Pollen Shed Research Articles

Multiple loci not only Rf3 involved in the restoration ability of pollen fertility, anther exsertion and pollen shedding to S type cytoplasmic male sterile in maize.

Thirty loci for fertility restoration of pollen fertility, anther exsertion and pollen shedding to maize CMS-S were identified by GWAS. S type cytoplasmic male sterile (CMS-S) is the main type of CMS in maize; poor understanding of the genetic architecture of fertility restoration to CMS-S is one of the reasons to impede its utility in hybrid breeding. In this study, genome-wide identification of genetic loci for fertility restoration ability to CMS-S was firstly conducted with a set of testcrossing association mapping panel in three environments. A total of 19, 3 and 8 significant loci (P < 1.8 × 10(-6), α = 1) for pollen fertility, anther exsertion and pollen shedding were identified, respectively, and individual locus explained up to 28.26% of phenotypic variation. Of them, only Rf3, the main restorer-fertility gene of CMS-S, was identified for the three traits simultaneously. In addition, 83 candidate genes within the 100 kb extension regions of these loci were predicted. These results revealed that besides Rf3 multiple genetic loci and mechanisms are involved in the fertility restoration ability to CMS-S. Results in this study would provide important information for understanding the genetic architecture of fertility restoration to CMS-S in maize.

Scientific Opinion on application (EFSA‐GMO‐DE‐2011‐95) for the placing on the market of genetically modified maize 5307 for food and feed uses, import and processing under Regulation (EC) No 1829/2003 from Syngenta Crop Protection AG

Maize 5307 was developed by Agrobacterium tumefaciens-mediated transformation to express two proteins: eCry3.1Ab, conferring resistance to certain coleopteran pests, and phosphomannose isomerase (PMI), used as selection marker. The molecular characterisation showed relevant similarities between the amino acid sequence of PMI and a known allergen, and between the amino acid sequence of eCry3.1Ab and a potential toxin. Some agronomic and phenotypic differences between maize 5307 and its conventional counterpart were observed (higher ‘heat units to 50 % pollen shed’, grain moisture, plant height, grain yield); however, the EFSA GMO Panel considered that these do not give rise to food/feed or environmental safety concerns. No differences in the compositional data requiring further safety assessment were identified. There were no concerns regarding the potential toxicity and allergenicity of the PMI protein. The EFSA GMO Panel could not conclude on the safety of the eCry3.1Ab protein due to the inadequate 28-day toxicity study provided. The outcome of a broiler feeding study with maize 5307 was not assessed by the EFSA GMO Panel, due to study weaknesses. There are no indications of an increased likelihood of the establishment and spread of feral maize plants. Interactions with the biotic and abiotic environment were not considered to be a relevant issue. Risks associated with the unlikely but theoretically possible horizontal gene transfer of recombinant genes from maize 5307 to bacteria were not identified. The post-market environmental monitoring plan and reporting intervals are in line with the scope of the application. In conclusion, in the absence of an appropriate assessment of eCry3.1Ab, the EFSA GMO Panel is not in a position to complete its food/feed risk assessment of maize 5307. However, the EFSA GMO Panel concludes that the maize 5307 is unlikely to have any adverse effect on the environment in the context of its scope.

Evaluation of Inbred Lines and Hybrid Maize (&lt;i&gt;Zea mays&lt;/i&gt; L.) for Tolerance to &lt;i&gt;Striga&lt;/i&gt; &lt;i&gt;hermonthica&lt;/i&gt; (Del.) Benth in the Guinea Savanna Agro-Ecological Zone of Ghana

The study was conducted at the experimental field of the Savanna Agricultural Research Institute (SARI) to screen maize inbred and hybrid lines for Striga tolerance. Maize seeds of hybrid and inbred lines were collected from the West and Central African Maize Collaborative Network (WECAMAN), Boake, La Cote d’Ivoire, for the experiment. The experimental design used was the Randomized Complete Block Design (RCBD) with fourteen treatments replicated four times for the hybrids. For the inbred lines, there were twelve treatments replicated three times. The results of the hybrid experiment indicated that varieties including 9914-14 STR, 8425-8 STR, 9925-49 STR, 9916-11 STR, 9925-3 STR, CLH105 STR and CLH109 STR were comparatively better off than the others in terms of field weight and tolerance to Striga. For the inbred lines, the results indicated that GH110-5, 991228-1 and 991233-1 performed better than the rest of the varieties in terms of yield components such as plant height, days to 50% pollen shed, days to 50% silking and Striga plant rating. On Striga infested Agricultural lands, farmers can therefore use cultivars or varieties like, 9914-14 STR, 8425-8 STR, 9925-49 STR, 9916-11 STR, 9925-3 STR, CLH105 STR and CLH109 STR or their crosses in order to improve yield and hence maximize profit.

Patterns of nectar and pollen presentation influence the attractiveness of four raspberry and blackberry cultivars to pollinators

SummaryFloral rewards such as nectar and pollen have a major influence on successful pollination and fruit-set, even in selffertile Rubus sp. (Rosaceae), which include most cultivated raspberries and blackberries. A 2-year study was designed to examine the diurnal dynamics of nectar secretion and pollen shedding in the raspberry cultivars ‘Autumn Bliss’ and ‘Malling Exploit’, and in the blackberry cultivars ‘Arapaho’ and ‘Hull’, in order to establish the effect of these traits on floral attractiveness to various insect visitors. The volume of nectar secreted per flower was measured using calibrated capillaries, and the concentrations of sugars in the nectar were measured using a hand-held refractometer. The four Rubus cultivars differed in their patterns of nectar and pollen presentation. Volumes of nectar and concentrations of sugars were influenced by year, cultivar, age of the flower, and time of sampling. The four cultivars exhibited different patterns of nectar secretion over the 2 years. In year-1, an early morning peak in nectar volume was followed by a rapid decline, while the concentrations of sugars increased during the day. In year-2, both the volume of nectar and the concentrations of sugars increased from the morning to the afternoon. The patterns of pollen presentation were similar in both years of study. Anther dehiscence took only 3 - 8 h per flower in the poorest nectar producer, ‘Arapaho’; while, in cultivars with higher nectar yields, pollen shedding lasted for 6 - 10 h. Pollen-shedding flowers secreted significantly higher volumes of nectar, with significantly lower concentrations of sugars, compared to pre-pollen-shedding flowers in year-1. The concentrations of sugars in the nectar were higher in both raspberry cultivars than in the blackberry cultivars, but both blackberry cultivars were as attractive to bees due to their more appealing nectar sugar composition. Bees were more attracted to flowers of cultivars which simultaneously offered ample nectar and some pollen (i.e., ‘Autumn Bliss’, ‘Malling Exploit’, and ‘Hull’) than to flowers with a rapid rate of pollen shedding, but a low nectar yield (i.e., ‘Arapaho’). Higher rates of bee-mediated cross-pollination may provide economically important increases in fruit yields and better quality fruit.

Turbulence-induced resonance vibrations cause pollen release in wind-pollinated Plantago lanceolata L. (Plantaginaceae).

In wind pollination, the release of pollen from anthers into airflows determines the quantity and timing of pollen available for pollination. Despite the ecological and evolutionary importance of pollen release, wind-stamen interactions are poorly understood, as are the specific forces that deliver pollen grains into airflows. We present empirical evidence that atmospheric turbulence acts directly on stamens in the cosmopolitan, wind-pollinated weed, Plantago lanceolata, causing resonant vibrations that release episodic bursts of pollen grains. In laboratory experiments, we show that stamens have mechanical properties corresponding to theoretically predicted ranges for turbulence-driven resonant vibrations. The mechanical excitation of stamens at their characteristic resonance frequency caused them to resonate, shedding pollen vigorously. The characteristic natural frequency of the stamens increased over time with each shedding episode due to the reduction in anther mass, which increased the mechanical energy required to trigger subsequent episodes. Field observations of a natural population under turbulent wind conditions were consistent with these laboratory results and demonstrated that pollen is released from resonating stamens excited by small eddies whose turnover periods are similar to the characteristic resonance frequency measured in the laboratory. Turbulence-driven vibration of stamens at resonance may be a primary mechanism for pollen shedding in wind-pollinated angiosperms. The capacity to release pollen in wind can be viewed as a primary factor distinguishing animal- from wind-pollinated plants, and selection on traits such as the damping ratio and flexural rigidity may be of consequence in evolutionary transitions between pollination systems.

Male sterility systems in wheat and opportunities for hybrid wheat development

The common wheat (Triticum aestivum L.) is a poly(hexa)ploid, derived from an amphi-diploidization process involving the donor species—Triticum urartu, Aegilops speltoides, Triticum turgidum, and Aegilops tauschii. The genetic diversity of the autogamous wheat is narrow, which is a major reason for lesser rate of yield gain in wheat, in contrast to rice and maize. It is desirable to encourage hybrid breeding, i.e., combining different lines into genetically divergent heterotic pools. Thus, hybrid plants are a unique combination of desired alleles produced by crossing between genetically different parental lines. Hybrid seed production in a crop requires male-sterile female parents along with a reliable outcrossing system. The male-sterile female parent prevents pollen shedding and self-fertilization, maintaining the purity of hybrid seeds. An outcrossing system enhances hybrid seed production. This article emphasizes the biological relevance of crossbreeding and self-pollination in wheat, and reviews different male sterility systems which could be utilized for the development of hybrid wheat. Several biotechnological approaches and their practical utility in generating cross-compatible male-sterile female parent lines have been discussed.

A field study examining the effects of exposure to neonicotinoid seed-treated corn on commercial bumble bee colonies.

Neonicotinoid insecticides have been studied as possible contributors to bumble bee declines in North America and Europe. This has potential significance in corn agro-ecosystems since this crop is frequently treated with neonicotinoids and dominates much of the agricultural landscape in North America and Europe where bumble bees and other pollinators are commonplace. We conducted an experiment where commercial bumble bee (Bombus impatiens) hives were placed during pollen shed next to corn (Zea mays) fields that were grown from "conventional" seed that was treated with neonicotinoids, or "organic" seed that was not treated with pesticides. Samples of pollen were collected from corn plants for neonicotinoid residue analysis, pollen types carried by worker bees returning to hives were determined, and in autumn hives were dissected to measure various endpoints that serve as markers of colony vigor. Clothianidin was detected (0.1-0.8ng/g) in pollen collected from all conventional fields, but was not detected in pollen from organic fields. Corn pollen was only rarely collected from bumble bee foragers and the vast majority of pollen was from wild plants around the corn fields. All hives appeared healthy and neonicotinoid seed treatments had no effect on any hive endpoints measured, except the number of workers, where significantly fewer workers were recovered from hives placed next to conventional fields (96±15 workers per hive) compared to organic fields (127±17 workers per hive). The results suggest that exposure during pollen shed to corn grown from neonicotinoid-treated shed poses low risk to B. impatiens.

FLORAL PHENOLOGY BEHAVIOUR OF COMMERCIALLY GROWN AND NEW INTRODUCED HAZELNUT CULTIVARS (CORYLUS AVELLANA L.) IN BIO BIO REGION, CENTRAL-SOUTH OF CHILE

The importance of floral phenological synchrony among genetically compatible pollinizers and the main cultivar in an orchard requires a permanent evaluation of commercially grown and new introduced cultivars in all different locations where hazelnut is suitable for growing. Floral phenology of introduced hazelnut cultivars and two Chilean ecotypes used as pollinizers, were evaluated during five years (2007-2011), at Santa Rosa Experimental Farm, Quilamapu Regional Research Center, Instituto de Investigaciones Agropecuarias (INIA), latitude 36’31°34”S, longitude 71°54’40”W, Chillan, Chile. The earliest cultivars shed pollen by early or middle June; ‘San Giovanni’, ‘Barcelona’, ‘TGDL’, ‘Tonda di Giffoni’, ‘Gem’, ‘Segorbe’, ‘Ennis’, ‘Pauetet’, ‘Mortarella’, ‘Ribet’, ‘Ghirara’ and ‘Ianussa Racinante’, while ‘Willamette’, ‘Montebello’, ‘Butler’, shed by middle of June and most of them during middle of July and early August; ‘Clark’, ‘Gamma’, ‘Lewis’, ‘Zeta’, ‘Santiam’, OSU 504-130 and ‘Delta’, while ‘Epsilon’ starts shedding pollen by the end of July and early August. Stigma receptivity in the other side, in the earliest ones took place by middle of May; ‘Negret’, middle or late June; ‘Mortarella’, ‘Amarillo’, ‘Barcelona’, ‘San Giovanni’ and ‘Iannusa Racinante’ and middle or end of July; ‘Ghirara’, ‘Butler’, ‘Verde’, ‘Pauetet’, ‘Lewis’, OSU 504-130, ‘Ribet’ and ‘Zeta’, while ‘Casina’, ‘Hall’s Giant’ and ‘Butler’ by end of July or early August. Finally, ‘Willamette’, ‘Gem’, ‘Segorbe’, ‘Epsilon’, ‘Ennis’, ‘Clark’, ‘Gamma’, ‘Delta’ and ‘Pauetet’ show receptive stigmas by middle or end of August.

Effect of spring and autumn sowing on morphological attributes of sweet corn genotypes

Two field experiments were conducted at National Agriculture Research council Islamabad during 2012-2013 growing season. The 15 sweet corn varieties from diverse geographic origins were chosen to study the morphological traits such as days to maturity, mid node antocyanin, internode length, cob leaf length and width, leaves per plant, ear height, plant height,50% pollen shedding, tessel characters, 50% silk emergence and cob characters. Seed characteristics have also been recorded to have an analysis on yield to check the effect of sowing season. Results showed spring sowing was on average has better effect on sweet corn growth as compared to autumn season. Spring season has resulted better plant height and yield as compared to autumn season.

Flowering Phenology of Eastern Filbert Blight-resistant Hazelnut Accessions in New Jersey

Hazelnuts (Corylus sp.) are monoecious and wind-pollinated with reproduction limited by a sporophytic self-incompatibility system. They flower during the winter and are dichogamous with the dates of flowering ranging from December to March in New Jersey depending on the genotype, geographic location, and year. Successful, consistent nut production depends on both genetic compatibility and the appropriate timing of flowering between pollinizing and nut-producing cultivars. While the disease eastern filbert blight (EFB), caused by Anisogramma anomala, has severely limited past hazelnut production in the eastern United States, resistant and tolerant genotypes are now available for testing. However, little is known of their flowering phenology in this region. In this study, the flower and budbreak phenology of 19 different EFB-resistant and EFB-tolerant hazelnut accessions was evaluated over 4 years, and the results compared with air temperature data collected during bloom. Results showed that the accessions followed a similar progression of bloom each year (both staminate and pistillate flowers), which allowed their placement into early-, mid-, and late-flowering groups. However, the date of bloom and duration of bloom, especially for pollen shed, differed each year, largely corresponding to average air temperature trends. Confirming previous reports from other cold regions, it was shown that consistently colder average temperatures delayed bloom until later in the winter, which then led to a compressed period of flowering once temperatures warmed. In contrast, relatively warm temperatures over the season led to earlier flowering as well as a significant lengthening of the duration of bloom, similar to responses reported in Mediterranean climates. Our study documents hazelnut flowering phenology under New Jersey’s variable winter climate, and the results provide a benchmark for selecting suitable pollenizers and breeding parents for future nut production, flowering research, and/or genetic improvement in this region.

FORAGES AND PASTURES SYMPOSIUM: Development of and field experience with drought-tolerant maize1

Drought-tolerant maize hybrids currently are being marketed by several seed suppliers. Such hybrids were developed by phenotypic and marker-assisted selection or through genetic modification and tested by exposing these hybrids to various degrees of water restriction. As drought intensifies, crop yields and survival progressively decline. Water need differs among plants due to differences in root structure, evaporative loss, capacity to store water or enter temporary dormancy, and plant genetics. Availability of water differs widely not only with rainfall and irrigation but also with numerous soil and agronomic factors (e.g., soil type, slope, seeding rates, tillage practices). Reduced weed competition, enhanced pollen shed and silk production, and deep, robust root growth help to reduce the negative impacts of drought. Selected drought-tolerant maize hybrids have consistently yielded more grain even when drought conditions are not apparent either due to reduced use of soil water reserves before water restriction or due to greater tolerance of intermittent water shortages. In DuPont Pioneer trials, whole plant NDF digestibility of maize increased with water restriction, perhaps due to an increased leaf to stem ratio. Efficiency of water use, measured as dry matter or potential milk yield from silage per unit of available water, responded quadratically to water restriction, first increasing slightly but then decreasing as water restriction increased. For grain production, water restriction has its greatest negative impact during or after silking through reducing the number of kernels and reducing kernel filling. For silage production, water restriction during the vegetative growth stage negatively impacts plant height and biomass yield. Earlier planting and shorter season maize hybrids help to avoid midsummer heat stress during pollination and can reduce the number of irrigation events needed. Although drought tolerance of maize hybrids has been improved due to genetic selection or biotech approaches, selecting locally adapted hybrids or crops, adjusting seeding rates, and modifying tillage and irrigation practices are important factors that can improve efficiency of use of available water by grain and forage crops.

Temperature DIP at the beginning of the photoperiod reduces plant height but not seed yield of maize grown in controlled environments

A semi-dwarf breeding line of maize (Zea mays L., PI 587154) was grown from seed to seed in a growth chamber either at 26.7°C days/18.3°C nights (control treatment) or at 15.6°C for the first 2h of each photoperiod before being returned to standard control temperature for the rest of the photoperiod (DIP treatment). Half of the plants in each 120-day production experiment were grown in 3-L containers and half in 9-L containers, both groupings at equivalent plant-to-plant spacing. Stalks of DIP-treated plants elongated 9–10% less than controls during seed-production cycles in both pot sizes. DIP reduced vegetative dry biomass of stalks 29% relative to controls when using small pots, and 19% for plants grown in medium pots. Root dry weight was reduced 22–25% by DIP in the two container sizes, but stalk/root ratios were not altered significantly by DIP treatment or pot size. Stalk diameter also was reduced 8–9% by DIP for both pot sizes. Neither seed number nor seed weight were affected significantly by temperature treatment or pot size. DIP slowed and prolonged stalk elongation but not differentiation of nodes for both pot sizes. Timing of tassel development and pollen shed were unaffected by temperature or pot size, but timing of silk development was delayed by DIP, slightly more for plants growing in small than in medium pots. Nevertheless, primary ears developed to complete seed fill, suggesting adequate time-window overlap between pollen shed and silk receptivity for effective pollination and fertilization to occur. Controlled-environment production of maize in restricted-height growth facilities or where adequate separation distance is required between the tops of crop stands and overhead high-intensity discharge light sources may be accommodated economically by use of DIP temperature treatments without compromising grain yield. Use of medium-volume containers stabilizes the mature maize stalks bearing grain-filled ears.

Polinização e biologia reprodutiva de Araticum-liso (Annona coriacea Mart.: Annonaceae) em uma área de cerrado paulista: implicações para fruticultura

Anonáceas, em geral, são espécies cantarófilas e altamente especializadas, apresentando pétalas espessas, carnosas e nutritivas que formam uma câmara floral com ocorrência de termogênege. Este estudo objetivou verificar os efetivos polinizadores e sistema reprodutivo prevalente em A. coriacea. Flores foram marcadas e acompanhadas durante períodos do dia e da noite para verificar os polinizadores legítimos. Tratamentos de polinização manual foram realizados para determinar o sistema reprodutivo. Besouros escarabeídeos Cyclocephala atricapilla e Cyclocephala quatuordecimpunctata (Dynastinae) foram atraídos pelo odor emitido pelas flores no início da noite já contendo pólen em seus corpos e penetraram na câmara floral, onde permaneceram por até 48h alimentando-se das pétalas e de pólen, copulando, e ao tocarem nos estigmas receptivos, depositaram pólen. Posteriormente, flores em fase masculina liberaram pólen que novamente sujou o corpo dos besouros e, com a queda da flor, voaram para outra flor recém-aberta e em fase feminina, iniciando novo ciclo de polinização. A. coriacea é uma espécie autocompatível e Cyclocephala foram polinizadores muito eficientes.

Characteristics of blooming and pollen in flowers of two Syringa species (f. Oleaceae)

The observations were conducted in long-term sequence studies in the years 2006, 2009, 2013, in the Lublin area, Poland (51o 16’ N, 22o 30’ E). The flowering phenology, diurnal pattern of blooming, pollen production and insect visitation to the shrubs of &lt;em&gt;Syringa oblata &lt;/em&gt;Lindl. &lt;em&gt;var. dilatata &lt;/em&gt;(Nakai) Rehd. and &lt;em&gt;S. meyeri ‘Palibin’ &lt;/em&gt;Schn. were examined. &lt;em&gt;Syringa oblata &lt;/em&gt;var. &lt;em&gt;dilatata &lt;/em&gt;and &lt;em&gt;S. meyeri &lt;/em&gt;‘Palibin’ blo- omed from the mid May till mid June. The species are characteristic of early morning diurnal pattern of blooming, with approx. of 60% of daily instalment of flowers opened before 9.00 (GMT + 2h). Both species studied had the corolla tube 2-fold deeper during the pollen shedding phase compared to bud stage (mean = 14.9 mm ± 3.2 SD vs. 7.8 mm ± 2.8). No species effect was found for the size of anthers, for the mass of pollen produced in anthers and for the pollen viability. A constant number of 2 stamens in the flowers of &lt;em&gt;Syringa &lt;/em&gt;species entailed the pollen yield was derivative mainly to the number of developed flowers. Therefore significant differences were noted for the pollen yield between individual shrubs (mean 0.9 kg for &lt;em&gt;S. meyeri &lt;/em&gt;‘Palibin’, and 8.1 kg/ha for &lt;em&gt;S. oblata &lt;/em&gt;var. &lt;em&gt;dilatata &lt;/em&gt;). The &lt;em&gt;Syringa oblata &lt;/em&gt;var. &lt;em&gt;dilatata &lt;/em&gt;and &lt;em&gt;S. meyeri &lt;/em&gt;‘Palibin’ due to their attractive flowering period, and the abundance of blooming are suitable for different ornamental designs in urban areas. Unfortunately, despite the entomophilous flower traits, the insect visitors appeared sporadically.

Origin and structure of Ubisch bodies in Pinus sylvestris

In &lt;em&gt;Pinus sylvestris&lt;/em&gt; Ubisch bodies are produced repeatedly, and each crop is formed at a distinct phase in the secretory cycles of tapetal cells. While each production has a Ubisch body wall similar to the then current state of the exine with regard to thickening and ornamentation, the survivers of previous productions do not change. Examples of all the structurally different Ubisch body wall forms can be seen when terminally, at the time of pollen shedding, the relict Ubisch bodies become spatially concentrated on the minimal surface area of the senescent cells of the tapetum. In angiosperms after one or a few periods of initiation Ubisch bodies may remain in association with the surface of tapetal cells where the Ubisch body wall undergoes changes like those of the maturing pollen exine. We conclude that as a consequence of Ubisch body detachment from the plasma membrane of tapetal cells there is in &lt;em&gt;Pinus sylvestris&lt;/em&gt; no updated information for modification of the wall and the Ubisch body wall remains static.

Discovery and Characterization of a Turf-type Triploid Seashore Paspalum

Seashore paspalum is a salt tolerant, predominately diploid (2n = 2x = 20) species that is well adapted to coastal regions in tropical and subtropical environments. Because a majority of the available cultivars are propagated vegetatively and most genotypes are cross-fertile, a sterile cultivar that does not produce segregating seedlings would benefit sod growers and turfgrass managers who demand uniformity for certification and performance. Therefore, an experiment was conducted to create a colchicine-induced polyploid seashore paspalum. One triploid (2n = 3x = 30) genotype (11-TSP-1) was identified and remains stable. Although there is a possibility that this event was triggered by the colchicine treatment, a more likely explanation is that it resulted from the union of a reduced and an unreduced gamete. Pollen shed was observed from 11-TSP-1 in 2011, but individual pollen grains stained with iodine–potassium iodide were irregularly shaped and typically had lower starch content than pollen from several diploid cultivars. The leaf width of 11-TSP-1 was statistically equal to that of the seashore paspalum cultivar SeaStar, indicating its potential for use as a fine turf. 11-TSP-1 had both superior visual color and a dark green color index when compared with ‘SeaStar’. Future study of the reproductive fertility and more extensive field testing of this genotype should be carried out to determine its turfgrass potential. Chemical names used: 4′, 6-diamidino-2-phenylindole (DAPI), dimethyl sulfoxide (DMSO), iodine-potassium iodide (I2-KI), propidium iodide (PI).

Temperature regulation of floral buds and floral thermogenicity in Magnolia denudata (Magnoliaceae)

The gynoecium in M. denudata was thermogenic, and the first peak in the female phase lasted longer than the second peak in the male phase during flowering. The floral biology of Magnolia denudata, including the thermogenesis of floral buds and blooming, were investigated using a portable infrared thermal imaging radiometer and digital infrared thermometer. We found that M. denudata buds have extremely dense trichomes that maintain internal temperatures above external temperatures. The pattern of thermogenesis in M. denudata anthesis consisted of two distinct episodes corresponding to apparent receptivity of the stigmas in the female phase and incipient shedding of pollen in the male phase: one begins in the female phase and lasts about 6 h and another occurs synchronously 24 h later and lasts about 4 h in the male phase. In addition, we found that the temperature was significantly elevated in the inner petals upon flowering, indicating that they may play an important role in producing a warm floral chamber. These results increase our understanding of the strategies used by Magnoliaceae blossoms to maintain an optimal microclimate at low temperatures in the early spring.

Updated Empirical Model of Genetically Modified Maize Grain Production Practices to Achieve European Union Labeling Thresholds

ABSTRACTAn updated empirical approach is proposed for specifying coexistence requirements for genetically modified (GM) maize (Zea mays L.) production to ensure compliance with the 0.9% labeling threshold for food and feed in the European Union. The model improves on a previously published (Gustafson et al., 2006) empirical model by adding recent data sources to supplement the original database and including the following additional cases: (i) more than one GM maize source field adjacent to the conventional or organic field, (ii) the possibility of so‐called “stacked” varieties with more than one GM trait, and (iii) lower pollen shed in the non‐GM receptor field. These additional factors lead to the possibility for somewhat wider combinations of isolation distance and border rows than required in the original version of the empirical model. For instance, in the very conservative case of a 1‐ha square non‐GM maize field surrounded on all four sides by homozygous GM maize with 12 m isolation (the effective isolation distance for a single GM field), non‐GM border rows of 12 m are required to be 95% confident of gene flow less than 0.9% in the non‐GM field (with adventitious presence of 0.3%). Stacked traits of higher GM mass fraction and receptor fields of lower pollen shed would require a greater number of border rows to comply with the 0.9% threshold, and an updated extension to the model is provided to quantify these effects.

Rate of Shattercane × Sorghum Hybridization In Situ

ABSTRACTCultivated sorghum [Sorghum bicolor (L.) Moench subsp. bicolor] can interbreed with a feral weedy relative shattercane [S. bicolor nothosubsp. drummondii (Steud.) de Wet ex Davidse]. Traits introduced from cultivated sorghum could contribute to the invasiveness of a shattercane population. An experiment was conducted to determine the potential for pollen‐mediated gene flow from grain sorghum to shattercane. Shattercane with juicy midrib (dd) was planted in soybean [Glycine max (L.) Merr.] fields during 2 yr in concentric arcs at varying distances from a 0.39 ha sorghum pollen source with dry midrib (DD). The arcs were placed so that prevailing winds would carry sorghum pollen to the shattercane. Seven hundred twenty seeds from each of over 300 shattercane panicles in anthesis during sorghum pollen shed each year were collected. Progeny were evaluated by phenotype to determine rate of hybridization. Hybridization averaged 3.6% within the source in 2008 and 16.0% in 2009 and declined as distance increased. Hybridization as high as 2.6% for an individual panicle was measured at the farthest distance evaluated (200 m). Wind direction and speed were also measured and their product affected hybridization rate for all pollination periods. Results indicate that genes from cultivated sorghum will likely be introduced into shattercane populations at distances of at least 200 m and that rate of hybridization is dependent on weather factors such as wind. Source size is also important in determining hybridization rate but was not studied here.

Studies On Genetic Divergence In Maize (Zea mays) Inbreds

Genetic divergence in 17 CIMMYT Maize inbred lines including one check were assessed based on some morphological traits and grain yield using Mahalanobis’ D2-statistics. The experiment was carried out in alpha lattice design with two replications at Regional Agricultural Research Station, Ishurdi Pabna during the winter 2010-2011. The genotypes were grouped into four clusters. The cluster II contained the highest number of lines (6), while the cluster I contained only single genotype. The maximum inter-cluster distance was noticed between the cluster I and IV and minimum between cluster I and II. The highest intra-cluster distance was observed in the cluster IV and lowest in cluster I. The genotypes in the cluster III showed better performances having shorter growth duration, short stature, shortest ear height, better shelling percentage and reasonable yielding ability. It is expected that crossing of inbred lines belonging high to medium D2 values may tend to produce high heterosis for yield. Ear aspect had the greatest contribution to the genetic divergence. Days to pollen shedding, silking, maturity, and 1000-grain weight were found to be responsible for primary differentiation. Bangladesh J. Agril. Res. 38(1): 71-76, March 2013 DOI: http://dx.doi.org/10.3329/bjar.v38i1.15191