Morphology and anatomy of pollen grains from male-fertile and male-sterile cultivars of chestnut (Castanea sativa Mill.)

Summary

Pollen morphology and ultrastructure are described for four male-fertile cultivars (‘Firdola’, ‘Karamehmet’, ‘Sar?a?lama’, and ‘Hac?ömer’) and two male-sterile cultivars (‘Osmanog?lu’ and ‘Vakit Kestanesi’) of chestnut (Castanea sativa Mill.) using light microscopy and both scanning and transmission electron microscopy. Pollen grains of both male-fertile and male-sterile chestnut cultivars are tricolporate, the germinal furrow extending almost the full length of the grain axis. Pollen grains have a slightly reticulate exine. Pollen grain length varied from 13.33 – 21.30 µm, and decreased significantly in the male-sterile cultivars. Three different pollen shapes were observed among the cultivars: prolate, perprolate, and sub-prolate. The ultrastructure of the pollen grains did not differ between male-fertile and male-sterile cultivars. Intine, exine and total wall thickness (exine + intine) of pollen grains were determined as: 83.2 – 153.1 nm, 432.8 – 520.0 nm, and 516.0 – 651.6 nm, respectively; and variations were significant (P ≤ 0.05) among cultivars. The percentages of in vitro germination of pollen grains of male-fertile cultivars were between 11 – 78%, and the variations among cultivars were significant (P ≤ 0.05). The percentages of empty pollen grains observed among cultivars ranged from 3 – 32%. The correlation coefficient between the percentage of normal pollen and the germination rate was r = 0.898 (P ≤ 0.01).     

Comparison of seed-derived with micropropagated male-sterile plants of Tagetes erecta L. for F1 hybrid seed production

Summary

To multiply large number of male-sterile marigold plants for F₁ hybrid seed production, an efficient protocol for in vitro cloning of field-grown differentiated male sterile plants has been developed. A comparative field performance study of tissue culture and seed-derived male sterile plants of two marigold genotypes was undertaken to test the possibility of using micropropagated plants in hybrid seed production. Tissue culture raised plants of both genotypes had superior field performance to the seed-derived counterparts. These plants were more vigorous in growth, i.e. in terms of plant height, number of secondary branches and number of leaves and plant spread, while the leaf chlorophyll contents were equal to that of seedling plants. Flowering was earlier by 2-3 weeks and the number of flowers per plant was also higher in such plants. Repeated hand pollination of sterile flowers with bagged flowers of cv. Pusa Narangi Gainda showed that seed set and bold seed yield were higher or almost comparable with the seed-derived plants. The results clearly indicate that the tissue culture can be adopted for the successful cloning of male-sterile plants, which could then be utilized for producing F₁ seeds with higher quantities of bold seeds with better storability.     

Temperature effects on male fertility and flower and fruit development in Capsicum annuum L.

Temperature conditions strongly influenced the development of flowers and fruits of pepper (Capsicum annuum L.) plants. Low temperatures (LTR; 18°C day/15°C night) had much more effect on flowers and fruits than intermediate (ITR; 23°C day/18°C night) or high (HTR; 28°C day/23°C night) temperatures. LTR caused the formation of abnormal petals, stamens and gynoecium in the flowers. Stamens produced were deformed, in some cases partly carpel-like, produced abnormal non-viable pollen, and were thus functionally male-sterile. In the gynoecium, the ovary size of LTR-grown flowers was larger than that of ITR and HTR flowers, but the style elongation was inhibited. Fruits produced under HTR were larger than ITR and were seeded under both temperature regimes. Under LTR, small seedless fruits were produced, but normal seeded fruits were formed if flowers were pollinated with pollen from ITR- or HTR-grown flowers.     

Factors affecting the quality and in vitro germination capacity of strawberry pollen

Summary

Poor pollen quality and germination capacity curtails early yield in strawberry. The aim of this study was to establish a reliable method for in vitro assessment of strawberry pollen germination ability and to investigate further the effects of photoperiod and gibberellin on pollen germination and quality. In the first part of the study, pollen from seven strawberry cultivars (Chandler, Selva, Tudla, Camarosa, Eris, Pajaro and Irvine) was collected and its germination capacity and incidence of deformed pollen grains assessed in vitro using the hanging-drop technique. Highest germination rates, in ‘Selva’, were observed in a nutrient medium of 10% sucrose. Addition of calcium nitrate to the medium decreased the germination percentages of all cultivars. There was no significant difference, on average, between the germination rate at 20° and 25°C. Genetic factors affected the incidence of deformed pollen grains significantly, with ‘Pajaro’ showing the highest percentage (76%). In the second part, groups of young strawberry plants, cultivar Seascape, grown either under natural early spring conditions or under long-day or short-day conditions were sprayed once with GA₃ at 0, 50, or 200 mg l^–1. Pollen germination and deformation and stamen length were assessed three months later. In plants of the first group, GA₃ at 50 mg l^–1 increased pollen germination and decreased the incidence of deformed pollen grains, while GA₃ at 200 mg l^–1 decreased pollen germination without affecting the formation of deformed pollen grains. Plants of the second group showed a higher rate of pollen germination under long than under short days. GA₃ at 200 mg l^–1 decreased pollen germination under either short- or long-day conditions compared with the controls but doubled the percentage of deformed pollen only under short days. Stamens in control plants grew four times as long under long- than short-day conditions. GA₃ did not affect stamen length under long days but significantly enhanced their growth under short days.     

Efficient reduction of biomass,seed and season long pollen production of common ragweed (Ambrosia artemisiifolia L.)

Ragweed (Ambrosia artemisiifolia L.) is a noxious plant that not only is a troublesome agronomic weed that causes economic damage to agricultural crops but also − and even more importantly − causes severe health problems due to its severe allergenicity. The pollen of invasive ragweed has become a major allergenic risk factor in urban areas in newly occupied regions. Many urban areas prohibit herbicide application; thus, mowing is the most widely used control measure. Counting pollen is labour intensive; therefore, pollen production data are mainly based on estimations. Field experiments were conducted to determine the effects of different mowing scenarios, plant density and cutting height on the biomass, pollen production and seed production of common ragweed plants. Ragweed plants were mown twice: just before the flowering of terminal racemes (BBCH 59) and when the flowers of the re-sprouting lateral shoots reached BBCH 59. A 1- to 3-cm cutting height produced the greatest pollen reduction compared to that of intact control plants (94%) based on a season-long pollen collection. The number of female flowers also significantly decreased (97%). Compared to the control, the onset of pollen discharge was delayed by 5 weeks and the length of the pollen discharge period decreased from 9 to 4 weeks. The season-long unique and reproducible pollen production data can be integrated with airborne pollen modelling and population management strategies.     

Photoperiod-sensitive male-sterile mutant in tomato and its potential use in hybrid seed production

Summary

The current practice of manual emasculation of tomato ¯owers for hybrid seed production is labour-intensive and contributes signi®cantly to the high cost of seed. Here we report on a photoperiod-sensitive, single gene male-sterile mutant (7B-1) in tomato which is 100% male sterile in long days (LD, minimum of 12.h daylength) in summer ®eld conditions, but produces many male-fertile ¯owers in short days (SD, 8.h). In LD, 7B-1 ¯owers contain stamens that are pale, short and in the anthers microspore mother cells are differentiated but meiosis does not occur, i.e. microspores and pollen grains are not formed. Unlike the wild type ¯owers, the style and stigma of 7B-1 ¯owers are well exposed and this allows for ready access for pollination without emasculation. In SD, mutant ¯owers possess normal-looking orange-yellow anthers that enclose the stigma and produce normal viable pollen, which when used for pollination of 7B-1 ¯owers yield good fruit- and seed-set. The 7B-1 seed in turn generate a 100% population of male-sterile plants all of which can be used as female parents for hybrid seed production. The female fertility is not affected in 7B-1 ¯owers in both LD and SD conditions. The 7B-1 mutant has been grown in various ®eld locations including, Saskatoon, California, Florida and in Chile, and at all locations it has shown stable male sterility. The 7B-1 mutant is a simple, natural and costeffective system that has a strong potential for use in commercial-scale production of tomato hybrid seed.     

Intergeneric hybridizations between Opisthopappus taihangensis and Chrysanthemum lavandulifolium

For the first time, reciprocal intergeneric hybridizations were produced between Opisthopappus taihangensis and Chrysanthemum lavandulifolium without emasculation. About 20% seed set was similarly obtained from reciprocal hybridization. Only 5 and 6 of the viable plants observed from 45 and 78 seedling survived present some conspicuous intermediate characteristics. Phenotypic evaluation among the progenies of the parents and the putative hybrids was performed carefully since an average of 5.3% seed set was produced in the type of self-pollination using pollen from the same flower and >10% seed set was similarly obtained in the types of self-pollination using pollen from different flowers in a plant and flowers in individual plants from different seeds. One individual of each hybrid shared the inflorescence habit with the pollen plant was confirmed further by the sequence of ncpGS. The two hybrids might be used as bridges of breeding of multi-generic hybrids.     

Microsporogenesis and anther culture in carob tree (Ceratonia siliqua L.)

An in vivo study was made on male flowers of carob tree (Ceratonia siliqua L.), in order to establish a correlation between the flower and anther development, and microsporogenesis. In addition studies were conducted to find which phase is more appropriate for anther culture and haploid production. During the development of male flowers, six stages were identified. The male gametophytic cycle begins when flowers are in developmental phase 0, with the formation of the epidermis, endothecium, primary sporogeneous tissue, primary parietal cells and pollen mother cells. During developmental phase I we observed the formation of pollen mother cells, the microspore tetrads, and uni- and binucleate pollen grains. At developmental phase II, uni- and binucleate microspores, and completely formed pollen grains were observed. In developmental phase III we could observe mature pollen grains ready to be released from the anthers as single binucleate pollen grains. Anthers from flowers at developmental phases I and II, with microspores at late uninucleate to early binucleate stage, were cultured in semi-solid Murashige and Skoog's (MS) medium supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D) combined with one of the citokinins: N⁶-benzyladenine (BA), kinetin (Kin), zeatin (Zea) and thidiazuron (TDZ). To obtain embryogenic calli anthers should be collected from flowers in developmental phase I. High frequencies of callogenesis were obtained, and the best medium for calli induction was MS supplemented with 0.5 mg l⁻¹ 2,4-D + 4 mg l⁻¹ TDZ. The frequency of haploid cells was found to be 17.2%.     

Pollination management for controlled hybridization of white yam

Pollination and fertilization success in white yam, Dioscorea rotundata Poir., depend on knowledge and good management of factors influencing the availability of open male flowers from which good pollen can be collected for effective use in pollinations of genetically compatible female plants under non-xeric conditions. In vitro germination of pollen from numerous genotypes demonstrated varied viability (0.3–85.0%). However, pollen from bisexual flowers on monoecious plants was inferior to pollen from unisexual flowers from dioecious plants. Natural pollination by thrips is inefficient, such that populations with higher ratios of male to female plants set more fruits. To improve fruit set, hand pollinations should be made with pollen from diverse genotypes, early in the flowering period when net water balance is positive. In crossing-blocks, male plants should be closely interpositioned with female plants to reduce pollination distance, thereby improving pollination and fruit set.     

Plant characteristics for distinction of diploid,triploid and tetraoloid lettuce

After colchicine treatments of lettuce cultivars, tetraploid plants have been obtained. Crosses between 4x and 2x plants resulted in 3x plants. Between these 3 ploidy levels differences occurred in many plant characteristics which can be used as selection criteria. The number of plastids per stoma is suitable for distinction between the 3 ploidy levels. Stomatal length, size of flower, pollen grain length, seed length and seed weight can be used for distinguishing 4x and 2x plants. The percentage of stained pollen grains and the seed production per plant can be used for distinguishing 3x and 2x plants.     

Induction of viable 2n pollen in sterile Oriental × Trumpet Lilium hybrids

In order to induce viable 2n pollen from highly sterile diploid Oriental × Trumpet (OT) (Lilium), N₂O was used to treat flower buds of four sterile diploid OT cultivars (‘Nymph’, ‘Gluhwein’, ‘Yelloween’, and ‘Shocking’) at different stages of meiosis. There was no pollen germination in the controls. However, after N₂O treatment at 600 kPa, three of the OT hybrids (‘Nymph’, ‘Gluhwein’, and ‘Yelloween’) not only exhibited fertile flower percentages (4.3–16%), but also higher rates of pollen germination (18.8–72.5%). In addition, both the fertile flower percentages and rates of pollen germination were higher following 48 h N₂O treatment at 600 kPa than the 24 h treatment. Following 72 h N₂O treatment at 600 kPa, most flower buds or plants were damaged and any undamaged flowers showed abnormal anthers at the time of flowering. This indicated that 48 h of N₂O treatment at 600 kPa was optimal to induce viable 2n pollen in three out of four sterile hybrid OT lily cultivars. These results also showed that prophase I – metaphase I was the optimum stage of meiosis at which to induce 2n pollen by N₂O treatment in lily hybrids.     

Methods for testing the fertility of tomato pollen formed at low temperature

A reliable indication of pollen fertility is the number of seeds per fruit produced following artificial pollination, but this method is laborious, and very slow because sampling needs ripe fruits. To seek faster techniques to test the fertility of tomato pollen produced at low temperatures, we cultivated a large collection of tomato cultivars and lines of related wild species under cold conditions with minimum nocturnal temperatures below 10°C. We compared numbers of seeds per fruit with: number of pollen tubes at the base of the style, index of natural fruit-set, percentage of pollen grains stained with acetocarmine, percentage of pollen grains giving fluorochromatic reaction with fluoresceine diacetate, and percentage of pollen grains which germinated in vitro. All these variates correlated positively and significantly between themselves. The number of pollen tubes at the base of the style most closely correlated with number of seeds. This technique is equally laborious, but is good for precise testing of small numbers of genotypes and results are quickly available. Both acetocarmine staining and fluorochromatic reaction were simple, fast techniques with potential for screening large collections to detect genotypes with highly fertile pollen at low temperature; acetocarmine was the best, but neither test would identify genotypes with low-fertile pollens. Index of natural fruit-set and germination in vitro did not effectively determine the fertility of pollen produced at low temperature.     

榨菜胞质雄性不育及其农艺性状的研究

榨菜（ＢｒａｓｓｉｃａｊｕｎｃｅａＣｏｓｓ．ｔｕｍｉｄａＴｓｅｎｅｔＬｅｅ）胞质雄性不育系的雄蕊形态有两种类型：１）雄蕊无花药结构；２）雄蕊花药瘦小而干瘪。不育系雄性器官败育时期有两种类型：１）孢子体败育型；２）配子体败育型，属小孢子发育受阻。不育系雄蕊内源激素ＩＡＡ和ＺＴ含量随花器发育而极缓慢地增长，在花盛开时，每枚雄蕊分别为８．０ｎｇ和２２．４ｎｇ，近保持系的１／４和１／６，出现明显的ＩＡＡ和ＺＴ含量亏损现象。雄性不育率和不育度均为１００％，不育性世代稳定。不育系９０％的植株雌蕊育性正常，人工授粉后平均单果结籽１４．６粒，比保持系多１．２粒。其余１０％的植株其雌蕊部分不育。在保持系为父本进行自然授粉条件下，不育系单株种子产量７．２ｇ，较正常株高１６．６％。不育系经济性状优良，基本达到保持系和栽培品种水平。     

Regulated deficit irrigation in potted Dianthus plants: Effects of severe and moderate water stress on growth and physiological responses

The purpose of this study was to analyze the physiological and morphological response of carnation plants to different levels of irrigation and to evaluate regulated deficit irrigation as a possible technique for saving water through the application of controlled drought stress. Carnations, Dianthus caryophyllus L. cultivar, were pot-grown in an unheated greenhouse and submitted to two experiments. In the first experiment, the plants were exposed to three irrigation treatments: (control); 70% of the control (moderate deficit irrigation, MDI) and 35% of the control (severe deficit irrigation, SDI). In the second experiment, the plants were submitted to a control treatment, deficit irrigation (DI, 50% of the control) and regulated deficit irrigation (RDI). After 15 weeks, MDI plants showed a slightly reduced total dry weight, plant height and leaf area, while SDI had clearly reduced all the plant size parameters. RDI plants had similar leaf area and total dry weight to the control treatment during the blooming phase. MDI did not affect the number of flowers and no great differences in the colour parameters were observed. RDI plants had higher flower dry weight, while plant quality was affected by the SDI (lower number of shoots and flowers, lower relative chlorophyll content). Leaf osmotic potential decreased with deficit irrigation, but more markedly in SDI, which induced higher values of leaf pressure. Stomatal conductance (g_s) decreased in drought conditions more than the photosynthetic rate (P_n). Osmotic adjustment of 0.3 MPa accompanied by decreases in elasticity in response to drought resulted in turgor less at lower leaf water potentials and prevented turgor loss during drought periods.     

Effects of cadmium and copper on pollen germination and fruit set in pea (Pisum sativum L.)

In this work, pea (Pisum sativum) plants exposed to increasing cadmium and copper concentrations were tested for heavy metals accumulation in flowers and for ‘in vivo’ pollen germination. Based on the Cd and Cu accumulation amounts in the flowers, an evaluation of the same metals effects on ‘in vitro’ pollen germination was achieved. Moreover, the effects of both metals on fruits number and weight and on seed set and yield at individual plant level were examined. While cadmium concentrations did not affect ‘in vivo’ pollen germination, only higher copper concentrations rendered a significant reduction. This is in contrast with the clear negative effect on pollen germination in vitro and might be explained by the different dynamic and bioavailability of both metals. A clear effect of Cd and Cu was observed on two important yield components ie, fruit weight and seed set. Although results obtained herein cannot give a clear cut relationship between the effect of Ca and Cu on reproductive development and its consequences on yields, they represent emerging results on the potential consequences of metals contamination on reproductive development in plants.     

Identification of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), in pollen

Within 15 min after application of pollen to the stigma of carnation flowers (Dianthus caryophyllus L. cultivar ‘White Sim’), ethylene (C₂H₄) production by the gynoecium had increased substantially. Pollen germination did not start until 1 h after pollination. Analysis of materials removed from pollen by a brief rinse with an aqueous solvent showed the presence of high concentrations of the C₂H₄ precursor, 1-aminocyclopropane-1-carboxylic acid (ACC). This compound, which was found to be present in pollen from a number of flower species and which increased in concentration as the anthers developed, may be an important mediator of the early response of flowers to pollination.     

Characterization and genetic linkage mapping of the horticulturally important mutation leafless inflorescence (lli) in periwinkle Catharanthus roseus

Catharanthus roseus is a seasonal to perennial garden plant and the exclusive source of the anticancer drugs vincristine and vinblastine. Its horticultural importance is due to the compound racemose inflorescence architecture of branches in which pairs of prominent flowers are subtended by one of the two leaves per node. Here is reported the construction of a molecular framework genetic linkage map and mapping on it of the LEAF-LESS INFLORESCENCE (LLI) locus. It is quantitatively shown that the adult lli mutant plants produce altered inflorescence of improved horticultural value, wherein axes are excessively branched, two flowers are formed per node that are bare of subtending leaves, and several times more open flowers are displayed each day, as compared to LLI plants.     

桔梗雄性不育突变体的发现与鉴定

从2a生桔梗群体中发现雄性不育种质PA-1个体,随后对桔梗花器进行了大量田间观察,相继发现桔梗雄性不育单株共12株,统一编号为PA-1至PA-12;同时对桔梗不育性状表现及特征特性进行初步研究.结果表明:与其相同来源的正常花相比,不育花雄蕊短小、花药干瘪萎缩,色泽为灰褐色;花粉进行I2-KI染色,败育花粉外形不规则,且不能被染色;不育花雌蕊、蜜腺发育正常,花冠略大,对授粉昆虫具有与正常花等同的吸引力;不育花强迫自交结籽率为0,异花人工授粉和天然授粉结籽率与正常花间无明显差异,初步表明PA单株为雄性不育材料,为桔梗杂种优势的利用开辟了新途径.     

韭菜新品种‘海韭 2 号’

 ‘海韭2号’是以‘小黄苗’韭菜雄性不育无性系为母本,‘平韭’的优良株系‘J-95-42’为父本,经过有性杂交,连续多代优株筛选,优系混合授粉等育种过程而育成的深休眠韭菜新品种。植株分蘖能力强,叶色深绿,平均叶宽0.8 cm,平均单株质量6.7 g,可溶性糖含量1.58%,粗纤维含量0.89%。具有抗寒性强、较耐热、适应性强等优点,年平均产量166 440 kg · hm^-2,适宜露地和早春保护地栽培。     

Germination and growth of sponge gourd (Luffa cylindrica) pollen tubes and FTIR analysis of the pollen tube wall

Emergence of multiple pollen tubes from single pollen grains occurred both in vitro and in vivo in sponge gourd (Luffa cylindrica (L.) Roem). The frequency with which pollen grains produced multiple pollen tubes in vivo (7.2%) was lower than that under in vitro conditions (14.9%). In pollen grains germinated in vitro, the total length of the multiple pollen tubes was greater than that of single pollen tubes, but individual tubes among the multiple tubes did not reach the same length as single tubes. Moreover, the growth of the single pollen tubes continued for a longer period in vitro than that of the multiple tubes. Fluorescence microscopy showed that callose was present throughout the pollen tube wall except in the apical part of growing pollen tubes, and nuclei moved into the longest of the multiple tubes. Results of Fourier transform infrared microspectroscopy indicated that abnormal cell wall components (peaks at 800–1000 cm⁻¹) were more frequent in multiple pollen tubes lacking nuclei, and the pectin content (1733 cm⁻¹) in multiple pollen tubes was much lower than that in single pollen tubes. These findings suggested that there were significant differences in pollen tube growth and wall composition between single and multiple pollen tubes, and that multiple pollen tubes had much less opportunity than single pollen tubes to reach the embryo sac and achieve double fertilization.