Ultrasonic treatment alleviated cadmium stress in sugarcane via improving antioxidant activity and physiological and biochemical status.

Cadmium (Cd) is a toxic element that endangers crop growth and affects food safety and human health. Therefore, the study of Cd mitigation technology is important. Ultrasonic treatment can improve crop growth and enhance their ability to resist various abiotic stresses. In this study, the effect of ultrasonic treatment on alleviating sugarcane Cd stress was studied in a barrel experiment using sugarcane varieties 'ROC22' and 'LC05-136' as test materials. Sugarcane buds without ultrasonic treatment and with ultrasonic treatment (20-40 kHz mixed frequency ultrasound for 2 min, dry treatment) were planted in soil with Cd contents of 0, 50, 100, 250, and 500 mg·kg-1. Compared with non-ultrasonic treatment, Ultrasonic treatment significantly increased the activities of antioxidant enzymes in sugarcane, significantly increased the content of osmoregulation substances, significantly reduced the content of superoxide anion (the highest decreases reached 11.55%) and malondialdehyde (the highest decreases reached 20.59%), and significantly increased the expression level of metallothionein (MT)-related genes, with the expression of ScMT1 increased by 8.80-37.49% and the expression of ScMT2-1-5 increased by 1.55-69.33%. In addition, ultrasonic treatment significantly reduced the Cd contents in sugarcane roots, stems, leaves, bagasse, and juice (the highest reduction in Cd content was 49.18%). In general, ultrasonic treatment regulated the metabolism of reactive oxygen species and MT-related gene expression in sugarcane, increased the Cd tolerance of sugarcane, promoted photosynthesis in sugarcane leaves, improved root morphology, enhanced sugarcane growth, and increased cane and sugar yield.

Revisiting the physical mutagenesis for sugarcane improvement: a stomatal prospective.

This study was conducted to investigate the influence of gamma rays on stomatal parameters and the interaction of these traits with agronomy of the sugarcane crop. Three genotypes of sugarcane (NIA-0819, NIA-98, and BL4) were exposed to four doses of gamma radiation (10, 20, 30, and 40 Gy) and then subjected to field trials. Stomatal length, width, and density were observed using scanning electron microscopy. Moreover, agronomic and sugar-related characteristics of the crop were determined at maturity. The stomatal parameters augmented at two lower doses of gamma radiation (10 and 20 Gy) and declined under higher doses (30 and 40 Gy). The maximum stomatal length was observed in NIA-0819 at 10 Gy (63.71 µm), whereas NIA-98 and BL4 demonstrated highest stomatal length under 20 Gy (54.11 and 57.40 µm, respectively), indicating a role of genetic factors in varietal response. Similar trend was noticed for stomatal width and density as well. The lowermost treatment (10 Gy) of NIA-0819 produced maximum stomatal density (115.31 stomata mm-2 on the abaxial surface). Adaxial stomatal density was significantly lower than the abaxial one. Sugar quality attributes revealed a different tendency. Sucrose contents of BL4 increased gradually from 12.33% at control to 14.54% at 40 Gy. Yield and yield-contributing traits of genotypes indicated a strong positive correlation with the stomatal parameters. The present study suggested that gamma radiations cause variations in stomatal characteristics of sugarcane. These changes further influence the photosynthetic activity and instigate a direct impact on the agronomic performance of the crop.

Foliar application of gamma radiation processed chitosan triggered distinctive biological responses in sugarcane under water deficit stress conditions.

Chitosan, being one of the most promising biological macromolecules, has an immense scope in agriculture to boost crop growth and defense responses. In this study, chitosan was exposed to gamma rays in order to obtain a low molecular weight derivative. Viscometric characterization showed a sharp decrease in molecular weight and FTIR based analysis confirmed retention of structural integrity of the polymer upon gamma irradiation. Assessments of various physiological and biochemical attributes were carried out on sugarcane plantlets that were subjected to progressive water deficit stress. The irradiated chitosan was found to differentially ameliorate water deficit stress tolerance against that of normal chitosan through positive modulation of various gas exchange parameters alongside significant improvement in relative tissue water content, SOD activity, soluble sugars and adenine energetics. Furthermore, application of irradiated chitosan significantly reduced cell membrane damage, lipid peroxidation, H2O2 and free-proline accumulations. This is the first report on the use of gamma irradiated chitosan to alleviate water deficit stress tolerance in sugarcane. Overall comparative assessments showed that differential plant responses were triggered upon foliar application of normal and gamma irradiated chitosan in sugarcane plants grown under water deficit stress conditions.

Plant growth, radiation use efficiency and yield of sugarcane cultivated in agroforestry systems: An alternative for threatened ecosystems.

Sugarcane (Sacharum officinarum L.) monocropping has had a great socio-economic and environmental impact in Brazil, and agroforestry systems have been considered as an alternative for more sustainable production; however, there is a lack of field research under such conditions. The aim of this study was to evaluate the growth rates, radiation use efficiency and yield traits in sugarcane cultivated in the understory of Aleurites fordii, in two agroforestry arrangements and monocropping systems. A field experiment was conducted from July 2015 to June 2016 in the city of Frederico Westphalen, Rio Grande do Sul, Brazil. The radiation use efficiency, assimilate partitioning, leaf area index, absolute growth rate, net assimilation rate, number of tillers, plant height, % of intercepted solar radiation, extinction coefficient, and yield in each system was evaluated. In agroforestry systems, the dynamic interactions between multiple plant species change with the time and can result in unique microclimates. The use of agroforestry systems in 12 x 12m arrangements should be prioritized because it enables greater yields and radiation availability in the understory. This study sought to provide new sustainable alternatives for farmers in order to increase the diversification of the rural property and maintain the preservation of existing agroecosystems.

Effect of growing media and fertilization on sugarcane flowering under artificial photoperiod.

The USDA-ARS Sugarcane Variety Development Program in Houma, LA aims to maximize the number of panicles available for crossing through artificial manipulation of the environment. In a three-year study, the effect of growing media, fertilizer treatment, and their interaction on sugarcane flowering (% of panicles emerged), and number of days to flowering (DTF) under an artificial photoperiod treatment were assessed. The commercially-available sugarcane cultivar, 'HoCP 96-540' was planted in 2.8-L pots and subjected to the standard local photoperiod treatment. The cultivar was planted in four growing media (RediEarth Seedling and Germination Mix, Fafard, Metro-Mix®902, and Metro-Mix®900) and subjected to three different fertilizer applications. In the control treatment, fertilizer application was stopped prior to the commencement of the photoperiod treatment as practiced in some sugarcane breeding programs. The continuous treatment consisted of an application of a 10 ml solution of a NPK three times a week between June and October. The partial treatment consisted of applications of the same NPK solution applied post-initiation between September and October. Nitrogen starvation prior to the commencement of the photoperiod treatment is generally accepted to improve flower initiation; thus the standard practice is to cease nitrogen application two weeks prior to beginning a photoperiod regime. The growing media used in this study did not have a significant effect on days to flowering or percent panicle emergence. In our study, the control fertilizer treatment showed a flowering percentage across all growing media types of 21.2% less than a continuous fertilization regime. Furthermore, a significant trend was observed between fertilization treatments and days to flowering, with the continuous treatment producing panicles, on average across growing media, four days earlier than the control treatment, and six days earlier than the partial treatment. Evidence across this three-year experiment indicates that we should consider modifying plant nutrition management as soil fertility was found to be inadequate.

Ozonolysis combined with ultrasound as a pretreatment of sugarcane bagasse: Effect on the enzymatic saccharification and the physical and chemical characteristics of the substrate.

Sugarcane bagasse (SCB) was treated in three stages using ozone oxidation (O), washing in an alkaline medium (B) and ultrasonic irradiation (U). The impact of each pretreatment stage on the physical structure of the SCB was evaluated by its chemical composition, using an infrared technique (FTIR-ATR), and using thermogravimetric analysis (TGA/DTG). The pretreatment sequence O, B, U provided a significant reduction of lignin and hemicellulose, which was confirmed by changes in the absorption bands corresponding to these compounds, when observed using infrared. Thermogravimetric analysis confirmed an increased thermal stability in the treated sample due to the removal of hemicellulose and extractives during the pretreatment. This pretreatment released 391mg glucose/g from treated SCB after the enzymatic hydrolysis, corresponding to a yield of 94% of the cellulose available.

Circadian rhythms of sense and antisense transcription in sugarcane, a highly polyploid crop.

Commercial sugarcane (Saccharum hybrid) is a highly polyploid and aneuploid grass that stores large amounts of sucrose in its stem. We have measured circadian rhythms of sense and antisense transcription in a commercial cultivar (RB855453) using a custom oligoarray with 14,521 probes that hybridize to sense transcripts (SS) and 7,380 probes that hybridize to antisense transcripts (AS).We estimated that 32% of SS probes and 22% AS probes were rhythmic. This is a higher proportion of rhythmic probes than the usually found in similar experiments in other plant species. Orthologs and inparalogs of Arabidopsis thaliana, sugarcane, rice, maize and sorghum were grouped in ortholog clusters. When ortholog clusters were used to compare probes among different datasets, sugarcane also showed a higher proportion of rhythmic elements than the other species. Thus, it is possible that a higher proportion of transcripts are regulated by the sugarcane circadian clock. Thirty-six percent of the identified AS/SS pairs had significant correlated time courses and 64% had uncorrelated expression patterns. The clustering of transcripts with similar function, the anticipation of daily environmental changes and the temporal compartmentation of metabolic processes were some properties identified in the circadian sugarcane transcriptome. During the day, there was a dominance of transcripts associated with photosynthesis and carbohydrate metabolism, including sucrose and starch synthesis. During the night, there was dominance of transcripts associated with genetic processing, such as histone regulation and RNA polymerase, ribosome and protein synthesis. Finally, the circadian clock also regulated hormone signalling pathways: a large proportion of auxin and ABA signalling components were regulated by the circadian clock in an unusual biphasic distribution.

Identification and cloning of molecular markers for UV-B tolerant gene in wild sugarcane (Saccharum spontaneum L.).

Previously we have selected wild sugarcane (Saccharum spontaneum L.) sterile lines that are tolerant or susceptible to UV-B radiation based on response index (RI) in a field screening test. The RI was established according to plant height, tiller number, leaf index, total biomass and brix under enhanced ultraviolet-B (UV-B, 280-310 nm) radiation. In this experiment, molecular markers linked to the UV-B tolerant and susceptible genes were identified and cloned. RAPD (Randomly amplified polymorphic DNAs) assay using 100 arbitrary primers followed by clustering analysis separated the tolerant and susceptible lines into two groups at the genetic distance of 0.380. The UV-B tolerant and susceptible gene pools were constructed and compared using the Bulked Segregate Analysis (BSA) approach. Of the 100 arbitrary RAPD primers, primer OPR16 produced polymorphic DNA banding patterns from both gene pools. The OPR16-1200 bp DNA fragment was only amplified from the tolerant lines and the OPR16-800 bp from the susceptible ones. These two PCR fragments were cloned onto T-vector. DNA sequence alignment analysis determined that 42% homology existed between the reverse and forward sequences of the OPR16-1200 bp clone, and 36% homology between the forward sequences of the OPR16-800 bp and OPR16-1200 bp clones. The two DNA clones were determined to be linked to the UV-B tolerant and susceptible genes, and they can be used to develop molecular markers for the associated traits.

Microwave modification of sugar cane to enhance juice extraction during milling.

Sugar extraction from cane requires shredding and crushing, both of which are energy intensive activities. Cane shredders account for almost 30% of the total power requirements for the juice extraction train in a sugar mill with four mills. Shredder hammers also wear quickly during the crushing season and need to be regularly maintained or replaced. Microwave pre-treatment of other plant based materials has resulted in significant reductions in total processing energy. This paper briefly reviews the underlying structure of sugar cane and how microwave pre-treatment may interact with sugar cane. Microwave treatment reduced the strength of sugar cane samples to 20% of its untreated value. This strength reduction makes it easier to crush the cane and leads to a 320% increase in juice yield compared with untreated cane when cane samples were crushed in a press. There was also a 68% increase in Brix %, a 58% increase in total dissolved solids, a 58% reduction in diffusion time, a 39% increase in Pol%, and a 7% increase in juice purity compared with the control samples after 60 minutes of diffusion in distilled water.

Elevated CO2 increases photosynthesis, biomass and productivity, and modifies gene expression in sugarcane.

Because of the economical relevance of sugarcane and its high potential as a source of biofuel, it is important to understand how this crop will respond to the foreseen increase in atmospheric [CO(2)]. The effects of increased [CO(2)] on photosynthesis, development and carbohydrate metabolism were studied in sugarcane (Saccharum ssp.). Plants were grown at ambient (approximately 370 ppm) and elevated (approximately 720 ppm) [CO(2)] during 50 weeks in open-top chambers. The plants grown under elevated CO(2) showed, at the end of such period, an increase of about 30% in photosynthesis and 17% in height, and accumulated 40% more biomass in comparison with the plants grown at ambient [CO(2)]. These plants also had lower stomatal conductance and transpiration rates (-37 and -32%, respectively), and higher water-use efficiency (c.a. 62%). cDNA microarray analyses revealed a differential expression of 35 genes on the leaves (14 repressed and 22 induced) by elevated CO(2). The latter are mainly related to photosynthesis and development. Industrial productivity analysis showed an increase of about 29% in sucrose content. These data suggest that sugarcane crops increase productivity in higher [CO(2)], and that this might be related, as previously observed for maize and sorghum, to transient drought stress.

Fractional and physico-chemical characterization of hemicelluloses from ultrasonic irradiated sugarcane bagasse.

The present study was undertaken to investigate the extractability of the hemicelluloses from bagasse obtained by ultrasound-assisted extraction methods. The results showed that the ultrasonic treatment and sequential extractions with alkali and alkaline peroxide under the conditions given led to a release of over 90% of the original hemicelluloses and lignin. This fact as well as the sugar composition and structural features of the isolated seven hemicellulosic fractions indicated that ultrasonication attacked the integrity of cell walls, cleaved the ether linkages between lignin and hemicelluloses, and increased accessibility and extractability of the hemicelluloses. Increasing alkali concentration from 0.5 to 2M and alkaline peroxide percentage from 0.5% to 3.0% resulted in degradation of hemicellulosic backbone as shown by a decrease in their molecular weights from 43,580 to 14,470 and 30,180 to 18,130gmol(-1), respectively. However, there were no significant differences in the structural features of the seven sequential alkali- or alkaline peroxide-soluble hemicellulosic fractions, which are composed mainly of L-arabino-(4-O-methyl-D-glucurono)-D-xylans. Ferulic and p-coumaric acids were found to be chemically linked with hemicelluloses.