Urediospores of rust fungi are ice nucleation active at > -10°C and harbor ice nucleation active bacteria

Various features of the biology of the rust fungi and of the epidemiology of the plant diseases they cause illustrate the important role of rainfall in their life history. Based on this insight we have characterized the ice nucleation activity (INA) of the aerially disseminated spores (urediospores) of this group of fungi. Urediospores of this obligate plant parasite were collected from natural infections of 7 species of weeds in France, from coffee in Brazil and from field and greenhouse-grown wheat in France, the USA, Turkey and Syria. Immersion freezing was used to determine freezing onset temperatures and the abundance of ice nuclei in suspensions of washed spores. Microbiological analyses of spores from France, the USA and Brazil, and subsequent tests of the ice nucleation activity of the bacteria associated with spores were deployed to quantify the contribution of bacteria to the ice nucleation activity of the spores. All samples of spores were ice nucleation active, having freezing onset temperatures as high as −4 °C. Spores in most of the samples carried cells of ice nucleation-active strains of the bacterium Pseudomonas syringae (at rates of less than 1 bacterial cell per 100 urediospores), but bacterial INA accounted for only a small fraction of the INA observed in spore suspensions. Changes in the INA of spore suspensions after treatment with lysozyme suggest that the INA of urediospores involves a polysaccharide. Based on data from the literature, we have estimated the concentrations of urediospores in air at cloud height and in rainfall. These quantities are very similar to those reported for other biological ice nucleators in these same substrates. However, at cloud level convective activity leads to widely varying concentrations of particles of surface origin, so that mean concentrations can underestimate their possible effects on clouds. We propose that spatial and temporal concentrations of biological ice nucleators active at temperatures > −10 °C and the specific conditions under which they can influence cloud glaciation need to be further evaluated so as to understand how evolutionary processes could have positively selected for INA.

Morphology of the Gas Bladder in Sea Catfishes (Siluriformes: Ariidae)

The morphology of the gas bladder and associated structures in sea catfishes (Siluriformes: Ariidae) is studied. The most simple gas bladder, exclusive to Galeichthys Valenciennes, is apple-shaped with weakly developed internal trabeculae, has smooth walls externally and a short Mullerian window associated with a broad, short Mullerian ramus that is firmly attached to Baudelot`s ligament and supracleithrum. Most genera of Ariidae have a cordiform bladder with well-developed trabeculae, smooth walls externally, an elongate Mullerian window and an elongate Mullerian ramus with an acute tip that is free from the Baudelot`s ligament and supracleithrum. Sciades proops (Valenciennes) and S. parkeri (Traill) have a similar gas bladder but with a well-developed secondary chamber. Other genera of Ariidae also have a cordiform bladder with well-developed trabeculae and elongate Mullerian window, but with lateral diverticula present as shallow rounded bulges or blister-like swellings along the peripheral margins of the bladder. The degree of development of lateral diverticula varies among and within species, with Osteogeneiosus Bleeker having the most highly-developed diverticula. Bagre pinnimaculatus (Steindachner) and Bagre bagre (Linnaeus) have unusual depressed gas bladders with complex network of internal trabeculae. The implications of gas bladder morphology for the taxonomy and phylogenetic relationships of the family are discussed.

A mixed model QTL analysis for sugarcane multiple-harvest-location trial data

Sugarcane-breeding programs take at least 12 years to develop new commercial cultivars. Molecular markers offer a possibility to study the genetic architecture of quantitative traits in sugarcane, and they may be used in marker-assisted selection to speed up artificial selection. Although the performance of sugarcane progenies in breeding programs are commonly evaluated across a range of locations and harvest years, many of the QTL detection methods ignore two- and three-way interactions between QTL, harvest, and location. In this work, a strategy for QTL detection in multi-harvest-location trial data, based on interval mapping and mixed models, is proposed and applied to map QTL effects on a segregating progeny from a biparental cross of pre-commercial Brazilian cultivars, evaluated at two locations and three consecutive harvest years for cane yield (tonnes per hectare), sugar yield (tonnes per hectare), fiber percent, and sucrose content. In the mixed model, we have included appropriate (co)variance structures for modeling heterogeneity and correlation of genetic effects and non-genetic residual effects. Forty-six QTLs were found: 13 QTLs for cane yield, 14 for sugar yield, 11 for fiber percent, and 8 for sucrose content. In addition, QTL by harvest, QTL by location, and QTL by harvest by location interaction effects were significant for all evaluated traits (30 QTLs showed some interaction, and 16 none). Our results contribute to a better understanding of the genetic architecture of complex traits related to biomass production and sucrose content in sugarcane.

Malva sylvestris, novo hospedeiro de Puccinia heterospora no Brasil

Observou-se a ocorrência de ferrugem em Malva sylvestris, causada por Puccinia heterospora, no Município de Garanhuns (PE). Esta espécie fúngica é microcíclica e apresenta apenas o estádio sexual, com a produção de teliósporos, com morfologia variada, podendo produzir, em menor número, teliósporos bicelulares do tipo Puccinia e, predominantemente teliósporos unicelulares do tipo Uromyces (mesosporos). A produção abundante de mesosporos é uma das características morfológicas mais marcantes da espécie. Essa ferrugem possui ampla distribuição geográfica, infectando plantas pertencentes à família Malvaceae. Este representa o primeiro registro dessa ferrugem sobre o gênero Malva no Brasil. Uma amostra de referência foi depositada no Herbário Dimitri Sucre Benjamin do Instituto de Pesquisas Jardim Botânico do Rio de Janeiro (JBRJ-RB). São apresentadas a descrição da morfologia do fungo com base na amostra coletada, ilustrações e comentários sobre a distinção entre essa espécie e outras morfologicamente semelhantes. Palavras-chave: ferrugem, Malvaceae, Pucciniales, teliósporos.

Simcluster: clustering enumeration gene expression data on the simplex space

Abstract Background Transcript enumeration methods such as SAGE, MPSS, and sequencing-by-synthesis EST "digital northern", are important high-throughput techniques for digital gene expression measurement. As other counting or voting processes, these measurements constitute compositional data exhibiting properties particular to the simplex space where the summation of the components is constrained. These properties are not present on regular Euclidean spaces, on which hybridization-based microarray data is often modeled. Therefore, pattern recognition methods commonly used for microarray data analysis may be non-informative for the data generated by transcript enumeration techniques since they ignore certain fundamental properties of this space. Results Here we present a software tool, Simcluster, designed to perform clustering analysis for data on the simplex space. We present Simcluster as a stand-alone command-line C package and as a user-friendly on-line tool. Both versions are available at: http://xerad.systemsbiology.net/simcluster. Conclusion Simcluster is designed in accordance with a well-established mathematical framework for compositional data analysis, which provides principled procedures for dealing with the simplex space, and is thus applicable in a number of contexts, including enumeration-based gene expression data.