Autocorrelation analysis for the unbiased determination of power-law exponents in single-quantum-dot blinking

We present an unbiased and robust analysis method for power-law blinking statistics in the photoluminescence of single nano-emitters, allowing us to extract both the bright- and dark-state power-law exponents from the emitters' intensity autocorrelation functions. As opposed to the widely-used threshold method, our technique therefore does not require discriminating the emission levels of bright and dark states in the experimental intensity timetraces. We rely on the simultaneous recording of 450 emission timetraces of single CdSe/CdS core/shell quantum dots at a frame rate of 250 Hz with single photon sensitivity. Under these conditions, our approach can determine ON and OFF power-law exponents with a precision of 3% from a comparison to numerical simulations, even for shot-noise-dominated emission signals with an average intensity below 1 photon per frame and per quantum dot. These capabilities pave the way for the unbiased, threshold-free determination of blinking power-law exponents at the micro-second timescale

Tolerance to ToLCNDV in Cucurbita spp

[EN] Tomato leaf curl New Delhi virus (ToLCNDV) is a bipartite begomovirus (Geminiviridae) firstly reported in India and neighboring countries. A severe outbreak of ToLCNDV in Zucchini (Cucurbita pepo) occurred in southern Spain in 2012. Mechanical inoculation and natural infection with Bemisia tabaci, in Almeria, were used to screen part of the COMAV's Cucurbita core collection. The tolerance was assessed by symptomatology and by a PCR-based diagnostic method that allows the detection of the two viral components in a single reaction. Mechanical transmission of ToLCNDV was confirmed in all the species. Severe symptoms were found 30 and 35 days after mechanical and natural inoculation, respectively, in C. pepo, in all accessions belonging to the Zucchini morphotype and to other morphotypes of the subsp. pepo, subsp. ovifera and even in the wild relative C. fraterna. Cucurbita maxima and C. ficifolia were also highly susceptible. The only species showing tolerance was C. moschata. Instead of curling, which was typically observed in most Cucurbita species, in C. moschata we observed mosaic and mottling, which suggest a differential response of this species. Under natural infection, a few C. moschata accessions remained asymptomatic and no virus was detected in the plant apex. Under mechanical inoculation, ToLCNDV symptoms were mild and delayed in these accessions and they were PCR positive. Some of the more tolerant accessions came from India.This work was supported by Project E_RTAE2013-00020-C04-03 from the Spanish Instituto Nacional de Investigaciones Agrarias (INIA) cofunded with FEDER funds.Sáez-Sánchez, C.; Martínez-Martínez, C.; Ferriol Molina, M.; Manzano, S.; Jamilena, M.; López Del Rincón, C.; Picó Sirvent, MB. (2017). Tolerance to ToLCNDV in Cucurbita spp. Acta Horticulturae. (1151):31-35. https://doi.org/10.17660/ActaHortic.2017.1151.6S3135115

Resistance to Tomato leaf curl New Delhi virus in Cucurbita spp

[EN] Tomato leaf curl New Delhi virus (ToLCNDV) is a bipartite begomovirus (family Geminiviridae) first reported in India and its neighbouring countries. ToLCNDV severely affects zucchini crop (Cucurbita pepo) in the main production areas of Southern Spain since 2012. This emerging begomovirus is a serious threat to this and other cucurbit crops. Breeding resistant cultivars is the most promising method for disease control, but requires the identification of sources of resistance in the Cucurbita genus. In this work, we screened for ToLCNDV resistance a large collection of Cucurbita spp. accessions, including landraces and commercial cultivars of the main cultivated species, C. pepo, Cucurbita moschata and Cucurbita maxima and wild species. The screening was performed using mechanical and whitefly inoculation. The level of resistance was assessed by scoring symptom severity and bymeasuring the virus content with quantitative polymerase chain reaction in selected genotypes. Diversity in the response was observed within and among species. Severe symptoms and high viral amounts were found at 30 days after mechanical and whitefly inoculation in C. pepo, in all accessions belonging to the Zucchini morphotype and to other morphotypes of both subspecies, pepo and ovifera, and even in the wild relative Cucurbita fraterna. C. maxima was also highly susceptible. This species showed characteristic symptoms of leaf decay and intense yellowing, different from those of mosaic, curling and internode shortening found in C. pepo. The only species showing resistance was C. moschata. Four accessions were symptomless or had some plants with only mild symptoms after three independent rounds of mechanical inoculation with different inoculum sources. Two of them also remained symptomless after virus inoculation with viruliferous whiteflies. ToLCNDV was detected in these asymptomatic accessions at 15 and 30 days post inoculation, but viral amounts were much lower than those found in susceptible genotypes, suggesting a high level of resistance. The symptoms in the susceptible accessions of this specieswere also different, with a characteristic leaf mottling, evolving to a severe mosaic. The newly identified C. moschata resistant accessions are good candidates for breeding programmes to avoid the damage caused by ToLCNDV.This work was supported by Projects E_RTAE2013-00020-C04-03 and E-RTA2013-00020-C04-01 from the Spanish Instituto Nacional de Investigaciones Agrarias (INIA) cofunded with FEDER funds.Sáez Sánchez, C.; Martínez Martínez, C.; Ferriol Molina, M.; Manzano, S.; Velasco, L.; Jamilena, M.; López Del Rincón, C.... (2016). Resistance to Tomato leaf curl New Delhi virus in Cucurbita spp. ANNALS OF APPLIED BIOLOGY. 169(1):91-105. https://doi.org/10.1111/aab.12283S91105169

Stratification strength and light climate explain variation in chlorophyll a at the continental scale in a European multilake survey in a heatwave summer.

To determine the drivers of phytoplankton biomass, we collected standardized morphometric, physical, and biological data in 230 lakes across the Mediterranean, Continental, and Boreal climatic zones of the European continent. Multilinear regression models tested on this snapshot of mostly eutrophic lakes (median total phosphorus [TP] = 0.06 and total nitrogen [TN] = 0.7 mg L 1), and its subsets (2 depth types and 3 climatic zones), show that light climate and stratification strength were the most significant explanatory variables for chlorophyll a (Chl a) variance. TN was a significant predictor for phytoplankton biomass for shallow and continental lakes, while TP never appeared as an explanatory variable, suggesting that under high TP, light, which partially controls stratification strength, becomes limiting for phytoplankton development. Mediterranean lakes were the warmest yet most weakly stratified and had significantly less Chl a than Boreal lakes, where the temperature anomaly from the long-term average, during a summer heatwave was the highest (+4 C) and showed a significant, exponential relationship with stratification strength. This European survey represents a summer snapshot of phytoplankton biomass and its drivers, and lends support that light and stratification metrics, which are both affected by climate change, are better predictors for phytoplankton biomass in nutrient-rich lakes than nutrient concentrations and surface temperature

Grafting Snake Melon [Cucumis melo L. subsp. melo Var. flexuosus (L.) Naudin] in Organic Farming: Effects on Agronomic Performance; Resistance to Pathogens; Sugar, Acid, and VOC Profiles; and Consumer Acceptance

The performance of snake melon [Cucumis melo var. flexuosus (L.)] in organic farming was studied under high biotic and salt stress conditions. Soilborne diseases (mainly caused by Macrophomina phaseolina and Neocosmospora falciformis), combined with virus incidence [Watermelon mosaic virus (WMV), Zucchini yellow mosaic virus (ZYMV), and Tomato leaf curl New Delhi virus (ToLCNDV)] and Podosphaera xanthii attacks, reduced yield by more than 50%. Snake melon susceptibility to M. phaseolina and Monosporascus cannonballus was proved in pathogenicity tests, while it showed some degree of resistance to Neocosmospora keratoplastica and N. falciformis. On the contrary, salt stress had a minor impact, although a synergic effect was detected: yield losses caused by biotic stress increased dramatically when combined with salt stress. Under biotic stress, grafting onto the melon F1Pat81 and wild Cucumis rootstocks consistently reduced plant mortality in different agroecological conditions, with a better performance compared to classic Cucurbita commercial hybrids. Yield was even improved under saline conditions in grafted plants. A negative effect was detected, though, on consumer acceptability, especially with the use of Cucurbita rootstocks. Cucumis F1Pat81 rootstock minimized this side effect, which was probably related to changes in the profile of sugars, acids, and volatiles. Grafting affected sugars and organic acid contents, with this effect being more accentuated with the use of Cucurbita rootstocks than with Cucumis. In fact, the latter had a higher impact on the volatile organic compound profile than on sugar and acid profile, which may have resulted in a lower effect on consumer perception. The use of Cucumis rootstocks seems to be a strategy to enable organic farming production of snake melon targeted to high-quality markets in order to promote the cultivation of this neglected crop.

The response of extracellular polymeric substances production by phototrophic biofilms to a sequential disturbance strongly depends on environmental conditions

Phototrophic biofilms are exposed to multiple stressors that can affect them both directly and indirectly. By modifying either the composition of the community or the physiology of the microorganisms, press stressors may indirectly impact the ability of the biofilms to cope with disturbances. Extracellular polymeric substances (EPS) produced by the biofilm are known to play an important role in its resilience to various stresses. The aim of this study was to decipher to what extent slight modifications of environmental conditions could alter the resilience of phototrophic biofilm EPS to a realistic sequential disturbance (4-day copper exposure followed by a 14-day dry period). By using very simplified biofilms with a single algal strain, we focused solely on physiological effects. The biofilms, composed by the non-axenic strains of a green alga (Uronema confervicolum) or a diatom (Nitzschia palea) were grown in artificial channels in six different conditions of light intensity, temperature and phosphorous concentration. EPS quantity (total organic carbon) and quality (ratio protein/polysaccharide, PN/PS) were measured before and at the end of the disturbance, and after a 14-day rewetting period. The diatom biofilm accumulated more biomass at the highest temperature, with lower EPS content and lower PN/PS ratio while green alga biofilm accumulated more biomass at the highest light condition with lower EPS content and lower PN/PS ratio. Temperature, light intensity, and P concentration significantly modified the resistance and/or recovery of EPS quality and quantity, differently for the two biofilms. An increase in light intensity, which had effect neither on the diatom biofilm growth nor on EPS production before disturbance, increased the resistance of EPS quantity and the resilience of EPS quality. These results emphasize the importance of considering the modulation of community resilience ability by environmental conditions, which remains scarce in the literature

Influence of phenological barriers and habitat differentiation on the population genetic structure of the balearic endemic Rhamnus ludovici-salvatoris Chodat and R. alaternus L

[EN] Rhamnus ludovici-salvatoris, endemic to the Gymnesian Islands, coexists with the related and widespread R. alaternus in Mallorca and Menorca. In both species, the population genetic structure using RAPD, and flowering during a 3-year period to check for possible phenological barriers, were analyzed. Rhamnus ludovici-salvatoris showed lower genetic diversity and stronger population structure than R. alaternus, the Cabrera population being less diverse and the most differentiated. Rhamnus ludovici-salvatoris flowered one month later, although flowering of both species coincided sporadically. These congeners seem to have diverged through isolation by time and differentiation in habitat. The population genetic structure of R. ludovici-salvatoris could mainly be due to the existence of small populations on the one hand, and a gene flow caused by rare hybridization events on the other, which may also explain the presence of morphologically intermediate individuals in Menorca. The conservation of R. ludovici-salvatoris populations may include population reinforcements and other in situ interventions.Ferriol Molina, M.; Llorens García, L.; Gil, L.; Boira Tortajada, H. (2009). Influence of phenological barriers and habitat differentiation on the population genetic structure of the balearic endemic Rhamnus ludovici-salvatoris Chodat and R. alaternus L. Plant Systematics and Evolution. 277(1-2):105-116. doi:10.1007/s00606-008-0110-3S1051162771-2Affre L, Thompson JD, Debussche M (1997) Genetic structure of continental and island populations of the Mediterranean endemic Cyclamen balearicum (Primulaceae). Amer J Bot 84(4): 437–451BOIB (2005) Decreto 75/2005. BOIB 106: 29–32Bolmgren K, Oxelman B (2004) Generic limits in Rhamnus L. s.l. (Rhamnaceae) inferred from nuclear and chloroplast DNA sequence phylogenies. Taxon 53(2):383–390Bolòs O, Molinier R (1958) Recherches phytosociologiques dans l’île de Majorque. 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Pyrolysis of medium-density fiberboard: optimized search for kinetics scheme and parameters via a genetic algorithm driven by Kissinger's method

The pyrolysis kinetics of charring materials plays an important role in understanding material combustions especially for construction materials with complex degradation chemistry. Thermogravimetric analysis (TGA) is frequently used to study the heterogeneous kinetics of solid fuels; however, there is no agreed method to determine the pyrolysis scheme and kinetic parameters for charring polymers with multiple components and competing reaction pathways. This study develops a new technique to estimate the possible numbers of species and sub-reactions in pyrolysis by analyzing the second derivatives of thermogravimetry (DDTG) curves. The pyrolysis of a medium-density fiberboard (MDF) in nitrogen is studied in detail, and the DDTG curves are used to locate the temperature of the peak mass-loss rate for each sub-reaction. Then, on the basis of the TG data under multiple heating rates, Kissinger’s method is used to quickly find the possible range of values of the kinetic parameters (<i>A</i> and <i>E</i>). These ranges are used to accelerate the optimization of the inverse problem using a genetic algorithm (GA) for the kinetic and stoichiometric parameters. The proposed method and kinetic scheme found are shown to match the experimental data and are able to predict accurately results at different heating rates better than Kissinger’s method. Moreover, the search method (K–K method) is highly efficient, faster than the regular GA search alone. Modeling results show that, as the TG data available increase, the interdependence among kinetic parameters becomes weak and the accuracy of the first-order model declines. Furthermore, conducting TG experiment under multiple heating rates is found to be crucial in obtaining good kinetic parameters

Allogamy-Autogamy Switch Enhance Assortative Mating in the Allotetraploid Centaurea seridis L. Coexisting with the Diploid Centaurea aspera L. and Triggers the Asymmetrical Formation of Triploid Hybrids

[EN] Hybridization between tetraploids and its related diploids is generally unsuccessful in Centaurea, hence natural formation of triploid hybrids is rare. In contrast, the diploid Centaurea aspera and the allotetraploid C. seridis coexist in several contact zones where a high frequency of triploid hybrids is found. We analyzed the floral biology of the three taxa to identify reproductive isolation mechanisms that allow their coexistence. Flowering phenology was recorded, and controlled pollinations within and between the three taxa were performed in the field. Ploidy level and germination of progeny were also assessed. There was a 50% flowering overlap which indicated a phenological shift. Diploids were strictly allogamous and did not display mentor effects, while tetraploids were found to be highly autogamous. This breakdown of self-incompatibility by polyploids is first described in Centaurea. The asymmetrical formation of the hybrid was also found: all the triploid intact cypselae came from the diploid mothers pollinated by the pollen of tetraploids. Pollen and eggs from triploids were totally sterile, acting as a strong triploid block. These prezygotic isolation mechanisms ensured higher assortative mating in tetraploids than in diploids, improving its persistence in the contact zones. However these mechanisms can also be the cause of the low genetic diversity and high genetic structure observed in C. seridis.Ferriol Molina, M.; Garmendia, A.; Ana Gonzalez; Merle Farinós, HB. (2015). Allogamy-Autogamy Switch Enhance Assortative Mating in the Allotetraploid Centaurea seridis L. Coexisting with the Diploid Centaurea aspera L. and Triggers the Asymmetrical Formation of Triploid Hybrids. PLoS ONE. 10(10):1-13. doi:10.1371/journal.pone.0140465S1131010Jiao, Y., Wickett, N. J., Ayyampalayam, S., Chanderbali, A. S., Landherr, L., Ralph, P. E., … dePamphilis, C. W. (2011). Ancestral polyploidy in seed plants and angiosperms. Nature, 473(7345), 97-100. doi:10.1038/nature09916Wood, T. E., Takebayashi, N., Barker, M. S., Mayrose, I., Greenspoon, P. B., & Rieseberg, L. H. (2009). The frequency of polyploid speciation in vascular plants. Proceedings of the National Academy of Sciences, 106(33), 13875-13879. doi:10.1073/pnas.0811575106ROMASCHENKO, K., ERTUǦRUL, K., SUSANNA, A., GARCIA-JACAS, N., UYSAL, T., & ARSLAN, E. (2004). New chromosome counts in the Centaurea Jacea group (Asteraceae, Cardueae) and some related taxa. Botanical Journal of the Linnean Society, 145(3), 345-352. doi:10.1111/j.1095-8339.2004.00292.xHardy, O. J., de Loose, M., Vekemans, X., & Meerts, P. (2001). Allozyme segregation and inter-cytotype reproductive barriers in the polyploid complex Centaurea jacea. Heredity, 87(2), 136-145. doi:10.1046/j.1365-2540.2001.00862.xKOUTECKÝ, P., BAĎUROVÁ, T., ŠTECH, M., KOŠNAR, J., & KARÁSEK, J. (2011). Hybridization between diploidCentaurea pseudophrygiaand tetraploidC. jacea(Asteraceae): the role of mixed pollination, unreduced gametes, and mentor effects. Biological Journal of the Linnean Society, 104(1), 93-106. doi:10.1111/j.1095-8312.2011.01707.xKoutecký, P. (2012). A diploid drop in the tetraploid ocean: hybridization and long-term survival of a singular population of Centaurea weldeniana Rchb. (Asteraceae), a taxon new to Austria. Plant Systematics and Evolution, 298(7), 1349-1360. doi:10.1007/s00606-012-0641-5Mráz, P., Španiel, S., Keller, A., Bowmann, G., Farkas, A., Šingliarová, B., … Müller-Schärer, H. (2012). Anthropogenic disturbance as a driver of microspatial and microhabitat segregation of cytotypes of Centaurea stoebe and cytotype interactions in secondary contact zones. Annals of Botany, 110(3), 615-627. doi:10.1093/aob/mcs120Olšavská, K., & Löser, C. J. (2013). Mating System and Hybridization of the Cyanus triumfetti and C. montanus Groups (Asteraceae). Folia Geobotanica, 48(4), 537-554. doi:10.1007/s12224-013-9155-3Španiel, S., Marhold, K., Hodálová, I., & Lihová, J. (2008). Diploid and Tetraploid Cytotypes of Centaurea stoebe (Asteraceae) in Central Europe: Morphological Differentiation and Cytotype Distribution Patterns. Folia Geobotanica, 43(2), 131-158. doi:10.1007/s12224-008-9008-7HARDY, O. J., VANDERHOEVEN, S., DE LOOSE, M., & MEERTS, P. (2000). Ecological, morphological and allozymic differentiation between diploid and tetraploid knapweeds (Centaurea jacea) from a contact zone in the Belgian Ardennes. New Phytologist, 146(2), 281-290. doi:10.1046/j.1469-8137.2000.00631.xFerriol, M., Garmendia, A., Ruiz, J. J., Merle, H., & Boira, H. (2012). Morphological and molecular analysis of natural hybrids between the diploidCentaurea asperaL. and the tetraploidC. seridisL. (Compositae). 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