Microsporogenesis and pollen formation in Larch Sukachev (Larix Sukaczewii Djil.) on permanent forest seed plot in Semiluksky forestry

The formation of male and female generative buds in the Sukachev larch in the conditions of Voronezh in the second decade of August is considered. The behavior of chromosomes in the meta-, ana -, and telophase of the first and second divisions of meiosis is analyzed. In each phase, 150–200 microsporocytes were taken into account. According to the results of the conducted studies, it was revealed that the microsporogenesis of larch proceeded asynchronously. A significant proportion of the disorders are caused by chromosome lag and the formation of bridges, the formation of a hexad, and the release of chromosomes outside the division spindle. The viability of Sukachev larch pollen is estimated to be high. A small number of disturbances in the process of meiotic divisions and the formation of gametophytes did not lead to the formation of a significant amount of sterile pollen. The average pollen size varies between 82.18–86.4 microns. Pollen has a spherical shape

Male meiosis and pollen morphology in diploid Indonesian wild bananas and cultivars

Breeding of banana is hampered by its genetic complexity, structural chromosome rearrangements and different ploidy levels. Various scientific disciplines, including cytogenetics, linkage mapping, and bioinformatics, are helpful tools in characterising cultivars and wild relatives used in crossing programs. Chromosome analysis still plays a pivotal role in studying hybrid sterility and structural and numerical variants. In this study, we describe the optimisation of the chromosome spreading protocol of pollen mother cells focusing on the effects of standard fixation methods, duration of the pectolytic enzyme treatment and advantages of fluorescence microscopy of DAPI stained cell spreads. We demonstrate the benefits of this protocol on meiotic features of five wild diploid Musa acuminata bananas and a diploid (AA) cultivar banana “Rejang”, with particular attention on pairing configurations and chromosome transmission that may be indicative for translocations and inversions. Pollen slides demonstrate regular-shaped spores except “Rejang”, which shows fertile pollen grains of different size and sterile pollen grains, suggesting partial sterility and unreduced gamete formation that likely resulted from restitutional meiotic divisions.

Pollination.

Pollination of flowers is the transfer of pollen grains (haploid male spores) from the anther (part of the androecium) to the stigma (part of the gynoecium) by biotic or abiotic factors (Sliwinska and Bewley, 2014). For seed and fruit production of agricultural crops the main pollinating agents are wind and insects (George, 2011). After a pollen grain is transferred to a receptive stigma, it absorbs water from the stigma surface and germinates. A pollen tube then grows down into the stigma, through the gynoecium and through the apical micropyle; from there it grows into an ovule in the ovary and double fertilisation then takes place. Two sperm are released into the embryo sac; one fertilises the ovule to produce a diploid zygote, and the other joins with two polar nuclei in the ovule to produce a triploid nucleus that will then develop into the nutrient-rich endosperm (Willmer, 2011). Pollen grain diameter is usually in the range 20-70 μm, and the surface structure and morphology varies considerably between plant species and dispersal mechanism (Wiltshire, 2010). Air temperature can have an effect on pollen formation and viability, with high temperatures potentially leading to sterile pollen (Bosland and Votava, 2012). Irradiated pollen grains are still able to germinate and produce pollen tubes that reach the ovule (Germana, 2012). Although they are unable to fertilise the egg cell, this process induces parthenogenesis and has been widely used to produce haploid fruits (Germana, 2012).

Biomonitoring of the toxic effects of industrial emissions

The article presents results of studying the impact of industrial emissions of the Apatit project (Murmansk region) on the fertility and sterility of pollen of Scotch pine (Pinus sylvestris L.). A low share of fertile pollen (49.3–57.4%) and high ratio of sterile pollen (42.6–50.7%) are revealed in the samples from the city of Apatity under study. The study calculated the palynotoxic effect of the industrial emissions. Shown the toxic effect of emissions of the apatite-nepheline complex on male gametophyte of Scotch pine and the process of gamete formation. The ecological safety of the city of Apatity is closely related to the problems of the complex use of apatite-nepheline ores and the minimization of storage of waste in tailing dumps.

Flower size dimorphism, perianth shape and sex ratio in a gynodioecious Prunella vulgaris (Lamiaceae)

Prunella vulgaris is a gynodioecious species that forms two types of flowers, perfect and female, on different plants. These two sexual types of flowers have significant differences in some characters of calyx, corolla, androecium, and gynoecium. The distinctiveness of gynodioecy in P. vulgaris consists in insignificant size differences in anthers, the formation of sterile pollen in female flowers, and the shape of a corolla in two sexual types of flowers. Hermaphrodite plants are dominated in P. vulgaris (59.8 to 87 percent). In flood plain meadows, the proportion of females is significantly higher (from 25.9 to 40.2 percent) than in dry and forest meadows (from 13 to 19.1 percent).

Genetics and Breeding of Heat Tolerance in Rice

Extreme weather events, especially heat waves, have become more frequent with global warming. High temperature significantly affects world food security by decreasing crop yield. Rice is intensively planted in tropical and subtropical areas in Asia, where high temperature has become a major factor affecting rice production. Rice is sensitive to high temperature, especially at booting and flowering stages. Rice varieties tolerant of high temperature are rare, and only a few heat-tolerant rice varieties have been identified. High temperature at booting and flowering stages causes sterile pollen, decreased pollen shedding, and poor pollen germination, which finally lead to a yield decrease. Heat-tolerant QTLs have been identified in different studies, but new breeding lines with considerable heat tolerance have not been bred using identified heat-tolerance donors and QTLs. Research on heat-tolerant donor identification, QTL mapping, gene cloning, and large-scale phenotyping technology is important for developing heat-tolerant rice varieties.

Quantitative methods in microscopy to assess pollen viability in different plant taxa

High-quality pollen is a prerequisite for plant reproductive success. Pollen viability and sterility can be routinely assessed using common stains and manual microscope examination, but with low overall statistical power. Current automated methods are primarily directed towards the analysis of pollen sterility, and high throughput solutions for both pollen viability and sterility evaluation are needed that will be consistent with emerging biotechnological strategies for crop improvement. Our goal is to refine established labelling procedures for pollen, based on the combination of fluorescein (FDA) and propidium iodide (PI), and to develop automated solutions for accurately assessing pollen grain images and classifying them for quality. We used open-source software programs (CellProfiler, CellProfiler Analyst, Fiji and R) for analysis of images collected from 10 pollen taxa labelled using FDA/PI. After correcting for image background noise, pollen grain images were examined for quality employing thresholding and segmentation. Supervised and unsupervised classification of per-object features was employed for the identification of viable, dead and sterile pollen. The combination of FDA and PI dyes was able to differentiate between viable, dead and sterile pollen in all the analysed taxa. Automated image analysis and classification significantly increased the statistical power of the pollen viability assay, identifying more than 75,000 pollen grains with high accuracy (R2 = 0.99) when compared to classical manual counting. Overall, we provide a comprehensive set of methodologies as baseline for the automated assessment of pollen viability using fluorescence microscopy, which can be combined with manual and mechanized imaging systems in fundamental and applied research on plant biology. We also supply the complete set of pollen images (the FDA/PI pollen dataset) to the scientific community for future research.

High day and night temperatures distinctively disrupt fatty acid and jasmonic acid metabolism, inducing male sterility in cotton

High temperature stress is an inevitable environmental factor in certain geographical regions. To study the effect of day and night high temperature stress on male reproduction, the heat-sensitive cotton line H05 was subjected to high temperature stress. High day/normal night (HN) and normal day/high night (NH) temperature treatments were compared with normal day/normal night (NN) temperature as a control. At the anther dehiscence stage, significant differences were observed, with a reduction in flower size and filament length, and sterility in pollen, seen in NH more than in HN. A total of 36 806 differentially expressed genes were screened, which were mainly associated with fatty acid and jasmonic acid (JA) metabolic pathways. Fatty acid and JA contents were reduced more in NH than HN. Under NH, ACYL-COA OXIDASE 2 (ACO2), a JA biosynthesis gene, was down-regulated. Interestingly, aco2 CRISPR-Cas9 mutants showed male sterility under the NN condition. The exogenous application of methyl jasmonate to early-stage buds of mutants rescued the sterile pollen and indehiscent anther phenotypes at the late stage. These data show that high temperature at night may affect fatty acid and JA metabolism in anthers by suppressing GhACO2 and generate male sterility more strongly than high day temperature.