Comparative physiological and transcriptome analysis in cultivated and wild sugarcane species in response to hydrogen peroxide-induced oxidative stress.

BACKGROUND: Sugarcane is an important energy crop grown worldwide,supplementing various renewable energy sources. Cultivated and wild sugarcane species respond differently to biotic and abiotic stresses. Generally, wild species are tolerant to various abiotic stresses. In the present study, the physiological and molecular responses of cultivated and wild sugarcane species to oxidative stress at the transcriptional levels were compared. Transcriptional responses were determined using RNAseq. The representative RNA-seq transcript values were validated by reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) and confirmed through physiological responses. RESULTS: Oxidative stress causes leaf-rolling and -tip drying in cultivated sugarcane, but the wild species are tolerant. Higher chlorophyll fluorescence was observed in the wild species than that in the cultivated varieties under stress. Wild species can maintain a higher chlorophyll stability index than the cultivated species, which was confirmed by the lower transcripts of the chlorophyllase gene in the wild species than that in the cultivated variety. Transcription factor genes (NAC, MYB, and WRKY) were markedly expressed in response to oxidative stress, revealing their involvement in stress tolerance. The analysis revealed synchronized expression of acetyl-transferase, histone2A, cellulose synthase, and secondary cell wall biosynthetic genes in the wild species. The validation of selected genes and 15 NAC transcription factors using RT-qPCR revealed that their expression profiles were strongly correlated with RNA-seq. To the best of our knowledge, this is the first report on the oxidative stress response in cultivated and wild sugarcane species. CONCLUSION: Physiological and biochemical changes in response to oxidative stress markedly differ between cultivated and wild sugarcane species. The differentially expressed stress-responsive genes are grouped intothe response to oxidative stress, heme-binding, peroxidase activity, and metal ion binding categories. Chlorophyll maintenance is a stress tolerance response enhanced by the differential regulation of the chlorophyllase gene.There is a considerable difference in the chlorophyll stability index between wild and cultivated varieties. We observed a substantial regulation of secondary wall biosynthesis genes in the wild species compared with that in the cultivated variety, suggesting differences in stress tolerance mechanisms.

Somatic Embryogenesis in Sugarcane (Saccharum spp.).

Somatic embryogenesis is the process by which embryos are formed from a single or small group of somatic cells in response to specific stimuli. Somatic embryogenesis has been applied to achieve mass clonal propagation on an industrial scale and to increase the agronomic performance of species of economic interest, including sugarcane. The use of somatic embryogenesis in sugarcane stands out as a biotechnological tool with a high potential for application in the clonal propagation of disease-free elite varieties, as an essential part of genetic transformation protocols, and in the production of synthetic seeds. A better understanding of each phase of somatic embryogenesis can help to optimize the process to enhance yields and produce high-quality emblings. In this chapter, we describe a detailed protocol for somatic embryogenesis in sugarcane (Saccharum sp.) to be used in research projects for small-scale production. This protocol comprises all steps from explant preparation to the establishment of sugarcane emblings.

Bacterial communities associated with sugarcane under different agricultural management exhibit a diversity of plant growth-promoting traits and evidence of synergistic effect.

Plant-associated microbiomes have been a target of interest for the prospection of microorganisms, which may be acting as effectors to increase agricultural productivity. For years, the search for beneficial microorganisms has been carried out from the characterization of functional traits of growth-promotion using tests with a few isolates. However, eventually, the expectations with positive results may not be realized when the evaluation is performed in association with plants. In our study, we accessed the cultivable sugarcane microbiome under two conditions of agronomic management: organic and conventional. From the use of a new customized culture medium, we recovered 944 endophytic and epiphytic bacterial communities derived from plant roots, stalks, leaves, and rhizospheric soil. This could be accomplished by using a large-scale approach, initially performing an in planta (Cynodon dactylon) screening process of inoculation to avoid early incompatibility. The inoculation was performed using the bacterial communities, considering that in this way, they could act synergistically. This process resulted in 38 candidate communities, 17 of which had higher Indole-3-acetic acid (IAA) production and phosphate solubilization activity and, were submitted to a new in planta test using Brachiaria ruziziensis and quantification of functional traits for growth-promotion and physiological tests. Enrichment analysis of selected communities has shown that they derived mainly from epiphytic populations of sugarcane stalks under conventional management. The sequencing of the V3-V4 region of the 16S rRNA gene revealed 34 genera and 24 species distributed among the phylum Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria. We also observed a network of genera in these communities where the genus Chryseobacterium stands out with a greater degree of interaction, indicating a possible direct or indirect role as a keystone taxon in communities with plant-growth promotion capacities. From the results achieved, we can conclude that the approach is useful in the recovery of a set of sugarcane bacterial communities and that there is, evidence of synergistic action providing benefits to plants, and that they are compatible with plants of the same family (Poaceae). Thus, we are reporting the beneficial bacterial communities identified as suitable candidates with rated potential to be exploited as bioinoculants for crops.

Plant-Growth Endophytic Bacteria Improve Nutrient Use Efficiency and Modulate Foliar N-Metabolites in Sugarcane Seedling.

Beneficial plant-microbe interactions lead to physiological and biochemical changes that may result in plant-growth promotion. This study evaluated the effect of the interaction between sugarcane and endophytic bacterial strains on plant physiological and biochemical responses under two levels of nitrogen (N) fertilization. Six strains of endophytic bacteria, previously selected as plant growth-promoting bacteria (PGPB), were used to inoculate sugarcane mini stalks, with and without N fertilization. After 45 days, biomass production; shoot nutrient concentrations; foliar polyamine and free amino acid profiles; activities of nitrate reductase and glutamine synthase; and the relative transcript levels of the GS1, GS2, and SHR5 genes in sugarcane leaves were determined. All six endophytic strains promoted sugarcane growth, increasing shoot and root biomass, plant nutritional status, and the use efficiency of most nutrients. The inoculation-induced changes at the biochemical level altered the foliar free amino acid and polyamine profiles, mainly regarding the relative concentrations of citrulline, putrescine, glycine, alanine, glutamate, glutamine, proline, and aspartate. The transcription of GS1, GS2, and SHR5 was higher in the N fertilized seedlings, and almost not altered by endophytic bacterial strains. The endophytic strains promoted sugarcane seedlings growth mainly by improving nutrient efficiency. This improvement could not be explained by their ability to induce the production of amino acid and polyamine composts, or GS1, GS2, and SHR5, showing that complex interactions may be associated with enhancement of the sugarcane seedlings' performance by endophytic bacteria. The strains demonstrated biotechnological potential for sugarcane seedling production.

Exploitation of new endophytic bacteria and their ability to promote sugarcane growth and nitrogen nutrition.

Few studies have evaluated endophytic bacteria in relation to plant growth promotion, nitrogen uptake and biological control. The aim of this study was to molecularly and physiologically characterize thirteen endophytic bacteria strains, evaluate their biological control properties and their ability to promote plant growth and plant N nutrition. All the strains produced indole acetic acid and promoted increase of plant biomass, N accumulative amount and N-use efficiency index. None of the strains carries the nifH gene. Four strains stimulated plant nitrate reductase activity, four solubilized phosphate, nine produced siderophores and none produced HCN. Seven strains inhibited Bipolaris sacchari growth and one was antagonistic to Ceratocystis paradoxa. The pathogens were inhibited by the production of diffusible and volatile metabolites by the bacterial strains. Moreover, this is the first study to demonstrate the effect of Delftia acidovorans on sugarcane plant growth, nitrogen metabolism improvement and antagonism to B. sacchari. The most efficient strains in promoting plant growth and exhibiting antagonistic activities towards fungal pathogens were Herbaspirillum frinsingense (IAC-BECa-152) and three Pantoea dispersa strains (IAC-BECa-128, IAC-BECa-129, and IAC-BECa-132). These bacteria show potential to be used as inoculants for sustainable agricultural management, mainly at the seedling production phase.

Assessment of chemical and sensory quality of sugarcane alcoholic fermented beverage.

This study aimed to verify the technological feasibility, chemical quality and sensory acceptance of alcoholic fermented beverage obtained from sugarcane juice. A completely randomized design was applied. Sugar and alcohol content, phenolic (HPLC-MS) and volatile (GS-MS) compounds, pH, density, dry matter and acidity of the fermented beverage of sugarcane were quantified, as well as the acceptance of the product was carried out. The complete fermentation of sugarcane lasted 7 days, and it was obtained an alcohol content of 8.0% v/v. Titrable acidity of the beverage was of 67.31 meq L-1, pH 4.03, soluble solids of 5 °Brix, reducing sugar of 0.07 g glucose 100 g-1, density of 0.991 g cm-3, reduced dry matter of 14.15 g L-1, sulfates lower than 0.7 g K2SO4 L-1. Various phenolic compounds, among which, gallic acid (10.97%), catechin (1.73%), chlorogenic acid (3.52%), caffeic acid (1.49%), vanillic acid (0.28%), p-coumaric acid (0.24%), ferulic acid (6.63%), m-coumaric acid (0.36%), and o-coumaric acid (0.04%). Amongst aromatic compounds, were found mainly esters with fruity aromas (ethyl ester hexanoic acid and ethyl ester octanoic acid). The sugarcane juice can be commercialized as an alternative wine, as it presented adequate features to an alcoholic fermented beverage and was sensory accepted by consumers.

Assessing resistance of sugarcane varieties to sugarcane borer Diatraea saccharalis Fab. (Lepidoptera: Crambidae).

In this study, we investigated resistance traits to the sugarcane borer Diatraea saccharalis Fab. (Lepidoptera: Crambidae) in the leaves and stalks of six sugarcane cultivars in a series of greenhouse and laboratory assays. Investigation of plant factors and infestation rates to better discriminate stalk damage by the sugarcane borer indicated that infestation of 7-month-old, single plants with 20 larvae at the third or fourth instar per plant was suitable to assess tunneling length. Three cultivars (i.e. SP803280, RB928064, and RB835486) had lower stalk damage (i.e. tunnel length) than cultivar SP891115, which exhibited relatively greater susceptibility to tunneling by the borer. The time required for the larvae to enter the sugarcane stalk was longer for cultivar SP803280, indicating resistance traits on the stalk surface, which correlated with lower stalk damage. Larvae feeding on SP813250 stalks had the lowest weight gain, indicating that this cultivar has resistance traits to larval development within its stalks. Cultivars RB867515 and SP891115 resulted in the highest mortality of early-stage larvae feeding on leaves, indicating the presence of resistance factors in their leaves. Multi-trait cluster and principal component analyses placed the cultivars into three and four clusters, respectively. The cultivars placed in different groups that exhibited resistance to leaf feeding, stalk entrance, and tunneling by the sugarcane borer could be used for crossings in sugarcane breeding programs with the goal of obtaining higher levels of resistance to D. saccharalis.

Host-Plant Resistance to Spittlebugs: A Life-Table Study With Mahanarva fimbriolata (Hemipera: Cercopidae) in Sugarcane Genotypes.

Understanding how host-crop genotypes affect the life history of insect pests is important for developing and using varietal resistance as a pest control measure. Here we determined how wild and cultivated sugarcane genotypes affect key life-history traits and the demographic performance of the root spittlebug, Mahanarva fimbriolata (Stål; Hemiptera: Cercopidae), a major pest of sugarcane, which produces most of the world's sugar and bioethanol. In the greenhouse, plants of four sugarcane genotypes (two wild and two cultivated) were infested with newly-ecloded spittlebug nymphs. A longitudinal life-table experiment was conducted recording developmental time, survival, reproductive output, and longevity of the released spittlebug nymphs. One of the promising sugarcane genotypes was the accession IM76-229 (Saccharum robustum Brandes & Jesw. ex Grassl), which allowed only 20% of nymph survival to adulthood and reduced the spittlebug longevity by 10 d. Such effects on these life-history traits led to a negative intrinsic rate of population growth (rm = -0.002) of the insects, indicating that the test population would eventually go extinct on this sugarcane genotype. An opposite trend (i.e., population growth) was obtained for the insects raised on Saccharum spp. (SP81-3250 and SP80-1816 cultivars) and Erianthus arundinaceus (Retz) Jeswiet (Kawandang genotype). These results show that S. robustum IM76-229 genotype has resistance traits that drastically reduce spittlebug population growth and indicate that it can be used in breeding programs aiming to develop sugarcane cultivars with resistance to spittlebugs.

Assessment of sucrose transporters, metabolites and sucrose phosphate synthase in different sugarcane tissues.

The expression of sucrose-phosphate synthase II (SPSII) and sucrose transporters ShSUT1A and ShSUT4 were determined by RT-PCR and qRT-PCR in the sink and source leaves and in rind and pith of mature internodes of four high-yielding Hawaiian sugarcane cultivars. Expression of SPSII, ShSUT1A, and ShSUT4 was lower in pith than in rind, except in one cultivar, but else quite similar in the cultivars. The strong expression of transporter ShSUT4 in the rind of the internodes may hint to a special role of ShSUT4 in the rind. ShSUT4-expression in the sink and source leaves was similar in all four cultivars, whereas large differences were found for the expression of ShSUT1A and SPSII between the source and sink leaves and between the cultivars. The levels of sucrose precursors were doubled in source leaves compared to sink leaves, whereas they were higher in immature internode compared to mature internode. The role of sucrose transporters and SPSII in leaves and internodes is discussed, but the large differences, which were observed in the transcript levels of SPSII and sucrose transporters between some cultivars, although all the cultivars were similarly high-yielding cultivars, show that SPSII and SUT transcript levels cannot be used as indicators of high-yield cultivars.

Development and nitrate reductase activity of sugarcane inoculated with five diazotrophic strains.

Diazotrophs are able to stimulate plant growth. This study aimed at evaluating the effect of inoculation of five diazotrophic strains on growth promotion and nitrate reductase (NR, EC 1.7.1.1) activity in sugarcane. An experiment was carried out from three stages of cultivation: sprouting, tubes, and in hydroponics. On the first two stages, seven treatments were adopted: uninoculated control; mixed inoculation with five strains; and individual inoculation with Gluconacetobacter diazotrophicus (Gd), Herbaspirillum rubrisubalbicans (Hr), Herbaspirillum seropedicae (Hs), Nitrospirillum amazonense (Na), and Paraburkholderia tropica (Pt). The four treatments showing the best performance were transferred to the hydroponic system for analysis of NR activity. Hs, Pt, and the mixture of all strains led to the highest seedling biomass in tubes, followed by Hr. In hydroponics, the mixture and the strain Hr had the highest growth-promoting effect. NR activity was influenced by inoculation only under low N supply conditions, with positive effect of Hr, Pt, and the mixture.

Microbial-enhanced lindane removal by sugarcane (Saccharum officinarum) in doped soil-applications in phytoremediation and bioaugmentation.

The aim of this study was to examine the effect of lindane-degrading yeast on the growth and lindane uptake by Saccharum sp., in doped garden soils. The rhizosphere of Saccharum plant was amended with yeast Candida VITJzN04 by root-inoculation. The bio-augment yeast was applied in two different forms viz., planktonic form and cells immobilized on sugarcane-bagasse, in the pot experiments. Garden soils (lindane∼100 mg/kg) exposed to various treatments were monitored for a period of 30 days, for residual lindane by gas-chromatography analysis. The lindane-removal rates in soil were expressed in terms of half-life period and were recorded as 13.3 days (yeast), 43.3 days (Saccharum), 9.8 days (free yeast-plant) and 7.1 days (immobilized yeast-plant). Additionally, Candida sp., was also identified as a plant growth promoting yeast due to its ability to produce growth hormone and solubilize insoluble phosphates in the soil for better uptake by the plant species. Bio-stimulation of the soil with yeast immobilized on sugarcane bagasse further enhanced the total yeast activity in the soil which in turn had a positive influence on lindane-removal. Combined treatment with bagasse immobilized yeast and plant showed the best lindane degradation. Results suggested that the synergistic activity of plant and yeast resulted in fast and efficient degradation of lindane. Thus, it can be concluded that Saccharum plant in combination with Candida VITJzN04 is an effective alternative for the conventional remediation strategies.

In planta production and characterization of a hyperthermostable GH10 xylanase in transgenic sugarcane.

Sugarcane (Saccharum sp. hybrids) is one of the most efficient and sustainable feedstocks for commercial production of fuel ethanol. Recent efforts focus on the integration of first and second generation bioethanol conversion technologies for sugarcane to increase biofuel yields. This integrated process will utilize both the cell wall bound sugars of the abundant lignocellulosic sugarcane residues in addition to the sucrose from stem internodes. Enzymatic hydrolysis of lignocellulosic biomass into its component sugars requires significant amounts of cell wall degrading enzymes. In planta production of xylanases has the potential to reduce costs associated with enzymatic hydrolysis but has been reported to compromise plant growth and development. To address this problem, we expressed a hyperthermostable GH10 xylanase, xyl10B in transgenic sugarcane which displays optimal catalytic activity at 105 °C and only residual catalytic activity at temperatures below 70 °C. Transgene integration and expression in sugarcane were confirmed by Southern blot, RT-PCR, ELISA and western blot following biolistic co-transfer of minimal expression cassettes of xyl10B and the selectable neomycin phosphotransferase II. Xylanase activity was detected in 17 transgenic lines with a fluorogenic xylanase activity assay. Up to 1.2% of the total soluble protein fraction of vegetative progenies with integration of chloroplast targeted expression represented the recombinant Xyl10B protein. Xyl10B activity was stable in vegetative progenies. Tissues retained 75% of the xylanase activity after drying of leaves at 35 °C and a 2 month storage period. Transgenic sugarcane plants producing Xyl10B did not differ from non-transgenic sugarcane in growth and development under greenhouse conditions. Sugarcane xylan and bagasse were used as substrate for enzymatic hydrolysis with the in planta produced Xyl10B. TLC and HPLC analysis of hydrolysis products confirmed the superior catalytic activity and stability of the in planta produced Xyl10B with xylobiose as a prominent degradation product. These findings will contribute to advancing consolidated processing of lignocellulosic sugarcane biomass.

Genome-wide association mapping of quantitative traits in a breeding population of sugarcane.

BACKGROUND: Molecular markers associated with relevant agronomic traits could significantly reduce the time and cost involved in developing new sugarcane varieties. Previous sugarcane genome-wide association analyses (GWAS) have found few molecular markers associated with relevant traits at plant-cane stage. The aim of this study was to establish an appropriate GWAS to find molecular markers associated with yield related traits consistent across harvesting seasons in a breeding population. Sugarcane clones were genotyped with DArT (Diversity Array Technology) and TRAP (Target Region Amplified Polymorphism) markers, and evaluated for cane yield (CY) and sugar content (SC) at two locations during three successive crop cycles. GWAS mapping was applied within a novel mixed-model framework accounting for population structure with Principal Component Analysis scores as random component. RESULTS: A total of 43 markers significantly associated with CY in plant-cane, 42 in first ratoon, and 41 in second ratoon were detected. Out of these markers, 20 were associated with CY in 2 years. Additionally, 38 significant associations for SC were detected in plant-cane, 34 in first ratoon, and 47 in second ratoon. For SC, one marker-trait association was found significant for the 3 years of the study, while twelve markers presented association for 2 years. In the multi-QTL model several markers with large allelic substitution effect were found. Sequences of four DArT markers showed high similitude and e-value with coding sequences of Sorghum bicolor, confirming the high gene microlinearity between sorghum and sugarcane. CONCLUSIONS: In contrast with other sugarcane GWAS studies reported earlier, the novel methodology to analyze multi-QTLs through successive crop cycles used in the present study allowed us to find several markers associated with relevant traits. Combining existing phenotypic trial data and genotypic DArT and TRAP marker characterizations within a GWAS approach including population structure as random covariates may prove to be highly successful. Moreover, sequences of DArT marker associated with the traits of interest were aligned in chromosomal regions where sorghum QTLs has previously been reported. This approach could be a valuable tool to assist the improvement of sugarcane and better supply sugarcane demand that has been projected for the upcoming decades.

Influencia de diferentes factores en el crecimiento de bacterias endófitas de caña de azúcar / Influence of different factors in the growth of endophytic bacteria of sugarcane

En Cuba, entre los esfuerzos por lograr la sostenibilidad en la agricultura se han empleado biopreparados a gran escala, los cuales han tenido un gran impacto económico, ecológico y social. La caña de azúcar constituye uno de los principales cultivos agrícolas para nuestro país y tiene gran importancia desde los puntos de vista económico y ecológico a nivel mundial. En el presente trabajo se demostró el efecto de diferentes fuentes de carbono y nitrógeno en el crecimiento de 5 cepas endófitas de caña de azúcar, 3 de Gluconacetobacter diazotrophicus, una de Bacillus licheniformis y una de Enterobacter agglomerans. De igual forma, se estudió la influencia de jugos provenientes de cinco variedades, así como diferentes concentraciones de las fitohormonas ácido 3 indolacético (AIA) y ácido giberélico (GA) en el crecimiento. Se demostró que la asparagina y el sulfato de amonio como fuentes de nitrógeno adicionadas al medio LGI posibilitan un mayor crecimiento de las bacterias endófitas estudiadas. El medio LGI suplementado con jugo de caña de azúcar favorece significativamente (p≤0,05) el crecimiento de los microorganismos endófitos y no existe relación directa entre el origen varietal del jugo y de las cepas. Por otra parte las fitohormonas en bajas concentraciones favorecieron el crecimiento, no ocurriendo así cuando se encuentran a elevadas concentraciones en el medio de cultivo. Es necesario estudiar todos los factores que pueden influir en la interacción entre la planta y los endófitos para poder utilizar sus potencialidades como promotores del crecimiento vegetal.

Among the efforts done in Cuba to the sustainability in the agricultural system, one of them is the use of bioproducts, which have a relevant economic, ecological and social impact. The sugarcane is one of main crops in our country and it has a great importance at world level. In the present work is demonstrated the effect of different carbon and nitrogen sources in the growth of 5 entophytic bacteria (three of Gluconacetobacter diazotrophicus, one of Bacillus licheniformis and one of Enterobacter agglomerans) were demonstrated. As the same form are studied the influence of juices from five varieties, as well as, different concentrations of fitohormones indole3acetic acid and giberelic acid on the growth. Was demonstrated that asparagine and ammonium sulfate as nitrogen sources added to LGI medium enhance the growth a major growth of the studied endophytic bacteria. The LGI medium supplied with juices of sugarcane enhance the growth of microorganisms (p≤0,05) and don't exist any relationships among the origin of the juice and the strains. On the other hand, the fitohormones at low concentrations don't affect the growth but at high levels of these hormones inhibit the growth. It's necessary to study the factors that have influence on the interaction between the plant and endophytes to use their potentialities as plant growth promoters.

Efeitos da fertirrigação sobre a ocorrência e danos de Mahanarva fimbriolata (Stål) (Hemiptera: Cercopidae) em cana-de-açúcar / Effects of fertigation on the occurence and damages of Mahanarva fimbriolata (Stål) (Hemiptera: Cercopidae) in sugarcane

O Brasil se destaca como o maior produtor mundial de cana-de-açúcar e sua produtividade está intimamente relacionada à disponibilidade de água e nitrogênio durante seu desenvolvimento e também à incidência de insetos-praga. Dentre as espécies mais nocivas à cana-de-açúcar no Brasil, destaca-se Mahanarva fimbriolata, a qual tem comprometido seriamente sua produtividade. Nesse contexto, o presente trabalho teve como objetivo avaliar o efeito da fertirrigação nitrogenada sobre a incidência e os danos ocasionados por M. fimbriolata em cana-de-açúcar. O experimento foi composto por cinco tratamentos e quatro repetições em delineamento de blocos casualizados (DBC). Os tratamentos foram constituídos por quatro doses de N-fertilizante e controle (0, 50, 100, 150 e 200 kg.ha-1) em sistema de irrigação por gotejamento. Os parâmetros avaliados foram: número de ninfas nas raízes, produtividade de colmos (TCH), produtividade de açúcar (TPH), açúcar total recuperável (ATR), pol de cana corrigido (PCC) e margem de contribuição agrícola. Foi observado que a produtividade de colmos e de açúcar aumentou com a adubação nitrogenada por meio da irrigação. O uso de 200 kg.ha-1 de N-fertilizante elevou a incidência de M. fimbriolata até os níveis de controle e dano econômico. O maior rendimento financeiro foi obtido com a dose de 150 kg.ha-1 de N-fertilizante.(AU)

Brazil stands out as the world's largest producer of sugarcane and its productivity is closely related to the availability of water and nitrogen during its development and also to the incidence of pest insects. Among the species most harmful to the sugarcane in Brazil, Mahanarva fimbriolata stands out, which has seriously endangered the yields. In this context, the present study aimed to evaluate the effect of the nitrogen fertirrigation on the incidence and damage caused by M. fimbriolata in sugarcane. The experiment was composed of five treatments and four replications in a randomized block design (RBD). The treatments were composed of four doses of N-fertilizer and control (0, 50, 100, 150, 200 kg.ha-1) in drip irrigation system. The parameters evaluated were: number of nymphs in the roots, stalk productivity, sugar content, percentage of sugar, total recoverable sugar and the agricultural contribution margin. It was observed that the fertirrigation increases the productivity of stalks and sugar with the increase of nitrogen fertilization by irrigation. The use of 200 kg.ha-1 of N-fertilizer increased the incidence of M. fimbriolata up to the control and economic damage levels. The biggest financial yield was obtained with the dose of 150 kg.ha-1 of N-fertilizer.(AU)

Produtividade e rendimento industrial da cana-de-açúcar em função de lâminas de irrigação / Productivity and industrial yield of sugarcane as a function of irrigation depths

O presente trabalho foi desenvolvido com o objetivo de determinar as lâminas de irrigação que resultem na máxima produtividade, no máximo rendimento econômico e no máximo rendimento industrial da cana-deaçúcar e a relação existente entre a lâmina de água e a formação de dextrana. O experimento foi instalado em outubro de 2010 em Jaíba/MG, em uma área irrigada por pivô central, com cana-de-açúcar no quarto ciclo de produção. Para a aplicação dos tratamentos, trocaram-se os bocais dos emissores, em cada vão entre torres do pivô central, de modo que fossem aplicadas as lâminas referentes a 25, 50, 75, 100, 125 e 150% da evapotranspiração da cultura, com o manejo da irrigação realizado para atender a demanda de 100%. Determinou-se a produtividade de colmos e o rendimento industrial da cana-de-açúcar, expressos em açúcares totais recuperáveis (ATR) e os teores de dextrana. Com os dados de produtividade e os custos relacionados à irrigação, calculou-se as lâminas para obtenção da máxima produtividade física (Lmpf) e do máximo rendimento econômico (Lmre), considerando-se a produtividade de colmos e de açúcares. Analisando-se os resultados obtidos, concluiu-se que: a lâmina que proporcionou a maior produtividade de colmos foi de 1.537 mm, para a produtividade de 112,3 t ha-1, ou seja, são necessários 136,9 m3 de água para se produzir uma tonelada de colmos. A lâmina de maior rendimento econômico foi de 1.334 mm para uma produtividade de 108,5 t ha-1. O maior rendimento de açúcares (158,1 kg t-1) foi obtido com lâmina de 1.373 mm. A lâmina que proporcionou a maior produtividade de açúcares (17,56 t ha-1) foi de 1.508,4 mm. O melhor rendimento econômico, em termos de açúcares por unidade de área, foi de 17,4 t ha-1(lâmina recomendada), com fornecimento de 1.406 mm de água, resultando na necessidade de 808 m3 de água para se produzir uma tonelada de açúcar. Lâminas acima de 1.000 mm no ciclo da cultura promoveram teores de dextrana acima dos limites estabelecidos para produção de açúcar. Recomenda-se para as indústrias de etanol e, principalmente de açúcar, introduzirem as análises de dextrana na rotina laboratorial.

The present work was developed due to determine the irrigation depths that result in the maximum productivity, maximum economic yield and the maximum industrial yield of sugarcane, and the relationship between water depth and the formation of dextran. The experiment was installed in October 2010 in Jaíba/MG, Brazil, in an area irrigated by a center pivot with sugarcane in the fourth cycle. For the application treatments the emitter nozzles were exchanged so that the depths were applied referring to 25, 50, 75, 100, 125 and 150% of crop evapotranspiration with irrigation management performed to meet the 100% of the demand. Stalk productivity and industrial yield of sugarcane were determined, as well as levels of ATR and dextran. With productivity data and irrigation costs, the maximum productivity (Lmpf), and maximum economic yield (Lmre) were calculated considering the stalk and sugar yields. The values obtained were subjected to analysis of variance and subsequently developed regressions. Analyzing the results, it was concluded that: the depth that provided the highest stalk yield was 1,537 mm, for a yield of 112.3 t ha-1, i.e. 136,9 m3 of water are necessary do produce one ton of stalks. The depth resulting in greatest economic yield was 1,334 mm for a yield of 108.5 t ha-1. The greatest sugar yield (158.1 kg t-1) was obtained with the depth of 1,373.1 mm. Highest sugar yield (17.56 t ha-1) was obtained from the depth of 1,508 mm. The best economic performance, in terms of sugar per unit area was 17.4 t ha-1, with supply of 1,405.9 mm of water, resulting in a water demand of 808 m3 to produce one ton of sugar. The best economic performance, in terms of sugar per unit area was 17.4 t ha-1 with the supply of 1,406 mm of water (recommended depth). Irrigation depths up to 1,000 mm in the crop cycle promoted dextran levels above the limits established for sugar production. It is recommended that the ethanol industries, and especially sugar industries, utilize dextran analyses in the laboratorial routine.

Indicadores morfo-fisiológicos do estresse hídrico para a cultura da cana-de-açúcar em função de lâminas de irrigação / Morpho-physiological indicators of water stress on sugarcane as a function of irrigation depths

O presente trabalho foi desenvolvido, objetivando-se encontrar as relações entre lâmina de água (chuva e irrigação) e indicadores morfológico (índice de área foliar) e fisiológicos do estresse hídrico (temperatura foliar, potencial hídrico foliar e índice de clorofila nas folhas) na cana-de-açúcar submetida a diferentes lâminas de irrigação. O experimento foi instalado em outubro de 2010 em Jaíba/MG, em uma área irrigada por pivô central, com cana-de-açúcar no quarto ciclo. Para a aplicação dos tratamentos, trocaram-se os bocais dos emissores, em cada vão entre torres, de modo que fossem aplicadas as lâminas referentes a 25, 50, 75, 100, 125 e 150% da evapotranspiração da cultura, com o manejo da irrigação realizado para atender a demanda de 100%. Foram medidos o índice de área foliar, o potencial hídrico foliar, a temperatura foliar e o índice de clorofila nas folhas. Os valores obtidos foram submetidos a análises de variância e, posteriormente, elaboradas regressões. Diante dos resultados, foi possível concluir que houve tendência de aumento do índice de área foliar (IAF) da cana-de-açúcar à medida que se aumentou a lâmina de irrigação no ciclo da cultura; o aumento do IAF foi mais acentuado nos tratamentos que receberam mais água; o potencial hídrico foliar foi menor para menores lâminas de irrigação, com destaque para o tratamento que recebeu menos água (25%); a temperatura foliar foi próxima à temperatura do ar nos tratamentos que receberam as maiores lâminas (100 a 150%), com tendência de aumento da diferença entre a temperatura das folhas, à medida que se reduziu o suprimento hídrico; houve tendência de aumento do índice de clorofila (ICF) à medida que se aumentou as lâminas, com leve queda nos tratamentos que receberam lâminas maiores que 100% da ETc.

The present study was developed to evaluate relationships between the water depths (rain and irrigation) and morphological (leaf area index) and physiological indicators (leaf temperature, leaf water potential and chlorophyll content in leaves) of water stress on sugarcane subject to different irrigation levels. The experiment was installed in October 2010 in Jaíba/MG, Brazil, in an area irrigated by a center pivot system with sugarcane in the fourth cycle. For the treatments, emitter nozzles were exchanged in each vain between pivots so that the depths applied related to 25, 50, 75, 100, 125 and 150% of evapotranspiration, with the irrigation management performed to meet 100% of the demand. The factors of leaf area index, leaf water potential, leaf temperature and leaf chlorophyll index were measured. The values obtained were subjected to analysis of variance and subsequently developed regressions. From the results, it was concluded that there was a trend of increased leaf area index (LAI) for sugarcane as increasing the water depth in the crop cycle; the increase in LAI was more pronounced in treatments that received more water; leaf water potential was lesser for smaller irrigation depths, with emphasis on the treatment that received less water (25%); leaf temperature was close to the air temperature in the treatment receiving the highest depths (100 and 150%) with a trend for an increased difference between the temperature of the leaves as reducing the water supply; the chlorophyll index (ICF) tended to increase as increasing the depths, with a slight drop in treatments receiving depths greater than 100% of the ETc.

Dinâmica de infestação de plantas daninhas em variedades de cana-de-açúcar / Infestation dynamics of weed in sugarcane varieties

A seleção de genótipos mais adaptados às condições de estresses bióticos e abióticos aliados com características agronômicas favoráveis são fatores preponderantes para o sucesso no cultivo da cana-de-açúcar. Neste contexto objetivou-se avaliar a dinâmica de infestação de plantas daninhas e o comportamento de variedades de cana-deaçúcar em condições do semiárido norte mineiro. O experimento foi disposto em blocos casualizados, com quatro repetições e oito variedades de cana-de-açúcar: RB72454, RB867515, RB739735, RB835486, SP81-3250, IAC86-2480, SP80-1842 e RB855536. Nos levantamentos fitossociológicos realizados aos 30 e 150 dias após o plantio (DAP), foram identificadas 25 espécies daninhas distribuídas em 10 famílias, sendo as mais representativas com relação ao número de espécies a Poaceae (9), Fabaceae (4), Malvaceae (3) e Convolvulaceae (2). As principais espécies encontradas no primeiro levantamento foram: Sida rhombifolia, Aeschynomene denticulata, Sida sp., Ipomoea triloba e Senna obtusifolia. Aos 150 DAP as espécies S. rhombifolia, Brachiaria decumbens, Sida sp., Panicum maximum, Sida cordifolia e Brachiaria brizantha obtiveram os maiores IVI e IVC. A similaridade entre as épocas de avaliação foi de 41,86% o que indica baixa homogeneidade das espécies presentes no canavial entre as duas fases da cultura. Entre as variedades a similaridade das comunidades foi alta na primeira avaliação e baixa aos 150 DAP, o que indica influência das variedades cultivadas sobre as plantas daninhas presentes. A variedade de cana-de-açúcar com menor IVE apresentou a maior biomassa de plantas daninhas aos 150 DAP. Dentre as variedades de cana-de-açúcar avaliadas as mais produtivas foram RB72454, RB867515 e SP81-3250.

The selection of adapted genotypes to the conditions biotic and abiotic stresses allies by favorable agronomic characteristics are critical factors for success in the grown of sugarcane. In this context aimed to evaluate the infestation dynamics of weed and behavior of sugarcane varieties in conditions of semi-arid northern Minas Gerais. The experiment was arranged a randomized block design four replicates and sugarcane varieties: RB72454, RB867515, RB739735, RB835486, SP81-3250, IAC86-2480, SP80-1842 and RB855536. In phyto-sociology surveys conducted at 30 and 150 days after planting (DAP), were identified 25 weed species distributed in 10 families, the most representative with respect to the number of species Poaceae (9), Fabaceae (4), Malvaceae (3) and Convolvulaceae (2). The main species found in the first survey were: Sida rhombifolia, Aeschynomene denticulata, Sida sp., Ipomoea triloba and Senna obtusifolia. The highest IVI and IVC in the survey 150 DAP were found for the species Sida rhombifolia, Brachiaria decumbens, Sida sp., Panicum maximum, Brachiaria brizantha and Sida cordifolia. The similarity between the evaluation periods was 41.86% which indicates low homogeneity of the species present in the sugarcane fields between the two phases of culture. Among the varieties of communities similar was high at the first evaluation and low at 150 DAP, indicating influences of grow varieties on weeds. A variety of sugarcane with lower IVE had the highest weed biomass at 150 DAP. Among the varieties of cane sugar worked were the most productive RB72454, RB867515 and SP81-3250.

Functional characterization of sugarcane mustang domesticated transposases and comparative diversity in sugarcane, rice, maize and sorghum.

Transposable elements (TEs) account for a large portion of plant genomes, particularly in grasses, in which they correspond to 50%-80% of the genomic content. TEs have recently been shown to be a source of new genes and new regulatory networks. The most striking contribution of TEs is referred as "molecular domestication", by which the element coding sequence loses its movement capacity and acquires cellular function. Recently, domesticated transposases known as mustang and derived from the Mutator element have been described in sugarcane. In order to improve our understanding of the function of these proteins, we identified mustang genes from Sorghum bicolor and Zea mays and performed a phenetic analysis to assess the diversity and evolutionary history of this gene family. This analysis identified orthologous groups and showed that mustang genes are highly conserved in grass genomes. We also explored the transcriptional activity of sugarcane mustang genes in heterologous and homologous systems. These genes were found to be ubiquitously transcribed, with shoot apical meristem having the highest expression levels, and were downregulated by phytohormones. Together, these findings suggest the possible involvement of mustang proteins in the maintenance of hormonal homeostasis.

Comparação de ambientes na germinação de cariopses de cana-de-açúcar / Environment comparison in the germination of sugarcane seeds

A obtenção de cariopses de cana-de-açúcar por meio de cruzamento de parentais é de primordial importância para os programas de melhoramento de cultivares. Objetivou-se, neste trabalho comparar o ambiente de germinação de cariopses da casa de vegetação do Programa Cana IAC com um ambiente de condições controladas, a fim de avaliar sua eficiência, no período de 30/09 a 09/10/2004. Foram desenvolvidos dois experimentos, em delineamento experimental de blocos casualizados com quatro repetições, em Jaú, SP. Um deles foi montado sob condições de laboratório em câmara de germinação e outro em casa de vegetação em condições não controladas, sendo cada tratamento constituído por 100 cariopses por repetição, provenientes de seis cruzamentos. Foram realizadas avaliações do índice de velocidade de germinação (IVG), da porcentagem ( por centoG) e dos dias para emergência (DE), em intervalos de 24 horas, após a instalação dos testes. A massa de 100 sementes de cada cruzamento também foi avaliada com o propósito de verificar sua influência nos demais atributos da germinação. Os resultados foram submetidos à análise de variância e a comparação de médias foi feita pelo teste de Tukey, a 0,05 de significância. A massa de 100 sementes foi diferente entre os cruzamentos, e interferiu, de maneira geral, nos atributos IVG e por cento G. Concluiu-se que a casa de vegetação utilizada pelo Programa Cana IAC proporciona porcentagens de germinação semelhantes às da câmara de germinação, porém condições controladas favorecem o IVG e os DE.

The production of true seeds of sugarcane through parental crossing is primordial for the breeding programs of cultivars. With the objective of comparing the efficiency of the environment greenhouse used for seed germination in the IAC Sugarcane Program with an environment with controlled conditions (germination chamber), two experiments were carried out in a completely randomized block with four replicates of 100 seeds each, in Jaú (SP), from 09/30 to 10/09/2004. In both places the treatments were composed of seeds from six crossings. The evaluations accomplished were speed of germination index (SGI), germination percentage ( percent G) and days for emergence (DE) in 24 h intervals after set up treatments. The mass of 100 seeds of each crossing was also evaluated with the purpose of measuring its influence on other germination attributes. The data were submitted to the analysis of variance and averages were compared by the Tukey test at 0.005 significance. The weight of 100 seeds differed among the crossings, and, in general, it interfered with the attributes SGI and percent G. It was concluded that the greenhouse used by the IAC Sugarcane Program provides germination percentages similar to the germination chamber; however, controlled conditions improve SGI and DE.