de viabilidade. O estigma apresentou receptividade desde a pré-antese até a pós-antese. Estas informações são relevantes para os melhoristas que desejam fazer seleção de genótipos ou hibridações em programas de melhoramento, contribuindo para aumentar o potencial da espécie que já se destaca como produtora de óleos essenciais.
Known as basil, Ocimum basilicum cv. Maria Bonita (Lamiaceae) is a species that presents aromatic, condimental and medicinal properties, since it is rich in essential oils. This species is largely used in pharmaceutical and food industries. The aim of this work was to study basil (cultivar Maria Bonita) pollen and stigma properties, identifying simple procedures that can contribute to plant breeding programs. To analyze pollen availability and viability, besides stigma receptivity, flower buds were collected at every hour throughout the day, and slides were mounted, stained and observed under an optical microscope. Basil presented diurnal asynchronous anthesis and most flowers opened between 10:00 and 11:00 a.m. As regards pollen analysis, viability was high throughout the day and its conservation until 90 days was good. Stigma presented receptivity from pre- to post-anthesis. These data are relevant to breeders who wish to select genotypes or hybridizations in plant breeding programs, contributing to improve the potential of this species, which already represents a producer of essential oils.
Subject(s)
Crosses, Genetic , Flowers/genetics , Genetic Enhancement/statistics & numerical data , Ocimum basilicum/growth & development , Pollen/genetics , Genotype , Regression AnalysisABSTRACT
O objetivo deste estudo foi avaliar a germinação in vitro de pólen de híbridos interespecíficos entre o caiaué e o dendezeiro das variedades dura, pisífera e tenera. O percentual de germinação de pólen (PGP) dos híbridos variou de 54,8 a 58,3%. As médias dos híbridos e do caiaué (73,1%) não diferiram estatisticamente entre si, mas foram inferiores ao do dendezeiro (84,8%). A germinação de pólen dos híbridos ésuficiente para o sucesso na realização de cruzamentos, nos programas de melhoramento interespecífico entre as espécies caiaué e dendezeiro.
The purpose of this study was to evaluate the in vitro pollen germination of interespecifics hybrids between caiaué and oil palm (varieties dura, tenera and pisifera). The percentage of pollen germination (PPG) of hybrids ranged from 54.8% to 58.3%. The averages of hybrids and caiaué (73.1%) did not differ statistically, but were lower than the oil palm (84.8%). The germination of pollen of hybrids is sufficient for the successful of crosses in interespecific breeding programmes between caiaué and oil palm.
ABSTRACT
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 percent until use. The method used was that of squashing the anthers and coloring with acetic orcein 2 percent. 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 percent to 87 percent in Aster squamatus, 85 percent to 92 percent in Pterocaulon polystachyum, and 64 percent to 92 percent 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 por cento até o uso. O método utilizado foi o de esmagamento de anteras e a coloração com orceína acética 2 por cento. 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 por cento a 87 por cento em Aster squamatus, de 85 por cento a 92 por cento em Pterocaulon polystachyum e de 64 por cento a 92 por cento 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.
ABSTRACT
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 percent. 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 por cento.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.
ABSTRACT
Reproductive studies were carried out on Brazilian accessions of ipecac, Cephaelis ipecacuanha. Meiotic behavior was studied using the squashing technique. Irregular chromosome segregation in meiosis I and II, many sets of chromosomes in telophase II, micronuclei, incorrect cytoplasm division, incomplete cytokinesis and anomalous post-meiotic products, mainly polyads, were observed. The mean meiotic index was lower than 72%. Pollen viability was analyzed using Alexander solution, and the percentages ranged between brevistylous and longistylous floral morphs (85.3 to 93.1%), and among different localities (82.5 to 92.6%) analyzed. The size of pollen ranged between viable and sterile, and empty and shrunken sterile. In its natural habitat, this species is known to propagate by vegetative multiplication, but sexual reproduction seems to be as important as the vegetative propagation to this species.
Estudos reprodutivos foram realizados em acessos brasileiros de poaia, Cephaelis ipecacuanha. O comportamento meiótico foi estudado usando a técnica de esmagamento. Foi observada segregação irregular de cromossomos durante meiose I e II, muitos grupos de cromossomos em telófase II, micronúcleos, divisão incorreta do citoplasma, citocinese incompleta e produtos pós-meióticos anômalos, principalmente políades. A média do índice meiótico foi inferior a 72%. A viabilidade polínica foi analisada utilizando-se solução de Alexander e a percentagem de pólen viável variou entre as formas florais, brevistila e longistila (85,3% a 93,1%), e entre as diferentes localidades (82,5% a 92,6%) analisadas. O tamanho do pólen variou entre viáveis e inviáveis, e entre os inviáveis vazios e contraídos. Em seu habitat natural, a poaia apresenta propagação por multiplicação vegetativa, mas a reprodução sexuada parece ser tão importante para essa espécie quanto a propagação vegetativa.
ABSTRACT
In the hexaploid (2n = 6x = 54) accession B176 of Brachiaria brizantha, one cytological characteristic differentiated it from the other accessions previously analyzed with the same ploidy level. Nearly 40% of meiocytes displayed the chromosome set arranged at two metaphase plates at the poles of the cell, close to the membrane. In these cells, both metaphase plates were arranged in an angle to form a typical tripolar spindle. Therefore, cells did not show normal chromosome segregation at anaphase I. Only nine univalent chromosomes migrated from each plate to the opposite pole with the remainder staying immobile on the plate. As a result of such spindle orientation and chromosome behavior, trinucleate telophases I were recorded. After telophase, cytokinesis eliminated the small nuclei into a microcyte. The second division proceeded normally, with the presence of microcytes in all phases. The origin of such an abnormality was explained on the hexaploid level of the accession which could have resulted by chromosome doubling of a triploid derived from species that did not display the same behavior for spindle organization. The high percentage of meiotic abnormalities recorded in this accession compromises fertility and renders it inadequate for the breeding program.