The oxidative stress caused by atrazine in root exudation of Pennisetum americanum (L.) K. Schum.

Pearl millet (Pennisetum americanum (L.) K. Schum) has been proven as a potential remediation plant of the pollution caused by atrazine. Plants used in remediation can release root exudates to communicate with rhizosphere microorganisms and accelerate the removal of pollutants in soil. However, the response of pearl millet root exudates under atrazine stress has remained unclear. In this study, hydroponic experiments were conducted at Northeast Agricultural University, Harbin, China, to investigate the oxidative stress response and the changes in composition of root exudates in pearl millet plants that were exposed to 19.4 mgL-1 of atrazine, compared to the untreated control. The experiment was established as six treatments with exposure to no atrazine for 2, 4 and 6 days (CK-2, CK-4, CK-6) and 19.4 mgL-1 atrazine for 2, 4 and 6 days (AT-2, AT-4, AT-6), respectively. The results suggest that the growth of the seedlings changed slightly when exposed to atrazine for 2 days. The content of thiobarbituric acid reactive substances exposed to atrazine for 6 days increased 26% compared with the treatment that was exposed for 2 days. Moreover, the reactive oxygen species in test plant obviously increased when exposed to atrazine for 6 days. In addition, the activity of superoxide dismutase increased from 30.82 ug-1 to 37.33 ug-1 fresh weight after 6 days of exposure to atrazine. The results of a nontargeted metabolomic analysis suggest that carbohydrate metabolism, fatty acid metabolism and amino acid metabolism in pearl millet were obviously affected by the oxidative stress caused by atrazine. The contents of sphinganine and methylimidazole acetaldehyde in CK-6 increased by 5.14 times and 2.05 times, respectively, compared with those of CK-2. Furthermore, the contents of (S)-methylmalonic acid semialdehyde and 1-pyrroline-2-carboxylic acid decreased by 0.56 times and 0.5 times, respectively, compared with the AT-6. These results strongly suggest that the changes observed in the composition of root exudates in pearl millet seedlings can be attributed to the oxidative stress caused by atrazine.

Effect of quarry activities on selected biological resources around quarry site within Onigambari forest plantation, Oyo State, Nigeria.

Quarry activities are creating diverse stress on biological resources in the rural areas where most of them are located globally. In this study, the effect of quarry activities on elephant grass (Pennisetum purpureum) leaves and soils around Onigambari Forest Reserve, Oyo State, Nigeria, were investigated. Soil and samples of elephant grass (Pennisetum purpureum) leaves were collected from two different distances from the quarry plant. Samples used as control were collected within the boundary of Cocoa Research Institute of Nigeria (CRIN), Oyo State, Nigeria estate. Samples were analysed using proton-induced X-ray emission, to determine the elements. The physiochemical parameters were also analysed in both soil and leaves samples. The mean concentration of the elements in the soil sample from Site 1 was higher in Mg, Cl, Ca, Ti, Cr, Mn, Fe, Zn and Zr than Site 2 and the control site. While in leaves, similar trend was observed. Cd and Ag were highly enriched.

Enhancing the atrazine tolerance of Pennisetum americanum (L.) K. Schum by inoculating with indole-3-acetic acid producing strain Pseudomonas chlororaphis PAS18.

Atrazine as a kind of herbicide could cause damage to the sensitive plants. Though plant growth promoting rhizobacteria (PGPR) have been proven with the potential to enhance the resistance of plants against various abiotic stresses, whether it could alleviate phytotoxicity caused by atrazine is sill unclear. In present study, the effects of strain Pseudomonas chlororaphis PAS18, a kind of PGPR enable to produce indole-3-acetic acid (IAA), on the growth and physiological responses of Pennisetum americanum (L.) K.Schum seedlings were investigated under three different levels (0, 20 and 100 mg kg-1) of atrazine in pot experiment. The results suggest that strain PAS18 could alleviate the growth and physiological interference caused by 20 mg kg-1 of atrazine. Physiological analysis showed strain PAS18 could further decrease the damaged extent of photosystem II, superoxide radical level and malondialdehyde content of test plant via up-regulating psbA expression, enhancing superoxide dismutase activity and reducing atrazine accumulation in the test plant. Moreover, ion flux measurements suggest that IAA could alleviate the Ca2+ exflux state of the test plant which caused by atrazine stress. Hence, it is plausible that strain PAS18 could alleviate atrazine-induced stress to P. americanum by enhancing the photosystem II repair and antioxidant defense ability as well as balancing the Ca2+ flux.

Two Phytotoxins Isolated from the Pathogenic Fungus of the Invasive Weed Xanthium italicum.

Alternariol and altenuisol were isolated as the major phytotoxins produced by an Alternaria sp. pathogenic fungus of the invasive weed Xanthium italicum. Altenuisol exhibited stronger phytotoxic effect compared with alternariol. At 10 µg/mL, alternariol and altenuisol promoted root growth of the monocot plant Pennisetum alopecuroides by 11.1 % and 75.2 %, respectively, however, inhibitory activity was triggered by the increase of concentration, with root elongation being suppressed by 35.5 % and 52.0 % with alternariol and altenuisol at 1000 µg/mL, respectively. Alternariol slightly inhibited root length of the dicot plant Medicago sativa at 10-1000 µg/mL, whereas altenuisol stimulated root growth by 51.0 % at 10 µg/mL and inhibited root length by 43.4 % at 200 µg/mL. Alternariol and altenuisol did not exert strong regulatory activity on another dicot plant, Amaranthus retroflexus, when tested concentration was low, however, when the concentration reached 1000 µg/mL, they reduced root length by 68.1 % and 51.0 %, respectively. Alternariol and altenuisol exerted similar effect on shoot growth of three tested plants but to a lesser extent. It is noteworthy to mention that this is the first report on the phytotoxicity of altenuisol.

Enhanced Enzymatic Hydrolysis of Pennisetum alopecuroides by Dilute Acid, Alkaline and Ferric Chloride Pretreatments.

In this study, effects of different pretreatment methods on the enzymatic digestibility of Pennisetum alopecuroides, a ubiquitous wild grass in China, were investigated to evaluate its potential as a feedstock for biofuel production. The stalk samples were separately pretreated with H2SO4, NaOH and FeCl3 solutions of different concentrations at 120 °C for 30 min, after which enzymatic hydrolysis was conducted to measure the digestibility of pretreated samples. Results demonstrated that different pretreatments were effective at removing hemicellulose, among which ferric chloride pretreatment (FCP) gave the highest soluble sugar recovery (200.2 mg/g raw stalk) from the pretreatment stage. In comparison with FCP and dilute acid pretreatment (DAP), dilute alkaline pretreatment (DALP) induced much higher delignification and stronger morphological changes of the biomass, making it more accessible to hydrolysis enzymes. As a result, DALP using 1.2% NaOH showed the highest total soluble sugar yield through the whole process from pretreatment to enzymatic hydrolysis (508.5 mg/g raw stalk). The present work indicates that DALP and FCP have the potential to enhance the effective bioconversion of lignocellulosic biomass like P. alopecuroides, hence making this material a valuable and promising energy plant.

Does seed size and surface anatomy play role in combating phytotoxicity of nanoparticles?

Rapid utilization of nano-based products will inevitably release nanoparticles into the environment with unidentified consequences. Plants, being an integral part of ecosystem play a vital role in the incorporation of nanoparticles in food chain and thus, need to be critically assessed. The present study assesses the comparative phytotoxicity of nanoparticle, bulk and ionic forms of zinc at different concentrations on selected plant species with varying seed size and surface anatomy. ZnO nanoparticles were chosen in view of their wide spread use in cosmetics and health care products, which allow their direct release in the environment. The impact on germination rate, shoot & root length and vigour index were evaluated. A concentration dependent inhibition of seed germination as well as seedling length was observed in all the tested plants. Due to the presence of thick cuticle on testa and root, pearl millet (xerophytic plant) was found to be relatively less sensitive to ZnO nanoparticles as compared to wheat and tomato (mesophytic plants) with normal cuticle layer. No correlation was observed between nanoparticles toxicity and seed size. The results indicated that variations in surface anatomy of seeds play a crucial role in determining the phytotoxicity of nanoparticles. The present findings significantly contribute to assess potential consequences of nanoparticle release in environment particularly with major emphasis on plant systems. It is the first report which suggests that variations observed in phytotoxicity of nanoparticles is mainly due to the predominant differences in size and surface anatomy of tested plant seeds and root architecture. Effect of various concentrations of nano ZnO, bulk ZnO and zinc sulphate on the growth of pearl millet (A), tomato (B) and wheat (C) seedlings.

Exogenous calcium induces tolerance to atrazine stress in Pennisetum seedlings and promotes photosynthetic activity, antioxidant enzymes and psbA gene transcripts.

Calcium (Ca) has been reported to lessen oxidative damages in plants by upregulating the activities of antioxidant enzymes. However, atrazine mediated reactive oxygen species (ROS) reduction by Ca is limited. This study therefore investigated the effect of exogenously applied Ca on ROS, antioxidants activity and gene transcripts, the D1 protein (psbA gene), and chlorophyll contents in Pennisetum seedlings pre-treated with atrazine. Atrazine toxicity increased ROS production and enzyme activities (ascorbate peroxidase APX, peroxidase POD, Superoxide dismutase SOD, glutathione-S-transferase GST); but decreased antioxidants (APX, POD, and Cu/Zn SOD) and psbA gene transcripts. Atrazine also decreased the chlorophyll contents, but increased chlorophyll (a/b) ratio. Contrarily, Ca application to atrazine pre-treated seedlings lowered the harmful effects of atrazine by reducing ROS levels, but enhancing the accumulation of total chlorophyll contents. Ca-protected seedlings in the presence of atrazine manifested reduced APX and POD activity, whereas SOD and GST activity was further increased with Ca application. Antioxidant gene transcripts that were down-regulated by atrazine toxicity were up-regulated with the application of Ca. Calcium application also resulted in up-regulation of the D1 protein. In conclusion, ability of calcium to reverse atrazine-induced oxidative damage and calcium regulatory role on GST in Pennisetum was presented.

Enzymatic antioxidant defense in resistant plant: Pennisetum americanum (L.) K. Schum during long-term atrazine exposure.

Plants belonging to the genus Pennisetum have been reported to be resistant to atrazine, a widely used herbicide that also can cause serious pollution of soil and water. To evaluate the enzymatic antioxidant defense mechanism to the oxidative stress of atrazine, experiments focusing on the malondialdehyde (MDA) content and antioxidant enzyme in the leaf and root of Pennisetum americanum (L.) K. Schum (P. americanum) during long-term (68days) atrazine exposure were carried out. The test plant had not suffered obvious lipid membrane peroxidation, which was further confirmed by the result that the MDA content in the root and the leaf of the test plant did not significantly increase when treated with various concentrations of atrazine. The activity of the well-known antioxidases, such as superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and peroxidase (POD), was increased when the plants were exposed to atrazine, especially at moderate concentrations (20mgkg-1 or below). These results revealed that antioxidant enzymes played important roles in protecting P. americanum from the oxidative damage induced by atrazine. The increased and more stable SOD activity in the leaf compared to in the root portion of the plant under increasing atrazine concentrations and increasing exposure time indicated that the leaf exhibited more pronounced superoxide radical scavenging ability than the root. Furthermore, correlation analysis showed that the studied antioxidases were positively correlated with the exposure time, suggesting that the antioxidant defense in P. americanum seedlings might become stronger as the plant matures. In conclusion, the increasing antioxidant enzyme activities enable P. americanum seedlings to cope with the oxidative stress induced by moderate concentrations (20mgkg-1 or below) of atrazine.

Enhancing Phytoremediation Potential of Pennisetum clandestinum Hochst in Cadmium-Contaminated Soil Using Smoke-Water and Smoke-Isolated Karrikinolide.

The use of plant growth regulators (PGRs) and biostimulants to enhance phytoextraction is gaining popularity in phytoremediation technology. This study investigated the stimulatory effects of smoke-water (SW), a smoke-derived compound karrikinolide (KAR1) and other known plant growth regulators (PGRs) [gibberellic acid (GA3), kinetin (Kin) and indole-3-butyric acid (IBA)] to enhance the phytoextraction potential of Pennisetum clandestinum. Pennisetum clandestinum seedlings were grown for 10 weeks in vermiculite using Hoagland's nutrient solution and were treated with cadmium (Cd) (2, 5, and 10 mg L(-1)) and SW, KAR1 and PGRs. KAR1 exhibited positive effects on shoot and root dry weight (140 and 137 mg respectively) at the highest concentration of Cd (10 mg L(-1)) compared to all the other treatments. KAR1 and SW treatments used in the present study significantly improved the phytoextraction potential of P. clandestinum (602 and 575 mg kg(-1) respectively) compared to the other tested PGRs. This is the first report on the use of SW and KAR1 to enhance phytoremediation potential in P. clandestinum. Further studies are needed to elucidate the exact mechanisms of smoke constituents involved in phytoextraction potential of plant species.

Studies on long-term impact of STCR based integrated fertilizer use on pearl millet (Pennisetum glaucum)-wheat (Triticum aestivum) cropping system in semi arid condition of India.

A long-term field experiment on pearl millet - wheat cropping system with soil test crop response correlation (STCR) based fertilizer application was initiated during kharif- 2003 on a sandy loam soil (Typic Halustept) at a research farm of Indian Agricultural Research Institute, New Delhi. The aim of the experiment was to study the impact of STCR based integrated fertilizer application for targeted yield of pearl millet - wheat cropping sequence yield and changes in soil health. The result showed a significant and positive impact of integrated use of the fertilizerwith FYM on productivity of the cropping sequence and soil fertility. The STCR based integrated fertilizer recommendations with FYM produced significantly higher grain and straw yields of pearl millet and wheat crops as compared to other treatments. The highest average (2003 to 2010-11) grain and straw yield of pearl millet (2.85 and 6.59 t ha(-1)) and wheat (5.32 and 7.17 t ha(-1)) was recorded with the application of STCR based integrated fertilizer recommendations (T2) for targeted level of yield 2.5 and 5.0 ha(-1), respectively. Average increase in grain and straw yield of pearl millet was 203 and 197% and 196 and 193% of wheat under T2 treatment over control (T4). After harvest of wheat crops (2010-11), the physical, biological properties and fertility status i.e. available N, P and K of soil were improved in the treatments where STCR based integrated fertilizer dose with 10 t FYM (T2) and FYM @20 t ha(-1)(T1) were applied in both the crops and were significantly higher as compared to T3 treatment except available phosphorus. Economic analysis based on average yield of eight cropping sequence (2003 to 2010-11), pearl millet - wheat cropping sequence gave maximum net return of Rs. 100,907 ha(-1) yr(-1) and total return of Rs. 64,992/ ha(-1)yr(-1) over control with STCR based integrated fertilizer recommendations (T2). It is concluded that STCR based integrated fertilizer can be adopted by the farmers of arid region for getting higher yield, profit and improving soil health.

Is pearl millet (Pennisetum glaucum) a good plant species for ecotoxicological tests?

Various plant species can be selected for environmental testing, including pearl millet (Pennisetum glaucum (L.) R. Br), a globally significant cereal crop. This study aims to assess millet's suitability as a species for ecotoxicological tests, examining (1) germination and initial development dynamics, (2) the minimum seed quantity for reliable sampling, (3) optimal experimental design with replication numbers, (4) suitability of positive control, and (5) the effectiveness of the protocol in evaluating toxic effects of environmental pollutants. Millet exhibited rapid and uniform germination as well as consistent initial seedling development. To establish the minimum number of seeds required for reliable experimentation, germination, and seedling growth were compared across plots containing 10, 25, and 50 seeds. Consequently, 10 seeds per plot were chosen for subsequent experiments to reduce labor and costs while maintaining reliability. To validate the selected experimental design, and to establish a positive control for assays, aluminum was used as a toxic element at concentrations ranging from 10-2 to 10-6 M. While aluminum did not affect the final percentage of germinated seeds, it did exhibit an impact on the Germination Speed Index (GSI). Significant differences in root and aerial growth, and with fresh weight, were observed. The 10-3M concentration was chosen as the positive control as the 10-2 concentration showed extreme toxicity. To assess the applicability of the established protocol in determining the toxic effects of environmental pollutants, millet roots were exposed to the toxic agents atrazine, cadmium, methyl methane sulfonate (MMS), and Spent pot liner (SPL). Millet demonstrated sensitivity and efficiency in response to these tests. In conclusion, millet proves to be an effective species for the toxicological risk assessment of environmental pollutants.

Uptake and translocation of cesium-133 in napiergrass (Pennisetum purpureum Schum.) under hydroponic conditions.

The present study reports the potential remediation of cesium (Cs) using napiergrass, which produces the largest biomass among the herbaceous plants in hydroponic culture containing stable Cs (Cs-133) at concentrations of 50, 150, 300, 1000, and 3,000 µM using cesium chloride (CsCl), with 0 µM Cs as a control concentration. Plant height was significantly decreased in higher Cs-treated conditions (300, 1000, and 3000 µM Cs) at 7 weeks after treatment (WAT), but tiller numbers tended to increase compared with the control plant. No significant difference was observed in the aboveground dry matter weight in all Cs treatments throughout the study period. Cs content in the roots, leaf blades, and leaf sheaths clearly increased with increasing Cs concentration in the solutions. Cs content in the aboveground parts (leaf blades and leaf sheaths) was consistently higher than in the roots at concentration of 3,000 µM. Total Cs contents in the aboveground parts were 6305 and 26,365 mg kg(-1) at 7WAT in 1000- and 3000-µM Cs treatments, respectively. Mean values of transfer factors (TFs) in the aboveground parts were 50 µM=0.78, 150 µM=1.02, 300 µM=0.86, 1,000 µM=0.68, and 3,000 µM=0.94, respectively at 7WAT. Due to its high Cs content and high TF in the aboveground parts, napiergrass may be a candidate plant with high potential for phytoremediation of Cs from Cs-137-contaminated soil.

Salt stress induced alteration in growth characteristics of a grass Pennisetum alopecuroides.

Salinity is one of the major abiotic stresses that adversely affect crop productivity and quality. The present investigation was carried out to study the alterations in the growth characteristics of a grass species, Pennisetum alopecuroides under the influence of sodium chloride (NaCl) salinity. From the results it is clear that shoot length of Pennisetum alopecuroides was increased by 13.17% at 100 mM NaCl concentration while the root length was observed to be increased at 50 mM NaCI concentration by 26.93%.Maximum height of the plant was observed by 18.23% at 50 mM while shoot to root ratio was higher at 300 mM concentrations by 29.17% increase over the control. Moreover, the maximum percent increase in leaf area was recorded as 11.17% (100 mM). Fresh weight was increased by 50.92% at 100 mM while dry weight of the experimental grass was increased by 33.64% at the same concentration of salt to the rooting medium while moisture percentage was increased to a maximum by 24.61% at 50 mM. It appears that the grass species studied exhibit a moderate salinity tolerance as far as linear growth of plant is concerned.

Nutritional quality, nutrient uptake and biomass production of Pennisetum purpureum cv. King grass.

The research was conducted to determine the effects of cutting interval and fertilization on the nutritional quality, nutrient uptake, and biomass production of King grass. The experimental design was a randomized complete block, using 4 blocks and 8 treatments per block; treatments consisted of 4 ages of cutting (30, 45, 60, and 90 days), with fertilization and without fertilization. The results showed increases of up to 72,000 kg ha-1 year-1 of dry matter (DM) when fertilization was implemented. There was a significant reduction in with an increase in the cutting days (12.70-6.53% protein). Fiber increased (48.79-72.99% NDF) when fertilization treatments were included and cutting days increased. The elements that were included in fertilization (N, P, K) showed a higher foliar content and also presented a reduction in foliar content with growth of the plant. Treatments with fertilization showed a nutrient uptake increase for all the elements up to 60 days, where a reduction in uptake capacity was observed. King grass is a plant with a high nutrient uptake capacity and, therefore, with high biomass and nutrient production. This is an advantage since it can be used in multiple applications, such as animal feed, biofuel production, and as a substrate for biodigestion, among others.

Amelioration of salt induced toxicity in pearl millet by seed priming with silver nanoparticles (AgNPs): The oxidative damage, antioxidant enzymes and ions uptake are major determinants of salt tolerant capacity.

Abiotic stresses in plants reduce crop growth and productivity. Nanoparticles (NPs) are effectively involved in the physiochemical processes of crop plants, especially under the abiotic stresses; whereas, less information is available regarding the role of AgNPs in salt-stressed plants. Therefore, in the current study, we investigated the effects of seed priming with commercially available silver nanoparticles (AgNPs) (size range between 50 and 100 nm) on plant morphology, physiology, and antioxidant defence system of pearl millet (Pennisetum glaucum L.) under different concentrations of salt stress (0, 120 and 150 mM NaCl). The seed priming with AgNPs at different levels (0, 10, 20 and 30 mM) mitigated the adverse impacts of salt stress and improved plant growth and defence system. The results demonstrated that salt-stressed plants had restricted growth and a noticeable decline in fresh and dry weight. Salt stress enhanced the oxidative damage by excessive production of hydrogen peroxide (H2O2), malondialdehyde (MDA) contents in pearl millet leaves. However, seed priming with AgNPs significantly improved the plant height growth related attributes, relative water content, proline contents and ultimately fresh and dry weight at 20 mM AgNPs alone or with salt stress. The AgNPs reduced the oxidative damage by improving antioxidant enzyme activities in the pearl millet leaves under salt stress. Furthermore, sodium (Na+) and Na+/K+ ratio was decreased and potassium (K+) increased by NPs, and the interactive effects between salt and AgNPs significantly impacted the total phenolic and flavonoid content in pearl millet. It was concluded that seed priming with AgNPs could enhance salinity tolerance in crop plants by enhancing physiological and biochemical responses. This might boost global crop production in salt-degraded lands.

Salt stress alleviation in Pennisetum glaucum through secondary metabolites modulation by Aspergillus terreus.

The growth promoting activities of the isolated endophyte Aspergillus terreus from Aloe barbendsis was studied in the salt stressed Pennisetum glaucum (pearl millet). A significant (P = 0.05) increase in the root-shoot lengths, fresh and dry weights and chlorophyll content of pearl millet seedlings was noticed after colonization by A. terreus under normal conditions. At 100 mM NaCl stress and A. terreus inoculation, the growth rate of pearl millet seedlings were significantly (P = 0.05) inhibited. Furthermore, the IAA production, relative water content (RWC), chlorophyll, soluble sugar, phenol and flavonoid contents were significantly decreased, whereas proline content and lipid peroxidation were increased. On the contrary, pearl millet seedlings inoculated with A. terreus retained significantly (P = 0.05) higher amounts of RWC, chlorophyll, soluble sugar, phenol and flavonoid contents under 100 mM salt stress. The higher IAA production in A. terreus associated seedlings rescued the plant growth and development under salt stress. Moreover, the LC MS/MS analysis of A. terreus cultural filtrate revealed the presence of quinic acid, ellagic acid, calycosin, wogonin, feruloylquinic acid, caffeic acid phenylethyl ester, D-glucoside, myricetin, propoxyphene and aminoflunitrazepam. The results of the study conclude that innoculation of A. terreus improves the NaCl tolerance in pearl millet by ameliorating the physicochemical attributes of the host plants.

Do silicon and nitric oxide induce resistance to Mahanarva spectabilis (Hemiptera: Cercopidae) in forage grasses?

BACKGROUND: Great efforts have been made to identify grasses that are resistant to spittlebugs (Hemiptera: Cercopidae). However, the time required to develop and launch new cultivars is relatively long. The employment of resistance inducers is a current strategy that may be useful for the control of insect pests. This analysis evaluates the feasibility of using the chemical inducers silicon and nitric oxide to increase spittlebug resistance based on changes in forage grass vegetative characteristics and the biological traits of Mahanarva spectabilis (Distant, 1909). RESULTS: Mahanarva spectabilis nymphs and adults can cause significant damage to forage grasses. Furthermore, silicon and nitric oxide inducers were not sufficient to lessen this damage by positively influencing the growth and development of forage grasses. These inducers did not negatively alter the biological parameters of M. spectabilis or diminish its population. However, phenolic compound concentrations increased when forage grasses were treated with silicon or attacked by adult insects, but this parameter was not useful to predict spittlebug resistance. This fact suggests that the physiological and biochemical changes caused by silicon should be further studied. CONCLUSION: The current analysis demonstrated that application of the chemical inducers silicon and nitric oxide is currently not a viable strategy for the effective and economic management of M. spectabilis on Brachiaria ruziziensis, Pennisetum purpureum and Digitaria sp. © 2019 Society of Chemical Industry.

[Salinity effect on germination, growth, and grain production of some autochthonous pear millet ecotypes (Pennisetum glaucum (L.) R. Br.)]. / Effet du stress salin sur la germination, la croissance et la production en grains chez quelques écotypes de mil (Pennisetum glaucum (L.) R. Br.) autochtones de Tunisie.

This study compared the behaviour of six autochthonous pear millet ecotypes collected through the Tunisian territory under salt stress from germination to maturity. It showed that salt has little effect on germination rate and coleoptile emergence. However, this effect is more significant for radicular growth and between ecotypes. Salinity did not influence plant height, which seems to be a varietal characteristic, but revealed a positive effect on the foliar expansion. On the productivity level, salinity did not exert a prejudicial effect over the length of the principal candle, but improved the yield component. This adaptation to salinity is mainly due to its root system. This effect varied according to stress intensity and ecotype. Vegetative growth and yield of high-straw ecotypes was decreased by severe salinity, while ecotypes with low or medium height appear very stable on the productivity level. Such ecotypes can play an important role in the conservation and development of fragile grounds, and also be useful as a source of desirable genes for genetic improvement in salinity conditions.

Chitosan enhances disease resistance in pearl millet against downy mildew caused by Sclerospora graminicola and defence-related enzyme activation.

BACKGROUND: The present study investigated the effect of chitosan seed priming on the induction of disease resistance in pearl millet against downy mildew disease caused by Sclerospora graminicola (Sacc.) Schroet. RESULTS: Pearl millet seeds were primed with chitosan at different concentrations: 0.5, 1.5, 2.5 and 3 g kg(-1) seed. Of the different concentrations, 2.5 g kg(-1) was found to be optimum, with enhanced seed germination of 99% and seedling vigour of 1782, whereas the untreated control recorded values of 87% and 1465 respectively. At optimum concentration, chitosan did not inhibit sporulation and release of zoospores from sporangia. Furthermore, pearl millet seedlings raised after seed treatment with chitosan showed an increased level of the defence-related enzymes chitosanase and peroxidase as compared with the untreated pearl millet seedlings on downy mildew pathogen inoculation. The effect of chitosan in reducing downy mildew incidence was evaluated in both greenhouse and field conditions, in which respectively 79.08 and 75.8% disease protection was obtained. CONCLUSION: Chitosan was effective in protecting pearl millet plants against downy mildew under both greenhouse and field conditions by inducing resistance against the pathogen. Thus, chitosan formulation can be recommended for seed treatment in the management of downy mildew disease.

Cadmium phytoextraction potential of king grass (Pennisetum sinese Roxb.) and responses of rhizosphere bacterial communities to a cadmium pollution gradient.

Screening for tolerant and high biomass producing plants is important for phytoextraction efforts in remediating agricultural soils contaminated by heavy metals. We carried out a greenhouse experiment involving a soil cadmium (Cd) concentration gradient (0.1, 0.5, 1, 2, 4, and 8 mg kg-1) to assess growth and phytoextraction capacity of king grass (Pennisetum sinese Roxb.) in soils contaminated by Cd and to explore changes in diversity and structure of rhizosphere soil bacterial communities in response to long-term Cd pollution. A significant positive relationship was observed between Cd concentrations in P. sinese stems, leaves, and roots and soil Cd concentration. The highest Cd concentrations in shoots and roots were 28.87 and 34.01 mg kg-1, respectively, at 8 mg kg-1of soil Cd supply. Total extraction amounts of Cd in P. sinese were 0.22-1.86 mg plant-1 corresponding to treatment with 0.5-8 mg kg-1 Cd. Most of the Cd was stored in shoots, and the largest accumulation was 1.56 mg plant-1 with 54.02 g dry shoot weight. After phytoextraction, changes in rhizobacterial community composition were found with different levels of Cd application, whereas there were no clear trends in diversity and richness. Results of this study show the feasibility of P. sinese in accumulating Cd and provide support for its application in remediation of soil moderately contaminated by Cd.