Effects of genotype and stigma development stage on seed set following intra- and inter-specific hybridization of Dianthus spp.

The caryophyllaceae is a family of flowering plants commonly known as the pink or carnation family. Members of this family are widely grown as ornamental plants. The species Dianthus chinensis, Dianthus barbatus, and Dianthus superbus include notable examples of such ornamental varieties. Intra- and inter-specific hybridization is important for the breeding of improved varieties and, therefore, it is desirable to optimize the efficiency of cross-pollination procedures within this family. Here, we conducted intra-specific pollination using four lines of D. chinensis, and inter-specific pollination between D. chinensis, D. barbatus and D. superbus genotypes. For each of these crosses we recorded information of pollen viability, stigma development stage at time of pollination, pollen germination on the stigma surface and pollen tube elongation within the stigma, and final seed set. Pollen viability levels were determined at the start of anther dehiscence, which occurred on day 1 of flower opening. The genotypes D. chinensis var. ‘Bz2’, D. barbatus var. ‘Xb’, and D. superbus wild species ‘Qm’ all displayed good levels of pollen viability (i.e. between 68% and 75%); D. chinensis vars. ‘H58III’, ‘H68I’ and ‘H6II’ showed lower levels of pollen viability (i.e. between 32% and 51%). In each Dianthus line, the stigma organs were observed to undergo morphological changes during the 1–7 d following flower opening. We have characterized these changes as five distinct development stages, namely, ‘column’ (day 1), ‘Y-like’ (day 2), ‘Y-shaped with slight curve’ (days 3–4), ‘Y-shaped horn-like’ (days 5–6), and ‘wilting’ (day 7). Pollen was artificially applied to stigma organs at each of these development stages and aniline blue staining was used to follow pollen tube germination on the stigma surface and pollen tube elongation down the length of the stigma. This showed that the ‘Y-shaped slightly curved’ stigma stage (3–4 d) was optimal for pollination. The ‘Y-shaped horn-like’ stage (5–6 d) was also receptive to pollination. By contrast, the earlier ‘Y-shaped’ (2 d) and ‘column’ (1 d) stages, and also the later ‘wilting’ (7 d) stage, were far less receptive. Parallel field experiments were conducted in which seed set was measured following the artificial pollination of flowers at different development stages. These data also indicated that the optimal time for pollination was during 3–4 d of flower opening. This conclusion held true for both intra- and inter-specific crosses of the various Dianthus lines. Thus, stigma receptivity in Dianthus does not become optimal until 3–4 d after flower opening. Since anther dehiscence occurs at 1 d (i.e. when stigma are at the unreceptive ‘column’ stage), this suggests that Dianthus employs a delayed self-fertilization strategy. We also found a significant effect of genotype on pollen tube growth and seed-set values. The highest numbers of seed per flower were achieved when the D. superbus wild species ‘Qm’ was the female parent in inter-specific crosses. Thus, genotype and stigma development are identified as key factors that determine the success of cross-pollination in Dianthus lines.     

Pollen load affects fruit set,size, and shape in cherimoya

Cherimoya (Annona cherimola Mill.) is a subtropical fruit crop that exhibits protogyny dichogamy and for which the original pollinators are not present in the main producing countries. Under such circumstances the achievement of profitable yields depends on hand pollination. The present work explores the effects of the amount of pollen applied on pollen–pistil interaction and on fruit set, size, shape and growth. Pollen dilution with Lycopodium spores reduced fruit set and size and favoured the appearance of misshapen fruits, whereas the application of double amount of pollen did not improve fruit size and increased fruit set only the first year. Pollen load did not affect fruit growth model, which always followed a double sigmoid pattern. Nevertheless, the slopes of the curves during the two rapid growth phases were higher when a larger amount of pollen grains was applied. Seed index (seed number per 100 g of fresh fruit weight) rose slightly as pollination level increased.     

Fructose inhibits pear pollen germination on agar medium without loss of viability

Pollen of Japanese pear (Pyrus pyrifolia Nakai) germinated well on agar medium containing 10% sucrose or glucose, but not on agar containing fructose. The inhibitory effect of fructose was dose-dependent. Sucrose enhanced pollen tube growth much more effectively than glucose. Addition of 5% fructose to 5% or 10% sucrose or glucose media suppressed germination completely. Ungerminated pollen, however, showed similar respiration rate and stainability against acetocarmine dye as germinated pollen. When pollen was transferred onto fructose medium after culturing it on glucose or sucrose medium for 1–2 h, germination was completely impeded. Reversely, pollen transferred to sucrose or glucose medium from fructose medium germinated at almost the same ratio as pollen on sucrose or glucose medium without transfer. Thus, pollen inhibition by fructose is reversible. Compared with uncultured pollen, cultured pollen contained less than half amount of total sugars, even if failed in germination on fructose medium. Germinated pollen on sucrose and glucose media contained sucrose and glucose, but ungerminated pollen on fructose medium contained only trace levels of these sugars, suggests that pollen on fructose medium predominantly uses sucrose and glucose as respiration substrates and cannot maintain the constant levels of these sugars. However, as pollen germination occurred on agar medium without any sugar, fructose may impede a physiological factor that triggers germination, and once the trigger is impeded, many physiological pathways including sugar biosynthesis may be blocked.     

Spray pollination as a labor-saving pollination system in Japanese pear (Pyrus pyrifolia (Burm.f.) Nakai): Development of the suspension medium

Effects of suspension media used for spray pollination on pollen grain viability were investigated in Japanese pear (Pyrus pyrifolia (Burm.f.) Nakai ‘Kosui’). The suspension media tested in this study consisted of pectin methylesterase (PME) and polygalacturonase (PG) combined with either 0.1% agar or 0.04% xanthangum (XG). We also evaluated the influences of spray pollination on fruit set and fruit quality. Pollen grain viability, as measured by germination and pollen tube growth rates, was maintained in media supplemented with 0.1 mg L⁻¹ PME or 0.1 mg L⁻¹ PG. The level of fruit set after spray pollination using media containing PME or PG in combination with either 0.1% agar or 0.04% XG was almost the same as the level after artificial pollination by hand (hand pollination). The media containing XG combined with either PME or PG seemed to show better results for pollen grain viability and fruit set, although the results were variable from year to year. With regard to fruit size, shape and other parameters for fruit quality, spray pollination and hand pollination gave comparable results, irrespective of the medium composition. The time required for spray pollination was less than half of that required for hand pollination, and the amount of pollen grain required for spray pollination was one-third or less than the amount required for hand pollination. Thus, spray pollination may be a time- and labor-saving pollination system for the cultivation of Japanese pear.     

Pollination studies in large cardamom (Amomum subulatum Roxb.) of Sikkim Himalayan region of India

Pollination studies in large cardamom were carried out at the research farm of ICAR Sikkim Centre, Gangtok, Sikkim, India during 2009–2010 to assess the effectiveness and efficiency of pollinators. Polleniferous flowers (65,890 ± 11,346.5 pollen/anther) of large cardamom produce spherical, large (108.64 μm × 96.32 μm) and echinate pollen with high pollen/ovule ratio (585.2 ± 134.8). Native bumblebee (Bombus braviceps Smith.), a nectar forager, was identified as the most effective pollinator in terms of pollination potential index score (0.88), pollen removal (55.39%) and deposition rate (4.5%), pollination efficiency and pollen delivery mechanism whereas honey bee acted as a pollen robber. Flowers appeared to be generalized; however, functional specialization was exhibited indicating that only bumblebee is adaptable for pollination moreover, pollination mechanism was an indicative of “pollination syndrome”.     

Rain effect on pollen–stigma adhesion and fertilization in almond

The fact that rainy weather negatively affects production in almond is well-known by growers. However, as far as we know, no previous study has been carried out in this species to determine if the rain is able to wash off pollen grains from the stigma surface and consequently affect fertilization efficiency. To answer this question, flowers of the self-compatible almond cultivar ‘Antoñeta’ were emasculated on branches of trees in the field, pollinated by hand with pollen of the cultivar ‘Marcona’, and sprayed with water to simulate the rain effect at 4, 8, 24 and 48 h after pollination. A control for which no treatment was applied was also included in the assay. Seven days after spraying the flowers, the number of germinated pollen grains on the stigma was recorded in 10 pistils for each treatment by fluorescent microscopic observation. In addition, for each treatment the initial and final fruit set were determined at 30 and 60 days after pollination, respectively. The following year additional assays were performed in the field and in the laboratory in order to complete the study with earlier treatment times. Thus, an assay of rain simulation in the field at 0 and 2 h, and other consisting on immersing a branch with flowers and shaking it in a water container in the laboratory at 0, 30, 60 and 120 min after pollination were performed. One sample more was immersed, shaken, then pollinated and again immersed and shaken. The results from field assays showed that adhesion of pollen grains to the stigma was very quick and strong, and the treatments did not significantly affect pollen–stigma adhesion and subsequent fruit set. On the other hand, laboratory results showed that all washing treatments decreased the number of germinated pollen grains on the stigma, mainly when the flowers were immersed before pollination. In conclusion, the results showed that the simulated rain was not able to completely wash off pollen grains from the stigma surface, although it seems to affect adhesion in forthcoming pollinations.     

桃92个品种的花粉量及其萌发特性的差异

在离体条件下,以92个桃品种为研究对象,探讨其花粉量及其萌发特性的差异。结果表明：单个花药的花粉量变化范围为0 ~ 3 500粒,可萌发花粉量为0 ~ 2 696粒,花粉萌发率为0 ~ 89.33％,花粉管生长长度为0 ~ 1.56 mm,品种间存在明显的差异。上述指标品种出现频率均不符合正态分布。对上述各项因子分别进行聚类分析,供试品种中可萌发花粉量少且花粉管生长速度慢的品种相对较多,占45.65%,这类品种在生产上应合理配置授粉树。     

黄瓜花药和花粉高温伤害与多胺和脯氨酸含量的关系

 黄瓜花药在开花期比花粉母细胞形成期(阶段1) 和单核花粉期(阶段2) 腐胺、精胺、亚精胺含量较低, 游离脯氨酸(Pro) 含量较高。高温(35 ℃/ 25 ℃) 使阶段1、阶段2 花药中上述3 种内源多胺含量及开花期花药和花粉中Pro 含量下降。黄瓜花粉在萌发培养基上培养1 h 时3 种内源多胺含量达峰值,此后下降; Pro 含量随着花粉萌发逐步下降; 高温(35 ℃) 下黄瓜花粉萌发后3 种内源多胺含量的上升和Pro 水平的下降趋势被抑制, 但耐热品系XC21、NY21 受高温的影响小于热敏品系新泰密刺或不受影响, 表明多胺和Pro 代谢与耐热性有关。外源鸟氨酸转氨酶(OAT) 的抑制剂3 氨基- 2 , 3 - 二羟基安息香酸(Gabaculine) 能降低黄瓜花粉的萌发能力, 同时提高花粉中内源多胺的含量并降低Pro 的含量, 表明黄瓜花粉萌发过程中可能存在由Pro 合成多胺的途径。     

Optimal pollination environment of tetraploid ginger (Zingiber officinale Roscoe) evaluated by in vitro pollen germination and pollen tube growth in styles

Pollen germination percentages in vitro of a tetraploid ginger (Zingiber officinale Roscoe), ‘4×Sanshu’, tended to be highest at around 20°C. Pollen tube growth in the styles was greatly enhanced at 17°C, i.e., pollen tubes penetrated into the entire stylar length in 66.7% of the styles used. Pollen stored for at least 3 h under 40–80% relative humidity (RH) almost completely lost its germinability, whereas pollen incubated for up to 3 h under 100% RH retained a relatively higher germinability. Moreover, the pollen germinability that was lowered under 40–80% RH did not recover when the pollen was re-humidified for 2 h under 100% RH before inoculation onto a medium. When stigmas were pollinated with fresh pollen at 17°C under 100% RH, pollen tubes penetrated into the entire stylar length in 26.7% of the styles tested. Under 40–80% RH, however, pollen tubes stopped growing at the middle or the base of styles. From these results, I concluded that the optimal pollination environment of the tetraploid ginger was at 17–20°C under 100% RH.     

Pollen biology of ornamental ginger (Hedychium spp. J. Koenig)

An improved in vitro pollen germination assay was developed to assess the viability of stored Hedychium pollen. The effect of polyethylene glycol (PEG) (10, 15, and 20%, w/v) on pollen germination and tube growth was evaluated for Hedychium longicornutum and two commercial Hedychium cultivars, ‘Orange Brush’ and ‘Filigree’. Overall, the inclusion of PEG 4000 in the medium improved both pollen germination and tube growth for the three different genotypes tested and the results varied depending on genotype. In vitro germination was used to assess the viability of Hedychium pollen stored up to two months. Pollen nucleus status was determined for four Hedychium cultivars, ‘Orange Brush’, ‘Anne Bishop’, ‘Filigree’, and ‘Daniel Weeks’. Pollens of ‘Orange Brush’, ‘Anne Bishop’, and ‘Daniel Weeks’ were found to be binucleate but ‘Filigree’ was shown to possess both binucleate and trinucleate pollens. High pollen:ovule ratio values were obtained in several Hedychium taxa. The results obtained on the nuclear pollen status and pollen:ovule ratios will further our understanding of the pollination biology and help clarify the taxonomy and phylogeny of Hedychium species.     

Ameliorative effect of polyamines on the high temperature inhibition of in vitro pollen germination in tomato (Lycopersicon esculentum Mill.)

Effect of polyamines on in vitro pollen germination at high temperatures in tomato (Lycopersicon esculentum Mill.) was investigated. Pollen germination and tube growth were significantly inhibited at 33°C and 35°C compared to those at 25°C. This inhibition was reversed by the addition of spermidine or spermine in the germination medium. Spermidine at 0.5 mM was slightly more effective than spermine at 0.05 mM. Spermidine at 0.05 and 0.5 mM and spermine at 0.05 mM slightly increased pollen germination rates at 25°C. Spermidine at 5 mM and spermine at 0.5 M were inhibitory to pollen germination, regardless of incubation temperatures. Spermidine also promoted germination of pollen grains incubated at 38°C for 1 and 3 h and then at 25°C for the rest of the 20 h incubation period. The effect was higher at 0.5 mM than at 0.05 mM. Treatment of spermidine to intact flowers 1 day before anthesis was also effective in ameliorating the high temperature inhibition of in vitro pollen germination on the polyamine-free medium. Here, the optimum concentration was 5 mM. These results demonstrate that polyamines can counteract the inhibitory effects of high temperature on pollen germination. They also suggest that the endogenous level of polyamines in germinating pollen grains is an important factor for the pollen germinability at high temperature.     

梨不同花龄自花与异花授粉的花柱内花粉管生长及坐果率的比较

对自交不亲和强度不同的梨品种丰水和菊水的不同花龄花进行自花授粉和丰水×菊水异花授粉后,用荧光显微镜观察花粉萌发及生长特性。结果表明,开花当天及以后的自花和异花授粉花粉在柱头上均有较高的萌发率;自花和异花花粉管在花柱内的生长速度及停止生长的位置不同,丰水自花授粉后花粉管生长的短且慢,菊水自花花粉管生长的长且快,而异花授粉的花粉管生长最快。自花授粉后,不同花龄对花粉管生长影响表现为:开花4d前的蕾期授粉以及开花4d后的延迟授粉,花粉管生长长度显著的长。开花6d前的各种授粉组合,花粉管生长均较差。这与田间授粉坐果率的高低基本一致,即整体表现为各个花龄的授粉都以异花授粉坐果率最高,其次为菊水自花授粉,丰水自花授粉坐果率最低。另外,自花授粉中,蕾期授粉和延迟授粉(开花2d后除外)坐果率都有提高,而异花授粉中蕾期授粉和延迟授粉的坐果率却有所下降。     

Effects of post-harvest foliar boron and calcium applications on subsequent season's pollen germination and pollen tube growth of pear (Pyrus pyrifolia)

The primary objective of this study was to evaluate the effects of foliar boron and calcium application after harvest on the quantity and activity of pollen in the ‘Housui’ and ‘Wonwhang’ pears on a subsequent year. Pollen grains of the ‘Housui’ pear were cultured on germination medium, to which had been added boric acid (0, 25, 75, 100, 200, 300, 400, and 500 mg L⁻¹) and calcium nitrate (0, 10, 25, 50, 100, 150, 200, 250, 300, 400, and 500 mg L⁻¹). Boric acid, which was added to the germination media, exerted a significant stimulatory effect on both pollen germination and pollen tube growth, although pollen tube growth was inhibited at higher concentrations than 300 mg L⁻¹. Calcium nitrate addition stimulated pollen germination, except at concentration of 500 mg L⁻¹. However, pollen tube growth was significantly inhibited with increasing concentrations of calcium nitrate. In the orchard experiment, boron and calcium were sprayed at concentrations of 0, 100, 200, 500 or 1000 mg L⁻¹ onto leaves after harvest, respectively. Boron and calcium content in the tissues as well as pollen production and growth were determined after these treatments. The foliar application of boron mainly resulted in an increase of boron concentration in buds. It also induced an increase in the weight of the anther and pollen in the following year. On the other hand, the foliar application of calcium resulted in an increase of calcium concentration mainly in the leaves, but pollen weight was decreased at high concentration treatment in the following year. The germination rate and tube growth of collected pollen were highest in the trees which had received boron treatment at a concentration of 200 mg L⁻¹. In contrast, the germination rate and tube growth of collected pollen were decreased by calcium application at concentrations of 500 and 1000 mg L⁻¹ without significant increase at lower concentrations. Consequently, the accumulation of boron in the developed buds of pear trees subjected to post-harvest foliar boron application generated positive effects on both the quantity and quality of pollen in the following year.     

日光温室条件下甜樱桃授粉受精期间环境因子对花粉行为的影响

以甜樱桃(Prunus avium L.)红灯为试材,采用荧光显微技术研究了日光温室和露地条件下甜樱桃花粉行为的差异,并观察记载了授粉受精期间日光温室和露地环境因子的变化情况。结果表明,环境因子影响了甜樱桃的花粉行为,日光温室内花粉萌发和花粉管伸长速率明显落后于露地。日光温室条件下,授粉后6h花粉萌发,120h花粉管进入子房;而露地条件下,授粉后3h花粉萌发,72h花粉管进入子房。其中,气温是影响日光温室甜樱桃授粉受精进程延缓的主要环境因子。     

果梅花不同发育阶段花粉原位萌发及花粉管生长特性

为探明自花、异花花粉在果梅花的不同发育阶段原位萌发及生长的特性,以细叶青果梅为材料,取开花前6、4、2d、开花当天和花后2d的花(花蕾),分别于自花、异花授粉(莺宿)后12、24、48、72、96h切取花柱,用FAA固定液处理,荧光染色后压片观察。结果表明,自花花粉在柱头上的萌发率略低于异花(开花前4d存在显著差异),开花前6、4d极显著低于其他各阶段,花蕾越幼小花粉萌发越差,开花当天花粉萌发率超过80%;开花前4d之前的花柱内异花花粉管数量显著低于开花前2d及之后各期的,果梅开花前4d以前的花发育不充分;开花后2d生长到花柱基部的异花花粉管数量较多,属于有效授粉期。果梅在开花前4d开始具备抑制自花花粉管生长的能力,并且随着花的发育逐渐增强,开花当天最强,开花后开始减弱。果梅自交授粉期以开花前2～3d为宜。     

油橄榄花粉生活力研究

油橄榄栽培过程中,合理配置授粉树是提高油橄榄坐果率的有效措施之一,而且花粉的产量及其质量直接影响到育种的成败,因此花粉生活力测定方法及测定标准一直是育种家关注的问题.选择恰当的花粉活力测定方法对其花粉活力的变化规律进行研究,对提高油橄榄繁殖效率具有重要意义.     

枣、酸枣授粉生物学基础研究

采用离体培养技术对27个枣品种和酸枣的枣吊花蕾量、单花花粉量、花药开裂时间、花粉发芽率以及枣和酸枣单花不同开放阶段的花粉生活力和花粉贮藏特性进行了系统研究。结果表明:(1)不同枣品种和酸枣的枣吊花蕾量、单花花粉量、花粉发芽率存在极大差异,利用数量性状的概率分级体系可将它们分别分为3级;(2)枣和酸枣的花药开裂时间在蕾黄或蕾裂期;(3)从蕾裂到瓣平期的花粉发芽率极显著的高于蕾黄期、雄蕊展平期和雄蕊下垂期;(4)花粉贮藏后发芽率表现为下降—上升—下降的大体趋势。对杂交育种中父母本的选择、花粉采集和去雄的适宜时期也进行了讨论。     

果梅花粉原位萌发及花粉管生长特性的研究

以软条红梅为试材,分别于白花授粉和异花授粉后的1、3、6、12、24、48、72、96、120 h切取花柱,用FAA固定液处理、荧光染色后压片观察,结果表明:异花和自花花粉都能在柱头上萌发,但在授粉后的48 h之内异花花粉的萌发率显著高于自花花粉的萌发率,如在授粉6 h后,异花花粉萌发率高达58％,而自花花粉的萌发率仅为23％。花柱内异花花粉管生长速度明显比自花的快,在授粉后花粉管到达花柱上部、中部及基部的数目均是异花高于白花。如授粉24 h后异花花粉管平均有30余根穿过花柱上部,约有14根到达中部,有2根到达基部;而自花授粉的花粉管分别仅有18、7和0根,且白花授粉时在72 h内均未见有花粉管到达花柱基部,主要在花柱中部前后停止生长。结果表明软条红梅自花授粉的花粉管主要是在花柱中部被抑制而停止生长,从而不能完成受精,表现出典型的配子体型自交不亲和性。     

Screening Capsicum species of different origins for high temperature tolerance by in vitro pollen germination and pollen tube length

Successful fruit set depends on several reproductive processes including pollen germination and tube growth processes. An experiment was conducted to determine the effects of temperature on pollen germination characteristics and to identify species/genotypic differences in Capsicum using the cumulative temperature response index (CTRI) concept. Pollen was collected from plants of seven genotypes from five Capsicum species, adapted to various parts of the world and grown outdoors in large pots. The pollen was subjected to in vitro temperatures ranging from 15 to 50 °C at 5 °C intervals. Pollen germination and tube lengths were recorded for all species after 24 h of incubation at the respective treatments. Species/genotypes differed significantly for in vitro pollen germination percentage and pollen tube length with mean values of 78% and 734 μm, respectively. The mean cardinal temperatures (T_min, T_opt, and T_max) averaged over genotypes, were 15.2, 30.7, and 41.8 °C for pollen germination and 12.2, 31.2, and 40.4 °C for pollen tube growth. The CTRI of each species/genotype calculated as the sum of eight relative individual stress response values, such as maximum pollen germination, maximum pollen tube length; T_min, T_opt, and T_max temperatures of pollen germination, and pollen tube lengths, identified species tolerance to high temperatures. Capsicum annum cv. Mex Serrano from Mexico was identified as tolerant, C. chacoense cv. 1312 and C. spp. cv. Cobanero from Argentina and Guatemala, respectively as intermediate and C. frutescens cv. Early Spring Giant from China, C. annum cv. Long Green from South Korea, C. spp. cv. NM89C130 and C. pubescens cv. 90002 from Guatemala as sensitive to high temperatures. The tolerant species/genotypes can be used in breeding programs to develop new genotypes that can withstand high temperature conditions both in the present climate and particularly in a future warmer climate.     

柑桔花药中游离脯氨酸含量与花粉育性的关系研究

本研究首次报道柑桔花药中游离脯氨酸含量同花粉育性具有极为密切的关系。采用磺基水杨酸浸提、酸性茚三酮比色法对12个柑桔品种的检测结果表明,不同育性品种间花药游离脯氨酸含量具有极为显著的差异。育性正常型品种花药中游离脯氨酸含量很高,败育型品种其含量极低,部分败育型品种则居于二者之间。相关分析表明,花药游离脯氨酸含量同花粉萌芽率和果实种子数呈极显著正相关。利用花药游离脯氨酸含量作育性指标,对供试柑桔品种进行了育性分类探讨。