Amount Of Pollen Grains Research Articles

Differential Variability of Maize (Zea mays L.) Inbred Lines to Moisture-stress at Reproductive Stages and DNA Methylation Studies of Identified Contrasting Genotypes under Moisture-Stress Conditions

An investigation was undertaken to assess the effect of moisture stress during the reproductive initiation stage on the quality and quantity of pollen grains produced in eight inbred lines (UASBM22, UASBM13, UASBM09, UASBM11, UASBM06, UASBM14, UASBM02 and UASBM10) under greenhouse conditions in three blocks viz., well-watered, stress I (for 21 days from 28 days after sowing) and stress II (for 22 days from 32 days after sowing). Moisture stress significantly affected the number of pollen grains per anther and other plant growth-related traits. The moisture stress effect was not uniform across inbred lines. The inbred lines UASBM22, UASBM13, UASBM09 and UASBM11 recorded a significant reduction in the total number of pollen grains per anther and an increase in pollen sterility while in inbred lines, UASBM06, UASBM14, UASBM02 and UASBM10, the moisture stress effect was not significant. The changes in the DNA methylation pattern in leaves and immature anthers under moisture stress of the contrasting inbred lines (UASBM06 and UASBM13) were studied through methylation- sensitive random amplification polymorphism. An increase in total DNA methylation level in both leaves and anthers was observed in drought tolerant inbred line, UASBM06 under stress while the increase was only in the leaves of the susceptible inbred line UASBM13. Leaves and anthers of UASBM06 showed hypermethylation compared to UASBM13 in moisture-stress conditions. In maize, increased DNA methylation seems to be an important mechanism associated with drought responses which probably regulates the methylation-sensitive gene expression and acclimation responses in maize.

Comparing the acetolysed and hydrated methods for the pollen analysis of honey

Melissopalynology is an integral part of honey analysis and indicates the honey's botanical and geographical origin. Two preparation methods for light microscopy are commonly and interchangeably used in laboratories: acetolysis and hydration of honey samples. In this study, an extended comparison of the two methods was performed. Eight honey samples from eight locations in central Europe were analysed according to both standard procedures. We identified the pollen grains with 1000× magnification to the lowest possible taxonomic rank and counted out the relative abundances of each pollen type in the sample. In addition, potential other biases that might affect the results were investigated by analysing one honey sample multiple times with each method, consecutively. Across all honey samples, more pollen types were identified with the hydrated method (136) compared to the acetolysed method (95). For the hydrated method, less washing steps were necessary and a higher amount of pollen grains remained. No taxa-specific loss could be observed, apart from Myosotis sp., which was present in significantly lesser amounts in acetolysed compared to hydrated samples. This study shows a detailed analysis of the advantages and disadvantages of the two methods, which are also highlighted in a side-by-side comparison box. Both methods are equally suitable to perform melissopalynological analysis of the most common pollen types and pollen type combinations in honey. However, to identify the largest variety of pollen types in honey samples, the hydrated method is more efficient.

Debunking wasp pollination: Wasps are comparable to bees in terms of plant interactions, body pollen and single‐visit pollen deposition

Abstract Wasps are understudied in their contribution to pollination services. In order to better understand the ecological contribution of wasp communities to plant pollination, we conducted three studies to compare bees and wasps by (1) the plant communities visited in agricultural and prairie environments, (2) body pollen composition as an indirect measure of pollination and (3) a single‐visit deposition study as a direct measure of pollination in the plant species complex Solidago canadensis. We found wasps visit a distinct early‐blooming exotic plant community from bees but have overlapping use of late‐blooming native plants and similar network interaction metrics. This suggests wasps may fill an ecological niche distinct from bees, while also serving as common native plant visitors. We also found that body pollen density and pollen fidelity in four and five (out of six) wasp families, respectively, were comparable to or greater than the bee family Colletidae. Three wasp families also showed comparable to or greater visit fidelity than two (out of five) bee families examined. These results suggest wasps may carry and potentially deliver substantial pollen to specific plants. In addition, controlled single‐visit deposition revealed the paper wasp Polistes fuscatus deposits a similar amount of pollen grains as the bumble bee Bombus impatiens, suggesting surprisingly high pollination efficiency that warrants further investigation. Our multi‐pronged study shows the importance of investigating the role of wasps as pollinators, especially by focusing on direct plant‐pollination metrics to determine wasp pollination efficacy.

Bee pollination efficiency in watermelon (Citrullus lanatus) crops in Panama

This study evaluated the bee pollination efficiency of wild neotropical bees visiting watermelon flowers in Azuero, Panama. We determined the quantity of pollen grains deposited on stigmas of excluded flowers by Apis mellifera, Nannotrigona perilampoides, Trigona corvina, Trigona fulviventris, and Lasioglossum spp. We also determined the number of produced fruits and their quality by weighing and counting the seeds inside the fruits produced by 1, 8, 12, and 16 visits of A. mellifera, N. perilampoides, and T. corvina. Finally, we calculated Spear's Pollination Efficiency Index. We found differences in the pollen grain number deposited by the studied bee species. On average, T. corvina deposited the largest amount of pollen (n = 379 ± 35), and T. fulviventris deposited the least (n = 86± 20). The fruit weight and seed number showed a positive correlation with the number of visits the flowers received. No differences were observed in weight and seed number in the fruits visited by the three bee species. The best quality fruits were obtained with 16 visits and no visit restriction treatment, with no differences between them. Our results show the studied bee species are capable of efficiently pollinating watermelon flowers, and have the potential for being used in the pollination of local crops. However, the best production results are obtained when the bee species act together.

Reproductive biology of Caryocar brasiliense (Caryocaraceae) in preserved and degraded Cerrado areas in Brazil

This study aimed to characterize the reproductive system and determine the importance of pollinators for fruit production of Caryocar brasiliense, an economically important tree, in preserved and degraded Cerrado areas in southeastern Brazil. For this purpose, we performed pollinator exclusion experiments to determine the frequency of self- and cross-pollination, and to determine fruit set. In general, fruit set was extremely low; only 2.92% and 2.71% of the flowers developed into fruits in the degraded and preserved areas, respectively. Fruit sets by manual cross-pollination and natural (open) pollination were higher than self-pollination in both areas. Pollen deposition was significantly higher at night and in the preserved area, although a relatively high amount of pollen grains is found in the stigmas during the day. The number of ripened and aborted seeds did not differ among areas, but fruits and seeds were heavier in the degraded area than in the preserved area. The abortion level was very high (64.5%), which may be related to low pollen quality due to selfing. Our study presents evidence that Cerrado degradation affects the reproductive biology of C. brasiliense, but whether such effect is a consequence of pollinator decline in degraded areas remains to be determined.

Taste for pollen comes in different shapes: Consumption by tadpoles from three divergent ecomorphotypes

AbstractPollen is a nutritive resource, but its role in aquatic food webs is little studied. Successful pollen acquisition may require behavioral adaptations for tadpoles with certain morphologies; however, pollen coats are hard to break to enable content assimilation. We investigated the consumption of pollen by tadpoles from three ecomorphotypes adapted to feed on the surface (neustonic), the water column (nektonic) and the bottom (benthic). We sampled three developmental stage ranges at both wet and dry seasons at a site in southeastern Brazil. We analyzed the pollen content and coat‐breaking level in three sections of tadpole guts and in their feces. We compared pollen composition in tadpole guts among groups based on species and developmental stages and between seasons. We also compared the total number of pollen grains and proportion of broken grains (as a surrogate for digestion capacity) in the guts among species, developmental stages, and between seasons. Ecomorphotype, developmental stage, and season influenced both composition and quantity of pollen consumed. Neustonic tadpoles in general consumed a greater amount of pollen grains and broke them faster, compared to the other ecomorphotypes. Tadpoles showed some variation in the amount of pollen consumed among developmental stages, which interacted with species, but developmental stages of the same species did not differ. Pollen consumption only varied between seasons for the nektonic tadpoles, being greater in the dry season. The high nutritive value of pollen is likely to make consumption by tadpoles rewarding and has an important effect in aquatic food webs, reinforcing the importance of conserving riparian habitats and their vegetation.

Phenology, floral and reproductive biology of Dichorisandra rhizantha Aona (Commelinaceae), an endemic endangered species in an Atlantic Forest fragment.

Commelinaceae is an important component of the Atlantic Forest and its analysis can provide information on the conservation of that species. This study had the objective of analyzing the phenology and floral and reproductive biology of Dichorisandra rhizantha, growing in an Atlantic Forest fragment, to obtain data related to the form of reproduction and pollination mechanism of this species. We monitored the phenophases and reproductive biology of the D. rhizantha in the area studied using different methodologies and microscopy techniques (LM, SEM and FM). The flowering period occurs during the dry season. The species is andromonoecious and has daytime anthesis (4:30 a.m.-1:30 p.m.). It has purple zygomorphic flowers and rimose but functionally poricidal anthers. The pollen viability was 97.6% and the two floral morphs investigated contained a large quantity of pollen grains. The time of greatest stigma receptivity (anthesis) coincided with the pollen viability. Cross-pollination was the only efficient reproductive system of the species, with observation of gametophytic self-incompatibility and pollen tubes growth only as far as the middle or lower third of the pistil. We observed bee species of the genera Xylocopa and Euglossa visiting the flowers and acting as effective pollinators. The immature fruits were formed after about 3.25 ± 1 days, and the presence was noted of ants of the genus Cephalotes acting as dispersers of the seeds, with aril serving as the reward. Although the natural reproductive system is efficient, D. rhizantha is endangered, mainly due to fragmentation of habitat caused by deforestation and urban encroachment.

Pollen in the Baltic Sea as viewed from space

Multi-sensor satellite images often show recurrent image slicks in the Baltic Sea. Based on historical reports, laboratory experiments, and spectral diagnostics, these image slicks are determined to be caused by pine (Pinus sylvestris) pollen aggregations as opposed to surface scums of cyanobacteria or other floating matters. This attribution is because the reflectance spectral shapes of these image slicks resemble those of pollen grains, which are all different from other floating matters. They all show rapid reflectance increase from ∼400 to ∼500 nm, beyond which the reflectance shape appears to plateau. During the 22-year period of 2000–2021, satellite images indicated large amounts of pollen grains in 14 years, with the earliest day being May 10 (in 2000) and the latest day being June 16 (in 2006). The longest duration in a single year is 22 days, from May 12 to June 2 of 2018. The waters containing pollen grains have expanded significantly in recent years, encompassing nearly the entire Baltic Sea. Because pollen grains contain a significant amount of carbon and have distinctive optical properties from other particles, these findings have significant implications on carbon sequestration, marine ecology, bio-optics, ocean color calibration/validation, and remote sensing of marine debris.

Innovative and Effective Spray Method for Artificial Pollination of Date Palm Using Drone

Traditional pollination of date palms is a time-consuming and labor-intensive process. Hence, the objectives of this study were 1) to develop a rapid, efficient, and low-cost pollination method that results in an acceptable level of fruit set (FS) with smaller amount of pollen grains, and labor costs using a platform-mounted robotic (drone) supplemented with water-suspended pollen grains, and 2) to investigate the effect of this method on date palm FS percentage, pollination efficiency (PE), fruit retention, total yield, and fruit quality. Date palm cultivars Barhi, Lulu, and Khesab were pollinated using traditional hand pollination (HP), spray pollination (HS), and drone pollination (DS) with water-suspended pollen grains (3 g/L). The results revealed that DS had a significantly lower FS percentage than the HP and HS methods in the Lulu and Khesab cultivars, but the difference was not statistically significant in Barhi cultivar. Fruit PE was unaffected by any of the pollination methods in Barhi and Lulu cultivars, but in the Khesab cultivar, DS pollination had lower PE (0.81) than HS (0.94) and HP (0.99) methods. DS had significantly lower levels of fruit retention and bunch weight than other methods. DS significantly improved fruit physical quality at harvest in all cultivars compared with HP and HS methods. Nevertheless, fruit color, firmness, total soluble solids (TSS) %, acidity, pH, and vitamin C level were unaffected by any of the pollination methods. Although the DS method produced lower FS percentage and bunch weight, the obtained FS percentages were within the commercially acceptable range for all cultivars. To the best of our knowledge, this is the first field study to indicate the possibility of pollinating date palm using drones with water-suspended pollen grain. To validate the commercial application, more research is needed to justify the optimum time and duration of application, which may vary according to cultivar and region.

Determination of Allergenic Pollens in the Atmosphere of Trabzon Province by Volumetric Method

Bu çalışmada, Trabzon ili atmosferinde bulunan polenler 01 Ocak 2016 – 31 Aralık 2016 tarihleri arasında volumetrik yöntemle VPSS 2000 (Lanzoni) cihazı kullanılarak araştırıldı. Bir yıllık çalışma süresince 45 taksona ait toplam 29150 polen m-3 Trabzon atmosferinde kaydedildi. Tespit edilen bu taksonların 24’ünün odunsu bitkilere (%69.78), 21’inin otsu bitkilere (%30.00) ve tanımlanamayan (%0.23) polenlere ait olduğu belirlendi. Çalışılan bölgede yoğun olarak saptanan odunsu taksonlar; Alnus sp. (%23.06), Cupressaceae-Taxaceae (%19.29), Pinaceae (%11.59), Betula sp. (%5.91), Platanus sp. (%3.38), Quercus sp. (%1.67), Ulmus sp. (%1.16) ve Fraxinus sp. (%1.05) olarak saptandı. Otsu bitkiler ise; Poaceae (%13.56), Urticaceae (%7.10), Boraginaceae (%2.12), Rumex sp. (%1.92), Mercurialis sp. (%1.36) ve Artemisia sp. (%1.25) olduğu belirlendi. Çalışılan bölgede polen yoğunluğunun en fazla olduğu aylar Şubat (%38.39), Mart (%11.88) ve Nisan (%15.67) olarak belirlendi.

Cannabis, an emerging aeroallergen in southeastern Spain (Region of Murcia)

The evolution of the behaviour of the Cannabis taxon in the Region of Murcia, Spain, has been analysed (in the cities of Cartagena, 1993–2020; Murcia, 2010–2020; and Lorca, 2010–2020). An attempt has been made to establish the origin of Cannabis pollen in this region to determine whether it is transported locally or from long distances based on air mass origins. Cannabis is an herbaceous, normally dioecious and anemophilous plant, which produces large quantities of pollen grains. It has been widely used for fibre (hemp), bird food (hempseed), essential oils and narcotics. The origin of Cannabis pollen grains has been established by calculating back trajectories at the altitudes of: 750, 1500 and 2500 m above mean sea level (m amsl); 350, 500 and 650 m amsl; and 10, 100 and 250 m amsl, using the HYSPLIT model. Considering this data, 29 days of Cannabis pollen potentially originating in Africa were identified in Cartagena, 19 days in Murcia and 15 days in Lorca. Of the remaining days, the air mass back trajectories showed local or regional pollen origins. These were 83 days in Cartagena, 61 days in Murcia and 57 days in Lorca. The presence of Cannabis in the bioaerosol of the Region of Murcia is irregular, and it is considered a minority pollen type. However, from 2017 to 2020, concentrations increased, with a positive and significant trend of 90% in the Annual Pollen Integral. The pollen season can be defined between June and August. This increase in the concentration of Cannabis pollen grains during this period coincides with an increase in local transport, suggesting the possibility of increased Cannabis cultivation in the study area.

Les pollens allergisants de la gelée royale d’origine française

Knowing allergenic pollens of royal jelly (RJ) product in France is important for allergic people. 16 RJ samples are studied using the allergomelissopalynology method. This process describes the spectrum of allergenic pollens and the allergenic potential of RJ pollens with the allergenic potential index system (APIS). RJ samples are made in France. Samples contain 2 to 8 allergenic pollens. The daily dose of 300 or 500mg of RJ provides a small amount of pollen grains (approximately 10,000). The APIS of mugwort and of polliniferous Asteraceae are the only higher than 10. APIS allows to define the allergenic potential of allergenic pollens of RJ.

Settling moths are the vital component of pollination in Himalayan ecosystem of North-East India, pollen transfer network approach revealed

Majority of the pollination related studies are based on the diurnal pollinators, and the nocturnal pollinators received less scientific attention. We reveal the significance of settling moths in pollination of angiosperm families in Himalayan ecosystem of North-East India. The refined and novel method of pollen extraction from the proboscides provides a more robust assessment of the pollen carrying capacity. The study is based on one of the largest data sets (140 pollen transporter moth species (PTMS)), with interpretation based on seasonal as well as altitudinal data. In the present study about 65% moths (91 species) carried sufficient quantities of pollen grains to be considered as potential pollinators (PPMS). Teliphasa sp. (Crambidae) and Cuculia sp. (Noctuidae) are found to carry the highest quantity of pollen. We found pollen grains of 21 plant families and the abundant pollen are from Betulaceae, Fabaceae, Rosaceae and Ericaceae. Species composition of PTMS and PPMS in pre-monsoon, monsoon, and post-monsoon revealed the dominance of Geometridae. Maximum diversity of PTMS and PPMS is found from 2000 to 2500 m altitude. The nocturnal pollen transfer network matrices exhibited high degree of selectivity (H2ʹ = 0.86).

Evaluation of Native and Nonnative Ornamentals as Pollinator Plants in Florida: II. Floral Resource Value

Consumer demand for novel, visually attractive ornamentals has often overshadowed the functional value plants may provide for flower-visiting insects. As native and nonnative species are hybridized for form, color, flowering, and disease resistance, it is important to assess whether some of these alterations influence plant nutrient quality for foraging insect pollinators. A study was conducted to ascertain the resource value of ornamental cultivars compared with their native congeners. The nectar volume and pollen quantity, viability, and protein content of 10 species of popular herbaceous flowering plants, commonly advertised as pollinator-friendly, were evaluated in northcentral Florida. Each genus encompassed a native and nonnative species, apart from pentas. Native species included blanket flower (Gaillardia pulchella), lanceleaf coreopsis (Coreopsis lanceolata), pineland lantana (Lantana depressa), and scarlet sage (Salvia coccinea). Nonnative species included Barbican™ yellow-red ring blanket flower (Gaillardia aristata ‘Gaiz005’), Bloomify™ rose lantana (Lantana camara ‘UF-1011-2’), mysty salvia (Salvia longispicata × farinacea ‘Balsalmysty’), Lucky Star® dark red pentas (Pentas lanceolata ‘PAS1231189’), ruby glow pentas (Pentas lanceolata ‘Ruby glow’) and UpTick™ Gold & Bronze coreopsis (Coreopsis × ‘Baluptgonz’). Floral rewards differed significantly across species. The native scarlet sage exhibited the largest nectar volume per flower in the summer (2.13 ± 0.17 µL), followed by the nonnative mysty salvia (1.26 ± 0.17 µL). In the fall, ruby glow pentas exhibited the largest nectar volume per flower (1.09 ± 0.17 µL) compared with all other ornamentals. The composite flowers of the native and nonnative blanket flower and coreopsis species had the lowest nectar volume per flower regardless of sampling date. Likewise, ruby glow pentas displayed the highest quantity of pollen grains (96.29 ± 0.12) per sample, followed by Lucky star pentas (52.33 ± 0.12), and Barbican blanket flower (50.98 ± 0.12). Pollen viability was similarly high (92% to 98%) among all species, apart from Bloomify rose lantana (20%) and pineland lantana (48%). Pollen protein content was highest in Uptick coreopsis (11.378 ± 1.860 μg/mg dry weight) and Lucky star pentas (10.656 ± 3.726 μg/mg dry weight), followed by lanceleaf coreopsis (7.918 ± 1.793 μg/mg dry weight). These results largely showed that the nonnative ornamentals selected provided resource-rich floral rewards, comparable to native congeners. Still, care should be taken in making similar assessments of other modern floral types.

Importance of biotic pollination varies across common bean cultivars

AbstractCommon bean (Phaseolus vulgaris L.) flowers are morphologically adapted to biotic pollination, although it is partially autogamous. We evaluated the effect of pollinator visits on pod and seed production of 14 local creole cultivars of P. vulgaris, commonly used in organic farming. We collected descriptive data observing the flower visitors and estimating the number and viability of pollen grains, flower size, nectar volume and nectar sugar concentration. Overall, exposure to flower visitors (legitimate pollinators and robbers) improved production in terms of quantity or quality of pods and/or seeds of eight cultivars and reduced production of two other cultivars. We found 10 insect species visiting flowers of the bean cultivars, but only Xylocopa bees behaved as legitimate pollinators. Other flower visitor species either pierced the corolla base to get the nectar or got the nectar without lowering the flower's wings and keels to touch anthers and stigma. Petal length and nectar features showed few variations among the cultivars. Two cultivars produced a larger amount of pollen grains than the remaining cultivars. Despite some variation across cultivars, our results suggest the importance of native bees to pollination and reproductive success of creole beans.

Distinct pollen release dynamics between stamens generate division of labour in pollen flowers of two Pleroma species (Melastomataceae)

Flowers that provide only pollen to pollinators should maximize pollen release for reproduction while minimizing pollen loss through consumption by bees. In flowers that are polymorphic for stamen type, the number of pollen grains produced as well as stamen morphology likely influences pollen release dynamics and favor the division of labor between stamens with different functions. However, few studies have evaluated such predictions. In this study, we tested the “division of labor hypothesis” considering not only the stamen morphology of pollen flowers but also their pollen release dynamics. Stamen morphology as well as the amount and viability of pollen were characterized in two Melastomataceae species, Pleroma granulosum and Pleroma raddianum. Using artificial vibrations, we estimated pollen release dynamics throughout anthesis in the anthers of short and long stamens from flowers of both species. P. granulosum flowers presented low heteranthery (i.e., anthers differed by only about 1 mm in length) and short stamens produced fewer pollen grains in both species. We also found similarly high viability of pollen from all anthers of both species. Although pollen grain release increased in all anthers over the flower´s lifespan, their dynamics were different between the two stamen sets in both species. Anthers of shorter stamens tended to release fewer and proportionally lower quantities of pollen grains at each time interval than anthers of longer stamens. Our study suggests that the number of pollen grains produced, as well as stamen morphology (beyond anther size) may control pollen release dynamics, leading to a division of labor between stamens in these pollen flowers.

Identification of Ms2, a novel locus controlling male-fertility restoration of cytoplasmic male-sterility in onion (Allium cepa L.), and development of tightly linked molecular markers

Cytoplasmic male-sterility (CMS) has been exclusively used to produce F1 hybrid seeds of onion (Allium cepa L.). A single nuclear locus, Ms, is known to restore male-fertility of CMS in onions. Unstable male-sterile onions producing a small amount of pollen grains have been identified in a previous study. When such unstable male-sterile onions were crossed with stable male-sterile onions containing CMS-R cytoplasm, male-fertility was completely restored, although genotypes of the Ms locus were homozygous recessive. Inheritance patterns indicated that male-fertility restoration was controlled by a single locus designated as Ms2. A combined approach of bulked segregant analysis and RNA-seq was used to identify candidate genes for the Ms2 locus. High resolution melting markers were developed based on single nucleotide polymorphisms (SNPs) detected by RNA-Seq. Comparative mapping of the Ms2 locus showed that Ms2 was positioned at the end of chromosome 2 with a distance of approximately 70 cM away from the Ms locus. Although 38 contigs containing reliable SNPs were analyzed using recombinants selected from 1344 individuals, no contig showed perfect linkage to Ms2. Interestingly, transcription levels of orf725, a CMS-associated gene in onions, were significantly reduced in male-fertile individuals of segregating populations. However, no significant change in its transcription level was observed in individuals of a segregating population with male-fertility genotypes determined by the Ms locus, suggesting that male-fertility restoration mechanism of Ms2 might be different from that of the Ms locus.

Unlikely transmission of Cowpea aphid-borne mosaic virus by hand pollination of passionflower

Passion fruit plants are self-incompatible and fruiting is exclusively dependent on cross-pollination, which in nature is performed by carpenter (mamangava) bees, especially Xylocopa spp. (family Apidae). To ensure satisfactory productivity, daily manual pollination is a common practice among passionflower growers. Therefore, we studied whether manual pollination mechanically transmits the cowpea aphid-borne mosaic virus (CABMV), the causal agent of the passion fruit woodiness disease. None of the eight healthy passion fruit plants manually pollinated with pollen from CABMV field-infected plants were infected, as confirmed by PTA-ELISA and RT-PCR. Healthy passion fruit plants mechanically inoculated with extracts of pollen collected from flowers of CABMV field-infected plants were not infected. CABMV was only detected by RT-PCR in groups of three anthers, and in pollen from groups of 20 anthers collected from flowers of infected passion fruit plants. RT-qPCR conducted with different amounts of pollen grains and anthers indicated extremely low virus titers. In addition to low virus titers, transmission failure may be associated with an absence of virus particles outside the pollen grains and/or absence of enough wounding produced on the stigmas by the fingertips. The improbability of CABMV transmission via pollen during manual pollination showed that this widely used cultural practice is a negligible factor in the epidemiology of passion fruit woodiness disease.

AtLURE1/PRK6-mediated signaling promotes conspecific micropylar pollen tube guidance.

Reproductive isolation is a prerequisite to form and maintain a new species. Multiple prezygotic and postzygotic reproductive isolation barriers have been reported in plants. In the model plant, Arabidopsis thaliana conspecific pollen tube precedence controlled by AtLURE1/PRK6-mediated signaling has been recently reported as a major prezygotic reproductive isolation barrier. By accelerating emergence of own pollen tubes from the transmitting tract, A. thaliana ovules promote self-fertilization and thus prevent fertilization by a different species. Taking advantage of a septuple atlure1null mutant, we now report on the role of AtLURE1/PRK6-mediated signaling for micropylar pollen tube guidance. Compared with wild-type (WT) ovules, atlure1null ovules displayed remarkably reduced micropylar pollen tube attraction efficiencies in modified semi-in vivo A. thaliana ovule targeting assays. However, when prk6 mutant pollen tubes were applied, atlure1null ovules showed micropylar attraction efficiencies comparable to that of WT ovules. These findings indicate that AtLURE1/PRK6-mediated signaling regulates micropylar pollen tube attraction in addition to promoting emergence of own pollen tubes from the transmitting tract. Moreover, semi-in vivo ovule targeting competition assays with the same amount of pollen grains from both A. thaliana and Arabidopsis lyrata showed that A. thaliana WT and xiuqiu mutant ovules are mainly targeted by own pollen tubes and that atlure1null mutant ovules are also entered to a large extent by A. lyrata pollen tubes. Taken together, we report that AtLURE1/PRK6-mediated signaling promotes conspecific micropylar pollen tube attraction representing an additional prezygotic isolation barrier.

Pollen Flow of Winter Triticale (x Triticosecale Wittmack) Investigated with Transgenic Line Expressing β-Glucuronidase Gene

A transgenic winter triticale line expressing the uidA gene, encoding β-glucuronidase, was used to assess the pollen flow in field experiments over two consecutive vegetation seasons in central Poland. The experimental design included two variants of mixed transgenic and non-transgenic lines. Pollen grains were collected using passive traps located at 0, 10, 30, 60 and 85 m from the transgenic line. GM pollen grains were detected histochemically by staining with x-Gluc. A positive effect of temperature increase, as well as the strength and direction of the wind on the number and spread of pollen grains was observed. Regardless of the experiment year and variant, only few pollen grains were observed at a distance of 85 m. In the first year of the study the amount of pollen grains at 85 m was 300-fold lower than at the source and 140-fold lower in the second year. The number of transgenic pollen grains was two times lower when the field with the transgenic triticale was surrounded by a non-transgenic line, compared to an empty field. On the basis of the obtained results, we suggest 100 m as the distance for triticale pollen migration, although longer flight incidents are possible in extreme atmospheric conditions.