Field-scale spatial correlation between contents of iron oxides and CO2 emission in an Oxisol cultivated with sugarcane

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Avaliação de resistência de cultivares de cana-de-açúcar ao Sugarcane yellow leaf virus (SCYLV) e ao seu afídeo vetor Melanaphis sacchari

Pós-graduação em Agronomia (Genética e Melhoramento de Plantas) - FCAV

Life cycle assessment of sugarcane ethanol and palm oil biodiesel joint production

Sugarcane (Saccharum spp.) and palm tree (Elaeis guianeensis) are crops with high biofuel yields, 7.6 m(3) ha (1) y(-)1 of ethanol and 4 Mg ha(-1) y(-1) of oil, respectively. The joint production of these crops enhances the sustainability of ethanol. The objective of this work was comparing a traditional sugarcane ethanol production system (TSES) with a joint production system (JSEB), in which ethanol and biodiesel are produced at the same biorefinery but only ethanol is traded. The comparison is based on ISO 14.040:2006 and ISO 14044:2006, and appropriate indicators. Production systems in Cerrado (typical savannah), Cerradao (woody savannah) and pastureland ecosystems were considered. Energy and carbon balances, and land use change impacts were evaluated. The joint system includes 100% substitution of biodiesel for diesel, which is all consumed in different cropping stages. Data were collected by direct field observation methods, and questionnaires applied to Brazilian facilities. Three sugarcane mills situated in Sao Paulo State and one palm oil refinery located in Para State were surveyed. The information was supplemented by secondary sources. Results demonstrated that fossil fuel use and greenhouse gas emissions decreased, whereas energy efficiency increased when JSEB was compared to TSES. In comparison with TSES, the energy balance of JSEB was 1.7 greater. In addition, JSEB released 23% fewer GHG emissions than TSES. The ecosystem carbon payback time for Cerrado, Cerradao, and Degraded Grassland of JSEB was respectively 4, 7.7 and -7.6 years. These are typical land use types of the Brazilian Cerrado region for which JSEB was conceived. (C) 2012 Elsevier Ltd. All rights reserved.

Microcollinearity between autopolyploid sugarcane and diploid sorghum genomes

Abstract Background Sugarcane (Saccharum spp.) has become an increasingly important crop for its leading role in biofuel production. The high sugar content species S. officinarum is an octoploid without known diploid or tetraploid progenitors. Commercial sugarcane cultivars are hybrids between S. officinarum and wild species S. spontaneum with ploidy at ~12×. The complex autopolyploid sugarcane genome has not been characterized at the DNA sequence level. Results The microsynteny between sugarcane and sorghum was assessed by comparing 454 pyrosequences of 20 sugarcane bacterial artificial chromosomes (BACs) with sorghum sequences. These 20 BACs were selected by hybridization of 1961 single copy sorghum overgo probes to the sugarcane BAC library with one sugarcane BAC corresponding to each of the 20 sorghum chromosome arms. The genic regions of the sugarcane BACs shared an average of 95.2% sequence identity with sorghum, and the sorghum genome was used as a template to order sequence contigs covering 78.2% of the 20 BAC sequences. About 53.1% of the sugarcane BAC sequences are aligned with sorghum sequence. The unaligned regions contain non-coding and repetitive sequences. Within the aligned sequences, 209 genes were annotated in sugarcane and 202 in sorghum. Seventeen genes appeared to be sugarcane-specific and all validated by sugarcane ESTs, while 12 appeared sorghum-specific but only one validated by sorghum ESTs. Twelve of the 17 sugarcane-specific genes have no match in the non-redundant protein database in GenBank, perhaps encoding proteins for sugarcane-specific processes. The sorghum orthologous regions appeared to have expanded relative to sugarcane, mostly by the increase of retrotransposons. Conclusions The sugarcane and sorghum genomes are mostly collinear in the genic regions, and the sorghum genome can be used as a template for assembling much of the genic DNA of the autopolyploid sugarcane genome. The comparable gene density between sugarcane BACs and corresponding sorghum sequences defied the notion that polyploidy species might have faster pace of gene loss due to the redundancy of multiple alleles at each locus.

Identification and expression analysis of microRNAs and targets in the biofuel crop sugarcane

Abstract Background MicroRNAs (miRNAs) are small regulatory RNAs, some of which are conserved in diverse plant genomes. Therefore, computational identification and further experimental validation of miRNAs from non-model organisms is both feasible and instrumental for addressing miRNA-based gene regulation and evolution. Sugarcane (Saccharum spp.) is an important biofuel crop with publicly available expressed sequence tag and genomic survey sequence databases, but little is known about miRNAs and their targets in this highly polyploid species. Results In this study, we have computationally identified 19 distinct sugarcane miRNA precursors, of which several are highly similar with their sorghum homologs at both nucleotide and secondary structure levels. The accumulation pattern of mature miRNAs varies in organs/tissues from the commercial sugarcane hybrid as well as in its corresponding founder species S. officinarum and S. spontaneum. Using sugarcane MIR827 as a query, we found a novel MIR827 precursor in the sorghum genome. Based on our computational tool, a total of 46 potential targets were identified for the 19 sugarcane miRNAs. Several targets for highly conserved miRNAs are transcription factors that play important roles in plant development. Conversely, target genes of lineage-specific miRNAs seem to play roles in diverse physiological processes, such as SsCBP1. SsCBP1 was experimentally confirmed to be a target for the monocot-specific miR528. Our findings support the notion that the regulation of SsCBP1 by miR528 is shared at least within graminaceous monocots, and this miRNA-based post-transcriptional regulation evolved exclusively within the monocots lineage after the divergence from eudicots. Conclusions Using publicly available nucleotide databases, 19 sugarcane miRNA precursors and one new sorghum miRNA precursor were identified and classified into 14 families. Comparative analyses between sugarcane and sorghum suggest that these two species retain homologous miRNAs and targets in their genomes. Such conservation may help to clarify specific aspects of miRNA regulation and evolution in the polyploid sugarcane. Finally, our dataset provides a framework for future studies on sugarcane RNAi-dependent regulatory mechanisms.

Evaluación de tecnologías de manejo de arvenses en el cultivo de la caña de azúcar (Saccharum spp. híbrido)

En Cuba, las arvenses que afectan al cultivo de la caña de azúcar son una de las causas fundamentales de los bajos rendimientos agrícolas y su control constituye unas de las principales partidas de gastos. En general, se aplican los herbicidas, así como otros métodos de control, sin tener en cuenta el tipo de suelo y las características de estas plantas. Sobre el manejo de arvenses no existen trabajos de investigación que aborden aspectos de eficiencia energética de las producciones y daños al ambiente. Por lo antes señalado, el objetivo de esta investigación fue evaluar diversas tecnologías de manejo de arvenses en el cultivo de la caña de azúcar (Saccharum spp. híbrido), en cepas de primavera y retoño, en tres tipos de suelos, con el propósito de obtener producciones sustentables. El área de estudio se localizó en los campos de la Empresa Azucarera del municipio “Majibacoa”, provincia de Las Tunas (oriente de Cuba), que posee condiciones edafoclimáticas que abundan a lo largo del país. Los tres tipos de suelos más representativos son Fersialítico Pardo Rojizo ócrico, Pardo Mullido y Vertisol Crómico gléyco. En dicha área se han identificado 31 especies de arvenses, 16 de la clase Liliopsida y 15 de la Magnoliopsida. En un primer grupo de experimentos, se desarrollaron nueve ensayos de campo para evaluar la efectividad de herbicidas y mezclas de estos en el manejo de arvenses en el cultivo de la caña de azúcar, tanto en cepas de primavera como de retoño, en los tres tipos de suelos. Se establecieron parcelas de 80 m2 distribuidas en bloques al azar con cuatro réplicas. La efectividad se evaluó por medio del porcentaje de cobertura por arvenses y la fitotoxicidad provocada a las plantas de caña, teniendo en cuenta el coste asociado a cada tratamiento. En aplicaciones preemergentes en caña planta de primavera, el herbicida más eficiente fue el Isoxaflutole con dosis de 0,15; 0,20 y 0,25 kg.ha-1 de producto comercial (pc) en los suelos Fersialítico, Pardo y Vertisol respectivamente. En aplicaciones postemergentes tempranas la mezcla más eficiente fue la de Isoxaflutole + Ametrina +2,4-D con las dosis de Isoxaflutole citadas anteriormente. En aplicaciones preemergentes en cepa de retoño, el herbicida más eficiente fue el Isoxaflutole a dosis de 0,20 kg.ha-1 pc para el suelo Fersialítico y a 0,25 kg.ha-1 pc para los suelos Pardo y Vertisol. En un segundo grupo, se realizaron seis ensayos de campo distribuidos en dos fases. En la primera fase, se desarrollaron tres experimentos, uno por cada tipo de suelo, para evaluar la eficiencia de nueve tecnologías de manejo de arvenses (químicas y físicas combinadas) en cepa de primavera de caña de azúcar. En la siguiente fase, los tres ensayos restantes (uno por tipo de suelo) evaluaron tecnologías de manejo de arvenses durante dos ciclos de producción de caña de azúcar (etapa de primavera y retoño). En la etapa de primavera se aplicó la tecnología más eficiente de los tres experimentos anteriores y durante la etapa de retoño se evaluaron otras nueve tecnologías propias de este tipo de cepa. En estos experimentos los diferentes tratamientos se aplicaron en franjas distribuidas al azar con cuatro réplicas. En las tecnologías evaluadas se emplearon los herbicidas y mezclas que resultaron más eficientes en el primer grupo de experimentos. En cada caso, se evaluaron la eficiencia energética de la producción de azúcar y otros derivados, la resistencia a la penetración de los suelos, la carga contaminante hacia la atmósfera producto de la combustión del diésel y los beneficios al aplicar las diferentes tecnologías. En la primera fase (cepa de primavera), la tecnología con mejor resultado fue la aplicación preemergente de Isoxaflutole inmediatamente después de la plantación, seguida de descepe químico con Glufosinato de amonio, más labor con grada múltiple aproximadamente a los 80 días de la plantación y aplicación pre-cierre con Glufosinato de amonio. En la segunda fase (dos ciclos del cultivo), el mejor resultado se obtuvo cuando en la etapa de retoño se realizó una aplicación preemergente de Isoxaflutole, descepe químico con Glufosinato de amonio y aplicación pre-cierre con este mismo herbicida. En los tres tipos de suelos durante los dos ciclos, la eficiencia energética tuvo valores de 7,2 - 7,5, la resistencia a la penetración 1,2 - 1,5 MPa, la carga contaminante hacia la atmósfera fue de 63,3 - 64,9 kg.t-1 de caña cosechada y beneficios de 8.324 - 8.455 pesos cubanos por hectárea. Este estudio demuestra que un control eficiente de las arvenses debe tener en cuenta necesariamente el tipo de suelo. Así, en los Vertisoles, con mayor contenido en arcilla, se requieren mayores dosis de Isoxaflutole y la eficiencia energética de la producción es menor. La persistencia de ciertas arvenses, especialmente de la clase Liliopsida, requiere de un manejo integrado que incluya diferentes tipos de herbicidas. ABSTRACT In Cuba, weeds affecting the sugarcane are one of the main causes of low agricultural yields, and their control constitutes some of the main items of expenditure. In general, herbicides are applied, as well as other control methods, without keeping in mind the soil type and the characteristics of these plants. Moreover, weed control research approaching aspects about energy efficiency of the crop production, and environmental damages are missing. Hence, the objective of this investigation was to evaluate diverse technologies of weed handling in sugarcane (Saccharum spp. hybrid), both in spring cane plant and ratoon, in three types of soils, with the purpose of obtaining sustainable productions. The study area was located in the fields of the Sugar Enterprise of the Municipality "Majibacoa”, Las Tunas province (east of Cuba) that possesses ecological conditions that are plentiful along the country. The three more representative types of soils are Fersialitic, Brown, and Vertisol. In this area 31 weeds species have been identified, 16 of the Class Liliopsida and 15 of the Magnoliopsida. In a first group of experiments, nine field rehearsals were developed to evaluate the effectiveness of herbicides and mixtures of these for weed handling in sugarcane, in spring cane plants as well as in ratoon, in the three types of soils. Plots of 80 m-2 were distributed at random blocks with four replications. The effectiveness was evaluated by means of the covering percentage by weeds and the provoked toxicity to the cane plants, keeping in mind the cost associated to each treatment. In preemergence applications in spring cane plant, the most efficient herbicide was the Isoxaflutole with dose of 0.15; 0.20 and 0.25 kg.ha-1 of commercial product (pc) in the soils Fersialítico, Brown and Vertisol respectively. In early postemergence applications the most efficient mixture was that of Isoxaflutole + Ametrina + 2,4-D with the doses of Isoxaflutole mentioned previously. In preemergence applications in ratoon, the most efficient herbicide was the Isoxaflutole at dose of 0.20 kg.ha-1 pc for the soil Fersialític and to 0.25 kg. ha-1 pc for the Brown soil and Vertisol. In a second group, six field rehearsals distributed in two phases were carried out. In the first phase, three experiments were developed, one for each soil type, to evaluate the efficiency of nine technologies of weed handling in spring cane plant. In the following phase, the three remaining rehearsals (one for each soil type) diverse technologies of weed handling were evaluated during two cycles of sugarcane production (spring stage and ratoon). In the spring stage the most efficient technology in the three previous experiments was applied and during ratoon stage other nine technologies were evaluated. In these experiments the different treatments were applied in fringes distributed at random with four replicas. In the evaluated technologies the herbicides and mixtures were used selecting those that were more efficient in the first group of experiments. In each case, the energy efficiency of the sugar production and other derivatives, the soil penetration resistance, the polluting load toward the atmosphere product of the combustion, and the benefits when applying the different technologies were all evaluated. In the first phase (spring cane plant), the technology with better result was the preemergence application of Isoxaflutole immediately after the plantation, followed by chemical eradication with Ammonia Glufosinate, hoeing work with multiple tier approximately to the 80 days of the plantation and pre-closing application with Ammonia Glufosinate. In the second phase (two cycles of the cultivation), the best result was obtained when a preemergence application of Isoxaflutole was carried out in sprout's stage, chemical eradication with Ammonia Glufosinate and pre-closing application with this same herbicide. In the three types of soils during the two cycles, the energy efficiency achieved values of 7.2 to 7.5, the resistance to the penetration 1.2 - 1.5 MPa, the polluting load toward the atmosphere was of 63.3 - 64.9 kg.t-1 of the harvested cane and the obtained benefits of 8,324 - 8,455 Cuban pesos per hectare. This study demonstrates that an efficient control of the weeds should necessarily keep in mind the soil type. This way, in the Vertisols, with more clay content, bigger dose of Isoxaflutole is required and the energy efficiency of the production is smaller. The persistence of certain weeds, especially of the class Liliopsida, requires of an integrated handling him to include different types of herbicides.

Posttranscriptional Gene Silencing in Transgenic Sugarcane. Dissection of Homology-Dependent Virus Resistance in a Monocot That Has a Complex Polyploid Genome1

RNA-mediated, posttranscriptional gene silencing has been determined as the molecular mechanism underlying transgenic virus resistance in many plant virus-dicot host plant systems. In this paper we show that transgenic virus resistance in sugarcane (Saccharum spp. hybrid) is based on posttranscriptional gene silencing. The resistance is derived from an untranslatable form of the sorghum mosaic potyvirus strain SCH coat protein (CP) gene. Transgenic sugarcane plants challenged with sorghum mosaic potyvirus strain SCH had phenotypes that ranged from fully susceptible to completely resistant, and a recovery phenotype was also observed. Clones derived from the same transformation event or obtained after vegetative propagation could display different levels of virus resistance, suggesting the involvement of a quantitative component in the resistance response. Most resistant plants displayed low or undetectable steady-state CP transgene mRNA levels, although nuclear transcription rates were high. Increased DNA methylation was observed in the transcribed region of the CP transgenes in most of these plants. Collectively, these characteristics indicate that an RNA-mediated, homology-dependent mechanism is at the base of the virus resistance. This work extends posttranscriptional gene silencing and homology-dependent virus resistance, so far observed only in dicots, to an agronomically important, polyploid monocot.

Caracterização fisiológica e do perfil de expressão gênica do transporte de nitrogênio em genótipos contrastantes para processo de fixação biológica de N2 de cana-de-açúcar (Saccharum spp.)

A cana-de-açúcar é uma cultura agrícola de grande importância econômica para o Brasil, e a expansão de seu cultivo para solos marginais requer uma maior utilização de fertilizantes à base de nitrogênio (N). Na maioria dos países produtores, a adubação nitrogenada se baseia em altas doses de aplicação, enquanto, no Brasil, o seu uso é relativamente baixo devido, em parte, ao processo de fixação biológica de nitrogênio (FBN) pela ação de bactérias diazotróficas. Além da FBN, as plantas adquirem fontes de N, como amônio e nitrato, por meio de transportadores de membranas localizados nas raízes. Há evidências que a associação com microrganismos pode favorecer as plantas por meio da regulação dos genes de transportadores de N. Desta forma, este trabalho teve como objetivo caracterizar o transporte de amônio e nitrato, avaliando a expressão gênica dos principais transportadores de N em cana-de-açúcar cultivada in vitro sob o efeito da associação com bactérias diazotróficas. Também foi descrita a comunidade bacteriana de plântulas in vitro, bem como o efeito da fertilização com N e da inoculação com bactérias diazotróficas em plantas maduras. Plântulas de \'SP70- 1143\' e \'Chunee\', que contrastam para FBN, foram empregadas em ensaios in vitro sob diversas concentrações e fontes de N em associação ou não com uma estirpe de Gluconacetobacter diazotrophicus ou um mistura de bactérias diazotróficas (G. diazotrophicus, Herbaspirillum seropedicae, H. rubrisubalbicans, Azospirillum amazonense e Burkholderia tropica). A caracterização do transporte de N por meio de ensaios de absorção de nitrato e amônio marcados (15N) revelou que a interação entre cana-de-açúcar x G. diazotrophicus induziu a expressão do gene do transportador de nitrato ScNRT2.1, o que levou a uma tendência no aumento no influxo de nitrato, assim como dos genes de transportadores de amônio ScAMT1.1 e ScAMT1.3, resultando em maiores influxos de amônio apenas para a cultivar \'SP70- 1143\'. Já a associação da cana-de-açúcar com a mistura de bactérias diazotróficas revelou que somente houve indução transcricional de ScAMT1.1, o que resultou na maior absorção de amônio em \'SP70-1143\'. Por sua vez, quando analisada a interação in vitro por 30 dias, a presença da bactéria, apesar de transiente, possivelmente favoreceu a expressão dos genes de transportadores de nitrato ScNRT1.1 e ScNRT2.1, e do transportador de amônio ScAMT1.1, resultando no maior acúmulo de 15N-nitrato de amônio nas plantas de \'SP70-1143\'. Foi detectada uma comunidade bacteriana associada a plântulas micropropagadas, a qual é distinta entre os genótipos \'SP70-1143\' e \'Chunee\' e se altera com a inoculação com G. diazotrophicus. Para as plantas cultivadas em campo, a comunidade bacteriana existente foi alterada pela fertilização de N, mas não pela inoculação com diazotróficas. Portanto, a inoculação com bactérias diazotróficas parece induzir a expressão dos principais genes transportadores de amônio e nitrato em plântulas do genótipo \'SP70-1143\' resultando na maior absorção de fontes inorgânicas de N.

Efeito da aplicação de composto orgânico sobre a qualidade do solo cultivado com cana-de-açúcar (Saccharum spp.)

A dinâmica ambiental possui capacidade limitada de reciclagem e a crescente utilização resíduos agroindustriais, especialmente na agricultura, pode levar a situações de poluição do solo e demais componentes ambientais. A manutenção da produtividade de ecossistemas agrícolas e naturais depende do processo de transformação da matéria orgânica e, por conseguinte, da biomassa microbiana do solo, e que é responsável pela decomposição e mineralização de resíduos no mesmo. A dinâmica natural dos microrganismos do solo, em constante mudança e adaptação, os torna um indicador sensível às mudanças resultantes de diferentes práticas de manejo agrícola. Sendo assim, conhecer essas alterações e suas interferências é fundamental para identificar estratégias adequadas de manejo, apontando técnicas de utilização adequadas. O objetivo deste trabalho foi avaliar a qualidade de um solo agrícola, cultivado com três variedades de cana-de-açúcar (Saccharum spp.), comparando a utilização de adubação mineral frente à utilização de fertilizante orgânico composto no período final de formação dos perfilhos (120 dias após o plantio). Foi implantado, em condições de campo, o cultivo de cana-de-açúcar (cana planta), utilizando as variedades RB 867515, RB 962869 e RB 855453, onde cada variedade foi cultivada de três formas distintas, sendo elas: plantio controle (CT) sem aplicação de insumos para adubação; plantio orgânico (OG) com aplicação de fertilizante orgânico; e plantio convencional (CV) com aplicação de adubação mineral, seguindo recomendações de adubação após análise química inicial do solo local. Cada parcela possuía 37 m2, com 5 sulcos de 5,0 m de comprimento e espaçamento de 1,5 m entrelinhas, sendo os três sulcos centrais formando a área útil. De acordo com a variedade e o tipo de adubação, foram formados nove tratamentos: T1 86CT, T2 96CT, T3 85CT, T4 6OG, T5 96OG, T6 85OG, T7 86CV, T8 96CV e T9 85CV, com delineamento estatístico de blocos ao acaso e quatro repetições. Os parâmetros químicos do solo analisados foram macronutrientes e micronutrientes; os parâmetros microbiológicos foram carbono da biomassa microbiana (CBM), respiração basal do solo (RBS), quociente metabólico (qCO2), número mais provável de fungos e bactérias do solo (NMP); e, por fim, a produtividade agrícola (t/ha). Os resultados foram submetidos a análise de variância (ANOVA) e à comparação das médias através do teste de Tukey (10%). Também foi realizada a análise de variância dos dados e correlação cofenética de Pearson para formação de dendogramas. Com base no período estudado, considerado como fase crítica da formação do canavial, concluiu-se que os parâmetros químicos que evidenciaram alterações no solo foram pH e os macronutrientes Mg, Al e SB, sendo os tratamentos orgânicos equivalentes e/ou melhores que os tratamentos convencionais. Para os parâmetros microbiológicos, o NMP de fungos apresentou os maiores valores nos tratamentos convencionais e controle. A produtividade agrícola não foi influenciada pelos diferentes tratamentos e insumos utilizados, independente da variedade de cana-de-açúcar utilizada. Por fim, foram observadas correlações positivas entre as variáveis CTC e quociente metabólico (qCO2) apontando potencial melhoria da qualidade do solo, com o emprego de insumos orgânicos

Investigation into the ability of Gluconacetobacter sacchari to live as an endophyte in sugarcane

The relatively low numbers and sporadic pattern of incidence of the acetic acid bacterium Gluconacetobacter sacchari with the pink sugarcane mealybug (PSMB) Saccharicoccus sacchari Cockerell (Homoptera: Pseudococcidae) over time and from different sugarcane-growing regions do not indicate that Glac. sacchari is a significant commensal of the PSMB, as has been previously proposed. This study was conducted to investigate the hypothesis that Glac. sacchari is, like its closest relative Glac. diazotrophicus, an endophyte of sugarcane (Saccharum officinarium L.). In this study, both Glac. sacchari and Glac. diazotrophicus were isolated from internal sugarcane tissue, although the detection of both species was sporadic in all sugarcane-growing regions of Queensland tested. To confirm the ability of Glac. sacchari to live endophytically, an experiment was conducted in which the roots of micropropagated sugarcane plantlets were inoculated with Glac. sacchari, and the plantlets were subsequently examined for the presence of the bacterium in the stem cells. Pure cultures of Glac. sacchari were grown from homogenized surface sterilized sugarcane stems inoculated with Glac. sacchari. Electron microscopy was used to provide further conclusive evidence that Glac. sacchari lives as an endophyte in sugarcane. Scanning electron microscopy of (SEM) sugarcane plantlet stems revealed rod-shaped cells of Glac. sacchari within a transverse section of the plantlet stem cells. The numbers of bacterial cells inside the plant cell indicated a successful infection and colonization of the plant tissue. Using transmission electron microscopy, (TEM) bacterial cells were more difficult to find, due to their spatial separation. In our study, bacteria were mostly found singularly, or in groups of up to four cells inside intercellular spaces, although bacterial cells were occasionally found inside other cells.

Growth responses of sugarcane to mycorrhizal spore density and phosphorus rate

Arbuscular mycorrhizal (AM) fungi, commonly found in long-term cane-growing fields in northern Queensland, are linked with both negative and positive growth responses by sugarcane ( Saccharum spp.), depending on P supply. A glasshouse trial was established to examine whether AM density might also have an important influence on these growth responses. Mycorrhizal spores ( Glomus clarum), isolated from a long-term cane block in northern Queensland, were introduced into a pasteurised low-P cane soil at 5 densities ( 0, 0.06, 0.25, 1, 4 spores/g soil) and with 4 P treatments ( 0, 8.2, 25, and 47 mg/kg). At 83 days after planting, sugarcane tops responded positively to P fertilizer, although responses attributable to spore density were rarely observed. In one case, addition of 4 spores/g led to a 53% yield response over those without AM at 8 mg P/kg, or a relative benefit of 17 mg P/kg. Root colonisation was reduced for plants with nil or 74 mg P/kg. For those without AM, P concentration in the topmost visible dewlap ( TVD) leaf increased significantly with fertiliser P (0.07 v. 0.15%). However, P concentration increased further with the presence of AM spores. Irrespective of AM, the critical P concentration in the TVD leaf was 0.18%. This study confirms earlier reports that sugarcane is poorly responsive to AM. Spore density, up to 4 spores/g soil, appears unable to influence this responsiveness, either positively or negatively. Attempts to gain P benefits by increasing AM density through rotation seem unlikely to lead to yield increases by sugarcane. Conversely, sugarcane grown in fields with high spore densities and high plant-available P, such as long-termcane-growing soils, is unlikely to suffer a yield reduction from mycorrhizal fungi.

The five families of sucrose-phosphate synthase genes in Saccharum spp. are differentially expressed in leaves and stem

Sucrose-phosphate synthase (SPS) is a key enzyme in the pathway of sucrose synthesis. Five different gene families encoding SPS have been reported in the Poaceae [Castleden CK, Aoki N, Gillespie VJ, MacRae EA, Quick WP, Buchner P, Foyer CH, Furbank RT, Lunn JE (2004) Evolution and function of the sucrose-phosphate synthase gene families in wheat and othergrasses. PlantPhysiology 135, 1753-1764]. Expression of the five families in leaf and stem tissues of Saccharum spp. at different stages of development was determined by quantitative real-time PCR. The type B and C families of SPS genes were predominantly expressed in both immature and mature leaves, whereas the two subfamilies making up the type D family were expressed at similar levels in all tissues examined. In the type A family, expression was lowest in leaves and increased from the meristem region down to internode 7 of the stem.

Recent advances in the molecular biology of Leifsonia xyli subsp. xyli, causal organism of ratoon stunting disease

Twelve years ago our understanding of ratoon stunting disease (RSD) was confined almost exclusively to diagnosis of the disease and control via farm hygiene, with little understanding of the biology of the interaction between the causal agent (Leifsonia xyli subsp. xyli) and the host plant sugarcane (Saccharum spp. hybrids). Since then, research has focused on developing the molecular tools to dissect L. xyli subsp. xyli, so that better control strategies can be developed to prevent losses from RSD. Within this review, we give a brief overview of the progression in research on L. xyli subsp. xyli and highlight future challenges. After a brief historical background on RSD, we discuss the development of molecular tools such as transformation and transposon mutagenesis and discuss the apparent lack of genetic diversity within the L. xyli subsp. xyli world population. We go on to discuss the sequencing of the genome of L. xyli subsp. xyli, describe the key findings and suggest some future research based on known deficiencies that will capitalise on this tremendous knowledge base to which we now have access.

Variation in acquisition of Fiji disease virus by Perkinsiella saccharicida (Hemiptera: Delphacidae).

Fiji leaf gall, caused the Fiji disease virus (genus Fijivirus, family Reoviridae, FDV), is a serious disease of sugarcane, Saccharum officinarum L., in Australia and several other Asia-Pacific countries. In Australia FDV is transmitted only by the planthopper Perkinsiella saccharicida Kirkaldy (Hemiptera: Delphacidae), in a propagative manner. Successful transmission of FDV by single planthoppers confined to individual virus free plants is highly variable, even under controlled conditions. The research reported here addresses two possible sources of this variation: 1) gender, wing form, and life stage of the planthopper; and 2) genotype of the source plant. The acquisition of FDV by macropterous males, macropterous females, brachypterous females, and nymphs of P. saccharicida from infected plants was investigated using reverse transcription-polymerase chain reaction to diagnose FDV infection in the vector. The proportion of individuals infected with FDV was not statistically related to life stage, gender, or adult wing form of the vector. The acquisition of FDV by P. saccharicida from four cultivars of sugarcane was compared to assess the influence of plant genotype on acquisition. Those planthopper populations reared on diseased 'NCo310' plants had twice as many infected planthoppers as those reared on 'Q110', 'WD1', and 'WD2'. Therefore, variation in FDV acquisition in this system is not the result of variation in the gender, wing form and life stage of the P. saccharicida vectors. The cultivar used as the source plant to rear vector populations does affect the proportion of infected planthoppers in a population.

Quantitative response of the longevity of seed of twelve crops to temperature and moisture in hermetic storage

Seeds of 39 seed lots of a total of twelve different crops were stored hermetically in a wide range of air-dry environments (2-25% moisture content at 0-50 degrees C), viability assessed periodically, and the seed viability equation constants estimated. Within a species, estimates of the constants which quantify absolute longevity (K-E) and the relative effects on longevity of moisture content (C-W) and temperature (C-H and C-Q) did not differ (P >0.05 to P >0.25) among lots. Comparison among the 12 crops provided variant estimates of K-E and C-W (P< 0.01), but common values of C-H and C-Q (0.0322 and 0.000454, respectively, P >0.25). Maize (Zea mays) provided the greatest estimate of K-E (9.993, s.e.= 0.456), followed by sorghum (Sorghum bicolor) (9.381, s.e. 0.428), pearl millet (Pennisetum typhoides) (9.336, s.e.= 0.408), sugar beet (Beta vulgaris) (8.988, s.e.= 0.387), African rice (Oryza glaberrima) (8.786, s.e.= 0.484), wheat (Triticum aestivum) (8.498, s.e.= 0.431), foxtail millet (Setaria italica) (8.478, s.e.= 0.396), sugarcane (Saccharum sp.) (8.454, s.e.= 0.545), finger millet (Eleusine coracana) (8.288, s.e.= 0.392), kodo millet (Paspalum scrobiculatum) (8.138, s.e.= 0.418), rice (Oryza sativa) (8.096, s.e.= 0.416) and potato (Solanum tuberosum) (8.037, s.e.= 0.397). Similarly, estimates of C-W were ranked maize (5.993, s.e.= 0.392), pearl millet (5.540, s.e.= 0.348), sorghum (5.379, s.e.=0.365), potato (5.152, s.e.= 0.347), sugar beet (4.969, s.e.= 0.328), sugar cane (4.964, s.e.= 0.518), foxtail millet (4.829, s.e.= 0.339), wheat (4.836, s.e.= 0.366), African rice (4.727, s.e.= 0.416), kodo millet (4.435, s.e.= 0.360), finger millet (4.345, s.e.= 0.336) and rice (4.246, s.e.= 0.355). The application of these constants to long-term seed storage is discussed.