Search

The β-glucosidase gene from Aspergillus nidulans FGSC A4 was cloned and overexpressed in the A. nidulans A773. The resulting purified β-glucosidase, named AnGH3, is a monomeric enzyme with a molecular weight of approximately 80 kDa, as confirmed by SDS-PAGE. Circular dichroism further validated its unique canonical barrel fold (β/α), a feature also observed in the 3D homology model of AnGH3. The most striking aspect of this recombinant enzyme is its robustness, as it retained 100% activity after 24 h of incubation at 45 and 50 ºC and pH 6.0. Even at 55 °C, it maintained 72% of its enzymatic activity after 6 h of incubation at the same pH. The kinetic parameters Vmax, KM, and Kcat/KM for ρ-nitrophenyl-β-D-glucopyranoside (ρNPG) and cellobiose were also determined. Using ρNPG, the enzyme demonstrated a Vmax of 212 U mg − 1, KM of 0.0607 mmol L − 1, and Kcat/KM of 4521 mmol L − 1 s − 1 when incubated at pH 6.0 and 65 °C. The KM, Vmax, and Kcat/KM using cellobiose were 2.7 mmol L − 1, 57 U mg − 1, and 27 mmol –1 s − 1, respectively. AnGH3 activity was significantly enhanced by xylose and ethanol at concentrations up to 1.5 mol L − 1 and 25%, respectively. Even in challenging conditions, at 65 °C and pH 6.0, the enzyme maintained its activity, retaining 100% and 70% of its initial activity in the presence of 200 mmol L − 1 furfural and 5-hydroxymethylfurfural (HMF), respectively. The potential of this enzyme was further demonstrated by its application in the saccharification of the forage grass Panicum maximum, where it led to a 48% increase in glucose release after 24 h. These unique characteristics, including high catalytic performance, good thermal stability in hydrolysis temperature, and tolerance to elevated concentrations of ethanol, D-xylose, furfural, and HMF, position this recombinant enzyme as a promising tool in the hydrolysis of lignocellulosic biomass as part of an efficient multi-enzyme cocktail, thereby opening new avenues in the field of biotechnology and enzymology. [ABSTRACT FROM AUTHOR]

Recently, metal nanoparticles synthesized by bio-fabrication methods were being used for various life-saving treatments. In our present study, AuNPs were fabricated using aqueous Panicum Maximum (P. Maximum) leaf extract. The analysis of UV–Visible spectrophotometer indicated the excitation of the formed AuNPs, specifically, a distinct SPR band positioned nearly at 530 nm. The formation of AuNPs with 45–50-nm size range was confirmed by TEM. Also, SAED pattern was utilized to characterize single crystalline nature of the biofabricated AuNPs. Further, the anticancer effects of synthesized AuNPs were studied against HepG2 cells. After incubating HepG2 cells with AuNPs, the amount of cytochrome c, CASP 9/CASP 8/CASP 3/BAX expression level, formation of ROS, and cell viability were analyzed. Outcomes of our study showed a dose determined cytotoxicity and half inhibitory concentration (IC50) of 75 μg/mL for the synthesized AuNPs. Cytotoxicity of AuNPs was accompanied by cell apoptosis and ROS induction in cell line of HepG2. Based on our results, AuNPs could have potential for development of new drugs for therapy of liver hepatocellular carcinoma in nursing care. [ABSTRACT FROM AUTHOR]

Manganese (Mn) is essential for plants but very toxic at high rates. However, hyperaccumulators can tolerate high Mn concentrations in plant tissue, especially when properly fertilized with N. Tanzania guinea grass (Megathyrsus maximus Jacq.) has been indicated as metal tolerant and a good candidate for Mn phytoextraction due to its fast growth and high biomass. The objective was to evaluate the Mn hyperaccumulator potential of Tanzania guinea grass grown as affected by proportions of nitrate/ammonium (NO3−/NH4+). An experiment in a growth chamber with nutrient solution, combining NO3−/NH4+ proportions (100/0 and 70/30) and Mn rates (10, 500, 1500, and 3000 μmol L−1), was carried out. The highest Mn concentration was verified in plants grown with 100/0 NO3−/NH4+ and Mn at 3000 μmol L−1, reaching up to 5500 and 21,187 mg kg−1 in shoots and roots, respectively, an overall concentration of 13,345 mg kg−1. These numbers are typically seen in hyperaccumulators. At that combination, Mn accumulation in shoots was also the highest, reaching up to 76.2 mg per pot, a phytoextraction rate of 23.1%. Excess Mn increased both H2O2 concentration in roots and non-photochemical quenching and therefore decreased net photosynthesis, stomatal conductance, electron transport rate, and photochemical quenching. Nevertheless, proline concentration in roots affected by excess Mn was high and indicates its important role for mitigating stress since Mn rates did not even affect the dry biomass. Tanzania guinea grass is highly tolerant to excess Mn as much as a hyperaccumulator. However, to show all its potential, the grass needs to be supplied with N as NO3−. We indicate Tanzania guinea grass as a Mn hyperaccumulator plant. [ABSTRACT FROM AUTHOR]

Crop irrigation requirements are usually estimated based on crop evapotranspiration (ETc) as determined by the reference evapotranspiration (ETo) and crop coefficient (Kc). There is a lack of knowledge on the irrigation requirements of tropical forage crops in Brazil, contrasting with the increasing use of irrigation in pastures. The effort of this study was to investigate what would be the water needs of tropical forages in Southern Brazil, based on a robust experimental database. The study was carried out in São Paulo State-Brazil using different forages species and their combinations [Guinea grass (GG); Guinea grass + black oat + ryegrass (GOR); Bermuda grass (BG), and Bermuda + black oat + ryegrass (BOR)]. The experimental fields were fully irrigated, and the Kc values were derived from ETc measurements on lysimeters; ETo was estimated using daily data from a nearby weather station and the standard FAO56 parameterization. Mean daily ETc values for GG, GOR, BG and BOR were 4.1, 2.9, 3.6, and 3.4 mm, respectively, and respective mean Kc values were 0.99, 0.90, 1.0, and 0.94. Average Kc values for all plots decreased as ETo increased, producing a negative Kc-ETo relationship, mainly when ETo reached values greater than 5 mm d−1. This was most likely due to internal plant stomatal resistance to vapor release from the leaves diffusing to the atmosphere at high ETo. So, the time-based Kc curves described by FAO 56 manual should be adjusted for the analyzed crops considering different ranges of ETo to improve the required irrigation depth. [ABSTRACT FROM AUTHOR]

Remote sensing can serve as a promising solution for monitoring spatio-temporal variability in grasslands, providing timely information about different biophysical parameters. We aimed to develop models for canopy height classification and aboveground biomass estimation in pastures of Megathyrsus maximus cv. Mombaça using machine learning techniques and images obtained from the Sentinel-2 satellite. We used different spectral bands from the Sentinel-2, which were obtained and processed entirely in the cloud computing space. Three canopy height classes were defined according to grazing management recommendations: Class 0 (< 0.45 m), Class 1 (0.45–0.80 m) and Class 2 (> 0.80 m). For modeling, the original database was divided into training data (85%) and test data (15%). To avoid dependency between our training and test datasets and ensure greater generalization capacity, we used a spatial grouping evaluation structure. The random forest algorithm was used to predict canopy height and aboveground biomass by using height and biomass field reference data obtained from 54 paddocks in Brazil between 2016 and 2018. Our results demonstrated precision, recall, and accuracy values of up to 73%, 73%, and 72%, respectively, for canopy height classification. In addition, the models showed reasonable predictive performance for aboveground fresh biomass (AFB) and dry matter concentration (DMC; R2 = 0.61 and 0.69, respectively). We conclude that the combined use of satellite imagery and machine learning techniques has potential to predict canopy height and aboveground biomass of Megathyrsus maximus cv. Mombaça. However, further studies should be conducted to improve the proposed models and develop software to implement the tool under field conditions. [ABSTRACT FROM AUTHOR]

Agroforestry systems are an alternative of land management and landscape restoration, where we can manage cover crops for increasing macronutrient cycling during off-season following harvesting, saving fertilization. However, it is necessary to find out the most effective species to maximize macronutrient cycling and biomass productivity. This study was carried out under a completely randomized design with four repetitions in a stabilized agroforestry system located in Goiânia, Brazil, during 2015 and 2016, among nine years old baru and bark trees. Cover crops were sown in single systems: Pigeon pea (PP); Stylosanthes Campo Grande (ST); Guinea grass (GG); and intercropping systems: PP + GG; and ST + GG. Dry biomass productivity and, plant shoot, and nutrient accumulations (nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur) were quantified twice during the growing season. Our results showed that GG was the best alternative as a cover crop to increase biomasss, potassium, magnesium and sulphur cycling in a single system, with 75% and 65% more shoot dry biomass than ST and PP, respectively. GG and ST increased phosphorus and calcium cycling. The low dry biomass productivity of legumes resulted in similar nitrogen accumulation in grasses and leguminous species. The accumulations of nitrogen, phosphorus, calcium and sulphur are similar between GG, ST and the ST + GG consortium. Our findings suggest that GG is the best alternative to increase macronutrient cycling in agroforestry systems, due its greater supply of biomass compensating the higher nutrient content found in legumes. [ABSTRACT FROM AUTHOR]

Soil contamination caused by improper waste disposal can affect plant growth. Tropical forage plants have rapid growth, high biomass production and vigorous regrowth. Chromium (Cr) is one of the most common contaminants in the environment. Sulfur (S) is a nutrient involved in various cell detoxification processes. The objective was to assess the effects of excess Cr on biomass production and concentrations of this metal, S and cationic micronutrients, under conditions of varying supply of S for Tanzania guinea grass. The experiment was conducted in randomized complete blocks in a 3 × 4 factorial scheme, corresponding to three levels of S (0.1, 1.9 and 3.7 mmol L−1) and four levels of Cr (0.0, 0.5, 1.0 and 2.0 mmol L−1) in three replicates. Root surface area, shoot and root biomass production, concentrations of total S, sulfate-S, Cr and cationic micronutrients, and Cr transport factor were determined. S level of 1.9 mmol L−1 reduced the toxicity by Cr in Tanzania guinea grass, expressed by the higher shoot and root dry weight production, greater stability in the cellular concentration of sulfate-S and higher concentrations of micronutrients. It was concluded that the high availability of S reduced the toxicity by Cr(VI) in Tanzania guinea grass, expressed by the higher shoot and root dry weight production, greater stability in the cellular concentration of sulfate-S and higher concentration of micronutrients in the grass shoots. [ABSTRACT FROM AUTHOR]

Although several grasses have been evaluated for cadmium (Cd) phytoextraction, there are few studies assessing how Cd is accumulated and distributed in the tissues of Panicum maximum grown in mildly spiked soils. The evaluation of tillering, nutritional status and biomass yield of this grass, mainly along successive shoot regrowths, is not well studied so far. Thus, P. maximum Jacq. cv. Massai was grown for two periods in an Oxisol presenting bioavailable Cd concentrations varying from 0.04 (control) to 10.91 mg kg−1 soil. Biomass yield of leaves and stems' growth has decreased under the highest Cd exposure, but it did not occur in the regrowth period, indicating that Cd-induced toxicity is stronger in the early stages of development of P. maximum. The tillering was not compromised even the basal node presenting Cd concentrations higher than 100 mg kg−1 DW. We identified a restriction on Cd transport upwards from basal node, which was the main localization of Cd accumulation. Apparently, P, K, Mg, S and Cu are involved in processes that restrict Cd translocation and confer high tolerance to Cd in P. maximum. The Cd-induced nutritional disorders did not negatively correlate with factors used to calculate phytoextraction efficiency. However, the nutritional adjustments of P. maximum to cope with Cd stress restricted the upward Cd transport, which decreased the phytoextraction efficiency from the available Cd concentration of 5.93 mg kg−1 soil. [ABSTRACT FROM AUTHOR]

The Cerrado is one of the most important regions for agricultural development in the world and is the main productive breadbasket of the Americas. One of the main agricultural activities in the region is high-tech livestock. Cerrado soils are predominantly low in fertility, and arbuscular mycorrhizal fungi play a fundamental role in plant nutrition in this biome. Understanding the behavior of mycorrhizal fungi in the soil under pasture is essential for the development of more efficient and sustainable management practices. Thus, this work aims to verify the activity of arbuscular mycorrhizal fungi in different species of forage grasses cultivated in cerrado soil. To measure mycorrhizal activity, soil spore density factors and mycorrhizal colonization rates in roots of 14 forage grass genotypes were investigated. No significant differences were identified in spore density values between the investigated genotypes. Panicum maximum cv and Mombasa showed the lowest values of mycorrhizal colonization, and the highest values were found in the roots of Brachiaria decumbens. Among the identified genera associated with the rhizosphere of the genotypes studied, Gigaspora, Scutelospora and Sclerocysts are less frequent, which indicates that the association with these fungal genera is less recurrent than with the others. [ABSTRACT FROM AUTHOR]

Nitrogen fertilization has been recognized as an essential tool towards the establishment of sustainable intensification of pasture-based livestock systems using tropical perennial grasses if, for a given ecosystem it is capable of increasing forage growth, stocking rates and animal performance. This study assessed pasture growth traits, nutritive value, animal and economic responses of Panicum maximum cv. Mombaça guinea grass pastures subjected to different levels of N fertilization (100 (N100), 200 (N200), and 300 (N300) kg N ha−1 yr−1). Pastures were managed under rotational stocking to maintain similar pre (80–90 cm) and post-grazing (45 cm) canopy heights. A partial budget and a Benefit–Cost Analysis were used to assess the economic returns on increasing N fertilization. N300 resulted in greater post-grazing herbage mass. A slightly higher neutral fiber and acid lignin detergent was observed at N100 (P < 0.05); crude protein increased linearly, and in vitro digestible organic matter reached maximum value at 265.4 kg N ha−1 yr−1. Annual averages of animal weight gain were 515, 590 and 660 g d−1, respectively, for N100, N200 and N300. There was a decrease from 3.7 to 1.9 kg of body weight gain per kg of additional N applied when increasing N rates from 100 to 200 and from 100 to 300 kg ha−1. The net profit improved with increasing N levels, but at reducing rates, reaching its maximum at the N300 level. The change from 100 to 200 kg N ha−1 presented the best return, with USD 3.73 for each additional dollar invested, while the change from 200 kg N ha−1 to 300 kg N ha−1 was economically less than optimal, recouping only USD 1.60 for each dollar. The N300 rate presented the highest net profit per hectare (accounting profit), even in a pessimist scenario (25% reduction in production). Despite being profitable, the N300 rate was less than optimal from an economic standpoint, since an additional 100 kg of Nitrogen ha−1 to change from N200 to N300 level reduced both the net returns and the Benefit–Cost ratio. Our results suggest that the economically optimal level of N fertilization for Mombaça guinea grass pasture should be between 200 and 300 kg ha−1. [ABSTRACT FROM AUTHOR]

Climate change increases the occurrence of droughts, decreasing the production of tropical forages through the induction of physiological stress. Si is expected to broaden the limit from physiological stress of forages grown under water restriction, which may come from an improvement in the stoichiometric homeostasis of Si with N and C, favoring physiological aspects. This study assessed whether Si supply via fertigation improves physiological aspects and the water content in the plant by means of an antioxidant defense system and changes in the C:N:Si stoichiometry during the regrowth of two cultivars of Panicum maximum grown under two soil water regimes (70 and 40% of the soil's water retention capacity). The forages studied are sensitive to water deficit without silicon supply. The application of Si via fertigation attenuated the water deficit, favoring plant growth by stabilizing the stoichiometric homeostasis C:N and C:Si, which are responsible for increasing the plant capacity of converting accumulated C in dry mass, favoring the water content of the plant tissue and the photosynthetic efficiency. This study highlights the importance of the physiological function of Si, and effects on the stoichiometry of C and N, which are neglected in most research on forages grown under water restriction. [ABSTRACT FROM AUTHOR]

Increasing mining and industrial discharge of untreated wastewater, as well as excessive use of fertilizers for agricultural purposes, and heavy metal contamination in soil have become one of the serious environmental problems worldwide. In the present study, pot experiments were conducted to evaluate the influence of arsenic contamination and other factors on the growth and development of local forage grasses like Purple guinea and Ruzi grasses under controlled conditions. Influence of arsenic concentration, soil properties, and fertilizers on biosorption and withstanding potential of grasses was studied using model soil and real-time arsenic-contaminated mine soil. High arsenic contents in soil significantly affected the growth as well as biomass production of grasses and declined the overall biomass production concerning exposure durations. Purple guinea and Ruzi grasses showed growth tolerance in arsenic-contaminated soils with concentrations of 100 and 150 mg/kg respectively. Grass species, soil compositions, and properties, fertilizers, growth duration, etc. potentially influenced arsenic accumulation in grasses. Both local forage grasses showed <1 bio-accumulation factor (BAF) and bio-concentration factor (BCF) after 45 days that indicates the minimum harvesting time of 45 days, and biosorption rate was found significant to the exposure duration. Maximum translocation factor (TF) values observed in Purple guinea and Ruzi grasses were 0.65 and 0.95, respectively which are < 1, therefore, these local forage grasses could be labeled as arsenic-metallophytes and ability to tolerate high levels of heavy metals without much biosorption. The results confirmed that local forage grasses have much growth tolerance potential against arsenic in real-time mine soil with desired fertilizers and these species could be used for sustainable management of ecological health of the Thung Kum gold mine area in Thailand. [ABSTRACT FROM AUTHOR]

Silicon (Si) is known as an attenuator for water deficit through increasing water status. The mechanisms involved in Si to mitigate this stress may be linked to decreasing oxidative stress and increasing phenolic compounds, associated with stoichiometric homeostasis of carbon (C), nitrogen (N), and Si, although there is a lack of research especially in forage crops. This research aimed to evaluate whether the supply of Si via fertigation improves the antioxidant defense system and modifies the C/N/Si stoichiometry and the growth of two cultivars of Panicum maximum cultivated under two soil water regimes (70 and 40% water retention capacity). Two experiments were developed, and the same treatments were applied using a 2 × 2 factorial arrangement, with Si applied via fertigation (2.5 mmol L−1) to the soil, while the control (without Si) was combined with two levels of soil moisture (70 and 40% of the soil water retention capacity). The two cultivars showed high accumulation of silicon in the shoot, low C content, low C/Si and C/N ratios, and high nutritional efficiency for the use of C in both water conditions. This is related to the potential of the Si to provide the greater antioxidant defense owing to higher production of phenolic compounds and decreased electrolyte leakage index. There was an increase in relative water content, leaf water potential, total chlorophyll content, and quantum efficiency of photosystem II, as shown by greater growth and dry mass production. Si application is a promising strategy to mitigate water deficit, ensuring new physiological and nutritional homeostasis, contributing to a more sustainable agriculture by means of feeding the herds that depend on pasturelands. [ABSTRACT FROM AUTHOR]

Streams draining through agricultural catchments are subjected to multiple stressors including pollution with nutrients and pesticides. Pesticides, in interaction with other agricultural stressors, can impact microbial diversity and key ecosystem processes underlying the delivery of ecosystem services from streams. The understanding of how such stressors interact to alter ecosystem structure and function and how responses of biota reflect their longer-term disturbance history remains limited. Effects of the fungicide chlorothalonil on litter breakdown rates of riparian tree leaves of Ficus racemosa and sedge Panicum maximum were assessed in 40-day indoor microcosm systems. Litter breakdown rates were analysed in microcosms treated with chlorothalonil concentrations of 0.01, 0.025, 0.10, 0.25 and 1.0 mg/L and in control tanks without pesticides using the ANCOVA test. The results of the study indicated a significant reduction (P < 0.05) of litter breakdown rate in chlorothalonil-treated tanks compared to the control tanks in terms of reduction percentage of dry weight and organic matter, microbial community sporulation and nutrient content. These alterations were modulated by the litter quality and microbial colonisations on leaf materials. Findings of the study emphasise the importance of considering indirect effects of pesticides on ecological processes. Stressing the need for deeper insight into how multiple stressors can affect the functioning of aquatic ecosystems and associated services. [ABSTRACT FROM AUTHOR]

Plants used for phytoextraction of metals need to tolerate toxicity conditions. Potassium (K) participates in physiological and biochemical processes that can alleviate toxicity by heavy metals, including cadmium (Cd). This study aimed to evaluate the effect of K on photosynthesis and on the changes in the antioxidant system of tanzania guinea grass [Panicum maximum Jacq. cv. Tanzania (syn. Megathyrsus maximus (Jacq,) B.K. Simon & S.W.L. Jacobs)] under Cd toxicity. Plants were grown in a greenhouse, in nutrient solution, in a randomized complete block design, arranged in a 3 × 4 factorial, with three replications. Plants were supplied with three K levels (0.4 [K deficiency], 6.0, and 11.6 mmol L-1) and exposed to four Cd levels (0.0, 0.5, 1.0, and 1.5 mmol L-1). Two plant growth periods were evaluated. High Cd level (1.5 mmol L-1) led to a reduction in net photosynthesis (76%) by causing low stomatal conductance and losses in quantum efficiency of photosystem II. However, high K supply (11.6 mmol L-1) increased the net photosynthesis by 15% in plants exposed to 1.0 mmol L-1 Cd, due to upregulation of proline synthesis. Cd toxicity resulted in increases in lipid peroxidation and hydrogen peroxide concentration (35 and 50%; 25 and 30%, at first and second harvest, respectively) and reduction by 80–100% in activity of the antioxidant enzymes: superoxide dismutase, catalase, ascorbate peroxidase, guaiacol peroxidase, and glutathione reductase in the shoots of the grass. However, the high K supply (11.6 mmol L-1) increased the activity of these enzymes (about 50–75%) and reduced lipid peroxidation (36%), restoring cellular homeostasis. Moreover, high K supply promoted a 25% increase in spermidine and spermine concentrations in the shoots. Therefore, K reduced the Cd-induced oxidative stress and increased the net photosynthesis in tanzania guinea grass by increasing the activity of antioxidant enzymes and proline and polyamines synthesis, which enhances the tolerance of this grass to Cd. [ABSTRACT FROM AUTHOR]

On a global scale, invasive grasses threaten biodiversity and ecosystem function. Nevertheless, the importation of forage grasses is a significant economic force driven by globalization. Pastureland and rangeland are of critical economic and ecological importance, but novel grass species may lead to invasion. Recognizing that economically important species can also be ecologically damaging creates a contentious debate for land managers, policymakers, and ecologists alike. Many Afrotropical perennial grass species have been intentionally introduced pantropically given their high forage production and resistance to stress. However, these traits may also confer competitive ability, increasing the possibility of unintended escape and invasion. Further, these traits have posed challenges for traditional control methods using chemicals, prescribed fire, and mowing. The use of classic biological control may alleviate the ecological impact in invaded areas. In this literature synthesis we examine Guinea grass (Megathyrsus maximus); whose economic value in many countries is undeniable, yet its impact on native ecosystems is a mounting concern. First, we introduce Guinea grass taxonomy, general biology and ecology, and the geographic and genetic origins. Second, we review the economic value and the ecological impacts. Third, we review the control of Guinea grass in undesired areas using chemical and mechanical means. Finally, we review current efforts to use biological control. [ABSTRACT FROM AUTHOR]

Silvopasture, an agroforestry practice combining forages, livestock, and trees, has been shown to optimize productivity and mitigate the effects of environmental stress on livestock, yet few ranchers in Panama deliberately incorporate trees into pastures. Panama's Azuero Peninsula experiences a five-month dry season that results in substantial losses in grass productivity. We studied three cultivars of Guinea grass (Megathyrsus maximus cv. Massai, cv. Mombaza, and cv. Tanzania) under open (O), moderate (M), and dense (D) tree canopies. We hypothesized that changes in soil properties, herbage mass, and nutritive value would be optimized in M in agreement with the stress gradient hypothesis, which predicts an increase in facilitation with increasing environmental stress. Results after two years showed few changes in soil chemical properties, but bulk density decreased with increasing tree cover. Annually, O produced more herbage mass than M and D and Massai produced more herbage mass than Mombaza, but not compared to Tanzania. Nutritive value improved under tree cover, with D and M showing higher relative feed values than O. Massai demonstrated the greatest tolerance to drought in M, producing more herbage mass in February when compared to D and O. Results partially support the hypothesis, suggesting that herbage mass is greatest in M for Massai during the dry season, but greatest in O over the year. The observed productivity under moderate tree densities could result in improved animal welfare between the months of December and May, the critical dry period for this region. [ABSTRACT FROM AUTHOR]

African mahogany (Khaya spp.) produces high-value wood, and its cultivation is expanding in tropical regions. The silvopastoral system is an alternative method for growing timber trees, but may involve cattle stripping bark from trees, which limits its usefulness. We evaluated cattle bark-stripping rates in two African mahogany species, K. grandifoliola and K. senegalensis, in a silvopastoral system with Guinea grass, Panicum maximum, in South-eastern Brazil. Cattle had free access to plantations of both tree species for 2 weeks in May 2018 and July 2019, when trees were 5 and 6 years old, respectively. In 2018, we found bark-stripping only in K. grandifoliola, but in 2019 both species were bark-stripped. The proportion of bark-stripped trees was higher for K. grandifoliola than for K. senegalensis. Considering both years, 29/155 (18.7%) K. senegalensis trees and 106/153 (69.3%) K. grandifoliola trees had some of their bark-stripped by cattle. Bark-stripped trees had lower trunk diameter growth than unaffected trees, and their growth was affected by the degree of bark-stripping. Some trees were girdled by bark-stripping. These trees dried up, and some of them fell down 1 year after girdling. In 2019, despite the high herbage mass, levels of crude protein in the pasture were very low, which may have stimulated bark-stripping. Although we could not identify the reasons for bark-stripping, we recommend avoiding the use of silvopastoral systems with cattle and African mahogany in times of the year when pasture has a low quality. [ABSTRACT FROM AUTHOR]

Aims: To identify factors driving soil respiration (Rsoil) in a tropical C4-dominated perennial managed grassland ecosystem exposed to elevated carbon (C) dioxide concentration ([CO2]) and temperature. Methods: The perennial grass Panicum maximum was grown at 600 μmol CO2 mol−1 and + 2 °C above ambient temperatures for one full growing cycle (from grazing to regrowth for about ~30–45 days) using a free-air CO2 and infrared warming system. Plant growth and CO2 fluxes were measured during the growing cycle. Results: Both high [CO2] and warming increased canopy photosynthesis but warming alone increased biomass by 53% and Rsoil by 26%. There was a strong diel effect on Rsoil, which was 16% greater at noon than at 18:00 h. Rsoil had low sensitivity to soil temperature (Q10 ~ 1) regardless of the CO2 treatment. Conclusions: In this tropical managed pasture, diel variation in photosynthesis strongly affected Rsoil, suggesting that Rsoil may be more limited by substrate availability than abiotic factors such as temperature. Predicted changes in climate for the region will likely affect the C dynamics of C4-dominated tropical pastures. Although, the short-term experiment may limit the extrapolations of our findings, the highly controlled settings of the experiment highlighted the role of canopy photosynthesis on Rsoil respiration in tropical C4-pastures. [ABSTRACT FROM AUTHOR]

Aims: Tropical perennial grasses that can rapidly establish deep roots have a greater potential to survive soil surface drying sooner after establishment. This research aimed to identify species that establish deep roots quickly and to investigate the mechanisms that drove rapid vertical root development. Methods: Perennial grass species Brachiaria brizantha, Brachiaria decumbens, Brachiaria humidicola, Brachiaria hybrid Mulato II, Brachiaria mosambicensis, Panicum maximum, Setaria sphacelata and Cynodon dactylon were grown in rhizotrons that facilitated measurement of the rate of root depth development, the rate of root length development, photosynthesis and morphological traits. Principal component analysis was employed to separate grass species according to functional traits of vertical root development and their growth strategies. Results: P. maximum established roots more rapidly to 50 cm depth than the other species examined and accumulated biomass and leaf area faster. It was differentiated from other species by a greater percentage of fine root length (< 0.2 mm diameter), a higher photosynthetic rate and ratio of root length to leaf area according to the principal component analysis. The growing degree days required for root establishment to 50 cm depth was negatively correlated with the percentage of fine root length, and positively correlated with root angle. The exponential rate of root depth development per growing degree day increased with average root diameter in B. humidicola and B. hybrid Mulato II, indicating a conservative growth strategy. Conclusion: Rapid vertical root development with a narrow root angle, higher photosynthetic rate, higher ratio of root length to leaf area and higher percentage of fine roots were apparent mechanisms that enabled P. maximum to establish deep roots faster than other species. P. maximum appears to be better able to avoid water stress during surface drying by accessing profile moisture. Greater average root diameter and percentage of root length with higher diameters was related to increased exponential rate of root depth development and wide root angle. [ABSTRACT FROM AUTHOR]

Citrus leprosis (CL) is one of the most important viral diseases in sweet orange orchards in Latin America. It is caused by members of at least five species of the so-called Brevipalpus-transmitted viruses (BTV), and the prevalent is Citrus leprosis virus C (CiLV-C). This virus has the broadest host range amongst all CL-associated viruses and is transmitted by Brevipalpus yothersi, a polyphagous mite that can colonize a large variety of host plants, including some spontaneous ground cover plants. But if, on one hand, spontaneous plants can host CL virus and vector, on the other hand, they can offer alternative food for predators, equally common in organic citrus orchards. Brevipalpus yothersi and predator mites were surveyed in 33 spontaneous plants of a Westin sweet orange orchard conducted under organic production system in Brazil, from June 2010 to April 2011. Predatory mites were identified as phytoseiids, and Iphiseiodes zuluagai was the prevalent species, representing 58% of all predators. Other phytoseiids were considered accidental species in the area. Ageratum conyzoides and Alternanthera tenella were the most represented plant host species to predators, comprising 28 and 10% of the total surveyed plants, respectively. Brevipalpus yothersi specimens were detected on various spontaneous species: A. conyzoides, A. tenella, Amaranthus deflexus, Bidens pilosa, Ipomoea quamoclit, I. cairica, Merremia cissoides, Solanum americanum, Panicum maximum, and, predominantly, Commelina benghalensis. The latter has been previously reported as host of CiLV-C as well and, therefore, it is recommended to eliminate this species from citrus orchards. [ABSTRACT FROM AUTHOR]

Grasses of the Urochloa genus have been widely used in crop-livestock integration systems or as cover crops in no-till systems such as in rotation with maize. Some species of Urochloa have mechanisms to reduce nitrification. However, the responses of microbial functions in crop-rotation systems with grasses and its consequence on soil N dynamics are not well-understood. In this study, the soil nitrification potential and the abundance of ammonifying microorganisms, total bacteria and total archaea (16S rRNA gene), nitrogen-fixing bacteria (NFB, nifH), ammonia-oxidizing bacteria (AOB, amoA) and archaea (AOA, amoA) were assessed in soil cultivated with ruzigrass (Urochloa ruziziensis), palisade grass (Urochloa brizantha) and Guinea grass (Panicum maximum). The abundance of ammonifying microorganisms was not affected by ruzigrass. Ruzigrass increased the soil nitrification potential compared with palisade and Guinea grass. Ruzigrass increased the abundance of N-fixing microorganisms at the middle and late growth stages. The abundances of nitrifying microorganisms and N-fixers in soil were positively correlated with the soil N–NH4+ content. Thus, biological nitrogen fixation might be an important input of N in systems of rotational production of maize with forage grasses. The abundance of microorganisms related to ammonification, nitrification and nitrogen fixing and ammonia-oxidizing archea was related to the development stage of the forage grass. [ABSTRACT FROM AUTHOR]

Silicon (Si) is a beneficial element which was proven to enhance the tolerance of plants to excess metal in a given growth medium. However, the efficacy of Si in mitigating Cu toxicity in plants can vary between plant species and with the amount of copper (Cu) present in the soil/medium. An experiment was performed to investigate the role of Si in alleviating Cu toxicity in Tanzania guinea grass (Panicum maximum cv. Tanzania). The experimental design consisted on complete random blocks with tree replicates containing three Si rates (0, 1, and 3 mmol L−1) and four Cu rates (0.3, 250, 500, and 750 μmol L−1). The grass was grown for 62 days in a greenhouse under hydroponic conditions, with a total of 36 pots. Thirteen days after sowing, seedlings were transplanted to pots and grown for further 25 days, and then exposed to the set Cu rates for 7 days. The plants were also evaluated more for 30 days after the first harvesting. The results confirmed that the Si supply to Tanzania guinea grass can alleviate the effects of excessive Cu. Plant yield increased with Si supply and decreased with the increment of Cu rates in both growth periods. Copper concentration in diagnostic leaves (DL) and in roots, and Cu content in shoots and roots were higher in plants exposed to Cu of 750 μmol L−1 with no Si application than in other combinations. Besides reducing Cu concentration in plant tissues, the most important Si role was reducing the transport of Cu from roots to shoots, which allowed successive harvesting. [ABSTRACT FROM AUTHOR]

Eucalyptus harvests generate residues that remain on the soil and affect the efficacy of preemergent herbicides in the following planting cycle. The objective of this work was to evaluate the dynamics of flumioxazin, sulfentrazone, and isoxaflutole herbicides applied on different amounts and compositions of eucalyptus harvest residues subjected to different rainfall depths; and evaluate the weed control effectiveness of these herbicides when applied under these conditions. A LC–MS/MS system was used for the evaluations and the results showed that a cumulative rainfall of 50 mm was sufficient for the maximum removal of herbicides from the eucalyptus residues, regardless of the residue composition. The amount of the flumioxazin, sulfentrazone, and isoxaflutole herbicides that reached the soil was lower in the treatment with the highest amount of eucalyptus harvest residue used (40 Mg ha−1). The greatest amount of herbicide reaching the soil was found with the use of 15 Mg ha−1 of residues without presence of bark. The highest amount of residue used (40 Mg ha−1) reduced the control of Brachiaria decumbens by sulfentrazone and isoxaflutole. The control of Commelina benghalensis was inefficient (> 80%) in the treatment with 15 Mg ha−1 of residues without barks, regardless of the herbicide. Sulfentrazone controlled Ipomoea grandifolia (> 90%) under the evaluated residue conditions. Spermacoce latifolia and Sida rhombifolia were controlled by all herbicides in the evaluated residue conditions. Isoxaflutole controlled Panicum maximum in all residue conditions. The choice between the herbicides depends on the residue condition, rainfall regime, and weed species to be controlled. [ABSTRACT FROM AUTHOR]

Understanding belowground morphological mechanisms of trees and grasses is a complicated task but can help in the design and management of silvopastoral systems. In this study, we evaluated the effect of the harvest intervals (i.e. 30 and 50 days) of aboveground biomass on the fine root density and vertical distribution in two silvopastoral systems (SPS): one comprising Leucaena leucocephala (legume tree) and Cynodon plectostachyus (grass) and the other L. leucocephala and Panicum maximum. We used a completely randomized design with four repetitions. We sampled fine roots by using a metal cylinder (8 cm diameter and 50 cm length) 7 days after each harvest. We washed the samples with pressurized water to separate them from the soil. The roots were digitalized at a resolution of 600 dpi to determine the diameter and specific root length by using IJ Rhizo® software. Samples were subsequently dried to quantify fine root mass. We found that the greater percentages of fine roots were between 0.4 and 0.8 mm for the legume and between 0.2 and 0.4 mm for grasses. The fine root length and mass density of P. maximum was higher (P < 0.001) compared to C. plectostachyus in both harvest intervals. However, the fine root density of L. leucocephala did not vary between SPS (P > 0.05). The effect of harvest interval was significant only in some soil layers in both SPS (P > 0.05). Most of the pasture roots were found in the upper soil layer (0–20 cm), while L. leucocephala roots were present to deeper soil layers. We conclude that P. maximum has a greater rooting capacity and a more rapid recovery than C. plectostachyus, which has greater diameters and lower root density. However, L. leucocephala presented deeper and thicker fine roots in both SPS, which is a good indication of its belowground recovery capacity to aboveground disturbances. [ABSTRACT FROM AUTHOR]

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is an economically important polyphagous pest native to the Americas. The pest has recently introduced to India and causing severe damage to maize and other crops. The occurrence of fall armyworm on fodder maize (Zea mays L), Guinea grass (Megathyrsus maximus) (Jacq.), para grass (Brachiaria mutica) (Forssk.) and green amaranth (Amaranthus viridis L) is reported first time from Goa, India. The damage incidence of 16 to 52% was recorded on fodder maize. The other host plants viz., Guinea grass, para grass and green amaranth recorded damage incidences of 9.0, 4.0 and 13.0%, respectively. The pest was identified based on morphological characters and molecular techniques. Phylogenetic analysis of COI gene sequence revealed that fall armyworm on fodder maize from Goa is clustering with the fall armyworm isolates from India, Nigeria, Ghana, Kenya, Canada and Brazil. Goa isolate is aligning with the "Rice" strain of fall armyworm and not with "Corn" strain. Studies on the biology of fall armyworm indicated that longer larval and pupal developmental period (18.6 and 10.7 days) was recorded on Guinea grass and green amaranth, respectively. The highest number of eggs was recorded from fall armyworm population reared on fodder maize as compared to those reared on other host plants. Longer life cycle was recorded on Guinea grass and green amaranth. Shortest larval and pupal period and faster life cycle of fall armyworm was recorded on fodder maize compared to other host plants indicating that fodder maize was the most preferred host for S. frugiperda in India. [ABSTRACT FROM AUTHOR]

The supply of potassium (K) is a strategy to increase the tolerance of plants exposed to Cd toxicity. The aim of this study was to verify the influence of K on the growth and potential of Tanzania guinea grass (Panicum maximum Jacq. cv. Tanzania (syn. Megathyrsus maximus (Jacq.) B.K. Simon & S.W.L. Jacobs)) for Cd phytoextraction as well as to evaluate nutritional attributes of this grass under conditions of Cd stress. The experiment was conducted in a randomized complete block design, using a 3 × 4 factorial arrangement, with three replications. Three rates of K (0.4, 6.0, and 11.6 mmol L−1) were combined with four rates of Cd (0.0, 0.5, 1.0, and 1.5 mmol L−1) in nutrient solution. Two plant growth periods were evaluated. The increase in K supply to plants exposed to Cd rates of up to 1.0 mmol L−1 caused increase in morphogenic and production attributes, as well as reduction in tiller mortality rate, in the second growth period. K concentrations (in both harvests) increased, while calcium and magnesium concentrations in the second harvest decreased with increasing Cd rates. The high availability of Cd (1.5 mmol L−1) in the nutrient solution caused decrease in relative chlorophyll index (RCI) in both harvests. The high supply of K to plants exposed to Cd resulted in high shoot dry mass production, reducing Cd concentration in the photosynthetic tissues (which means great tolerance of the plant) and increasing the accumulation of this metal in the shoots that can be harvested. Therefore, K increases the Cd phytoextraction capacity of Tanzania guinea grass. [ABSTRACT FROM AUTHOR]

Two common tropical grassland species, Panicum maximum Jacq. (Guinea grass) and Cenchrus ciliaris (Buffel grass) of Indo-Gangetic plains were assessed for their responses under future level of O3 (ambient +30 ppb) using open top chambers. Plants were assessed for foliar injuries, pigments, growth, biomass accumulation, histochemical localization of reactive oxygen species (ROS), antioxidant defense system and ROS scavenging activities at two stages. Foliar injuries were noticed at an early stage in P. maximum compared to C. ciliaris. Significant reductions were observed in total chlorophyll, growth and total biomass in both species. Significant increases in contents of melondialdehyde and ascorbic acid in P. maximum while total phenolics and thiols in C. ciliaris were found. Histochemical analysis showed more production of superoxide radicals and hydrogen peroxide in leaf tissues of P. maximum compared to C. ciliaris. It can be concluded that higher level of primary antioxidants (total phenolics and thiols) along with superoxide dismutase and ascorbate peroxidase scavenged O3 effectively in C. ciliaris causing less reduction of biomass which is used as a feed for cattles. In P. maximum, more photosynthates were allocated for defense, leading to higher reduction in total biomass compared to C. ciliaris. The leaf area ratio was higher in P. maximum compared to C. ciliaris under elevated O3. The study further suggests higher susceptibility of P. maximum compared to C. ciliaris under future level of O3 exposure. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to evaluate the removal of total petroleum hydrocarbons (TPH), alkanes and polycyclic aromatic hydrocarbons (PAH). Materials and methods: Using phytoremediation (Panicum maximum) (G), vermiremediation (Pontoscolex corethrurus) (E), and bioaugmentation (encapsulated bacterial consortium) (B), individually and in combination, in contaminated soil by oil (PS) with sterilized (St) and non-sterilized treatments. Grass and earthworm biomass and the number of cocoons were determined after 112 days. Results and discussion: The biomass of the P. maximum increased significantly from 1.7 to 2.6-folds overtime when it was cultivated in contaminated soil, either alone, in combination with earthworms, or with the bacterial consortium. After 112 days, the earthworm biomass significantly increased 2.0–2.6-folds with the highest increase in combination with the bacterial (PS+E+B), and its population increased from 4.9 to 8.5 times. P. corethrurus was not affected by the contamination so that deposition and hatch of cocoons (12–20) were observed. In sterilized treatments, no earthworms were detected after 112 days, which indicated that soil microorganisms are necessary for the earthworm's survival and colonization. Most alkane and PAH removal occurred within 28 days; at 112 days, the alkane was 78.5–94.5% and the PAH 54.5–77.2% in non-sterilized soil. Panicum maximum treatment (SP+G) removed 74–99% of alkanes from C10 to C38 and also removed PAHs in 43–50% (2–3 rings), 46–90% (4 rings), 73% (5 rings), and 59% (6 rings) after 112 days. The combination of the grass with P. corethrurus and the bacterial increased the PAHs removal of 2 and 3 rings (54–62%), 4 rings (56–92%), 5 rings (80%), and 6 rings (70%) after 112 days. In non-sterilized treatments, the highest TPH removal was with earthworms plus bacterial (E+B) (86.4%), followed by E+G+B (82.7%) and B (82.6%). Conclusions: The use of endogeic earthworms and plants species from the same contaminated field can be an efficient alternative for increasing hydrocarbon removal. [ABSTRACT FROM AUTHOR]

In the present study, we pretreated the plant Guinea grass (Panicum maximum) with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate [EMIM][OAc] to expose its cellulose fibers. For this, we first determined the composition of Guinea grass, with 6.87 ± 1.21% of ash, 14.33 ± 1.18% of lignin, 70.55 ± 1.15% of holocellulose, 29.9 ± 1.20% of cellulose, and 40.65 ± 1.20% of hemicellulose. After characterizing the material, we determined the IL pretreatment conditions that maximized the enzymatic and acid hydrolysis stages [namely: temperature = 157 °C, reaction time = 30 min, and biomass concentration (relative to total mass) = 14%]. Under these conditions, the enzymatic hydrolysis conversions of glucose and total reducing sugars were respectively 69.8 and 54.2%, determined by enzymatic and DNS methods. The acid hydrolysis was also carried out, and conversions of 57.4 and 27.2% were verified by the enzymatic and DNS methods, respectively. Finally, the hydrolysate obtained after the enzymatic hydrolysis was fermented by the yeast Saccharomyces cerevisiae, and the ethanol yield (81.9%) was determined through gas chromatography. [ABSTRACT FROM AUTHOR]

Purpose: Cadmium has caused serious environmental problems due to its phytotoxicity, requiring solutions to reduce its concentration in the environment. Because S can alleviate the phytotoxicity caused by heavy metals, the evaluation of the effects of S supply is a promising approach to address this problem. The aim of this study was to determine the influence of S in reducing the phytotoxicity caused by Cd to Panicum maximum Jacq. cv. Tanzania (guinea grass) and to evaluate the potential of this grass for Cd phytoextraction. Materials and methods: Tanzania guinea grass was cultivated in a nutrient solution to evaluate the combinations of five rates of S (0.1, 1.0, 1.9, 2.8, and 3.7 mmol L) and five rates of Cd (0.0, 0.5, 1.0, 1.5, and 2.0 mmol L), in a 5 fractional factorial design with six replications. Six plants were grown per pot in two growth periods to evaluate the effect of Cd on the establishment (51 days of age) and on the regrowth (18 days of growth) of the plants. During regrowth, Cd was not supplied in the nutrient solution. At the end of each growth period, growth parameters, concentrations of S and Cd, Cd transport factor, and concentrations of hydrogen peroxide (HO), malondialdehyde, reduced glutathione, and oxidized glutathione were evaluated. Results and discussion: On the establishment of Tanzania guinea grass, application of Cd reduced mass production by 39 % due to the increases in the concentration of Cd (30 times compared with the treatment without Cd) and in lipid peroxidation (124 %). During regrowth, the residual effect of Cd resulted in a lower number of tillers (62 %) and leaves (89 %) caused by the increase in concentrations of Cd, HO (49 %), and lipid peroxidation, which resulted in a 65 % lower dry mass production. The proper supply of S reduced concentration of Cd and tiller mortality rate due to the residual effect of Cd on the regrowth of the grass. Mass production by the roots was 43 % lower because of Cd, but the transport of Cd from roots to shoots increased. The increase in the concentration of glutathione (GSH) associated with a possible higher activity of antioxidant enzymes alleviated the phytotoxic effects of Cd on the guinea grass. Conclusions: The supply of S reduces the phytotoxicity caused by Cd to guinea grass, especially during the regrowth of the plant, when the concentration of Cd is higher because of the transport from roots to shoots. Tanzania guinea grass showed to be very promising for phytoextraction of Cd due to its high mass production, even when Cd was largely available in the nutrient solution. [ABSTRACT FROM AUTHOR]

This work reports the complete genome sequence, production of a polyclonal antiserum, and host range of a Brazilian strain of johnsongrass mosaic virus (JGMV) found infecting Panicum maximum in the state of São Paulo, Brazil. The complete genome sequence of this potyvirus, comprising 9874 nucleotides, showed 82 % amino acid sequence identity in the polyprotein to that of an isolate of JGMV from Australia. The experimental host range of this virus included mainly fodder species. Cultivated species such as rice, oats, sugarcane, rye, corn and wheat were not infected, suggesting that current isolates of this potyvirus do not represent a threat to these crops in Brazil. [ABSTRACT FROM AUTHOR]

Deposited in plant cells and their intercellular space, phytoliths, a special form of silica, could be used to determine information on plant structure and physiology especially their size and content. With the hypothesis that phytolith in plant would change under variable climate and environment, the dominant plant species in Songnen grassland, guinea grass ( Leymus chinensis), was treated by an open-top chamber (OTC) to elevate CO concentration, infrared heaters, and artificial nitrogen (N) addition for three years from 2006-2008. Phytoliths were extracted by wet-ashing method and analyzed by variance analysis and so on. We found that the responses to elevated CO are complicated, and warming is positive while N addition is negative to the deposition of phytoliths in L. chinensis leaves. Especially, warming could reduce the negative impact of N addition on phytolith in L. chinensis. The short cell's taxonomic in graminea is significant because of no disappearance with simulated environmental changes. The phytolith originated in the long cell and plant intercellular space are more sensitive to elevated CO concentration, warming, and N addition, and could become some new indicators for environmental changes. In conclusion, different phytolith types have various responses to simulated warming, N addition and elevated CO concentration. [ABSTRACT FROM AUTHOR]

The objective of this work was to develop and evaluate agrometeorological models to simulate the production of Guineagrass. For this purpose, we used forage yield from 54 growing periods between December 2004-January 2007 and April 2010-March 2012 in irrigated and non-irrigated pastures in São Carlos, São Paulo state, Brazil (latitude 21°57′42″ S, longitude 47°50′28″ W and altitude 860 m). Initially we performed linear regressions between the agrometeorological variables and the average dry matter accumulation rate for irrigated conditions. Then we determined the effect of soil water availability on the relative forage yield considering irrigated and non-irrigated pastures, by means of segmented linear regression among water balance and relative production variables (dry matter accumulation rates with and without irrigation). The models generated were evaluated with independent data related to 21 growing periods without irrigation in the same location, from eight growing periods in 2000 and 13 growing periods between December 2004-January 2007 and April 2010-March 2012. The results obtained show the satisfactory predictive capacity of the agrometeorological models under irrigated conditions based on univariate regression (mean temperature, minimum temperature and potential evapotranspiration or degreedays) or multivariate regression. The response of irrigation on production was well correlated with the climatological water balance variables (ratio between actual and potential evapotranspiration or between actual and maximum soil water storage). The models that performed best for estimating Guineagrass yield without irrigation were based on minimum temperature corrected by relative soil water storage, determined by the ratio between the actual soil water storage and the soil water holding capacity.irrigation in the same location, in 2000, 2010 and 2011. The results obtained show the satisfactory predictive capacity of the agrometeorological models under irrigated conditions based on univariate regression (mean temperature, potential evapotranspiration or degree-days) or multivariate regression. The response of irrigation on production was well correlated with the climatological water balance variables (ratio between actual and potential evapotranspiration or between actual and maximum soil water storage). The models that performed best for estimating Guineagrass yield without irrigation were based on degree-days corrected by the water deficit factor. [ABSTRACT FROM AUTHOR]

Secondary forests and shrub thickets with low suitability for cattle raising are widespread in the Chaco region (NW Argentina). Concerns about the ecological sustainability of these ecosystems favor vegetation clearing methods for improving standing forage and accessibility for livestock operations that retain native tree and shrub species, a system called ' silvopasture' locally. These areas are characterized by a reduction of sunlight availability if compared with treeless pastures. The objective of this research was to assess the growth rate and the effect of two harvesting intervals (15 and 30 days) on the annual yield (BM) and forage quality of Panicum maximum (Jacq.) var Trichoglume cv Petrie (Green Panic) in such a system, using two approaches: successive harvests and functional, during three growth seasons (2000-01, 2001-02 and 2002-03). Correlation of growth features of Green panic with rainfall (mm), growing degree days (°C, GDD), and soil moisture (%) at two soil depths (0-15 and 15-30 cm) was also assessed. BM varied between 3,500 and 11,500 kg dry matter ha. The absolute growth rate presented two annual peaks, located in early and late summer, irrespective of growth season and harvesting interval. Growth season and harvesting interval significantly affected the relative growth rate ( p > F = 0.0015 and p > F = 0.0002, respectively). BM was significantly correlated with rainfall and GDD observed between sampling dates, the magnitude of the coefficients were higher for the 30-day than for the 15-day harvesting interval. Correlation between BM and soil moisture content was not significant for both soil depths. Resting periods should be longer than 30 days to maintain the stability of the grazing system. [ABSTRACT FROM AUTHOR]

Soil pollution with trace elements is a growing problem with serious environmental impacts and developing strategies to reduce those impacts is a high priority. The objectives of this study were to assess the role of sulfur (S) in reducing the phytotoxic effects of copper (Cu) and the appearance of oxidative stress due to excess Cu in the growth medium and to assess the potential of guinea grass for Cu phytoremediation. The experiment was carried out in a greenhouse, where the forage grass Panicum maximum cv. Tanzânia was grown with a nutrient solution containing combinations of three S concentrations (0.1, 2, and 4 mmol L) and four Cu concentrations (0.3, 100, 500, and 1,000 μmol L) using a 3 × 4 factorial design in complete randomized blocks with four replicates. The following variables were measured: shoot and root dry mass production, leaf and tiller number, S and Cu concentrations in diagnostic leaves and roots, HO, lipid peroxidation, and proline levels in the diagnostic leaves. Very high Cu availability (1,000 μmol L) that resulted in Cu concentration higher than 60 mg kg in diagnostic leaves caused more than 50 % reduction in shoot and root dry mass production about 30-40 % in the number of leaves and tillers around 20 % increase in lipid peroxidation and more than 10 times increase in proline production. Plants properly fed with S showed mitigation to Cu toxicity. Guinea grass showed promise as an agent in the phytoremediation of Cu-polluted areas. [ABSTRACT FROM AUTHOR]

The effect of tree canopy on the growth, productivity and forage quality of Megathyrsus maximus and changes in soil properties were evaluated over three seasonal periods. Four adjacent plots (15 m × 17 m each) in a tropical secondary deciduous forest having 12 years of growth and dominated by Gliricidia sepium were randomly assigned to two treatments: removal of trees (SCA) in two of the plots and leaving trees intact (COA) in the other two. In all plots, M. maximus was planted with 50 cm spacing among plants. Tree removal significantly increased the incident photosynthetically active radiation (PAR, P < 0.001) and grass size (12.5 % in height, P < 0.01, and 16.5 % in clump diameter, P < 0.05), but did not significantly affect any other variable. Season significantly affected grass height (P < 0.003), tiller number (P < 0.001), clump diameter (P < 0.001), net CO assimilation rate (P < 0.001), forage biomass production (P < 0.003), and acid detergent fiber content (P = 0.033). Primary soil changes after 1 year of establishment of the grass were the decline by 3 % in organic carbon (P = 0.03), and qualitative changes in soil structure, regardless of tree presence. Results are consistent with the ability of M. maximus to tolerate shade. We conclude that under the conditions of the study there was no evidence for a negative effect of tree canopy on M. maximus mediated by a reduction in PAR. [ABSTRACT FROM AUTHOR]

Reduction in forage production (FP) under trees in the humid tropics is well known, but information on how different levels of nitrogen (N) fertilizer influence FP under trees is meager. The present study reports effects of four N fertilizer levels (0, 60, 80 and 120 kg ha N) on net soil N mineralization rate (NMR) and soil moisture (SM), FP, shoot biomass/root biomass ratio (SB/RB), N concentration in SB, N uptake and nitrogen use efficiency (NUE) of three grasses [guinea ( Panicum maximum Jacq.), para ( Brachiaria mutica (Forssk) Stapf) and hybrid-napier ( Pennisetum purpureum Schumach.)] under three canopy positions [under canopy (UC, representing high shade), between canopy (BC, representing low shade) and open] of coconut trees ( Cocos nucifera L.) in a coconut based silvopastoral system in the humid tropical climate of South Andaman Island of India. The study was performed for two annual cycles (2005-2006 and 2006-2007). The hypotheses tested were: (1) FP would decline under tree shades, both in N fertilized as well as no N fertilized conditions, when SM was not growth limiting in the open. However, amount of decline in the FP would depend on grass species and intensity of shades i.e., higher was the shade greater would be the decline; (2) N fertilizer would increase FP under tree shades, but the increase depended on grass species, intensity of shades and amount of N applied. Amount of N applied, however, would not annul the shades effects when SM was not growth limiting in the open. The study revealed that the tree reduced light 59% under UC and 32% under BC positions, but the N fertilizer levels increased NMR by 11-51% under UC and 3-44% under BC positions compared to the open. SM did not differ across the canopy positions. Under all situations, FP of all grasses declined under UC (47-78%) and BC (18-32%) positions compared to the open; the decline was greater in Hybrid-napier than Guinea and Para grasses. Forage production of all grasses increased with N fertilizer increments under all canopy positions reaching 32 t ha dry matters for hybrid-napier at 120 kg ha N in the open. Both guinea and para grasses outyielded hybrid-napier grass under UC but not under BC or in the open. N concentration in the forage (SB) also increased as N fertilizer level increased. These observations support our hypotheses and suggest that forage production under coconut palms can be increased by the application of N fertilizer with both guinea and para grasses being more productive than hybrid-napier grass under the high shade. Where light conditions are better, hybrid-napier would produce more forage than the other species. [ABSTRACT FROM AUTHOR]

Abstract: In savannas, isolated large trees can form ‘islands of fertility’, referring to their elevated soil nutrients and their effect on light and water availability in their direct surroundings. Consequently, a quality difference between understorey grasses and open grassland can develop, creating patches of highly nutritious forage for grazing ungulates. Grass species composition beneath and outside of tree canopies was determined in a savanna system of Kruger National Park, South Africa. Direct observations were used to test whether grazing ungulates, i.e., impala, Burchell''s zebra and blue wildebeest graze relatively more often beneath than outside of large tree canopies. Additionally, it was investigated whether they selected feeding locations according to allometric scaling and to their sex, and if feeding behaviour was influenced by weather conditions. Instantaneous scan sampling showed that ungulates preferred beneath-canopy grasses, independently of weather conditions. Grass species composition differed beneath and outside tree canopies, and beneath-canopy grasses exhibited more bite marks than outside canopy grasses. Blue wildebeest grazed least often beneath canopies compared to the other species. Females of impala were found to feed on beneath-canopy forage more often than males. Thus, large isolated trees strongly influenced the feeding behaviour of grazing ungulates. The current decline in large savanna trees should therefore be retarded and protective measures should be taken. [Copyright &y& Elsevier]

One hundred and sixty accessions representing global germplasm of guinea grass ( Panicum maximum Jacq.), an important apomictic (aposporous) fodder crop, were subjected to study on reproductive diversity in apomictic seed development utilizing ovule clearing and flow cytometric seed screen (FCSS). Single seed FCSS of selected 14 tetraploid and five hexaploid lines demonstrated uncoupling between the three apomixis components, viz. apomeiosis, parthenogenesis and functional endosperm development, in natural as well as experimental populations, though it differed across ploidy levels and genotypes. Reconstruction of reproductive pathways yielded a total of eight different pathways of seed development, arising by uncoupling/recombination between apomixis components. Amongst these, two pathways involving modifications in embryo-sac (ES) (presence of two polar nuclei in aposporous ES that fuse prior to fertilization) and fertilization process (fusion of only one polar nucleus in a sexual ES) have been reported for the first time. Some of the combinations, such as MI (haploids arising from parthenogenetic development of reduced egg cell), were found viable only in hexaploid background. Germplasm lines with higher expression of individual components were also identified. These components (including autonomous endosperm development) were also experimentally partitioned in hexaploid progenies (derived from a tetraploid parent viz. accession IG 04-164) that showed segregation in their reproductive capacities, and are reported for the first time. Occurrence of several apomixis recombinants (phenotypic) in guinea grass lines suggested their hybrid origin, favors a multigene model for apomixis, with their penetrance affected by modifiers and epigenetic mechanisms, in contrast to earlier reports of single locus control. Implications of partitioning components on apomixis research are discussed. [ABSTRACT FROM AUTHOR]

Summary. The genomic nucleotide sequences of the cloned agroinfectious genomes of three South African mastreviruses obtained from Zea mays, a Setaria sp., and Panicum maximum (designated MSV-Kom, MSV-Set, and PanSV-Kar respectively), were determined. Additionally, their relative infectivities and virulence were analysed in a range of differentially susceptible wheat, maize, and barley genotypes. MSV-Kom produced moderate to severe streak symptoms in all maize genotypes tested, but only moderate to very mild symptoms in the wheat and barley genotypes. MSV-Set infected only the susceptible to tolerant maize genotypes, but was generally more severe in the barley and wheat genotypes than MSV-Kom. PanSV-Kar was incapable of infecting any of the wheat and barley genotypes and only produced very mild symptoms on the three most sensitive maize genotypes. Genomic characteristics in common with related mastreviruses were identified. Phylogenetic analysis indicated that while MSV-Kom was closely related to previously sequenced MSV isolates, MSV-Set and PanSV-Kar represented distinctly novel strains of MSV and PanSV respectively. In the case of MSV-Set, this is the most distantly related MSV strain yet characterised. [ABSTRACT FROM AUTHOR]

Adapted tree+grass combinations make a valuable contribution to forage production in the Indian peninsula, but knowledge of the interactive effects between trees and grasses on their production is limited. We, therefore, conducted a field experiment involving combinations of four trees and grasses, besides monospecific grass controls, for seven years, to investigate grass productivity in association with leguminous and non-leguminous multipurpose trees (MPT) having disparate canopy architecture, and to assess the end-of-rotation soil fertility changes. Post rotation changes in herbage productivity were evaluated by growing teosinte ( Zea mexicana) for three years. The four MPTs were Acacia auriculiformis, Ailanthus triphysa, Casuarina equisetifolia and Leucaena leucocephala. Grasses included Pennisetum purpureum (hybrid napier), Brachiaria ruziziensis (congo signal), Panicum maximum (guinea grass) and teosinte. Lower tree branches were pruned from fifth year. Understorey herbage production increased until three years in all tree+grass combinations, but declined subsequently, as tree crowns expanded. Overall, casuarina among MPTs, and hybrid napier and guinea grass among forage crops, were more productive than others. Pruning MPTs generally favoured greater herbage production. Understorey light levels for acacia, ailanthus, casuarina and leucaena were 17, 60, 55 and 55% of that in the open at five years. During the post-rotation phase, MPT plots were characterised by higher soil nutrient capital and consequently teosinte yields were higher than in the treeless control treatment. All previous tree-grass combinations showed an increasing trend till two years after MPT felling. Yield levels declined subsequently, despite at variable rates. Careful selection of the tree and grass components is, therefore, crucial for optimising herbage productivity in silvopastoral systems. [ABSTRACT FROM AUTHOR]

Plants were regenerated by somatic embryogenesis from cultured leaf segments of Panicum maximum Jacq. (Guinea grass). All plants were phenotypically similar to the donor plant from which expiants were obtained for culture. Examination of the cytological and morphological characteristics of the regenerated plants did not show any changes in mitotic (root tip) chromosome number, structural rearrangements of chromosomes, pollen stainability and morphological characteristics. [ABSTRACT FROM AUTHOR]

Somatic embryogenesis was induced in proliferating leaf segments of Panicum maximum Jacq., cultured on Murashige and Skoog's nutrient medium containing 2,4-dichlorophenoxyacetic acid and coconut milk. The embryoids gave rise to plants on a medium containing gibberellic acid. The plants were successfully transplanted to soil and grown to maturity. Histological examination of proliferating leaves showed that the embryogenic callus tissue was formed by divisions in cells of the lower epidermis as well as the mesophyll tissue. The regenerated plants showed the normal chromosome number of 2n=4x=32. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) phytoextraction efficiency basically depends on Cd accumulation in their tissues. Thus, our aim in this study was to select biochemical, morpho-physiological, nutritional, and productive responses associated to Cd accumulation in the roots, stems and sheaths, and leaf blades of Panicum maximum cv. Massai (Massai grass), using the random forests analysis. Massai grass was exposed to combinations of three sulfur (S) concentrations (0.1, 1.9, and 3.7 mmol L−1) and two Cd concentrations (0.0 and 0.1 mmol L−1) in nutrient solutions. The dry biomass production of Massai grass exposed to Cd decreased by around 50% in relation to control. However, there were no visual symptoms of Cd toxicity in the shoot of this plant, even with Cd concentrations in their shoot exceeding 100 mg kg−1 DW. The lowest dry biomass production of the plants exposed to Cd combined with the absence of visual symptoms of Cd toxicity indicates us that Massai grass is a bioindicator plant that can greatly cope with the Cd-induced stress, but in a little bit different way from other plants. Antioxidant enzymes apparently are not essential for Massai grass cope with Cd-induced stress, differently of other mechanisms (e.g., higher synthesis of thiol compounds and amino acids involved on reactive oxygen species (ROS) scavenging and Cd chelation). Probably, the plant responses that most explained Cd accumulation in Massai grass can be used to identify grasses with high capacity to accumulate Cd in phytoremediation programs with this group of plants. [ABSTRACT FROM AUTHOR]

Introduction: By mid-century, global atmospheric carbon dioxide concentration ([CO2]) is predicted to reach 600 μmol mol−1 with global temperatures rising by 2 °C. Rising [CO2] and temperature will alter the growth and productivity of major food and forage crops across the globe. Although the impact is expected to be greatest in tropical regions, the impact of climate-change has been poorly studied in those regions. Objectives: This experiment aimed to understand the effects of elevated [CO2] (600 μmol mol−1) and warming (+ 2 °C), singly and in combination, on Panicum maximum Jacq. (Guinea grass) metabolite and transcript profiles. Methods: We created a de novo assembly of the Panicum maximum transcriptome. Leaf samples were taken at two time points in the Guinea grass growing season to analyze transcriptional and metabolite profiles in plants grown at ambient and elevated [CO2] and temperature, and statistical analyses were used to integrate the data. Results: Elevated temperature altered the content of amino acids and secondary metabolites. The transcriptome of Guinea grass shows a clear time point separations, with the changes in the elevated temperature and [CO2] combination plots. Conclusion: Field transcriptomics and metabolomics revealed that elevated temperature and [CO2] result in alterations in transcript and metabolite profiles associated with environmental response, secondary metabolism and stomatal function. These metabolic responses are consistent with greater growth and leaf area production under elevated temperature and [CO2]. These results show that tropical C4 grasslands may have unpredicted responses to global climate change, and that warming during a cool growing season enhances growth and alleviates stress. [ABSTRACT FROM AUTHOR]