Pollen Germination Percentage Research Articles

Temperature dependence of pollen germination and tube growth in conifers relates to their distribution along an elevational gradient in Washington State, USA.

Pollen germination and tube growth are essential processes for successful fertilization. They are among the most temperature-vulnerable stages and subsequently affect seed production and determine population persistence and species distribution under climate change. Our study aims to investigate intra- and inter-specific variations in the temperature dependence of pollen germination and tube length growth and to explore how these variations differ for pollen from elevational gradients. We focused on three conifer species, Pinus contorta, Picea engelmannii, and Pinus ponderosa, with pollen collected from 350 to 2200m elevation in Washington State, USA. We conducted pollen viability tests at temperatures from 5 to 40°C in 5°C intervals. After testing for four days, we took images of these samples under a microscope to monitor pollen germination percentage (GP) and tube length (TL). We applied the Gamma function to describe the temperature dependence of GP and TL and estimated key parameters, including the optimal temperature for GP (Topt_GP) and TL (Topt_TL). Results showed that pollen from three species and different elevations within a species have different GP, TL, Topt_GP, and Topt_TL. The population with a higher Topt_GP would also have a higher Topt_TL, while Topt_TL was generally higher than Topt_GP, i.e., a positive but not one-to-one relationship. However, only Pinus contorta showed that populations from higher elevations have lower Topt_GP and Topt_TL and vice versa. The variability in GP increased at extreme temperatures, whereas the variability in TL was greatest near Topt_TL. Our study demonstrates the temperature dependences of three conifers across a wide range of temperatures. Pollen germination and tube growth are highly sensitive to temperature conditions and vary among species and elevations, affecting their reproduction success during warming. Our findings can provide valuable insights to advance our understanding of how conifer pollen responds to rising temperatures.

Pollen thermotolerance of a widespread plant, Lotus corniculatus, in response to climate warming: possible local adaptation of populations from different elevations.

One of the most vulnerable phases in the plant life cycle is sexual reproduction, which depends on effective pollen transfer, but also on the thermotolerance of pollen grains. Pollen thermotolerance is temperature-dependent and may be reduced by increasing temperature associated with global warming. A growing body of research has focused on the effect of increased temperature on pollen thermotolerance in crops to understand the possible impact of temperature extremes on yield. Yet, little is known about the effects of temperature on pollen thermotolerance of wild plant species. To fill this gap, we selected Lotus corniculatus s.l. (Fabaceae), a species common to many European habitats and conducted laboratory experiments to test its pollen thermotolerance in response to artificial increase in temperature. To test for possible local adaptation of pollen thermal tolerance, we compared data from six lowland (389-451 m a.s.l.) and six highland (841-1,030 m a.s.l.) populations. We observed pollen germination in vitro at 15 °C, 25 °C, 30 °C, and 40 °C. While lowland plants maintained a stable germination percentage across a broad temperature range (15-30 °C) and exhibited reduced germination only at extremely high temperatures (40 °C), highland plants experienced reduced germination even at 30 °C-temperatures commonly exceeded in lowlands during warm summers. This suggests that lowland populations of L. corniculatus may be locally adapted to higher temperature for pollen germination. On the other hand, pollen tube length decreased with increasing temperature in a similar way in lowland and highland plants. The overall average pollen germination percentage significantly differed between lowland and highland populations, with highland populations displaying higher germination percentage. On the other hand, the average pollen tube length was slightly smaller in highland populations. In conclusion, we found that pollen thermotolerance of L. corniculatus is reduced at high temperature and that the germination of pollen from plant populations growing at higher elevations is more sensitive to increased temperature, which suggests possible local adaptation of pollen thermotolerance.

Genome-wide investigation of the LARP gene family: focus on functional identification and transcriptome profiling of ZmLARP6c1 in maize pollen

BackgroundThe La-related proteins (LARPs) are a superfamily of RNA-binding proteins associated with regulation of gene expression. Evidence points to an important role for post-transcriptional control of gene expression in germinating pollen tubes, which could be aided by RNA-binding proteins.ResultsIn this study, a genome-wide investigation of the LARP proteins in eight plant species was performed. The LARP proteins were classified into three families based on a phylogenetic analysis. The gene structure, conserved motifs, cis-acting elements in the promoter, and gene expression profiles were investigated to provide a comprehensive overview of the evolutionary history and potential functions of ZmLARP genes in maize. Moreover, ZmLARP6c1 was specifically expressed in pollen and ZmLARP6c1 was localized to the nucleus and cytoplasm in maize protoplasts. Overexpression of ZmLARP6c1 enhanced the percentage pollen germination compared with that of wild-type pollen. In addition, transcriptome profiling analysis revealed that differentially expressed genes included PABP homologous genes and genes involved in jasmonic acid and abscisic acid biosynthesis, metabolism, signaling pathways and response in a Zmlarp6c1::Ds mutant and ZmLARP6c1-overexpression line compared with the corresponding wild type.ConclusionsThe findings provide a basis for further evolutionary and functional analyses, and provide insight into the critical regulatory function of ZmLARP6c1 in maize pollen germination.

Optimized Protocol for in vitro Pollen Germination in Brinjal (Solanum melongena L.)

Background: Understanding floral and pollen biology is essential for efficient artificial hybridization in hybrid seed production. This knowledge helps ensure proper fertilization of the ovary and optimal fruit and seed set. Selecting suitable pollen parents and preserving pollen for future use allows for better control and optimization of hybridization practices in brinjal breeding programs. To achieve this, a robust protocol for pollen collection and viability testing is necessary to monitor pollen quality in the field and during storage. This information is crucial for maintaining desired characteristics and genetic traits in the resulting hybrid seeds. Methods: This study; aimed at optimizing the pollen germination assessment protocol for brinjal. The step wise modification standard medium composition was done, the optimal growth condition was tested and in vivo predictions were made. So, the study aimed to standardization of media for in vitro pollen germination evaluate and viability in brinjal in ambient as well as cold storage conditions. The pollen germination was tested in vitro as well in vivo, by incubating the pollen grains for 3 hours at 25°C in different concentrations of sucrose, boron and agar media and distilled water at interval of 12 hours. Result: The most favorable germination of fresh pollen was achieved with a treatment consisting of 1% Agar, 12% Sucrose and 300 ppm Boron. Comparing the two storage conditions, pollen stored in the refrigerator exhibited higher in vitro germination percentages compared to ambient storage conditions. The highest in vitro pollen germination and viability percentages were observed in fresh pollen collected within 12 hours (95.00%). As the duration of pollen storage increased in both storage conditions, the in vitro pollen germination decreased. This decline in in vitro pollen germination was reflected in the in vivo fertilization fruit set percentage. The highest fruit set percentage was observed when pollen was stored in the refrigerator (64.52%) and when female flowers were pollinated with pollen stored for less than 12 hours (84.66%).

Evaluation of viability and germination of pollen grains of three local caprifig cultivars and their effect on some characteristics of fig fruits (Ficus carica L.)

This research was carried out in fig fields in the village of Kafar-Jales, in the north of Syria. The analyses were conducted in the laboratories of the Faculty of Agriculture at Idlib University during the 2022 farming season, to evaluate the viability and germination of three local varieties of Caprifig (Bunduqi, Azraq, Panjani). The morphological characteristics, the date of the exodus of insects (Blastophaga psenes) from male fruits, the quantity of pollen, and the percentage of germination and viability were studied on four nutritive media at a temperature of 27°C. The measurements were taken after 24 h, 48 h, and 72 h. These three pollinators were used to pollinate three varieties of edible figs (white Satehi, Safrawi, and Habashi) to study the effect of pollen source on the productive characteristics of edible fig fruits. The result showed significant superiority of the Bunduqi cultivar over the rest of the cultivars in traits of the fruit’s early ripening, pollen quantity, and date of departure of insects. The Azraq cultivar is found to be superior to Bunduqi and Panjani cultivars in the germination rate of pollen at all stages of the experiment and in all used media. The addition of stigma flower extract in culture media increased germination percentage by 35% for all studied Caprifig cultivars. The addition of 10% sucrose in the cultivation environment increased the percentage of pollen germination by 20%. The cultivars that were inoculated with the Panjani pollinator outperformed the characteristics of the length, diameter, and weight, demonstrating that the fruit’s quality characteristics are affected by the genotype of the pollinator used. The results of this research can be beneficial for both fig growers and plant breeders, as they help to select the best pollinators and contribute to the development and improvement of the quality of the cultivated fig fruits.

A Modified Method for Transient Transformation via Pollen Magnetofection in Lilium Germplasm.

Lily (Lilium spp.) is a popular ornamental plant. Traditional genetic transformation methods have low efficiency in lily, thus development of a high-efficiency genetic transformation system is important. In this study, a novel transient transformation method involving pollen magnetofection was established and optimized pollen viability, and exogenous gene expression in magnetofected pollen and that of different germplasm were assessed. The highest germination percentage of Lilium regale pollen was 85.73% in medium containing 100 g/L sucrose, 61.5 mg/L H3BO3, and 91.5 mg/L CaCl2. A 1:4 ratio of nanomagnetic beads to DNA plasmid and transformation time of 0.5 h realized the highest transformation efficiency (88.32%). The GFP activity in transformed pollen averaged 69.66%, while that of the control pollen was 0.00%. In contrast to the control, transgenic seedlings obtained by pollination with magnetofected pollen showed strong positive GUS activity with 56.34% transformation efficiency. Among the lily germplasm tested, 'Sweet Surrender' and L. leucanthum had the highest transformation efficiency (85.80% and 54.47%), whereas L. davidii var. willmottiae was not successfully transformed. Transformation efficiency was positively correlated with pollen equatorial diameter and negatively correlated with polar axis/equatorial diameter ratio. The results suggest that pollen magnetofection-mediated transformation can be applied in Lilium but might have species or cultivar specificity.

Pollen Viability and Germination Levels with Amount of Pollen Production of Some Important Olive Cultivars in Türkiye

This research was carried out to determine the pollination abilities of Domat, Gemlik and Sarı Ulak olive cultivars. Pollen viability rate, germination rate and amount of pollen production were examined during the periods when 25%, 50% and 75% of the flowers were opened. According to the results obtained from three years’ experimental study, the highest percentages of pollen viability were found in Gemlik (81.51%) and Domat (81.50%), whereas Sarı Ulak cultivar (77.41%) showed the lowest viability. In pollen germination percentages, the highest values on the basis of cultivars were determined 59.85% (Domat), 59.74% (Gemlik) and 52.12% (Sarı Ulak). The highest amount of pollen production in a flower was found in the Sarı Ulak cultivar (329,046) while it was followed by Domat (319,693) and Gemlik (306,385). Despite the high pollen production in Sarı Ulak cultivar, the pollen viability and germination rates were found to be low. In Gemlik and Domat cultivars, all values were obtained relatively near. In addition, it had been noted that the values related to pollen viability, germination and production amount were higher during 50% and 75% flowering periods than 25%.

Optimization of In Vitro Germination, Viability Tests and Storage of Paeonia ostii Pollen.

Paeonia ostii is an important woody oil crop mainly cross-pollinated. However, the low yield has become an important factor restricting the industrial development of P. ostii. Cross-pollination has become one of the important measures to increase the seed yield. Therefore, conservation of pollen with high vitality is crucial to ensure successful pollination of P. ostii. In this study, we found an effective methodological system to assess the viability, ability to germinate, and optimal storage conditions of P. ostii pollen grains. The optimal medium in vitro was 50 g/L sucrose, 100 mg/L boric acid, 50 g/L PEG6000, 100 mg/L potassium nitrate, 300 mg/L calcium nitrate, and 200 mg/L magnesium sulfate at pH 5.4. Optimal germination condition in vitro was achieved at 25 °C for 120 min, allowing easy observation of the germination percentage and length of the pollen tubes. In addition, the viability of pollen grains was assessed by comparing nine staining methods. Among them, MTT, TTC, benzidine-H2O2, and FDA were effective to distinguish between viable and non-viable pollen, and the results of the FDA staining method were similar to the pollen germination percentage in vitro. After evaluation of pollen storage, thawing and rehydration experiments showed that thawing at 4 °C for 30 min and rehydration at 25 °C for 30 min increased the germination percentage of pollen grains stored at low temperatures. The low-temperature storage experiments showed that 4 °C was suitable for short-term storage of P. ostii pollen grains, while -80 °C was suitable for long-term storage. This is the first report on the in vitro germination, viability tests, and storage of P. ostii pollen grains, which will provide useful information for P. ostii germplasm conservation and artificial pollination.

Assessment of Cytomorphological Differences in Sorghum Fertility Restoration

Sorghum (Sorghum bicolor L. Moench) is ranked fifth as a cereal crop after maize, rice, wheat, and barley based on global cultivation area. However, heat and drought stresses cause improper fertility restoration and inefficient pollination, severely affecting sorghum productivity. The discovery of cytoplasmic male sterility (CMS) is a milestone for commercializing hybrids. This study assessed the pollen fertility and in vitro pollen germination percentage of male and female lines and F1 hybrids of sorghum using two years of pooled data with multivariate analysis. The principal component analysis (PCA) of female and male lines showed that PC1 represented 82.8% of the variation, whereas PCA of hybrids revealed a significant genetic divergence of 97.1%. Agglomerative hierarchical clustering marked that cluster II genotypes have a high pollen fertility contribution, which can generate superior and high-yielding hybrids. Three male-sterile lines exhibited 100% pollen sterility, with morphological attributes, viz., pinpointed, flattened, low anther extrusion, and starch-digested pollens. Pollen fertility restoration behavior revealed that nine hybrids were fully fertile, eighteen were partially fertile, and three were completely sterile amongst thirty hybrids. The findings of this study will facilitate the identification of potential restorers for the exploitation of high-yielding hybrids in sorghum breeding programs.

Effects of Caprifig (Ficus carica var. caprificus) Storage Temperature and Duration on the Fruit Productivity and Quality of ‘Bursa Siyahi’ Figs

Caprification is the process of hanging caprifig fruits on edible fig trees to transfer the pollen inside the caprifig to the edible fig via the wasp (Blastophaga psenes) living in the caprifig. It needs to be repeated several times for the proper fruit set of edible figs. The present study was conducted to determine the change in the number of Blastophaga psenes, the duration of Blastophaga’s exit, and pollen viability in case the caprifigs to be used in the caprification process are stored until use. The number of Blastophaga and in vitro pollen viability were tested at day 0 (harvest day) and after 4, 8, 12, 16 and 20 days of storage at three different temperatures (0, 4, and 8 °C). Afterwards, the effect of pollination frequency on the edible fig fruit set and quality was determined by using Blastophaga psenes as a vector in the pollination of stored caprifig fruits, pollinating five times with 4-day intervals and three times with 8-day intervals. Approximately a 50% reduction in the number of B. psenes was detected after 4 (180.22), 12 (174.11) and 16 (192.66) days of caprifigs storage at 0, 4, and 8 °C, respectively. The pollen germination percentage of the caprifigs increased with storage and was higher in those stored at 8 °C (43.96%) and 4 °C (41.70%). The highest fruit set was obtained when the caprifigs stored at 4 °C (76.41%) and 8 °C (71.38%) five times with 4-day intervals were used for pollination. The pollination practice repeated five times with 4-day intervals resulted in a lower proportion of extra-large fruits with a weight of >100 g, a higher proportion of fruits with no or slight ostiole damage and early ripening of fruits. These results suggest that B. psenes and pollen viability can be preserved by storing caprifigs at 4 or 8 °C and that fruit set and fruit characteristics would be positively affected with the use of stored caprifigs in the pollination practice repeated five times with 4-day intervals.

Effects of temperatures on pollen germination and pollen tube growth in apple

Apple cultivars in Korea have been experiencing poor fruit sets due to early spring low temperatures and global warming. Therefore, the present study aimed to investigate the effects of temperature on fruit setting and to select apple cultivars tolerant to extreme temperatures based on the temperature response of their pollen. The effect of temperature on pollen germination percentage (PGP) and on pollen tube length (PTL) was determined under laboratory conditions using the pollen of ten apple cultivars. The two parameters were evaluated using a pollen germination medium, at temperatures ranging from 5 to 45 °C, at 5 °C intervals. The temperature variations considerably affected pollen germination and tube growth in all the examined cultivars. The maximum pollen germination percentage ranged from 61.5 (“Green Ball”) to 99.9% (“Shinano Gold”) with a mean of 85.2%, whereas the maximum pollen tube length ranged from 716.5 (“Tsugaru”) to 989.8 µm (“Arisoo”) with mean of 855.1 µm. There were differences in the cardinal temperatures (Tmin, Topt, and Tmax) of PGP and PTL between cultivars. Mean cardinal temperatures Tmin, Topt, and Tmax computed using the modified bilinear model were 4, 27.7, and 44.9 °C and 6.3, 28.6, and 43.7 °C for PGP and PTL, respectively. Our preliminary results may be used to select low-temperature and global warming-friendly apple cultivars for farmers and can also be exploited to develop temperature-tolerant apple cultivars during flowering.

The effect of grafting on pollen fertility and seed production of diploid interspecific hybrid and tetraploid eggplant genotypes

Solanum melongena is susceptible to diverse diseases and parasites, in particular the wilts (bacterial, Fusarium and Verticillium), nematodes, and some insects. Solanum torvum is robust to Verticillium and some bacterial wilts and root-knot nematode. It was reported that interspecific hybrid plants originated out of the hybridization of these species were sterile. In our previous studies that have been carried out to overcome this interspecific hybridization barrier, only from Faselis F1 that was used as the female parent, many interspecific hybrid seeds were obtained and 9.07% of the seeds grew into plants in vitro. The percentage of pollen viability and germination of tetraploid interspecific hybrid (amphidiploid) genotypes that have been produced by in vitro colchicine treatment, were 6.8 and 3.4 fold of its source diploid genotype, respectively. However, the increment was not high enough to overcome the interspecific hybridization barrier between S. torvum and S. melongena. In this study, the changes in pollen fertility of diploid interspecific hybrids and tetraploid plants, which have grafted on Pala or Faselis F1 , were investigated. Pollen viability and germination percentage in diploid genotypes were not affected by grafting, although they increased significantly (51.54% and 119.73%, respectively) in tetraploid genotypes by grafting. It was determined that the fertile diploid rootstock used for the tetraploid genotypes that produced by chromosome doubling from cultured eggplants could increase the number of seeds per fruit. It was concluded that some fertile diploid varieties can be used as rootstocks in order to increase pollen viability, germination rate and seed yield of tetraploid genotypes with low pollen yield obtained from cultivated eggplant by chromosome doubling.

POLLEN GRAIN STRUCTURE AND POLLINATION IN THE <i>RIBES</i> (GROSSULARIACEAE) REPRESENTATIVES

Currant is an important small-fruit crop that has long been used for medicinal purposes. The systematic position of the genus Ribes in the kingdom Plantae is perceived by researchers unambiguously. However, the internal taxonomy of the genus Ribes and the systematic position of some species in the genus remains a matter of debate.The study of the morphology, fertility and viability of pollen grains is also an important indicator in determining phylogenetic relationships in the genus Ribes. Comparative poral-colpus analysis of pollen makes it possible to determine the similarities and differences in different species and the degree of genetic relatedness of the compared forms. The processes of pollination and germination of pollen in the pistil style in the Grossulariaceae are poorly covered in the cited literature.These problems became the ground for the study, the purpose of which was to determine the characteristics of pollen grains, pollination and germination of pollen on both the pistil stigma and artificial nutrient medium in Ribes species in order to identify species characterized by pollen of maximum viability, suitable for breeding work in the conditions of St. Petersburg.The objects of the study were plants of the Ribes species from the open ground collection of the Komarov Botanical Institute RAS (R. sachalinense, R. sanguineum, R. rubrum, R. mandschuricum, R. spicatum, R. saxatile, R. aureum, R. alpinum, R. nigrum), as well as the species growing in nursery of the N.I. Vavilov All-Russian Institute of Plant Genetic Resources: R. dikuscha, R. hudsonianum, R. nigrum subsp. europeum, R. nigrum subsp. sibiricum, R. pauciflorum, R. ussuriense. Pollen was examined using a Zeiss EVO-40 scanning electron microscope at the Center for Collective Use of Atomic Force and Electron Microscopy, Herzen University.It was revealed that the studied Ribes plants have normally developed pollen grains of a spherical or elliptical shape, with concave lateral planes, the pollen is porate-colpate. Currant pollen is characterized by wide polymorphism both between different species and within the same species. In all studied species, there are deviations in morphological structure of pollen grains; such pollen does not germinate on an artificial nutrient medium. The most deformed pollen was observed in Ribes mandshuricum, R. ussuriense, R. alpinum, R. dikusha, and R. pauciflorum (12.7–6.7%). The pollen of medium size (21–49 μm) is the most suitable for fertilization. The largest share of the medium-sized pollen is found in Ribes sanguineum, R. ussuriense, R. saxatile and R. aureum (91.8–94.6%). The studied plants have a high percentage of morphologically formed (fertile) pollen (the share of stained pollen is 80.3–96.4%). At the same time, the pollen has a rather low viability when germinated on an artificial nutrient medium, with the pollen of Ribes sanguineum, R. spicatum, R. nigrum, R. ussuriense, R. aureum germinates germinating better than the others (45–29%). Often, the pollen grains germinate with disturbances, which is reflected in the direction of their growth. In some species of Ribes, pollen is able to germinate while still inside the anther. The percentage of pollen germination inside the anther is unequal in the flowers taken from different parts of the inflorescence; the best germination is found in the pollen from the flowers of the central zone of the inflorescence.The pollinators of the Ribes flowers in St. Petersburg are representatives of genera Apis, Bombus and a lacewing Chrysopa oculata. There are 2 peaks of pollinators’ activity: in the morning (10–11 a.m.) and in the evening (5–6 p.m.).The germination of pollen grains on the pistil stigma in the studied plants is active. At a relatively high air temperature, the passage of the pollen tube to the ovule takes 3–5 days. In the ovules on the first day of flowering, mature embryo sacs ready for fertilization are observed. On the walls of the ovary, 4 hemi-orthotropic ovules develop, arranged in 6–10 “levels”. The pollen enters the stigma in a two-celled state. The division of the generative cell into two spermia occurs in the pollen tube during the growth of the latter. The germination of the pollen tube in the canal of the pistil style often occurs with disturbances.The conducted studies allow to recommend the species Ribes sanguineum, R. spicatum, R. nigrum, R. aureum for use in Ribes breeding in the conditions of St. Petersburg.

Effectiveness of Pollen Germination Media for Improving Storage Potential in Pomegranate (Punica granatum) Germplasm

Viable pollen grains with the ability to germinate after fertilization are necessary for fruit and seed formation. Pollens are sensitive to environmental conditions and quickly lose their viability after anthesis. In vitro storage potential of pollen grains depends on species, genotype, flower type, and storage conditions. The present study's objective was to evaluate pomegranate germplasm's storage potential and to study germination media's influence on short-term stored pollen's germination percentage. Pollens of fifteen pomegranate genotypes were collected and stored at 4 °C for 30 days. Pollen viability was assessed using in vitro pollen germination by the agar-Petri method. The germination media was composed of different concentrations of sucrose, boric acid, and agar. The results showed that germination media (12.5% sucrose + 0.2% agar) supplemented with 10 ppm boric acid gave the highest germination among all cultivars. Among genotypes, maximum (58.3%) germination was observed in Desi and Kandhari red pollens, and minimum (16.3%) was observed in Sandhora. The concentration of boric acid in germination media influenced pollen germination. The highest pollen germination was found at 10 ppm, followed by 5 ppm, and the lowest germination was found in media with no boric acid. Conclusively genotypes show variation in storage potential, and germination media influences post-storage germination rate. The utilization of effective germination media can increase the pollen germination rate for pomegranate genotypes.

Foliar application of selenium affecting pollen viability, grain chalkiness, and transporter genes in cadmium accumulating rice cultivar: A pot study

Under Cadmium (Cd) stress, rice grain quality and quantity are compromised, affecting human health. Application of Selenium (Se) mitigating Cd stress in rice was already reported, but its role in rescuing Cd induced damage in the reproductive parts in rice plants has not been studied before. To investigate the underlying mechanism, Se mediated alleviation of Cd-stress induced damage to pollen viability, germination rate, and grain chalkiness were studied. A grain Cd accumulating rice genotype was selected and treated with 10 μM Cd and sprayed with 5 μM Se during tillering, elongating and heading stages.A significant reduction in pollen viability, germination percentage, and accumulation of higher amount of ROS in the reproductive parts were observed in Cd treated plants. However, Se supplementation (i.e. Cd + Se), decreased the ROS accumulation in anther, pistil, pollen and enhanced the pollen viability and germination percentage. Cd translocation was prevented from flag leaf to grains, under Se treatment. As a result, a significantly higher seed setting rate, and yield were observed. Additionally, Se improved grain nutrient content and grain quality. Therefore, the recent study suggests that the use of foliar spray of Se could be a cost-effective strategy to prevent Cd-induced yield loss and quality in rice.

Pollen: A Potential Explant for Genetic Transformation in Wheat (Triticum aestivum L.)

The use of biotechnology for the genetic improvement of wheat (Triticum aestivum L.) has been hampered by its recalcitrance to standard transformation and regeneration protocols. Male gametes present a potentially useful option for introducing gene edits via clustered regularly interspaced short palindromic repeats (CRISPR). However, the utility of male gametes for introducing genetic improvements would be dependent on the retention of viability after treatment to introduce the CRISPR components. We have studied wheat pollen morphology and its viability in a range of germination media to identify conditions that optimize the viability of in vitro hydrated pollen. The size, shape, and aperture from seven different wheat genotypes were compared using scanning electron microscope (SEM). The SEM results revealed that the pollen of all of the wheat genotypes examined in this study were monoporate; however, a significant variation in the size of the mature pollen grains was observed. The hydrated pollen of the wheat genotypes remained viable for up to five hours at 20 ± 2 °C. Of all of the germination media tested, the medium containing 5% sucrose, 10% PEG4000, 100 mg/L boric acid, 200 mg/L calcium nitrate, 100 mg/L potassium nitrate, and 100 mg/L magnesium sulphate at pH 6.5 achieved the highest percentage of pollen germination after 5 h of hydration. Impedance Flow Cytometry (IFC) provided similar results to the in vitro germination study. This work elucidates important factors that can form the basis for a pollen-based non-genetically modified system for gene editing in wheat.

Cytological investigation on pre and post fertilization barriers in interspecific cross of pigeonpea

The research deals with cytological investigation on pre and post-fertilization barriers, pollen fertility assessment and in vitro pollen germination in Cajanus cajan (CO 8) and C. cajanifolius. To determine the fertility of the species potassium iodide test was done. Cajanus cajan (CO 8) and Cajanus cajanifolius, were found to have fertility more than 97 per cent. Through in vitro pollen germination, it was ascertained that Cajanus cajan (CO 8) and Cajanus cajanifolius were found to be equally viable. Pollen-pistil interaction in wide crosses was analysed by fluorescent microscopy. At 2 HAP, higher pollen germination percentage was found in direct (83.6%) and reciprocal crosses (81.2%). At 24 HAP, lower pollen tube growth percentage was found in direct (46.7%) and reciprocal crosses (26.8%). In direct cross, pod set per cent was found to be less, indicating post-fertilization barrier. In reciprocal cross, there was no pod set, which indicates pre-fertilization barrier. Keywords: Fluorescence microscopy, C. cajan, C. cajanifolius, Aniline blue technique, pollen pistil interactions

Effects of Various Carbohydrates on the in vitro Pollen Germination of Vinca rosea and Cucumis melo var. Utilissimus

Pollen germination is a crucial stage of plant development that significantly depends on the presence of carbohydrates as a primary energy source. In this study, we analysed the differential effects of four sugars (Glucose, Sucrose, Galactose, Fructose) with varying concentrations on the pollen germination of Vinca rosea Linn. and Cucumis melo var. utilissimus Duth and Fuller using Brewbaker and Kwack medium as germination medium and hanging drop method after incubation of an hour. Sucrose and glucose aided the pollen germination but galactose and fructose significantly inhibited the pollen germination of Vinca rosea. In Cucumis melo var. utilissimus, all four types of sugars supported pollen germination. The study suggests that 15% sucrose, for Vinca rosea, and 12% galactose, for Cucumis melo var. utilissimus, depict the highest pollen germination percentage when used in the pollen germination medium.

SNP-Based Genome-Wide Association Mapping of Pollen Viability Under Heat Stress in Tropical Zea mays L. Inbred Lines.

Global environmental changes with more extreme episodes of heat waves are major threats to agricultural productivity. Heat stress in spring affects the reproductive stage of maize, resulting in tassel blast, pollen abortion, poor pollination, reduced seed set, barren ears and ultimately yield loss. As an aneamophelous crop, maize has a propensity for pollen abortion under heat stress conditions. To overcome the existing challenges of heat stress and pollen abortion, this study utilized a broad genetic base of maize germplasm to identify superior alleles to be utilized in breeding programs. A panel of 375 inbred lines was morpho-physiologically screened under normal and heat stress conditions in two locations across two consecutive planting seasons, 2017 and 2018. The exposure of pollen to high temperature showed drastic decline in pollen germination percentage. The average pollen germination percentage (PGP) at 35 and 45°C was 40.3% and 9.7%, respectively, an average decline of 30.6%. A subset of 275 inbred lines were sequenced using tunable genotyping by sequencing, resulting in 170,098 single nucleotide polymorphisms (SNPs) after filtration. Genome wide association of PGP in a subset of 122 inbred lines resulted in ten SNPs associated with PGP35°C (p ≤ 10−5), nine with PGP45°C (p ≤ 10−6–10−8) and ten SNPs associated with PGP ratio (p ≤ 10−5). No SNPs were found to be in common across PGP traits. The number of favorable alleles possessed by each inbred line for PGP35°C, PGP45°C, and the PGP ratio ranged between 4 and 10, 3–13 and 5–13, respectively. In contrast, the number of negative alleles for these traits ranged between 2 and 8, 3–13 and 3–13, respectively. Genetic mapping of yield (adjusted weight per plant, AWP−1) and flowering time (anthesis-silking interval, ASI) in 275 lines revealed five common SNPs: three shared for AWP−1 between normal and heat stress conditions, one for ASI between conditions, and one SNP, CM007648.1-86615409, was associated with both ASI and AWP−1. Variety selection can be performed based on these favorable alleles for various traits. These marker trait associations identified in the diversity panel can be utilized in breeding programs to improve heat stress tolerance in maize.

The Relationship between Pollen Viability and Filled Grains in Native Indonesian Rice Cultivars under High Temperature at Flowering Stage

Background: The research was conducted to screen rice cultivars with resistance ability to high-temperature conditions and analyze the relationship between pollen viability and filled grain of native Indonesia rice cultivars. Methods: The rice seeds were germinated, sown into a tray and then transplanted into pots filled with sandy loam and compost 3:1. After 20% of flowering, four pots of each cultivar were kept under ambient temperature (28-32°C) and the other four pots were transferred to high-temperature (33-38°C) conditions. Pollen stainability and pollen germination were conducted using IKI solution and by germinating them under in vitro conditions respectively before being viewed under the light microscope. Yield characters were analyzed to obtain a relationship with pollen viability. Result: Percentage of pollen germination, filled and empty grains of rice cultivars significantly differed between the two conditions by t-test. Ciherang and Sigeudop were two resistant cultivars for high-temperature treatment, with filled grain percentage more than 85%. There was a strong relationship between pollen germination and filled grains at ambient temperature (r=0.95; p less than 0.01) and high temperature (r=0.94; p less than 0.01). Rice cultivars that show high pollen germination under high-temperature conditions would produce a high percentage of filled grains.