Repositório RCAAP

ABSTRACT Uptake of nutrients and cadmium (Cd) are dependent upon many factors, including plant species, ions concentration and pH. Tolerance to Cd-induced oxidative stress can be modulated by phytohormones such as abscisic acid (ABA), which induce the production of reactive oxygen species, activating proteins and enzymes involved in stress response and possibly stress tolerance. The present study aimed to evaluate the biochemical variations induced by Cd in ABA-deficient sitiens tomato mutant (sit) and its wild-type counterpart, Micro-Tom (MT), grown at different pH conditions. The plants were cultivated in nutrient solution (pH 5, 6 and 7; 20-days) and were then further grown over a 48-h period in 0 or 50 ?M CdCl2 at pH 6. Before Cd addition, the concentrations of nitrogen, sulfur, copper, iron and zinc were determined and variations in nutrients concentrations were observed. After Cd addition, sit roots grown at pH 5 and 7 did not exhibit differences in ascorbate peroxidase (APX) activity in 0 or 50 ?M CdCl2, and sit root grown at pH 6 exhibited lower glutathione reductase (GR) activity in the presence of Cd. Moreover, sit shoot grown at pH 5 showed decreased activities of superoxide dismutase (SOD), Mn-SOD II and Cu/Zn-SOD V, in 0 and 50 ?M CdCl2. The results indicated that pH modulates the plant nutrition in a complex way and may involve multiple ABA signaling pathways. Likewise, ABA status seems to be related with the Cd-translocation within the plant, suggesting that Cd, ABA and pH responses cannot be evaluated as isolated systems.

ABSTRACT The application of an adequate rate and splitting of nitrogen is essential for wheat grain yield and protein content. The aim of this work was to adjust nitrogen management approaches regarding agronomic performance and protein content of wheat cultivars in various environments. Field experiments were conducted under no-tillage system on soybean mulch during the 2011 and 2012 growing seasons in Londrina and Pato Branco regions. The experimental design was a randomized block in split plot with four replicates. Four wheat cultivars (IPR Catuara TM, BRS Gaivota, Quartzo, CD 120) were tested with six nitrogen (N) management forms. Were evaluated: number of ears per unit area (NEA); plant height (PH); thousand-kernel weight (TKW); test weight (TW); grain yield (GY); and protein content (PC). The combined ANOVA (p ? 0.01) and Tukey’s test (p ? 0.01) were used. The interaction between cultivars and environments influence all yield components, GY and PC. The interaction management forms of N and environments affected the TKW, NEA, GY and PC. The results showed that in low-rainfall environments, nitrogen topdressing could be suppressed with no negative effects on GY or PC. Under ideal weather conditions, the GY of wheat cultivars was enhanced on application of 60 kg.ha–1 N of urea at the beginning of tillering as well 20 kg.ha–1 of N at booting. Matching the appropriate cultivars to the ideal growth environment is essential for achieving high GY values. The nitrogen forms on the topdressing do not influence the PC of cultivars in Pato Branco.

ABSTRACT Stalk rots compromise the translocation of water and nutrients, affecting grain filling. This study aimed to quantify the incidence of stalk rots in corn hybrids depending on sowing time and nitrogen topdressing rate, and to assess any correlation with grain yield. The experiment was conducted under field conditions in Atalanta, Santa Catarina state, Brazil, using a split-split-plot randomized block design. The hybrids AG 9025 PRO3 (super-early) and 30F53 VYH (early) were sown in the preferential (September 20) and late (December 5) sowing seasons with four nitrogen rates (0, 150, 300, and 450 kg·ha–1). The population density was 75,000 plants·ha–1 andthe nitrogen topdressing was carried out at the V4, V8, and V12 stages. The fungus Colletotrichum graminicola predominated in both hybrids and its presence was negatively correlated with stalk diameter and yield. The hybrid AG9025 PRO3 was more susceptible to stalk rot (35.1%) than the hybrid 30F53 VYH (8.8%). A higher incidence of stalk rot was observed in the late sowing season (31.1%) than in the preferential sowing season (11.2%). A decrease in the incidence of stalk rot was observed in the hybrid AG9025 PRO3 as nitrogen rates increased, but this behavior was not clearly observed in the hybrid 30F53 VYH.

ABSTRACT Eucalyptus globulus is one of the most commonly planted hardwood species for industrial use in various temperate regions around the world. The present study aimed to evaluate 62 full-sib families of E. globulus in one of the southernmost progeny trials of the species in the south of Chile. Estimates of genetic parameters for stem straightness, branching quality and growth traits were based on a Bayesian modelling approach using Gibbs sampling. A Bayes Factor (BF) analysis supported the hypothesis of significant additive genetic variation for all traits under study. Conversely, the BF supported a model with significant dominance effects for the diameter at breast height and stem volume, which explained up to 25% of the phenotypic variation. The greatest narrow-sense heritability estimates were found for the tree height and stem straightness, which were 0.15 (0.08 to 0.26) and 0.18 (0.10 to 0.28), respectively (mean of posterior distributions and 90% credible sets). In turn, the branching quality had a low heritability (narrow-sense) that varied from 0.05 to 0.10 (90% Bayesian credible region). The mean posterior estimate of genetic correlation between both quality traits was 0.22 (0.01 to 0.63, 90% credible set from a bi-trait threshold model), which indicates that stem straightness is positively related to branching quality. Our findings reveal that the study population responds to common patterns of breeding populations of E. globulus. This information is valuable for the development of improved seeds in the southern zone of Chile.

ABSTRACT The residue of imidazolinone herbicides in soil can be detrimental to soybean cultivation in rotation with Clearfield® rice. Thus, this research aimed to evaluate the ryegrass phytoremediation capacity on the imazapyr+imazapic residue in the soil in two soil moisture conditions in the off-season, and the effect on soybean growth in the next growing season. Two experiments were conducted between 2016 and 2017 in Santa Maria, Rio Grande do Sul state, Brazil. It was used the randomized block design in a 3 × 2 factorial. The first factor being the residue in the soil of 0, 210 and 420 g c.p.·ha–1 of the formulated mixture of the herbicides imazapyr+imazapic(525 + 175 g a.i.·kg–1) applied to rice in the 2015/2016 growing season, and the second factor being the presence or absence of ryegrass in the off-season. One experiment was conducted under soil moisture above 70% of field capacity in the off-season, and the other under ambient condition of soil moisture. The soil residue of the application of 420 g c.p.·ha–1 of the imazapyr+imazapic herbicides performed129 days before planting caused phytotoxicity and reduced dry matter of ryegrass under high soil moisture condition in the off-season in irrigated rice areas. Soybean, when planted 359 days after application, has its initial root and shoot growth affected by the residue of 210 and 420 g c.p.·ha–1 rates in high soil moisture condition in the off-season, regardless of ryegrass cultivation during the same period. However, grain yield is not affected.

ABSTRACT Residual biomass from grains has potential as an energetic source. Biomass composition determines this potential and is related to plant nutrition, which may vary according to soil fertility. The aim of this 23-year field study was to evaluate changes in chemical attributes of a Brazilian Oxisol and in the energetic potential of oat (Avena sativa L.) and soybean (Glycine max (L.) Merr) residual biomasses provided by tillage systems and fertilizer rates. The trial was performed since 1989, assessing soil chemical attributes in no-tillage (NT), conventional (CT), minimum (MT) and no-tillage plus chisel plough (NT+CP), with two fertilizer rates (normal and reduced, since 1994). Oat and soybean (2012/2013) residual biomasses were collected and analyzed by its elemental composition, higher heating value (HHV) and theoretical potential for electricity production. The NT system presented higher P-resin availability; NT and NT+CP provided higher OM and total P content on soil surface. Without appropriate amounts of K and P fertilizer, P-resin and P total contents diminished mainly in 0-0.1 m depth, while exchangeable, non-exchangeable and total K+ fractions were mined even in deeper layers (0-0.3 m). The better general fertility conditions were achieved by conservative tillage systems, with normal fertilizer rate. Soil fertility levels changed chemical composition of both biomasses but had no effect on biomass HHV. Considering a system with oat and soybean grain production plus residual biomasses for energetic exploitation, it could be possible to generate 2,941 GWh·year–1, while still achieving 70% residue coverage under no-tillage maintenance.

ABSTRACT Rosehip, Rosa canina L. fruit, is valued for its flavor, taste, color and aroma, in accordance with its recognition as one of richest sources of pro-health compounds. Screening, preservation and propagation of the most valuable local populations of rosehip are performed for food, pharmacological, and cosmetic applications. Eleven native R. canina genotypes from the Interior Aegean region, Turkey, were collected and analyzed regarding organic acids, phenolic compounds, sugars, and DPPH scavenging activity within this study. Regarding biochemical profile of fruits, protocatechuic acid and quercitrin were the most dominant compounds among 12 identified phenolics. The dominant organic acids were malic and citric and fructose and glucose were the dominant sugars. There was no correlation between DPPH scavenging activity and the analyzed chemicals in fruits. Although levels of certain compounds varied significantly between consecutive years, the ranking of genotypes according to the levels of particular chemicals was maintained. Generally, the most promising chemotype regarding biological value was 64US03. The chemical composition and the presence of bioactive compounds make the native to Interior Aegean R. canina genotypes a valuable source of bioactive agents preventing oxidative-stress related diseases.

ABSTRACT The study of weed interference periods and the economic threshold level (ETL) of weeds on crops allows the adoption of management methods and the rationalized use of herbicides. The objective of this study was to determine the periods of interference and to test mathematical models to determine the economic threshold level of ryegrass in the wheat crop. Two experiments were carried out in a randomized block design with four replications. The first experiment was conducted in the 2014/2015 agricultural season. The periods of interference and control of ryegrass were studied in wheat. The periods of interference and/or control were: 0, 10, 20, 30, 40, 50 and 120 days after emergence (DAE). The second experiment was conducted in the 2016/2017 agricultural season. The ETLs were studied, being the treatments composed of wheat cultivars and 12 populations of ryegrass, in competition with the respective cultivars. The results allowed concluding that the management methods of weed ryegrass must be adopted in the period between 11 and 21 days after crop emergence, which is described as a critical period of control of this weed. The wheat grain yield loss competing with ryegrass reached 59% when grown with ryegrass. For ETL, the linear regression model of the rectangular hyperbola adequately estimates grain yield losses in the presence of ryegrass. The cultivar presenting the lowest values of ETL, that is, less capacity to live with the weed, was TBIO Alvorada. The other cultivars presented similar ETL values.

ABSTRACT Biochemical assays in a time-course were employed to evaluate stresses induced by glyphosate treatment in resistant and sensitive biotypes of Conyza bonariensis. Two experiments were conducted assessing glyphosate doses and time-course after treatment. The doses of glyphosate ranged from 0 to 11840 g ae·ha–1 and assessments performed until 552 h after glyphosate treatment (HAT). The objectives of this study were to evaluate the oxidative stress and differential antioxidant enzyme activity in glyphosate-resistant and -sensitive biotypes of hairy fleabane after glyphosate treatment. After treatment, both studied biotypes accumulated similar levels of shikimic-acid until 96 h. The sensitive biotype died at192 HAT. Shikimic-acid and hydrogen peroxide (H2O2) accumulation in glyphosate-resistant biotype were transient and did not differ from untreated plants at 288 and 500 HAT, respectively. In both glyphosate-resistant and -sensitive biotypes, a correlation analysis established a cause-and-effect relationship after glyphosate treatment, which leads to shikimic-acid and hydrogen peroxide accumulation, lipid peroxidation (indicates tissue damage) and an enhancement in the activity of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) enzyme. However, in the glyphosate-resistant biotype, the oxidative stress and tissue damage were lower, and antioxidant enzyme activities SOD, CAT, and APX were higher than in the -sensitive biotype. It indicates that antioxidant enzyme in glyphosate-resistant biotype might be related to the glyphosate-resistance process in Conyza bonariensis. This study is the first report of differential antioxidant enzyme activity in hairy fleabane.

ABSTRACT Considering the importance of silicon (Si) to increase rice resistance to blast, this study investigated the nutritional status of rice plants supplied with this element in response to Pyricularia oryzae infection. Plants were grown in nutrient solutions containing 0 and 2 mmol·L-1 of Si (referred to -Si and +Si plants, respectively). The area under blast progress curve decreased for +Si plants due to a significant increase of 714% on the foliar Si concentration in contrast to -Si plants. For +Si plants, the foliar N, P, K, Ca, Mg, Cu, and B concentrations were significantly lower in comparison to -Si plants. On infected plants, the foliar N, K, and Cu concentrations were significantly lower in comparison to noninfected ones. The foliar Zn, Fe, and Mn concentrations were significantly lower for -Si inoculated plants in comparison to -Si noninoculated ones. The foliar Mn and S concentrations were significantly lower for +Si inoculated plants in comparison to +Si noninoculated ones. The foliar Fe concentration was significantly lower for +Si inoculated plants in comparison to +Si noninoculated ones. Foliar Zn and Mn concentrations were significantly lower for +Si plants in comparison to -Si plants regardless of their inoculation with P. oryzae. Foliar Fe and S concentrations were significantly lower for +Si plants in comparison to -Si plants, respectively, for noninoculated and inoculated plants. Taken together, Si stood for itself in reducing blast symptoms without the need of high foliar concentrations of either macro or micronutrients that could affect plantgrowth.

ABSTRACT Considering the importance of blast, caused by Pyricularia oryzae, to impact wheat yield, this study investigated whether the foliar spray of potassium silicate (PS) could affect the photosynthesis of wheat plants and its potential to reduce disease symptoms. The Exp. 1 aimed to determine the effect of the foliar spray of PS on the photosynthetic performance of plants and was arranged in a completely randomized design with six treatments (plants sprayed with PS rates of 2.5, 5.0, 7.5, 10.0, and 12.5 g·L-1 at 35 days after emergence) and six replications. The leaf gas exchange (net CO2 assimilation rate (A), internal CO2 concentration (Ci), stomatal conductance to water vapor (gs), and transpiration rate (E)) as well as fluorescence of chlorophyll a (maximal photosystem II quantum yield (Fv/Fm), quantum yield of non-regulated energy dissipation [Y(NO)], photochemical yield [Y(II)], electron transport rate (ETR), and quenching non-photochemical [Y(NPQ)]) parameters were evaluated. The Exp. 2 was carried out to determine the effect of PS on blast control and also on the photosynthetic performance of plants. Plants at 35 days after emergence were sprayed with PS rate of 12.5 g·L-1, which did not affect photosynthesis on plants from Exp.1. This experiment was a 2 × 4 factorial and arranged in a completely randomized design with six replications. The factors studied were plants non-inoculated or inoculated plants and the spray of water, PS, fungicide (trifloxystrobin 10% + tebuconazole 20%; 0.75 L/ha), and fungicide + PS. There were no significant changes in the values of A, gs, E, Ci, Fv/Fm, Y(NO), Y(II), Y(NPQ), and ETR for plants sprayed three times (every 96 h interval) as the PS rates increased from 2.5 to 12.5 g·L-1. There was no significant relationship between the PS rates with either absorbance, reflectance or transmittance on the leaf blades. Linear regression model best described the foliar Si concentration-PS rates relationship. Foliar Si concentration significantly increased by 44 and 42%, respectively, for the PS and PS + fungicide treatments compared to water-sprayed plants. The area under disease progress curve was significantly lower by 64, 58, and 53%, respectively, for the fungicide, PS, and fungicide + PS treatments in comparison to water-sprayed plants. The photosynthetical process, primarily related to the Fv/Fm parameter, on wheat leaves was greatly impaired during the infection process of P. oryzae, but to a lesser extent on the leaves of PS-sprayed plants. In conclusion, the foliar spray of PS can be an environmentally friendly strategy to control wheat blast without causing perturbation to the photosynthetic machinery of wheat plants.

ABSTRACT Selenium (Se) is considered a beneficial chemical element for plants, but in high concentrations it may present symptoms of toxicity. The present study aimed to evaluate 11 concentrations of Se (0; 0.1; 0.5; 1; 5; 10; 20; 40; 80; 400; 800 mg.L-1) to determine the low and high (toxicity) critical levels to seed germination of cowpea (Vigna unguiculata). In addition, alterations in the rate of photosynthetic pigments, lipid peroxidation and sugars during the initial growth development of seedlings were analysed. Seeds exposed to 800 mg.L-1 of Se showed a decrease of 20% of seed germination index compared to the control treatment. The decrease in seedling growth reflected in the increase of total sugars and sucrose concentration in both the shoot and root in response to exposure to Se concentration. There was a decrease in the concentration of leaf chlorophyll, carotenoids and pheophytin from seedlings exposed to high Se concentration. The rate of lipid peroxidation and the hydrogen peroxide concentration in the shoot was reduced up to the concentration of 1 mg.L-1 with subsequent increase in response to Se concentration applied. In the roots, the lipid peroxidation rate increased at concentrations higher than 80 mg.L-1. The highest oxidation rate of the cellular lipid membrane in response to Se occurred in the shoot, due to oxidation reactions in the chloroplast. Degradation of photosynthetic pigments and accumulation of total sugars and sucrose can be considered efficient biomarkers to indicate the toxicity of Se in cowpea seedlings and probably in other crops.

ABSTRACT This study evaluated the effects of cover crops on yield and soil hydraulic properties of a persimmon orchard in Turkey. Soil samples were taken from 0-20 and 20-40 cm. Profiles of a clay soil and field capacity, permanent wilting point, available water capacity and saturated hydraulic conductivity of the samples were determined. Festuca rubra subsp. rubra, Trifolium repens, Festuca arundinacea, a mixture of them [Trifolium repens (40%) + Festuca rubra rubra (30%) + Festuca arundinacea (30%)], Vicia villosa R., and Trifolium meneghinianum were used as the cover crops. The experiment was conducted in a randomized complete blocks design with four replications including a mechanically cultivated and herbicide treated control plots. The greatest mean persimmon yield (16.2 Mg·ha-1) was observed in the Vicia villosa treatment and the lowest mean yield (3.6 Mg·ha-1) was observed in the bare control. The cover crops increased soil hydraulic properties, with increased aggregate stability, total porosity, reduced bulk density, and penetration resistance. The greatest increases in organic matter contents at 0-20 cm soil depth in the persimmon orchard were observed in the Vicia treatments (73.4% in the first and 74.5% in the second year). The highest aggregate stability (67.4%) and total porosity (60.9%) values were obtained on the Vicia treatments. To increase persimmon yield and improve soil physical and hydraulic properties, cover crops, especially Vicia villosa and Trifolium repens are suggested for clay soils.

ABSTRACT This study aimed to characterize the volatile composition and sensory characteristics of virgin olive oils (VOOs) from eight olive cultivars grown in the southeast region of Brazil. The volatiles were extracted by Solid Phase Micro Extraction (SPME) and analyzed by Gas Chromatography coupled to MassSpectrometry (GC-MS). The dominant sensory attributes were determined by Temporal Dominance of Sensations (TDS). C5 and C6 alcohols and C6 aldehydes were the most abundant volatiles in the investigated VOOs. E-2-hexenal was among the majorityof volatiles in all investigated olive oils, mainly in VOOs fromcultivars Arbequina, Arbosana and Grappolo 541, in which it had the most of their chromatographic area (about 60-80%). VOOs from cultivars Maria da Fé, Mission, Arbosana and Arbequina were characterized by the dominance of pungency sensation, as well as Frantoio regarding to bitter. Grappolo yielded an olive oil withpredominance of bitter, and a blended VOO (Grappolo 541 and Arbequina) had predominance of green leaf. VOO from Ascolano cultivar had dominance of fruity and pungency. Overall, pungent was the main dominant sensation in most of the investigated VOOs, which can be related to C5 and C6 volatiles.

ABSTRACT Different responses of two melon (Cucumis melo L.) genotypes (Şemame, drought and salt-tolerant and Ananas, drought and salt-sensitive) to drought stress with or without humic acid (HA) treatment were studied. The experiment was carried out under greenhouse conditions. The experimental design was two factorial randomized block with 4 replicates. HA treatment increased the shoot fresh and dry weights and leaf area of both genotypes under drought stress. HA stimulated accumulation of K and Ca ions, chlorophyll (SPAD value) and antioxidant enzyme activity (superoxide dismutase-SOD, catalase-CAT and glutathione reductase-GR) in both genotypes. This effect was more clear in the Şemame genotype than in Ananas.As a result, HA treatment has been proved to influence the ability of melon genotypes to cope with drought stress and to increase their tolerance.

ABSTRACT Brazil is one of the leading countries in the production of maize (Zea mays), with great potential for growing green maize, which has a superior commercial value in relation to maize marketed in the form of grains. Although important, the availability of cultivars recommended for the production of green maizeis still very scarce. The objectives of the present study were to estimate genetic parameters and to identify promising hybrid combinations for the development of new green maize cultivars to farmers. In the summer crop of 2016/17, ten hybrid combinations obtained through a complete diallel of five maize populations, with attributes for in natura consumption, were evaluated in two sites of the state of São Paulo, Brazil: the Instituto Agronômico(IAC) in Campinas and Tatuí. A randomized block design was used with two additional checks, with three replications, in plots with four five-meter rows spaced by 0.9 m in Campinas and 0.8 m in Tatuí, with 5 plants per meter. The following agronomic traits were assessed: grain yield, ear yield with straw and ear yield without straw, using Griffing’s method 4. Significant effects of genotypes, environments and interaction genotypes × environments were detected for all traits. Estimates of the general combining ability led to the selection of populations P2, P4, and P5 as the ones with a higher concentration of favorable alleles for the characters evaluated. Estimates of specific combining ability and improved grain yield performance allowed P2xP3 to be selected as the most promising for production of green maize.

ABSTRACT The aim of this study was to identify resistance of tolerance type in Citrus and Poncirus genotypes towards the citrus leafminer (CLM), Phyllocnistis citrella. The quantitative variables leaf and shoot lengths, leaf width, number of larvae and new shoots, and fresh and dry shoots weights, and qualitative variables associated with foliar damage were evaluated in six Citrus-related genotypes infested with CLM. In preliminary trials with lime Rough lemon (C. jambhiri), the variables that best discriminated the infestation effect of CLM were established as the numbers of larvae and new shoots per plant together with the percentages of partially rolled leaves (PRL), rolled leaves (RL) and total damage (TD = RL + PRL). In subsequent tests with all six genotypes, the variables new shoots per plant, percentage of attacked but not rolled leaves (ANRL), RL and TD were found to be significant. Trifoliata Limeira (P. trifoliata) and hybrid C × R4 (C. sunki × P. trifoliata) presented the lowest percentages of RL and TD and the highest values of ANRL. A cluster analysis was performed considering all the variables analyzed and the most tolerant genotypes for CLM, namely hybridsC × R4, C × R315 (C. sunki × P. trifoliata), M × P222 [C. sinensis × Tangor Murcott (C. reticulata × C. sinensis)] and Trifoliata Limeira (P. trifoliata) were grouped apart from the less tolerant genotypes Sunki mandarin (C. sunki) and lime Rough lemon. In conclusion, genotypes Trifoliata Limeira and its hybrid C × R4 are the most tolerant to CLM.

ABSTRACT Salt stress is an environmental challenge that adversely influences plant responses. Silicon (Si) nutrition plays critical roles in plant tolerance to salt stress. Apple (Malus domestica Borkh.), a salt sensitive fruit species, was used in the present experiment to investigate the influences of Si on salt stress as well as on alterations of biochemical responses. Apple cv Fuji grafted on M9 clonal rootstock was exposed to salt stress for 4 months with 35 mmol·L-1 NaCl. CaSiO3 doses (0.5, 1 and 2 mmol·L-1) were applied to the roots of the salt-stressed apple plants except control. Si application resulted in mitigation of salt stress in apple plants. The highest chlorophyll a, b and a + b were obtained from the 1 mmol·L-1 Si treatment (5.37, 2.41 and 7.78 μg·g-1 fw, respectively). Moreover, Si treatment had higher chlorophyll content compared to the control as well as salt exposed plants. Silicon applications led to a reduction in malondialdehyde (MDA) content even lower than control. The 0.5 mmol·L-1 Si treatment had the highest values of ascorbate peroxidase (APX) and phenolic content. The results show that Si nutrition plays important roles in apple salt tolerance via biochemical mechanisms and that it can be used in areas subject to salt stress for apple growing.

ABSTRACT Availability of a three-way data analysis to characterize two consecutive tomato (Solanum lycopersicum) generations is necessary to continue a plant breeding program with less uncertainty. The aim of this work was to analyze tomato fruit quality from F2 and F3 populations by two three-way data analysis: multiple factorial analysis (MFA) and generalized procrustes analysis (GPA). These techniques have the same main objective, searching for a common structure, but they achieve it in different ways. This work evaluated 18 tomato genotypes, represented by individual plants in F2 and selfed families in F3. The same quantitative traits related to fruit quality were measured in both generations. The first two axes of the MFA represented 51.0% of the total variability. From the representation of the genotypes on these axes, traits differing from one generation to another were identified. The first two axes of the GPA represented 56.4% of the total variability. This analysis provided a table of analysis of variance (ANOVA), which corroborated the graphic and analytical interpretations of the MFA, a technique that provides the composition of the obtained axes. The comparison between the results obtained from these techniques indicated that both MFA and GPA allowed the detection of genotypes with discrepancies between the two generations. The MFA technique presented the advantage of studying graphically and analytically the nature and degree of phenotypic differences among genotypes in both generations, while the GPA complemented the analysis with an ANOVA, achieving the quantification of statistical significances for the discrepancies or similarities between them.

ABSTRACT Seed germination and seedling growth are the stages most sensitive to salt stress, which can induce ion-specific effects and oxidative stress. Although silicon (Si) has been known to improve plant defense systems against stressful-conditions, little is known about seed priming with Si and mechanisms of Si-mediated alleviation of salt stress in seedlings. To further the modulation of salt-stress responses and their relation with Si, seed priming with calcium silicate (0, 0.05 and 0.1 mM Ca2SiO4) was used in lettuce seeds to improve seedgermination and tolerance on subsequent salt-stress exposure (0 and 50 mM NaCl). The effect of Si-priming was assessed on germination, germination rate index and mean germination time and survival of seedlings in salt-stressful conditions supported by biochemical approach involving antioxidant responses. Overall results indicated that Si plays a role in alleviating the negative effects of salt stress by improving germination performance and displayed increased SOD, CAT and GR activities and reduced malondialdehyde and H2O2 contents. Thus, our findings demonstrate that seed-priming with Si is an efficient management technique thatcan be used to alleviate deleterious effects of salt-stressful on germination of lettuce seeds and enhance salt tolerance of seedlings due the increased activity of ROS- scavenging enzymes.