Viable Pollen Grains Research Articles

Meiotic behavior of interspecific hybrids between artificially tetraploidized sexual Brachiaria ruziziensis and tetraploid apomictic B. brizantha (Poaceae)

The meiotic behavior of four interspecific promising hybrids was evaluated by conventional cytological methods. The female genitors were two artificially tetraploidized sexual accessions of B. ruziziensis (R41 and R44, 2n = 4χ = 36), which were crossed to an agronomically superior natural tetraploid apomictic genotype of B. brizantha (B140 - BRA003395). Three of them (HBGC313, HBGC 315, and HBGC324) were sexual and one (HBGC325) apomictic. Analyses of some cells in diakinesis revealed multivalent chromosome configurations, suggesting that genetic recombination and introgression of some genes could be present. The four hybrids had different types of meiotic abnormalities at various frequencies. Abnormalities related to irregular chromosome segregation due to polyploidy were common among these hybrids, and characterized by precocious chromosome migration to the poles, laggard chromosomes, both generating micronuclei in telophases and tetrads and, as a consequence, unbalanced gametes. One abnormality genotype-specific, related to spindle orientation (a putative divergent spindle mutation), was recorded for the first time in two of the hybrids, HBGC313 and HBGC325. The sexual hybrid HBGC324 had the lower rate of abnormalities, and it could be used as a female genitor in future crosses in the breeding program. The abnormalities present in these hybrids may impact fertility and affect seed production. Based on the results, HBGC324 is the single hybrid recommended to the breeding program. Hybrids must produce a good amount of viable seeds, besides good overall dry matter production and nutritive value, in order to be widely utilized and adopted in production systems. Due to pseudogamy, the desirable superior apomictic hybrids need viable pollen grains to fertilize the secondary nucleus of the embryo sac and thus ensure normal and vigorous endosperm development and plenty of seed set.

Walnut Tree Pollen Quality in Cultivars with Various Flowering Times

The increase in walnut tree crop is related to assortment, and also to good knowledge of biology in each cultivar. Walnut tree quality has a key role in choosing the pollination variety. A condition for doing a good pollination variety is to have good quality pollen, with high germination ability. Pollen quality is an important element on which flowers fecundation depends upon.. This paper proposed to study pollen in six walnut tree cultivars, having various flowering times. Local cultivars studied were ‘Germisara‘, ‘Roxana‘, ‘Mihaela‘, ‘Geoagiu 65‘, ‘Jupânesti‘ and ‘Orastie‘, all of them being considered to have good perspectives, owing to their fruit quality and high level of crops. Observations made were focused on flowering time, size of pollen grain, number of germinative pores, viability and germination of pollen grains, length of pollen tubes. Similar researches were conducted by de Luza J. G., V. S. Polito, (1985, 1988), G. Vergano, L. Radicati, I. Martino (1990), Pintea M. (1998), Sutyhemez M., S. Eti (2005) Research methods used were the ones recommended in the literature. Pollen grains size varied between 38.5 and 44.7 µ, the average number of germinative pores was 7, viability percentage was 96.9%, higher than germination percentage of 62.7%, and the average length of pollinic tubes was 159.5 µ, 12 hours after sowing. Variation limits for pollen grains and its viability are not in direct connection with flowering type. The results obtained were influenced both by cultivar, and by certain experimental and incidental factors.

Analysys on Pollen and Seed Productivity and Effectivenes in Gentiana Lutea L.

ABSTRACTA study on the viability of pollen grains and embryos in Gentiana lutea distributed in Bulgarian flora has been carried out. Degenerative processes predominantly of the mature pollen were observed. As a result of that, in the studied populations, the effective mature pollen grains in the anthers reduce in different amount. The used tetrazolium test shows that in the mature seeds the viability of embryos reduced progressively during the three consecutive years of the present study.

The role of pollen in the changing environmental conditions of Scots pine

Rapid climate warming poses a challenge to forest trees adapted to cooler conditions. However, a genetic safety net may exist for wind pollinated tree species in the form of long distance gene flow mediated by pollen containing alleles that are (pre)adapted to a warmer climate. In order to examine long distance gene flow in Scots pine (Pinus sylvestris L.), we monitored flowering phenology in central, northern, and northernmost Finland and measured the amount and viability of airborne pollen over four years. Viable airborne pollen grains were detected during female flowering periods and prior to local pollen shedding in all study sites. Depending on the year and study site, female flowers were exposed only to pollen originating elsewhere for between one and four days. Foreign airborne pollen represented 2.3% of all viable grains detected and varied between years and study sites. Artificial pollination trials were conducted to evaluate the effect of pollen origin on seed siring success. Pollen genotypes originating from southern Finland sired 76% and 48% of seeds in competition experiments where pollen from both populations was introduced simultaneously into the female strobilus. Furthermore, we investigated the importance of pollen arrival order by introducing pollen of northern and southern genotypes in to the strobilus at two-hourly intervals. Northern genotypes sired 76% of the analysed seeds when injected first but when southern genotypes were supplied first, both pollen types enjoyed equal success. The first pollen grain in the pollen chamber did not always fertilize the ovum. Instead there is likely a more subtle and complex form of competition between genotypes and their pollen grains. To examine chemically-mediated pollen interactions we conducted an in vitro germination experiment where different genotypes were in chemical but not physical contact. Both positive and negative interactions were found. We found highly negative effects in the germinability of northern pollen grains when in contact with southern pollen, and an increase in the germinability of southern pollen when in contact with northern pollen. There was no variation in the size of dry pollen grains between sources, but after hydration and germination, northern pollen grains were larger than southern pollen. Genotypes with high hydration rates had low germinability and slow pollen tube growth rates. This suggests that early germination and growth of the pollen tube is more dependent on pollen storage materials and less dependent on water intake. Pollen source affected the outcome of competition experiments and therefore is an important factor in long distance gene flow. However, genotype also plays a role and must be taken into account.

Impacts of drought on pollination of Trigonella moabitica (Fabaceae) via bee visitations

This experiment was conducted to evaluate the effect of drought stress on the attractivity of Trigonella flowers to worker honey bees, seed set and yield of T. moabitica under semi-arid Mediterranean conditions during the flowering stage. At this stage plants were exposed to one of three water regimes: either well-watered, moderately-watered, and drought stress. Results showed that flowers of well-watered plants attracted more bee flower visitors compared to plants grown under drought stress conditions. Plants grown under drought stress conditions were shorter, had fewer numbers of inflorescences, and fewer flowers per plant compared to well and moderately-watered plants. Furthermore, drought-stressed plants produced lower quantities of viable pollen grains, and lower pod and seed set.

Variation in pollen formation and its cytological mechanism in an allotriploid white poplar

Variation in pollen formation and its cytological mechanism in an allotriploid white poplar were investigated by the squashed technique and indirect immunofluorescence. Besides 0.5% stuck pollen grains, this allotriploid produced regularly spherical pollen grains. It was estimated that 90.3% of pollen grains were viable. Diameters of the viable spherical pollen grains ranged from 23.2 to 72.9 μm, with a bimodal frequency distribution. Numerous meiotic abnormalities were found, including highly irregular chromosome pairing, lagging chromosomes and chromosome bridges, micronuclei, and multiple spindles, which indicate highly genetic imbalance of this allotriploid. Some micronuclei triggered minispindle formation in metaphase II and participated in cytokinesis to form microcytes in sporads. Abnormal orientation of metaphase II spindles contributed to production of dyads and triads, which produced unreduced microspores. However, parallel orientation of spindles was not necessary for dyad formation, because an organelle band positioned in the equatorial region prevented the spindles from coalescing. Some microsporocytes exhibited a complete or partial absence of cytokinesis, which resulted in the formation of monads and the increased frequency of dyads and triads. The perspective of this triploid in the polyploid breeding program of white poplar is discussed.

Efficient transformation of Kalanchoe blossfeldiana and production of male-sterile plants by engineered anther ablation

Engineered male sterility in ornamental plants has many applications such as facilitate hybrid seed production, eliminate pollen allergens, reduce the need for deadheading to extend the flowering period, redirect resources from seeds to vegetative growth, increase flower longevity and prevent gene flow between genetically modified and related native plants. We have developed a reliable and efficient Agrobacterium-mediated protocol for the genetic transformation of different Kalanchoe blossfeldiana commercial cultivars. Transformation efficiency for cv. 'Hillary' was 55.3% whereas that of cv. 'Tenorio' reached 75.8%. Selection was carried out with the nptII gene and increasing the kanamycin concentration from 25 to 100 mg l(-1) allowed to reduced escapes from 50 to 60% to virtually 0%. This method was used to produce male-sterile plants through engineered anther ablation. In our approach, we tested a male sterility chimaeric gene construct (PsEND1::barnase) to evaluate its effectiveness and effect on phenotype. No significant differences were found in the growth patterns between the transgenic lines and the wild-type plants. No viable pollen grains were observed in the ablated anthers of any of the lines carrying the PsEND1::barnase construct, indicating that the male sterility was complete. In addition, seed set was completely abolished in all the transgenic plants obtained. Our engineered male-sterile approach could be used, alone or in combination with a female-sterility system, to reduce the invasive potential of new ornamentals, which has become an important environmental problem in many countries.

Three cotton genes preferentially expressed in flower tissues encode actin-depolymerizing factors which are involved in F-actin dynamics in cells

To investigate whether the high expression levels of actin-depolymerizing factor genes are related to pollen development, three GhADF genes (cDNAs) were isolated and characterized in cotton. Among them, GhADF6 and GhADF8 were preferentially expressed in petals, whereas GhADF7 displayed the highest level of expression in anthers, revealing its anther specificity. The GhADF7 transcripts in anthers reached its peak value at flowering, suggesting that its expression is developmentally-regulated in anthers. The GhADF7 gene including the promoter region was isolated from the cotton genome. To demonstrate the specificity of the GhADF7 promoter, the 5′-flanking region, including the promoter and 5′-untranslated region, was fused with the GUS gene. Histochemical assays demonstrated that the GhADF7:GUS gene was specifically expressed in pollen grains. When pollen grains germinated, very strong GUS staining was detected in the elongating pollen tube. Furthermore, overexpression of GhADF7 gene in Arabidopsis thaliana reduced the viable pollen grains and, consequently, transgenic plants were partially male-sterile. Overexpression of GhADF7 in fission yeast (Schizosaccharomyces pombe) altered the balance of actin depolymerization and polymerization, leading to the defective cytokinesis and multinucleate formation in the cells. Given all the above results together, it is proposed that the GhADF7 gene may play an important role in pollen development and germination.

COMPARATIVE EVALUATION OF SOME MALE PALMS IN THREE DISTRICTS IN EGYPT

This investigation was carried out at three Egyptian Governorates, i.e. New Valley (El-Dakhla oasis), Damietta (Kafr El-Batikh) and Wady El-Natron at private orchard during two successive seasons of 2005 and 2006, to evaluate date palm males used for pollination of female palm in these districts. The obtained results showed that, males differed in their morphological spathe characteristics. Time of flowering also differed between males in each governorate. At the NewValley flowering was earlier than at the other two governorates. Viability of pollen grains ranged from 82.9 to 85.2 %. Males from NewValley produced significantly more amount of pollen grain comparing to other regions. The number of retained flowers on strands differed significantly between the three governorates under investigation but the new valley gave the highest percentage of retained flowers on the strands.

Caracterização citogenética, viabilidade de pólen e hibridação artificial em gérbera

Este trabalho foi conduzido com o objetivo de confirmar o número de cromossomos em cultivares de Gerbera hybrida Hort., determinar o número de cromossomos em acessos não comerciais de Gerbera sp., avaliar a viabilidade de pólen e a possibilidade de cruzamentos entre cultivares e acessos não comerciais. Foram coletados ápices de raízes e pólen de seis cultivares e de sete acessos não comerciais. O material coletado foi corado com carmim acético a 45%. A contagem dos cromossomos foi realizada em células metafásicas intactas e a estimativa de viabilidade de pólen realizada por meio da contagem do número de grãos de pólen viáveis e não viáveis. A possibilidade de cruzamento entre as cultivares e entre as cultivares e acessos não comerciais foi avaliada por meio da hibridação entre os genitores femininos, cv. Terra Fame e acesso A8, e masculinos, cvs. Cariba e Azteca. Todos os acessos contiveram cinqüenta cromossomos, indicando que a variação morfológica nos capítulos (simples, semidobrado e dobrado) não é devida a mutações cromossômicas numéricas ou a poliploidia. A viabilidade do pólen variou de 87,67% a 99,27%. A formação de sementes foi de 4,46% nos cruzamentos entre cultivares, e de 50% entre o A8 e as cultivares. A compatibilidade genômica entre os acessos, a alta viabilidade do pólen e o sucesso na obtenção de sementes entre acessos comercias e não comerciais, revela a possibilidade de produção de híbridos com novas combinações alélicas e transferência de caracteres desejáveis dos acessos não comerciais para os comerciais

Cytogenetics, Embryology, and Stem Anatomy of a Cassava Interspecific Hybrid

Cytogenetical analysis of the interspecific hybrid between M. esculenta (cassava) and M. oligantha revealed a fair chromosome pairing and a high viability of pollen grain. Studying ovule structure by clearing method showed multiembryony in 2.7% of ovules studied. Doubling chromosome number resulted in an increase of multiembryony up to 18% and reduction of pollen viability. Multivalent formation was observed too. In anatomical stem study of diploid and tetraploid hybrids it was noted larger number of vascular bundles in tetraploid type.

Pollen grain traits of oil species from the Novi Sad collection

The collection of oil species in Novi Sad contains 12 species represented with 1-4 cultivars or landraces. In the continuous work on this collection in the sense of breeding of some of those species and their usage as a source of 'desirable genes' we analyzed pollen grain morphology (shape and size), as well as pollen viability. To determine mentioned pollen traits we used Axiovert 40C microscope together with a software package (AxioVision LE; Rel.4.3.) for measurement of pollen length and width. Pollen viability was determined using a staining method (ALEXANDER, 1969). The results showed that species differ by pollen grain shape (round, egg-shaped, triangular and rod) as well as by shape of exine (thick and spiky, thick to thin). In some species there was a specific number of apertures present (1-11). The size of viable pollen grains ranged from 29,10/12,58? (coriander) to 176,63/169,94? (oil gourd), while non-viable pollen grains were always smaller (27,27/10,97? to 119,62/100,86?) at the same plant species. Pollen viability of most species was around 80%. Lowest pollen viability was found in white flax (56,98%), and the highest in oil pumpkin (91,43%).

Reproductive ecology of medicinally important Kashmir Himalayan species of Digitalis L.

AbstractReproductive biology, encompassing phenology, floral biology, pollination and breeding systems, was investigated in three pharmaceutically important and anthropogenically exploited species of Digitalis in the montane habitats of the Kashmir Himalaya. Flowers in all three species (Digitalis purpurea, Digitalis grandiflora and Digitalis lanata) are aggregated in racemes. Corollas are characteristically bell shaped enclosing four, didynamously arranged stamens. The stigma is deeply bifid only in D. purpurea. The three species over‐winter as underground tubers and sprouting during the following spring occurs first in D. lanata, followed by D. purpurea and D. grandiflora. Floral bud opening in an inflorescence in all three species occurs sequentially from the bottom upwards in an acropetal succession and male and female phases are temporally separated with basal flowers entering the male phase first followed by the upper flowers in a regular sequence. Only after shedding the pollen grains completely do the flowers shift to the female phase. Resource allocation in all three species is more towards maleness than femaleness during anthesis. The species are principally insect pollinated and selfing is denied because of protandry and spatial separation of the stigma and anthers. Copious amounts of viable pollen grains produced by these species aid in successful pollination, fertilization and seed production. Studies revealed that none of these species operates autogamy because hand‐pollinated flowers with self‐pollen or bagged flowers (foreign pollen excluded) failed to set seed. High seed output in open‐pollinated flowers and high pollen–ovule ratios also indicate the outbreeding nature of these species. Thus, any reduction in the number of individuals constituting a population would significantly reduce the floral display and consequent rewards to the pollinators, with a subsequent influence on seed production. Hence, data on the reproductive biology of overexploited species, such as Digitalis spp., is of pivotal importance in formulating effective conservation strategies.

In vitro germination and viability of pollen grains of banana diploids

The objective of this study was to evaluate the influence of pH on in vitro germination and pollen grain viability of banana diploids (AA) generated by the breeding program of Embrapa Mandioca e Fruticultura Tropical. The pollen grains were inoculated in culture medium containing 15% sucrose, 0.01% H3BO3, 0.01% KNO3, 0.03% Ca(NO3)2.4H2O, 0.02% MgSO4.7H2O, solidified with 0.8% agar and pH adjusted to 5.8 or 7.0. Pollen viability was evaluated by staining with 1% acetic carmine. The germination percentages of the genotypes 9187-01 (90.0%) and M-53 (89.7%) in pH 7.0 medium were highest, while the pollen tube length of genotype 9187-01 was approximately half the size (1.79mm) of genotype M-53 (3.84mm). The pollen viability of the genotypes evaluated was higher than 85%, even for the diploids with a low in vitro germination percentage.

Pollen morphology and viability of some Indian mangroves

A study on pollen morphology of four common Indian mangroves from Sundarbans mangrove swamps, three species from the family Rhizophoraceae (Bruguiera sexangula Laur., Ceriops tagal Perr.and Rhizophora mucronata Lamk.) and one species from the family Avicenniaceae (Avicennia marina Forsk.) was carried out. Shape of the pollen grains were prolate, prolate spheroidal and subprolate with tricolporate apertures. Surface ornamentation of the studied taxa was reticulate, finely reticulate or scabrate. Pollen grain viability of the said taxa was determined by stain test (1% aceto-orcein) under in situ condition and percentage of viable pollen production was recorded. The result revealed that all the studied taxa produce a fairly good amount of viable pollen grains in natural condition, an indication that they are good propagule producer in the long run. Pollen grain germination and measurements of pollen tube length using different sucrose concentrations (0.2, 0.6, 1.0, 1.2, 1.6 and 2.0%). Maximum pollen fertility and pollen tube length occurred in 2% sucrose solution in case of A. marina and B. sexangula, whereas 1.6% in C. tagal and 1.0% in R. mucronata. A strong positive correlation exist between pollen germination and pollen tube length, but there was a hardly relation between sucrose concentration and pollen tube length.

Impact of Humidity on Temperature‐Induced Grain Sterility in Rice (Oryza sativa L)

AbstractHigh temperature‐induced grain sterility in rice is becoming a serious problem in tropical rice‐growing ecosystems. We studied the mechanism of high temperature‐induced grain sterility of different rice (Oryza sativa L) cultivars at two relative humidity (RH) levels. Four varieties of Indica and Japonica rice were exposed to over 85 % RH and 60 % RH at 36/30 °C, 34/30 °C, 32/24 °C and 30/24 °C day/night air temperatures from late booting to maturity inside sunlit phytotrons. Increasing both air temperature and RH significantly increased spikelet sterility while high temperature‐induced sterility decreased significantly with decreasing RH. Neither Indica nor Japonica rice types were superior to the other in the response of their spikelets to increased air temperature and RH. Increased spikelet sterility was due to increased pollen grain sterility which reduced deposition of viable pollen grains on stigma. Reduction in sterility with decreased RH was more due to decreased spikelet temperature than to air temperature. Thus the impact of RH should be considered when interpreting the effect of high temperature on grain sterility. Spikelet fertility was curvilinearly related to spikelet temperature. Grain sterility increased when spikelet temperature increased over 30 °C while it became completely sterile at 36 °C. The ability of a variety to decrease its spikelet temperature with decreasing RH could be considered as avoidance while the variability in spikelet sterility among varieties at a given spikelet temperature could be considered as true tolerance.

Viability and in vitro germinability of pollen grains of olive cultivars and advanced selections obtained in Italy

In the frame of a breeding programme of olive, started in 1971 and carried out at the Department of Horticulture of the University of Florence (Italy), 134 advanced selections are under evaluation. Viability and germinability have been evaluated on pollen grains collected from trees (11 advanced selections and four culti- vars, 'Carolea', 'Frantoio', 'Leccino'and 'Moraiolo') grown at Spoleto (province of Perugia). Pollen grains have been stored at different temperatures (-20°C, +4°C and +20°C) and for 7, 35 and 200 days from full bloom. Via- bility was assessed by means of fluorescence microscopy; in vitro germinability was evaluated on pollen grains cultivated in 10 different growing media. Pollen grains showed different rates of viability and germinability in relation to storage length, storage temperature, genotype and their interactions. Storage length had a statistical - ly significant effect both on pollen grain viability and germination. No linearcorrelation has been found between viability and germination rates. Some advanced selections showed levels of pollen grain viability and germina - bility comparable to those of cultivars used also as pollinizers.

Standardization of the fluorochromatic reaction test to assess pollen viability

The fluorochromatic reaction that viable pollen grains exhibit when exposed to fluorescein diacetate (FDA) is an easy, quick and accurate tool for assessing pollen viability in many plants. Despite its widespread use, the method as initially proposed by Heslop-Harrison and Heslop-Harrison lacks specificity in some respects that are essential for comparing simultaneously the viability of different pollen sources. We have determined the time needed for the fluorochromatic reaction to take place and fade, and the lifetime and most effective concentration of the FDA working solution. Our results show that consistent records of pollen viability in samples of olive (bicellular pollen grains) and cherimoya (tricellular pollen grains) can be obtained within minutes, but that measurement must be completed in the first hour after pollen exposure to FDA. The lifespan of the FDA working solution is 1 h, whereas concentrations between 1.5×10−5 M and 1.8×10−3 M are equally valid. Pollen grains of both species responded similarly, although some differences were observed in the persistence of fluorochromasia.

Pollen viability and meiotic analysis of Solanum commersonii commersonii Dun., Solanum commersonii malmeanum Bitt. and Solanum tuberosum L.

Meiotic abnormalities in potato hamper sexual recombination, due to their influence on pollen production and viability rate. In this study we evaluated pollen viability and meiosis of three clones of Solanum commersonii commersonii Dun. (SCC), two of Solanum commersonii malmeanum Bitt. (SCM) and seven clones and four cultivars of Solanum tuberosum L., with the purpose of indicating promising genotypes for genetic breeding of potato. Early chromosome migration at metaphases I and II and chromosome pairing anomalies were the main causes of pollen inviability in the evaluated genotypes. Clones SCC 07 and SCM 60 are the most suitable for sexual recombination, owing to the high percentage of viable pollen grains and low frequencies of meiotic abnormalities.

Male fertility and occurrence of 2n gametes in East African Highland bananas (Musa spp.)

The quantity and quality of pollen produced by a genotype are important attributes to be considered in the selection of male parents for breeding. The objective of this research was to determine the quantity and quality of pollen in 13 selected East African Highland bananas (EAHB) in relation to six diploids commonly used as male parents. Pollen quantity was scored on a scale of 0–6 while the variation of pollen stainability along the rachis was determined using acetocarmine glycerol jelly. Actual male fertility was determined by using pollen from the EAHB varieties on M. acuminata spp. burmannicoides, ‘Calcutta 4’, as the female. The diameter of 200 viable pollen grains was measured under a microscope with the aid of a graduated eyepiece. Significant differences were obtained for mean pollen stainability and pollen diameter. The pollen stainability for diploids was higher than that for the EAHB. Node numbers contributed significantly to variation of pollen stainability in EAHB (P ≤ 0.01) and ‘Pisang lilin’ (P ≤ 0.001). ‘Pisang lilin’ and the EAHB varieties had about 100 nodes as opposed to about 200 in other diploids. The EAHB varieties produced less pollen than most of the diploids. The actual male fertility of EAHB varieties was low (1 seed/bunch), compared to that of ‘Calcutta 4’ (223.3 seeds/bunch) and ‘Pisang lilin’ (13.7 seeds/bunch). Although the production of 2n pollen in EAHB varieties was low (0–7%), the potential exists for using them in new breeding approaches.