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To gain a deeper understanding of the flowering pattern and reproductive characteristics of Epimedium sagittatum, to enrich the research on the flower development of E. sagittatum and its reproductive regulation, and to screen the methods suitable for the rapid detection of pollen viability of E. sagittatum and to promote its cross-breeding. The characteristics of its flower parts were observed, recorded and measured, and the pollen viability of E. sagittatumwas determined by five methods, including TTC staining, I2-KI staining, red ink staining, peroxidase method and in vitro germination method. The flowering process of E. sagittatum can be divided into five stages: calyx dehiscence, bract spathe, petal outgrowth, pollen dispersal, and pollination and withering. The results of I2-KI staining and peroxidase method were significantly higher than those of other methods; the in vitro germination method was intuitive and accurate, but the operation was complicated and time-consuming; the red ink staining method was easy to operate and had obvious staining effect, and the results were the closest to those of the in vitro germination method; and it was found that the pollen of E. sagittatum was not as effective as the in vitro germination method at the bud stamen stage, the flower stigma and the flower bud. It was also found that the pollen viability and germination rate of E. sagittatum pollen were higher in the three periods of bud spitting, petal adductor and pollen dispersal. Comparing the five methods, the red ink staining method was found to be a better method for the rapid detection of pollen viability; the best pollination periods of E. sagittatum were the bud stamen stage, petal adductor stage, and pollen dispersal stage of flowers at the peak of bloom. This study on the flowering and fruiting pattern of E. sagittatum, and the related mechanism of sexual reproduction, can be used as a reference for the next step of research on the breeding of E. sagittatum. [ABSTRACT FROM AUTHOR]

In vitro pollen germination is considered the most efficient method to assess pollen viability. The pollen germination frequency and pollen tube length, which are key indicators of pollen viability, should be accurately measured during in vitro culture. In this study, a Mask R-CNN model trained using microscopic images of tree peony (Paeonia suffruticosa) pollen has been proposed to rapidly detect the pollen germination rate and pollen tube length. To reduce the workload during image acquisition, images of synthesized crossed pollen tubes were added to the training dataset, significantly improving the model accuracy in recognizing crossed pollen tubes. At an Intersection over Union threshold of 50%, a mean average precision of 0.949 was achieved. The performance of the model was verified using 120 testing images. The R 2 value of the linear regression model using detected pollen germination frequency against the ground truth was 0.909 and that using average pollen tube length was 0.958. Further, the model was successfully applied to two other plant species, indicating a good generalizability and potential to be applied widely. [ABSTRACT FROM AUTHOR]

Crossbreeding is a multi-stage process with inherent challenges and risks in developing new varieties. Success hinges on selecting highly fertile parents. In species like lisianthus, uncertainty persists regarding the optimal methods for assessing pollen quality, which is crucial for evaluating pollen parent fertility. This study seeks to identify the most reliable techniques for this purpose. Fresh and dead pollen from four lisianthus (Eustoma grandiflorum) varieties was used. The dead pollen was obtained by thermal inactivation. Five chemical staining methods (iodine-potassium iodide, 2,3,5-triphenyltetrazolium chloride - TTC, lactophenol cotton blue, safranin, acetocarmine) were employed to assess pollen viability, and two biological methods (Petri dishes, hanging drops) were used to determine the germination rate. Four solid medium cultures were employed in Petri dishes, while the hanging drop utilised four liquid medium cultures. Thirteen tests were conducted for each variety, evaluating fresh and dead pollen. The study found significant variations in pollen quality among lisianthus varieties and methods. Fresh pollen showed viability rates ranging from 56.87% to 99.41% and germination rates from 0.20% to 45.11%. TTC exhibited the lowest viability rate across all varieties, while the highest germination rate was observed in the liquid culture medium with only boric acid and PEG1500. Notably, TTC was the sole viability method that did not stain dead pollen, and no germination occurred in any method for dead pollen. TTC is the most reliable staining method, and a liquid culture medium with boric acid and PEG1500 effectively determines lisianthus pollen quality. Varying boric acid and PEG1500 concentrations are advisable. [ABSTRACT FROM AUTHOR]

• Comprehensive phenology from the onset of the primordial bud to the senescence phase, is documented for Macrotyloma uniflorum. • Floral organs exhibits ultrastructural variation in Macrotyloma uniflorum. • Macrotyloma uniflorum accessions from Republic of Benin are non-echinate; other accessions exhibit spinuliferous pollen. • There is a positive correlation between days to flowering and most floral traits. • Pollens of Macrotyloma uniflorum are viable during the day. The absence of information on the reproductive biology of some nutritive legumes has been an obstacle to their genetic improvement. Gathering information on reproductive biology contributes significantly to the interest of breeders to have adequate tools for initiating the improvement program through crosses among high performing genotypes. To contribute to this, we examined the flowering phenology, pollen biology, stigma receptiveness at bud dehiscence and anthesis phases, and the in-vitro germination of the pollens in horsegram (Macrotyloma uniflorum). Pollens of horsegram were found to be either tricolporate or triporate, echinates in all accessions except in the collections from Benin. Ovaries in horsegram showed great variation in the number of ovules and activities of peroxidase indicated the receptiveness of stigma at bud dehiscence phase and during anthesis. A high number of ovules per ovary was found in accessions from Australia (Leichardt 1 and 2), Mali (LeichardtMali) and India (CPI22679). Pollen viability analysis implies the possibility of better results when pollinating during the day and immediately after the flower opens. The study provides information on the reproductive biology of horsegram for future hybridization program in order to enhance the performance of the crop and increase production. It also reveals differences in accessions from Benin compared with all other accessions from Mali, India or Australia. [ABSTRACT FROM AUTHOR]

• Pollen viability was reduced in high UV treatments. • Pollen viability was lower where floral UV-bullseye was larger. • Across studies, UV impacts pollen viability, pollen germination and tube growth. Ultraviolet (UV) radiation is known to be an important environmental stressor of plants. Evidence of its effects on plant reproduction is mixed, with studies usually showing that short doses of UV lead to a reduction in pollen viability, but that longer exposure can improve viability. Here, we tested the effect of UV intensity (control, low-UV, high-UV) and the duration in which the plants were exposed for different time periods prior to flowering (long: from seed; short: exposed after 7 days of growth) on pollen viability of Brassica rapa. We also tested how changes in floral morphology (UV-absorbing area) related to pollen viability, before carrying out a meta-analysis on the effects of UV on pollen performance. We found that high UV intensity reduced pollen viability, but there was no effect of UV exposure prior to anthesis on pollen viability. Unexpectedly, we found a negative relationship between UV-absorbing area and pollen viability. Our meta-analysis showed a significant negative effect of UV on pollen viability, tube growth and germination. In summary, our results show that high UV generally negatively impacts pollen viability. [ABSTRACT FROM AUTHOR]

The study was carried out at the Trans-Himalayan Herbal Garden, located at the National Institute of Sowa Rigpa-Leh, from 2021 to 2023. An assessment of pollen viability was conducted using seven significant medicinal and aromatic plants from the Ladakh region. Analysis of pollen vitality was conducted using the acetocarmine staining technique. The pollen viability of Inula racemosa Hook. f. ranged from 91.08 ± 1.39 % to 82.44 ± 1.48 % in Ephedra gerardiana Wall. Among the genus Inula racemosa, the highest percentage (91.08%) of viable pollens indicates a normal meiosis, whereas Ephedra gerardiana recorded the lowest percentage. Among the chosen species, Inula racemosa, Verbascumthapsus, Hyoscyamus niger, and Dracocephalum heterophyllum stand out for their exceptional pollen viability. These species can be effectively utilized for conservation purposes and as male parents in hybridization. The result for the average pollen density varied from 1533.07 ± 106.32 in Capparis spinosa L. to 276.00 ± 10.20 in Dracocephalum heterophyllum. [ABSTRACT FROM AUTHOR]

East African diploid cooking bananas, commonly called Mchare, are a staple crop for millions of subsistence farmers in Tanzania, particularly in the Pangani region in northern Tanzania. Several pathogens constrain Mchare production significantly and threaten food security. Sources of resistance to these pathogens have been identified; however, partial male and female sterility impedes successful resistance introgression, complicating the breeding process. Mchare cultivars are also the only known surviving representatives of a diploid banana subgroup that contributed unreduced gametes to many of the most widely grown and successful triploid dessert bananas (‘Cavendish’, ‘Gros-Michel’, ‘Silk’, and ‘Prata’). As such, they represent an essential intermediate step in the conventional improvement of bananas worldwide. We assess the amount and viability of pollen among Mchare and wild genotypes to identify the most fertile Mchare cultivars that can be used in conventional banana improvement. Pollen was collected from 14 banana genotypes for quantification and viability testing over 7 months, and the optimal time for pollen collection was determined to be 0800 HR. Significant variation among banana genotypes in terms of both overall pollen production and percentage of pollen viability was observed. The wild-type bananas ‘Calcutta 4’ (International Musa Germplasm Transit Center (ITC) 0249] and ‘Borneo’ (ITC0253) had the greatest overall pollen production (> 31,000 pollen grains/anther) and viability (~74%), whereas ‘Ijihu Inkundu’ (ITC1460; Mchare genotype) was the least productive (almost completely sterile), with an average pollen production of a few hundred grains per anther and a viability of 7%. There were significant differences among months in terms of pollen viability, with the greatest average viability observed in May, April, and February (> 51%), and the lowest average pollen viability in July (41%). Significant differences were observed among the Mchare genotypes, with ‘Huti-White’, ‘Huti green bell’ (ITC1559), and ‘Mchare Laini’ consistently producing more substantial amounts of total pollen and an overall more significant proportion of viable pollen. This information is vital to improve Mchare bananas and the global breeding of dessert bananas. The choice of Mchare banana used in improvement programs could affect fertility and the likelihood of breeding success. [ABSTRACT FROM AUTHOR]

Cannabis (Cannabis sativa) is a versatile crop belonging to the Cannabaceae family, and is dioecious, typically with separate male and female plants. The flowers of female plants, especially the trichomes, accumulate relatively higher contents of cannabinoids compared with those of male plants. For this reason, to obtain seeds that are genetically female, it is desirable to induce the development of male flowers on a female plant that produces genetically female haploid gametes. Silver thiosulfate (STS) is a highly effective chemical for male flower induction. We investigated male flower induction in three commercial cultivars of female cannabis (Spectrum303, SuperwomanS1, and CBGambit) regarding the treatment frequency, stage of application, and concentration of STS applied as a foliar spray. All three cultivars showed adequate induction of male flowers in response to 1.5 mM STS applied at the early reproductive stage. In particular, SuperwomanS1 was most highly responsive to induction of male flowers, even when treated with 0.3 mM STS at the early reproductive stage. Treatment with three applications of STS was more effective compared with a single application, but a single application of 1.5 mM STS at the early reproductive stage was sufficient for male flower induction. A single STS application during the middle stage of reproductive growth was inadequate for induction of male flowers. However, 6 weeks after three applications of STS, CBGambit exhibited approximately 54% male flower induction at 0.3 mM STS, Spectrum303 showed approximately 56% induction at 3 mM STS, and SuperwomanS1 yielded approximately 26% induction at 1.5 mM (expressed as percentage of total number of individuals with the induced male flowers). Pollen stainability tests using KI-I2 solution and Alexander's staining showed high pollen viability with over 65% at different single STS concentrations, indicating that pollen grains induced by STS have sufficient viability for the self-pollination. This study demonstrated that different cultivars of cannabis respond diversely to different STS concentrations and highlighted the potential benefits of three STS applications during the middle reproductive stage for cannabis breeding. [ABSTRACT FROM AUTHOR]

Background and Aims: To date, current research involving pollen viability has been evaluated in a relatively low number of orchid species. In the present study, we focused on five related Mediterranean orchid genera (Anacamptis, Orchis, Dactylorhiza, Ophrys and Serapias) that are characterized by different types of deceptive pollination., Methods: The in vitro germination ability of increasingly aged pollinaria of eight food-, seven sexually and two shelter-deceptive species was evaluated. Pollination experiments on two food-, one sexually and one shelter-deceptive species were also performed and the percentage of embryonate seeds derived from the increasingly aged pollinaria was checked., Key Results: All of the examined species showed long-term viabilities (=50 % pollen tube growth) that ranged from 8 to 35 d. Species with the same deceptive pollination strategies exhibited the same pollen viability trends. Interestingly, pollen viabilities of species groups with different deception types have shown significant differences, with sexually and shelter- deceptive species exhibiting a shorter life span than food-deceptive species., Conclusions: This study confirms the prolonged germination and fertilization capacities of orchid pollinaria, and to our knowledge is the first report demonstrating a clear relationship between pollen viability and pollination system. It is proposed that this relationship is attributed to the different types of reproductive barriers, pre- or post-zygotic, that characterize Ophrys and Serapias and the food-deceptive species, respectively.

Objective: To provide the basal data for artificial cross breeding of Chinese herb Salvia miltiorrhiza from 7 provinces in China and its 4 relatives., Method: The pollen viability was evaluated by TTC (2, 3, 5-triphenylte trazolium chloride) test and the stigma receptivity was evaluated by benzidine-H2O2 method., Result: The pollen viability of S. miltiorrhiza from 6 provinces in China and its 4 relatives deceased during time of pollen shedding. Their highest pollen viability was in 2 or 3 days after blooming. But the pollen viability of S. miltiorrhiza (wild and culture) from Hean province in China declined with time after blooming. The most obvious variation of the pollen viability was in S. miltiorrhiza from Shanxi province (RSD 71.3% ) and the least was in wild S. miltiorrhiza from Henan province (RSD 12.4%). The highest average pollen viability was wild S. miltiorrhiza (72.3%) from Henan province while the lowest was S. yunnanensis (38.8%). The stigmas of all the accessions had receptivity when blooming. The stigma receptivity of S. brevilabra was strong in 2 to 4 days after blooming, while the others had less change after blooming. The life span of pollen grains and stigmas could be maintained from 3 to 5 days., Conclusion: The optimum artificial pollination time of S. miltiorrhiza and its relatives was 2 to 3 days after blooming.

Objective: To increase the reproduction efficiency of Iris plants., Method: Pollen viability, stigmatic receptivity, the color of anther and stigma of 5 Iris plants were observed during blooming., Result: 1. The highest pollen viability was in 4 hours after blooming; 2. The stigmatic receptivities of I. sichuanensis, I. leptophylla, I. lactea and I. goniocarpa were strong in 4 hours after blooming, while that of I. lactea var. chinensis was strong in 2 hours after blooming; 3. The color of anther could reflect the pollen viability, but could not indicate the viability level; 4. The stigma color could not reflect the receptivity of stigma., Conclusion: The optimum artificial pollination time of these five species were 12:00 -14:00.

Intergeneric and interspecific hybridization has been employed for the breeding of Phalaenopsis to transfer desirable traits between species, producing novel phenotypes with improved size, color, form, and flower-bearing ability. These characteristics are often enhanced; however, many of these hybrids are triploids and have reduced or complete sterility, for example, Phalaenopsis Queen Beer 'Mantefon', an important novelty-type cultivar in Asia, particularly in China, Japan, and Republic of Korea. Despite the increasing demand for the crop for ornamental purposes, little is known about its cytogenetics, which is essential for breeding and, consequently, crop improvement. In this study, karyotyping using fluorescence in situ hybridization, meiotic chromosome behavior analysis, pollen staining, and in vitro viability germination tests were performed to understand the cause of hybrid sterility and pollen abnormality in Phalaenopsis Queen Beer 'Mantefon' from a cytogenetic perspective. Viability tests revealed pollen infertility at all flower developmental stages, confirmed by the absence of pollen tube growth. Aberrant chromosomal behavior was observed in pollen mother cells (PMCs), frequently forming univalents, chromosomal bridges, and laggards during the entire meiotic process. PMCs were also divided irregularly into sporads with varying numbers of micronuclei, which may be responsible for pollen sterility in this cultivar. Altogether, the cytogenetic analyses provided insights into the pollen development of Phalaenopsis Queen Beer 'Mantefon' and the conceivable causes of its infertility. [ABSTRACT FROM AUTHOR]

Cryopreservation of pollen is a complementary conservation strategy and can be used for conserve the diversity in the genus Psidium. The present study aims to cryopreserve the pollen of Psidium species to overcome asynchronous flowering. The pollen of different Psidium species were germinated in vitro in an optimized medium of germination. In vitro / in vivo pollen viability assessment and SEM analysis were carried out to determine the changes after cryopreservation. The in vitro pollen viability was determined at monthly intervals starting from fresh pollen until six months of cryopreservation. The in vivo fertility tests were carried out by pollination using both fresh and cryopreserved pollen. The cryopreserved pollen showed in vitro germination ranging from 1.78% (in P. molle) to 81.67% (in "H 12–5") compared to fresh pollen (2.16% in P. molle to 86.08% in P. guineense). In vivo fertility was tested by controlled pollination using six-month-old cryopreserved pollen and it resulted in fruit setting ranged between 3.33% (P. cattleianum var. cattleianum) and 27.66% (P. chinensis) as compared to fresh pollen between 4.0% (P. cattleianum var. cattleianum) and 30.66% (P. chinensis). Seed set and germination was also recorded in all the crosses attempted using cryopreserved pollen. These in vitro and in vivo results indicated that cryopreservation is an effective technique for breeding and conserving the haploid gene pool in cryo genebank. Scanning Electron Microscopic studies of pollen revealed no significant variation in shape and size after cryopreservation when compared to fresh pollen. • Method of collection and optimum pollen germination media for different Psidium species were standardized. • Cryopreservation of pollen of wild Psidium species were carried to overcome asynchronous flowering and used for wide hybridization resulted in fruit and seed set. • Pollen morphology assessment of fresh and cryopreserved pollen in guava genotypes and wild Psidium species using SEM. • A pollen cryobank established for Psidium genotypes. [ABSTRACT FROM AUTHOR]

Success artificial pollination with viable pollen is crucial process in the production chain of date palms. This study evaluated the impact of pollen storage temperature and duration, pollination time following spathe cracking, and the hour of daytime on pollen viability, germinability, fruit set and yield of 'Deglet Nour' date palm cultivar. In in vitro tests, fresh pollen showed the maximum viability (96.3%) and germination (85%) but it decreased thereafter upon the storage temperature (28, 4 and −30 °C) and duration (3, 6, 9 and 12 months). In this respect, pollen stored at −30 °C retained highest viability and germinability followed by those stored at 4 and then at 28 °C. In filed experiments, fruit set was 85, 75, 65, and 45% with pollination using fresh pollen, or pollen stored at −30, 4 and 28 °C, respectively. Fruit set was 95%, 75%, and less than 50%, for pollination performed on the same day of spathe cracking, 6 and 12 days later, respectively. The highest fruit set percentage and yield/bunch were obtained with pollination performed between 12.0 pm and 15.0 pm in contrast to 8.0–11.0 am or 16.0–17.0. [ABSTRACT FROM AUTHOR]

Reproductive barriers are the single largest impediment in breeding of Solanum aethiopicum (Shum and Gilo cultivars). Knowledge of these barriers is important for prudent germplasm utilization and genetic improvement of the species. This study investigated compatibility barriers between S. aethiopicum and its relatives. A randomized complete block design and a full diallel mating method were used to evaluate crossability and floral traits of six genotypes of four different species (S. aethiopicum, S. macrocarpon, S. anguivi and S. incanum) across two seasons. Parameters assessed were petal opening time, stigma receptivity, anther dehiscence, pollen quantity, pollen viability and crossing success. Most flowers for all parental genotypes were opened by 08:00 am. Mean number of open flowers was higher (12 ± 6) for S. aethiopicum Shum (N11) and lowest (n = 3 ± 1) for S. macrocarpon (E12; (p < 0.001), with other genotypes being intermediate. Stigma receptivity differed (p < 0.001) among genotypes and seasons and was highest for N11 at 3.31 ± 1.32 and lowest for S. incanum (In1) at 2.24 ± 1.27; other genotypes were intermediate. All genotypes possessed high pollen viability (µ > 80%) though species differed (p < 0.01). All genotypes exhibited self-compatibility to varying degrees with N11 showing the highest fruit success (67.9 ± 15.6%), seeds per fruit (82 ± 51), and F1 germination rate (79 ± 18%). Interspecific crosses using S. macrocarpon, S. anguivi and S. incanum as females showed poor or no fruit and seed. N11 (S. aethiopicum Shum) was the top performer as a female; crosses with S. macrocarpon (N11xE12) showed highest fruit success (65.9 ± 26.5), with S. anguivi (N11xA1) showing the highest seed set (n = 56 ± 34) and S. incanum (N11xIN1) showing the highest F1 germination (64 ± 19). The F1 intraspecific cross between S. aethiopicum Shum (N4) and S. aethiopicum Gilo (G4) did not germinate. Female parent functioning may be a key feature for the failure of interspecific crosses where S. aethiopicum is a donor as observed by the unilateral incompatibility. [ABSTRACT FROM AUTHOR]

The common bean (Phaseolus vulgaris L.) is an important nutritional source globally but is sensitive to high temperatures and thus particularly vulnerable to climate change. Derived from a breeding program at CIAT (Colombia), a heat-tolerant breeding line, named heat-tolerant Andean-type 4 (HTA4), was developed by a series of crosses of parents with a small-bean tepary genotype (Phaseolus acutifolius L.) in their pedigree, which might be the donor of heat stress (HS) tolerance. Importantly, in HTA4, the large, commercially desirable Andean-type beans was restored. To assess underlying tolerance mechanisms, HTA4, together with a heat-sensitive Colombian variety (Calima), was exposed to HS (31 °C/24 °C HS vs. 26 °C/19 °C day/night) under controlled environment conditions. Vegetative growth and photosynthetic performance were not negatively impacted by HS in either genotype, although senescence was delayed in Calima. HS during the reproductive stage caused an increase in pod number in Calima but with few fully developed seeds and many pods aborted and/or abscised. In contrast, HTA4 maintained a similar filled pod number under HS and a higher seed weight per plant. Pollen showed high sterility in Calima, with many non-viable pollen grains (24.9% viability compared to 98.4% in control) with a thicker exine and fewer starch granules under HS. Calima pollen failed to adhere to the stigma and germinate under HS. In HTA4, pollen viability was significantly higher than in Calima (71.1% viability compared to 95.4% under control), and pollen successfully germinated and formed pollen tubes in the style under HS. It is concluded that HTA4 is heat tolerant and maintains a high level of reproductive output due to its ability to produce healthy pollen that is able to adhere to the stigma. [ABSTRACT FROM AUTHOR]

Main Conclusion: This work mainly found that the stigma and style of Q. variabilis did not completely lose the specific recognition towards heterologous pollen, a fact which is different from previous studies. Quercus is the foundation species in the Northern Hemisphere, with extreme prevalence for interspecific hybridization. It is not yet entirely understood whether or how the pollen tube-female tissue interaction contributes to the "extensive hybridization" in oaks. Pollen storage conditions correlate with distant hybridization. We conducted hybridization experiments with Q. variabilis as female and Q. variabilis and Q. mongolica as male parents. And the differences in pollen tube (PT) development between intra- and distant interspecific hybridization were studied by fluorescence microscopy and scanning electron microscopy (SEM). Our results showed that -20 °C allowed pollen of both species to maintain some viability. Both Q. variabilis and Q. mongolica pollen germinated profusely on the stigmas. SEM results indicated that in the intraspecific hybridization, Q. variabilis pollen started to germinate at 6 h after pollination (hap), PTs elongated significantly at 12 hap, and entered the stigma at 24 hap. By contrast, Q. mongolica pollen germinated at 15 hap, and the PTs entered the stigma at 27 hap. By fluorescence microscopical studies it was observed that some PTs of Q. variabilis gathered at the style-joining at 96 hap, unlike the Q. mongolica which reached the style junction at 144 hap. The above results indicate that the abundant germination of heterologous pollen (HP) on the stigma and the "Feeble specificity recognition" of the stigma and transmitting tract to HP may create opportunities for the "extensive hybridization" of oaks. This work provides a sexual developmental reference for clarifying the causes of Quercus "extensive hybridization"., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Pollination presents a risky journey for pollen grains. Pollen loss is sometimes thought to favour greater pollen investment to compensate for the inefficiency of transport. Sex allocation theory, to the contrary, has consistently concluded that postdispersal loss should have no selective effect on investment in either sex function. But the intuitively appealing compensation idea continues to be raised despite the lack of theoretical endorsement. We address the theoretical issue with a model that directly represents pollen loss (and ovule loss through floral demise or loss of receptivity) as rate-dependent dynamical processes. These loss rates can be varied to examine the effect of pollination efficiency on optimal sex allocation. Pollen-ovule ratios follow from the sex allocation based on the resource costs of pollen and ovule production. This model confirms conventional findings that pollen loss should have essentially no effect on sexual resource allocation in large, panmictic populations. Pollen limitation of seed set does not alter this conclusion. These results force us to rethink the empirical association of pollination efficiency with low pollen-ovule ratios. This pattern could arise if efficient pollen transport commonly results in stigmatic deposition of cohorts of related pollen. Empirical evidence of correlated paternity supports this explanation., (© 2024 The Authors. New Phytologist © 2024 New Phytologist Foundation.)

Elaeis oleifera chromosomes are similar to those of E. guineensis, with close gene pools for the production of interspecific O x G hybrids. The pollen viability and germination of E. oleifera ‘Coarí’ and E. guineensis ‘La Mé’ were compared to their interspecific hybrid O x G (‘Coarí’ x ‘La Mé’). The pollen viability was determined by the acetocarmine staining method (0.5 %) and the pollen germination by in vitro incubation on agar-sucrose medium (1.2-11.0 g in 100 mL of distilled water). The pollen viability and germination of the ‘Coarí’ x ‘La Mé’ hybrid were significantly lower than those of their parents. The percentage of pollen viability by acetocarmine staining was higher than that of in vitro germination, indicating that not all pollen grains classified as viable germinated on the agar-sucrose medium. The pollen germination test is a more reliable indicator than the staining viability test, because the latter only reveals that the pollen contains the enzymes necessary to initiate germination, while the germination test determines the emission and development of the pollen tube.

Fragmented ash populations due to ash dieback may lead to a limited gene flow and pollination success. Therefore, the viability of ash pollen plays a major role for the survival of the species. The extent to which the long-distance transport of pollen affects pollen viability was investigated with experiments in a climate chamber using ash pollen samples from a seed orchard in Emmendingen, Germany. Furthermore, experiments with a volumetric pollen trap were conducted. A suitable storage temperature for ash pollen was determined by using four viability tests; TTC test, pollen germination, Alexander's stain and Acetocarmine. An optimization of the germination medium was performed. We found a strong influence of prevailing temperatures on pollen viability, which decreased faster under warmer conditions. At moderate temperatures, viable pollen could still be observed after 28 days. Thus, a possible successful pollination can also be associated to long-range transported pollen. Storage experiments showed that pollen viability could be maintained longer at temperatures of −20 °C and −80 °C than at 4 °C. In particular, the TTC test has proven to be suitable for determining viability. Therefore, properly stored pollen can be used for breeding programs to support the survival of Fraxinus excelsior. [ABSTRACT FROM AUTHOR]

Temperature is the major factor in global warming and strongly influences the success of plant sexual reproduction. Therefore, there is an urgent need to assess the vulnerability of species for breeding and planning effective actions. In this study, effects of different temperatures and storage duration on pollen viability and in vivo pollen tube growth were analysed in Citrus sinensis 'Kozan yerlisi'. The pollens were obtained before anthesis and stored at 10 °C, 20 °C and 30 °C for 1, 2 or 3 days before analysis. The pollen viability decreased with increasing temperatures and storage duration from 61.3% to 5.8%. In vivo pollen germination results showed that for one day storage, the pollen growth rates were similar to the control treatment while storing pollens two or three days differed from the control. Pollen germination after storage at 10 °C was lower and not efficient, while after storage at 30 °C no pollen tube germination at all was seen on the stigma. At the same time, storing pollen in low temperature caused delay in pollen tube germination and pollen tube growth, suggesting that pollen that are stored in low temperatures pass into a dormancy process for three to five days. In conclusion, this study indicated that pollen storage in 30 °C for a long time causes loss of pollination ability while storage in 10 °C causes dormancy in pollen. [ABSTRACT FROM AUTHOR]

Pollen storage is the only way how to overcome the differences in phenology of forest trees and geographically determined reproductive barriers between them during controlled pollination. Pollen viability of Scots pine (Pinus sylvestris L.), mountain dwarf pine (P. mugo Turra) and their hybrid swarms was evaluated after 3-years storage at -20°C using in vitro germination test. One population of each P. sylvestris and P. mugo were involved into study along with three hybrid swarms. Germination potential of the stored pollen grains was reduced significantly in comparison with freshly collected pollen. Profound decrease in germination rate was recorded in the two hybrid swarms (4.0-4.7%), less profound in the remaining three populations (0.6-2.4%). Pollen tube length, as the second pollen viability trait was reduced in stored pollen grains in a larger extend ranging between 51.4% and 54.3%. The pollen grains of the species P. mugo was exception in this respect yielding pollen grains whose growth was retarded of 21.9% only. Analysis of variance confirmed significant differences between fresh and stored pollen grains. Statistically significant were also the differences between compared populations and between tested individuals of the respective populations. [ABSTRACT FROM AUTHOR]

Abstract Background Low pollen viability may limit grapevine yield under certain conditions, causing relevant economic losses to grape-growers. It is usually evaluated by the quantification of the number of viable and non-viable pollen grains that are present in a sample after an adequate pollen grain staining procedure. Although the manual counting of both types of grains is the simplest and most sensitive approach, it is a laborious and time-demanding process. In this regard, novel image-based approaches can assist in the objective, accurate and cost-effective phenotyping of this trait. Results Here, we introduce PollenCounter, an open-source macro implemented as a customizable Fiji tool for the high-throughput phenotyping of pollen viability. This tool splits RGB images of stained pollen grains into its primary channels, retaining red and green color fractionated images (which contain information on total and only viable pollen grains, respectively) for the subsequent isolation and counting of the regions of interest (pollen grains). This framework was successfully used for the analysis of pollen viability of a high number of samples collected in a large collection of grapevine cultivars. Results revealed a great genetic variability, from cultivars having very low pollen viability (like Corinto Bianco; viability: 14.1 ± 1.3%) to others with a very low presence of sterile pollen grains (Cuelga; viability: 98.2 ± 0.5%). A wide range of variability was also observed among several clones of cv. Tempranillo Tinto (from 97.9 ± 0.9 to 60.6 ± 5.9%, in the first season). Interestingly, the evaluation of this trait in a second season revealed differential genotype-specific sensitivity to environment. Conclusions The use of PollenCounter is expected to aid in different areas, including genetics research studies, crop improvement and breeding strategies that need of fast, precise and accurate results. Considering its flexibility, it can be used not only in grapevine, but also in other species showing a differential staining of viable and non-viable pollen grains. The wide phenotypic diversity observed at a species level, together with the identification of specific cultivars and clones largely differing in this trait, pave the way of further analyses aimed to understand the physiological and genetic causes driving to male sterility in grapevine.

Pollen viability affects the probability that a pollen grain deposited on a plant's stigma will produce a viable seed. Because a mature seed is needed before a gene flow event can occur, pollen viability will influence the risk of escape for genetically engineered (GE) crops.Pollen viability was measured at intervals for up to 2 h following removal of the pollen from the anthers. It was quantified at three temperatures and for different alfalfa varieties, including both conventional and Roundup Ready (RR) varieties. Pollen viability was assessed using in vitro germination.Time since removal from the anthers was the most prevalent factor affecting pollen viability in alfalfa. Pollen viability declined with increasing time at all three temperatures and for all varieties tested. Pollen viability was not affected by temperatures ranging between 25 and 37 °C and did not vary among plant varieties, including conventional and RR varieties.Bee foraging behaviour suggested pollen viability within the first 10 min following pollen removal from a flower to most affect seed production. Pollen longevity was predicted to have little impact on seed set and gene flow. Linking pollinator behaviour to pollen viability improved our understanding of its impact on gene flow risk. [ABSTRACT FROM AUTHOR]

Most Aristolochiaceae species studied so far are from temperate regions, bearing self-compatible protogynous trap flowers. Although self-incompatibility has been suggested for tropical species, the causes of self-sterility in this family remain unknown. To fill this gap, we studied the pollination of the tropical Aristolochia esperanzae, including the physical and physiological anti-selfing mechanisms. Floral visitors trapped inside flowers were collected to determine the pollinators. Protogyny was characterized by observing the temporal expression of sexual phases and stigmatic receptivity tests. The breeding system was investigated using hand-pollination treatments. Pollen tube growth was observed using epifluorescence to identify the self-incompatibility mechanism. Flies were the most frequent visitors found inside A. esperanzae trap flowers, with individuals from the family Ulidiidae being potential pollinators since they carried pollen. The characteristic flower odour and presence of larvae indicate that A. esperanzae deceives flies through oviposition-site mimicry. Although this species showed incomplete protogyny, stigmatic receptivity decreased during the male phase, avoiding self-pollination. Fruits developed only after cross- and open pollination, indicating that the population is non-autonomous, non-apomictic, and self-sterile. This occurred through a delay in the growth of geitonogamous pollen tubes to the ovary and lower ovule penetration, indicating a late-acting self-incompatibility mechanism. Our findings expand the number of families in which late-acting self-incompatibility has been reported, demonstrating that it is more widespread than previously thought, especially when considering less-studied tropical species among the basal angiosperms., (© 2024 Wiley‐VCH GmbH. Published by John Wiley & Sons Ltd.)

Premise: Gynodioecy is a rare sexual system in which two genders (sensu Lloyd, 1980), cosexuals and females, coexist. To survive, female plants must compensate for their lack of siring capacity and male attractiveness. In European chestnut (Castanea sativa), an outcrossing tree, self-pollination reduces fruit set in cosexual individuals because of late-acting self-incompatibility and early inbreeding depression. Could this negative sexual interaction explain the presence of females in this species?, Methods: We studied gender variation in wild populations of European chestnut. In addition, we compared fruit set (the proportion of flowers giving fruits) and other key female fitness components as well as reproductive allocation between genders. We then performed emasculation experiments in cosexual trees, by removing nectar-producing fertile male inflorescences. We also removed sterile but nectar-producing male inflorescences from female trees, as a control., Results: We found a highly variable proportion of male-sterile individuals in the wild in European chestnut. In the experimental plot, trees from each gender had similar size, flower density, and burr set, but different fruit set. Removing nectar-producing male inflorescences from branches or entire trees increased fruit set in cosexual but not in female trees., Conclusions: These results show that self-pollination impairs fruit set in cosexual trees. Female trees avoid these problems as they do not produce pollen but continue to attract pollinators thanks to their rewarding male-sterile inflorescences, resulting in a much higher fruit set than in cosexuals. This demonstrates that even outcrossed plants can benefit from the cessation of self-pollination, to the point that unisexuality can evolve., (© 2024 The Authors. American Journal of Botany published by Wiley Periodicals LLC on behalf of Botanical Society of America.)

Anther dehiscence controls optimal interaction between pollen and stigma, thereby determining the successful sexual reproduction. The regulators or mechanisms of this process remain elusive. Here, two CRISPR/Cas9 mutants of a rice exocyst subunit gene SEC3A, sec3a-1 and sec3a-2, showed anther indehiscence at anthesis and male sterility at maturity. Pollen viability and germination in the mutants were partly defective, whereas their female gametes undergone a normal development. Hybrid or selfpollinated seeds could be produced by artificial pollination, suggesting potential use of a weak sec3a mutant as a female line during hybrid breeding. SEC3A is widely expressed in various tissues, including anther walls. Further results showed an excessive IAA accumulation and no endothecium lignification in sec3a-1/2 anthers. Our findings suggest that SEC3A appears to regulate anther dehiscence by modulating auxin signaling, providing insights into regulation of anther dehiscence and function of exocyst in plants [ABSTRACT FROM AUTHOR]

Asynchronous maturation of male and female flowers in date palm trees is frequently occurs, making pollen storage operation necessary to ensure pollination. The aim of this study was to investigate the effect of pollen storage temperatures on pollen viability, fruit set and fruit quality of six date palm male cultivars. Pollen grains of six date palm cultivars namely ‘Bouhlesse’, ‘Deglat Beida’, ‘Deglet Nour’, ‘Ghars’, ‘Halwaya’ and ‘Moch Deglat’ were stored at room temperature (24 ± 2 °C), 4 °C or −20 °C. In vitro pollen germination and pollen tube growth were examined after 0, 1, 3 and 13 months of storage. Influence of pollen storage on fruit set and fruit quality were also analyzed. Storage temperature, storage duration, cultivar and interaction between all variables had highly significant effect on pollen viability and pollen tube length (p < 0.0001). High values of pollen germination (up to 87%) and pollen tube length were recorded in fresh pollen (at 0 months of storage). For all cultivars, pollen stored at room temperature lost the most of their viability between the 2 or 3 months of storage. However, pollen viability was extended over time when pollen was stored under low temperature, with a storage temperature of −20 °C preferable to 4 °C. Fruit and pulp weight decreased slightly but significantly in most cultivars as a result of pollen storage temperature, although fruit set was not affected. The pollen of ‘Deglet Nour’ showed high pollen viability after 1 year of storage at −20 °C (∼89%) and may be used as good cultivar for storage. [ABSTRACT FROM AUTHOR]

Aquilaria sinensis (Lour.) Spreng is a known medicinal plant producing agarwood. To date, studies on the floral biology of A. sinensis have been limited. In this study, the floral micro- and ultra-structures, pollen viability, stigma receptivity, and artificial pollination of A. sinensis were investigated. The results show that the flower's development can be divided into five stages, including the flower bud differentiation stage (2–7 d), the flower bud stage (7–13 d), the flowering stage (14 d), the pollination stage (14–15 d), and the fruiting stage (15–25 d). The floral organs mainly include: 4–6 split calyces, 10 petals, 10 stamens, and 1 pistil. The anther is oblong, with four pollen sacs the pollen is round, with maximum viability 6 h after flowering; and stigma receptivity is at its best 6 h before flowering. Artificial pollination is successful in the field. These findings will provide useful information for producing and breeding A. sinensis. [ABSTRACT FROM AUTHOR]

The success of assisted pollination in oil palm is essential for oil production, since it determines the amount of well-formed fruits; in this process, the pollen quality, expressed as viability and germinability, is of great importance. This work was carried out in the Salamanca Oleaginosas S.A. Laboratories, in order to determine the viability, germination and pollen tube growth of pollen grains of Guineensis, Amazon, Coari x Lame and Unipalma genotypes, stored during 0, 5, 15 and 30 days at room temperature, and -13 °C. Using an unrestrictedly randomized design with a factorial arrangement and four replications, the variables percentage of viability and germination, length and growth rate of the pollen tube were analyzed. Guineensis pollen had the highest germination and viability values, which ensure a good pollination efficiency, while the other cultivars had values below the recommended, although pollen tube growth of the few grains that germinated was similar to Guineensis.

[Objective] The study aims to reveal the pollination Ottelia acuminata and O. acuminata var. crispa, elucidate the factors affecting successful pollination, and provide theoretical and technical guidance for hybrid breeding between the two species. [Methods] Using O. acuminata and O. acuminata var. crispa as subjects, by observing their flowering dynamics, insect visitation behaviors, and measuring pollen viability, stigma receptivity, and hybrid compatibility index, the study investigated their pollination characteristics and hybrid compatibility. [Results] The flowering dynamics of O. acuminata and O. acuminata var. crispa were fundamentally similar, with each flower lasting 7-11 h. The main pollinating insects include Episyrphus balteatus and Apis cerana. The vitality of the pollen and the receptivity of the stigma both showed an initial increase followed by a decrease. The peak pollen viabilities for O. acuminata and O. acuminata var. crispa were 88.27% and 88.34%, respectively, and the stigmas were all the highest at anthesis Ⅱ. The fruit set rates for direct and reciprocal crosses were 85.71% and 91.33%, respectively, with hybrid compatibility indices both greater than 53. The average number of seeds per fruit for self-pollination were 54 and 69, respectively, and for direct and reciprocal crosses, 73 and 71, respectively. The seed germination rates for self-pollination were 71.7% and 27.3%, respectively, and for direct and reciprocal crosses, 22.6% and 19.7%, respectively. [Conclusion] The flowering dynamics of O. acuminata and O. acuminata var. crispa are fundamentally similar, with each having a short flowering period. There are fewer types of pollinating insects, which affects sexual reproduction, yet there is no significant evidence of hybrid incompatibility.

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Background: Sweetpotato is an important vegetable and food crop that is bred through sexual crosses and systematic selection. The use of in vitro germination of sweetpotato pollen to test its viability has important theoretical and practical implications for improving the efficiency of sweetpotato crossbreeding by controlling pollination and conducting research on sweetpotato pollen biology. Results: In this study, we observed the morphological structure of sweetpotato pollen under a scanning electron microscope (SEM), developed an effective method for the in vitro germination of sweetpotato pollen, and examined the viability of sweetpotato pollen after treating plants at different temperatures before blossoming. Sweetpotato pollen grains are spherical, with an average diameter of 87.07 ± 3.27 μm (excluding spines), with multiple germination pores and reticulate pollen surface sculpture. We applied numerous media to sweetpotato pollen germination in vitro to screen the initial medium and optimised the medium components through single-factor design. The most effective liquid medium for in vitro sweetpotato pollen germination contained 50 g/L Sucrose, 50 g/L Polyethylene glycol 4000 (PEG4000), 100 mg/L Boric acid and 300 mg/L Calcium nitrate, with a pH = 6.0. The optimum growth temperature for pollen development in sweetpotato was from 25 to 30 °C. Neither staining nor in situ germination could accurately determine the viability of sweetpotato pollen. Conclusions: In vitro germination can be used to effectively determine sweetpotato pollen viability. The best liquid medium for in vitro germination of sweetpotato pollen contained 50 g/L Sucrose, 50 g/L Polyethylene glycol 4000 (PEG4000), 100 mg/L Boric acid and 300 mg/L Calcium nitrate, with the pH adjusted to 6.0. This study provides a reliable medium for the detection of sweetpotato pollen viability, which can provide a theoretical reference for sweetpotato genetics and breeding. [ABSTRACT FROM AUTHOR]

Globalization has drastically reduced the number of autochthon apple cultivars in the Serbian market and most of them have nearly disappeared; however, some of these cultivars, such as Petrovača, Budimka, Kolačara Pozna, and Kožara, have extraordinary quality, good pomological characteristics, and pest and disease resistance. The present study was conducted to develop a protocol for the storage of pollen for further use in the conservation and breeding of these cultivars. Viability and germination of the mature pollen were tested in vitro , at four storage temperatures (20, 4, −20, and −80°C), right after harvest or 1, 2, 3, 4, 5, and 6 months after storage. Differences in fresh pollen viability and germination between cultivars were statistically significant and ranged from 60 to 88% and 59 to 98%, respectively. Fresh pollen of cv. Budimka showed the highest viability and germination in comparison with other cultivars, especially cv. Kožara. Pollen viability and germination decreased over the storage period, and it was the lowest after 6 months of storage at room temperature in all tested cultivars. Storage at 4°C prolonged the pollen viability and germinability of 1–5 fold, depending on the cultivar and treatment duration; however, the pollen longevity of all cultivars was significantly extended when stored at −20 or −80°C. After 6 months, pollen of cv. Budimka stored at −20 and −80°C showed 14–15 fold higher germination rates in relation to pollen storage at room temperature for the same period. The results of the present study suggest that the pollen of these apple cultivars could be efficiently maintained at −20°C and could be further used for breeding purposes, e.g., for crossings between cultivars that flower at different times of the year. [ABSTRACT FROM AUTHOR]

Studies on floral morphology, phenology and biology of wild melon revealed that the ratio of staminate and pistillate flowers was 3.40:1. The longevity of the male flowers were between 5 and 6 days, whereas, female flowers between 6 and 7 days. Anthesis was observed from 4.00 am to 10.00 am, while, the anther dehiscence started from 5.00 am which was continued to 7.00 am. The peak anthesis was observed from 8.00 am to 9.00 am and anther dehiscence from 6.00 am to 6.30 am. Freshly opened flowers showed pollen viability up to 98.35%, decreased upon closure and crashed to 17.48% in 3 days. Pollen germination was occurred after 15 minutes of incubation and continued up to 24 h of incubation. The stigma receptivity lasts from one to two days of anthesis. Major pollinator of wild melons observed was honey bee, mostly visited between 9:00 am to 6:00 pm. [ABSTRACT FROM AUTHOR]

Cannabis sativa L. is cultivated globally for its cannabinoid-dense inflorescences. Commercial preference for sinsemilla has led to the development of methods for producing feminized seeds through cross-pollination of cosexual (masculinized) female plants. Although the induction of cosexuality in Cannabis plants is common, to date, no work has empirically tested how masculinization of female Cannabis plants impacts male flowering, pollen production, pollen fitness, and related life-history trade-offs. Here, we cultivated a population of Cannabis plants (CFX-2) and explored how the route to cosexuality (drought vs. chemical induction) impacted flowering phenology, pollen production, and pollen fitness, relative to unsexual male plants. Unisexual males flowered earlier and longer than cosexual plants and produced 223% more total pollen (F2,28 = 74.41, p < 0.001), but per-flower pollen production did not differ across reproductive phenotypes (F2,21 = 0.887, p = 0.427). Pollen viability was 200% higher in unisexual males and drought-induced cosexuals (F2,36 = 189.70, p < 0.001). Pollen non-abortion rates only differed in a marginally significant way across reproductive phenotypes (F2,36 = 3.00, p = 0.06). Here, we demonstrate that masculinization of female plants impacts whole-plant pollen production and pollen fitness in Cannabis sativa. [ABSTRACT FROM AUTHOR]