Scielo RSS <![CDATA[Chilean journal of agricultural research]]> vol. 74 num. 2 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>Impact of tembotrione and flufenacet plus isoxaflutole application timings, rates, and adjuvant type on weeds and yield of maize</b>]]> Due to the steadily increasing cost of weed control in corn (Zea mays L.) and possible negative impact of chemicals on environment the demand for less and more efficient herbicide use is rising. Field studies were carried out in 2010 and 2011 in the Middle-West Poland in order to assessment the effective weed control. Treatments included herbicides tembotrione and flufenacet + isoxaflutole at recommended (88.0 and 36.0 + 7.5 g ha-1) and reduced rates (44 and 22 g ha-1; 19.2 + 4.0 or 9.6 + 2.0 g ha-1) with addition of methylated seed oil (MSO) and ammonium nitrate (AMN) adjuvants. Tembotrione was applied once at the stage of 3-5 maize leaves and flufenacet + isoxaflutole once at pre-emergence of maize. Mixtures of these herbicides were applied sequentially post-emergence, at 16-20-d intervals, after successive weed emergence. Results indicate that herbicide applied at reduced rates with adjuvants provided satisfactory weed control in maize. Application of reduced rates of tembotrione (44 and 22 g ha-1) and especially mixture of tembotrione with flufenacet + isoxaflutole and MSO + AMN adjuvants applied twice provided similar grain yield of maize as from treatments where tembotrione or flufenacet + isoxaflutole herbicides were applied only once at recommended rates (9.5, 9.7, and 10.0 t ha-1, respectively). <![CDATA[<b>Trait analysis, diversity, and genotype x environment interaction in some wheat landraces evaluated under drought and heat stress conditions</b>]]> Both drought and heat stress are responsible for decline in wheat (Triticum aestivum L.) production in many regions of the world. Intergovernmental Panel on Climate Change (IPCC) has predicted increase in these areas. Development of heat and drought tolerant genotypes is on priority. Landraces are unexploited genetic resources for various agronomic traits contributing tolerance to abiotic stress. Twenty-five wheat genotypes were evaluated in irrigated timely, rainfed timely and irrigated late sown conditions for 2 yr using 10 agronomic traits for their response to drought and heat stress and four stress indices (stress susceptibility index, stress tolerance index, mean productivity, and stress tolerance) were calculated. Variability averaged over traits was highest under rainfed conditions. Grain yield, plant height, and productive tillers were more sensitive and test grain weight as tolerant under drought. Under heat stress grain yield, grain weight, test grain weight and phenological traits were more sensitive. Productive tillers and grain number per spike were identified as important selection parameters for drought and grain weight (per spike and test grain weight) as for heat tolerance. Genotypes IC 321987, IC 322005, IC 138852, IC 138870 adapted to stressed environments or genotypes CPAN 4079 and NEPAL 38 stable over all environments can be used for introgression of the stress tolerance in elite cultivars. <![CDATA[<b>Genetic variability in Chilean pepino <i>(Solanum muricatum</i> Aiton) fruit</b>]]> Solanum muricatum Aiton is an herbaceous perennial fruit species native to the Andean region of Colombia, Ecuador, and Peru. In Chile, it was probably introduced in pre-Columbian times as a domesticated species and is presently grown in the coastal areas of the north-central regions of Coquimbo and Valparaíso. The species has been bred, but little information is available on its genetic variability in Chile. To characterize the genetic variability in this species, fruits were collected from 14 different ecotypes and seeds were sown to generate approximately 60 segregants from each accession. Segregants were planted at two different locations to characterize their fruits and fruiting habits. Fruit weight ranged from 30 to 485 g, while length was 3.5 to 16.7 cm, equatorial diameter 3.4 to 9.5 cm, pulp firmness 1.7 to 10 N, and soluble solids content 6.3 to 13.5° Brix. Fruit shape ranged from flat to oblong. When analyzing the estimated variance components with a mixed linear model, most of the variability between different ecotypes was in fruit shape, length, and weight, which resulted in a genetic contribution of 34.6%, 29.3%, and 18.1% of the total variability of these traits, respectively. Genetic variability was also found for pulp firmness and soluble solids content. Therefore, enough variability is available in seed-propagated pepinos from Chilean ecotypes to allow genetic improvement of these fruit quality traits. There was also variability from genotype x environment interactions; therefore, selections must be performed for specific environments or stable selections must be found. <![CDATA[<b>Analysis of tomato matrix effect in pesticide residue quantification through QuEChERS and single quadrupole GC/MS</b>]]> The detection of pesticide in tomato (Solanum lycopersicum L.) matrix using Gas Chromatography hyphenated to Mass Spectrometry detector (GC/MS) can affect the sensitivity of the analysis by enhancement or suppression of their chromatography response, the percentages of recoveries and leading to errors in the quantification of the pesticides. In this study, the matrix effect was investigated using nine pesticides, and "Quick, Easy, Cheap, Effective, Rugged and Safe" (QuEChERS)-GC/MS analytical technique was validated for pesticides multiresidue analysis. The matrix effect was determined using not statistical and statistical procedures including ANOVA, with similar results. Strong negative matrix effect was found for the pesticides trifluralin, 4,4'-DDT, and permethrin, resulting in the increment of the chromatogram background and a decrease in their detection responses. Contrary, an enhancement induced by the matrix presence was obtained for carbaryl and azinphos methyl, showing a positive medium matrix effect. While, dimethoate, simazine, 4,4'-DDE, and iprodione did not exhibit matrix effect. The detection limits (LOD) obtained, varied from 0.003 to 0.1 mg kg-1. Reproducibility was less than 20% for each pesticide. Recoveries were found to be between 71% and 121%, except for dimethoate, carbaryl, and azinphos methyl which reached values lower than 70%. Recoveries relative standard deviations were less than 22%. QuEChERS-GC/MS technique was used for evaluation of fresh commercial tomatoes samples, detecting carbaryl in all of them, but in concentration levels lower than the maximum residue limits according to regulations of Codex. <![CDATA[<b>Repeated applications of CPPU on highbush blueberry cv. Duke increase yield and enhance fruit quality at harvest and during postharvest</b>]]> Applications of N-(2-chloro-4-pyridyl)-N'-phenylurea (CPPU) can increase blueberry (Vaccinium corymbosum L.) yield and fruit size, but their impact on postharvest is unknown. We studied repeated CPPU applications effects on yield and quality (harvest, postharvest), over 2 yr on mature 'Duke' plants in South-Central Chile. The first year, 5 or 10 mL L-1 CPPU was applied at 3, 10, and/or 17 d after full bloom (DAFB) plus a non-sprayed control. The second year, 5 or 10 mL L-1 CPPU were sprayed 10 and 17 DAFB plus a control. The first year, only 10 mL L-1 CPPU sprayed 3+17 DAFB increased yield (32.5% &gt; control); 10 mL L-1 CPPU applied 10 or 3+17 DAFB had highest fruit diameter; and 10 mL L-1 CPPU at 17 DAFB or at 3+10+17 DAFB had highest soluble solids. Overall, 10 mL L-1 CPPU applied 3+17 DAFB, was the best treatment for year one, since it increased fruit yield and diameter, while soluble solids and postharvest weight loss were similar to control. The second year, 10 mL L-1 CPPU reduced fruit coloration (blue color coverage index: BCCI) and soluble solids, but not firmness at harvest. This rate increased berry weight (24.2%) and fruit wax (59% &gt; wax coverage index: WCI) at harvest. Harvest and postharvest WCI increased consistently as CPPU rate increased. CPPU reduced fruit rotting (15% at 45+5 evaluation). During storage, CPPU-treated-fruit had a slower decrease in firmness (30.5% < control at 30+1), but no difference at 30+5. CPPU-treated-fruit usually had higher post harvest soluble solids. Ten mL L-1 CPPU retarded color evolution at harvest and at 30+1, but not at 30+5, 40+1 or 40+5. <![CDATA[<b>Transcriptional analysis of cell wall and cuticle related genes during fruit development of two sweet cherry cultivars with contrasting levels of cracking tolerance</b>]]> Rain-induced cracking before harvest is the major cause of crop loss in sweet cherry (Prunus avium [L.] L.) In order to better understand the relationship between cherry fruit cracking and gene expression, the transcriptional patterns of six genes related to cell wall modification and cuticular wax biosynthesis were analyzed during fruit setting (FS), fruit color change (FC) and fruit ripening (FR), employing two contrasting cultivars: the cracking resistant 'Kordia' and the cracking susceptible 'Bing'. The transcription levels of AP2/EREBP-type transcription factor (PaWINB), wax synthase (WS), ß-ketoacyl-CoA synthase (PaKCS6), and ß-galactosidase (ß-Gal) showed higher levels in 'Kordia' than in 'Bing' during the FS stage, while similar values were observed in both cultivars at FR stage. In contrast to that pattern, transcription levels of expansin (PaEXPl) were higher at FR stage in 'Kordia' than in 'Bing'. Transcript profile of lipid transport protein gene (PaLTPGl) decreased during fruit development, with higher levels in 'Bing' than in 'Kordia' at FC and FR stages suggesting no relation with cracking tolerance. The expression profiles of PaWINB, WS, PaKCS6, and ß-Gal suggest that they are genes involved in conferring cracking tolerance, likely due to their function in cuticle deposition during early stages of fruit development. In addition, a greater expression level of expansin gene would allow for a faster growth rate in 'Kordia' at FR stage. <![CDATA[<b>Prevalence and phylogenetic analysis of honey bee viruses in the Biobío Region of Chile and their association with other honey bee pathogens</b>]]> Different episodes of mortalities of honey bee (Apis mellifera L.) colonies have been associated with the presence of honey bee pathogens. Since the Biobío Region has among the highest number of apiaries in Chile, the aim of the present study was to identify viruses in the Region affecting honey bees, evaluate their relation to other pathogens, and conduct a phylogenetic analysis. Pupae and adult bees were collected from 60 apiaries of Apis mellifera L. in the Biobío Region over 2 yr. RNA viruses were detected by reverse transcription PCR (RT-PCR), and Acarapis woodi, Nosema spp., and Varroa destructor via PCR. Three viruses were detected: Acute bee paralysis virus (ABPV), Black queen cell virus (BQCV) and Deformed wing virus (DWV) in 2%, 10%, and 42% of the apiaries, respectively. No statistical correlation was observed between the presence of the different viruses, V. destructor, A. woodi, and the two Nosema species, and the bee development stages. One year after the first sampling, DWV and BQCV were detected mainly in foraging adult bee samples. Three percent of the apiaries were infected with N. apis and 18% with N. ceranae, 5% were positive for V. destructor, while A. woodi was not detected. PCR products were sequenced and compared to the Genbank database. Chilean sequences of ABPV, BQCV, and DWV showed high percentages of similarity to other isolates in South America. <![CDATA[<b>Insecticide effect of cyantraniliprole on tomato moth <i>Tuta absoluta</i> Meyrick (Lepidoptera: Gelechiidae) larvae in field trials</b>]]> The tomato moth (Tuta absoluta Meyrick, Lepidoptera: Gelechiidae) has traditionally been managed in Chile with organophosphate, pyrethroid, and nereistoxin insecticides; all of these have wide action spectra and high toxicity and many of them have developed rapid resistance. It is therefore important to have new molecules which are effective in controlling this pest; how ever, these molecules must have lower toxicity and greater selectivity for beneficial fauna to produce a more sustainable tomato (Solanum lycopersicum L.) production. The objective was to evaluate the effectiveness of T. absoluta control with cyantraniliprole insecticide, which has desirable characteristics for programs of integrated pest management of tomato; we thus performed three trials in the 2009-2010 and 2010-2011 seasons in the Coquimbo Region, Chile. These trials evaluated the control of T. absoluta using different doses of two formulations: cyantraniliprole 10 OD (oil dispersion) with or without surfactants (Dyne-Amic, Codacide) applied to leaves and cyantraniliprole 20 SC (suspension concentrate) applied to soil. Trials used a randomized complete block design with four replicates. The effect of treatments was compared with standard insecticides and a control without insecticide. The degree of control was estimated by foliar and fruit damage at harvest. Results indicate a reduction in fruit damage between 75% and 85% for foliar applications and 82% for soil applications of cyantraniliprole. It is concluded that both formulations of cyantraniliprole were effective to reduce damage caused by the tomato moth larva in both the foliage and fruit of tomato. <![CDATA[<b>Assessment of SPLAT formulations to control <i>Grapholita molesta</i> (Lepidoptera: Tortricidae) in a Brazilian apple orchard</b>]]> Mating disruption is a technique that uses synthetic copies of sex pheromones to control insect pests. We aimed to control Oriental fruit moth (OFM) Grapholita molesta (Busck) (Lepidoptera: Tortricidae) with formulations of SPLAT Grafo (SG) and SPLAT Grafo Attract and Kill (SGAK) in small (1 ha) apple (Malus domestica Borkh.) orchards. Our experiment was conducted in a commercial orchard with 'Gala' trees (spacing 1.5 x 4.5 m) in Vacaria, Rio Grande do Sul State, Brazil. We evaluated the effect of four treatments on G. molesta population densities: a) SG at 1 kg ha-1 (300 point sources of 3.3 g each), b) SGAK at 1 kg ha-1 (1000 point sources of 1 g each), c) insecticides as recommended by Integrated Apple Production (IAP), and d) untreated control (no treatment). Specialized Pheromone and Lure Application Technology (SPLAT) treatments were applied on 1 August 2004 and reapplied after 120 d (1 December 2004). The treatment effect was evaluated by weekly counts of males captured in Delta traps baited with commercial synthetic sex pheromone lures (eight traps per treatment). We assessed fruit damage caused by G. molesta in eight replicates of 200 fruits each on 26 October, 30 November 2004, and 5 and 31 January 2005. Applying 1 kg ha-1 of SG and SGAK in August and December 2004 significantly reduced the number of male moths caught in Delta traps. Damage to fruits at harvest, however, did not differ significantly from the control. This indicates a decline in the efficacy of mating disruption when SG and SGAK are used to protect small areas (1 ha) under high Oriental fruit moth pressure. <![CDATA[<b>Transcriptomic responses of the aphid <i>Myzus persicae nicotianae</i> Blackman (Hemiptera: Aphididae) to insecticides</b>: <b>Analyses in the single Chilean clone of the tobacco aphid</b>]]> The tobacco aphid Myzus persicae nicotianae Blackman is a subspecies of the highly polyphagous and agricultural pest Myzus persicae (Sulzer). For its control, insecticide applications are widely used, but resistance to numerous molecules has been reported, displaying at least three insecticide resistance mechanisms, including: (i) elevated carboxylesterases (E-Carb), (ii) modification of the acetylcholinesterase (MACE), and (iii) kdr and super-kdr insensitivity mutations. In Chile, populations of the tobacco aphid are characterized by the presence of a single predominant clone, which is also present in high proportions in other countries of the Americas. This aphid clone exhibits low levels of carboxylesterase activity and is kdr susceptible, but the MACE mechanism of insecticide resistance has not been studied. In order to characterize the tobacco aphid in terms of the MACE mechanism and to identify a preliminary group of aphid genes putatively involved in insecticide resistance, a cDNA microarray was used to study the transcriptomic responses when aphids are sprayed with a carbamate insecticide. The single Chilean clone of the tobacco aphid was characterized as MACE susceptible, but we found 38 transcripts significantly regulated by insecticide exposure (13 up- and 25 down-regulated genes). The expression of six of them was validated by qRT-PCR experiments at several time points (6, 12, 18, 24, 30, 36, and 42 h) after insecticide application. This mutational and transcriptomic characterization of the tobacco aphid responding to insecticide spray opens new hypotheses in the understanding of the molecular mechanisms underlying insecticide resistance. <![CDATA[<b>Toxicity of the phenolic extract from jabuticabeira <i>(Myrciaria cauliflora</i> (Mart.) O. Berg) fruit skins on <i>Spodoptera frugiperda</i></b>]]> Fall armyworm, Spodoptera frugiperda J.E. Smith, 1797 (Lepidoptera: Noctuidae) is the main pest of maize, besides attacking sorghum and cotton crops. The control of this pest has been accomplished mainly with the use of synthetic insecticides but, due to the growing concern about the environment and food quality, phenolic compounds have shown their potential for the biological control of this insect. Thus, the objective of the present study was to evaluate the efficiency of the extract of jabuticabeira, Myrciaria cauliflora [Mart.] O. Berg (Myrtaceae) fruit skin flour in the control of S. frugiperda. Skins of M. cauliflora Sabará genotype were dried at 45 °C in a forced air oven. In order to obtain the extract, 1.0 g flour was mixed with 10 mL acetone: water solution (7:3 v/v). Forty-eight-hour-old S. frugiperda caterpillars were placed in glass tubes with an artificial diet containing the extract at concentrations of 0, 250, 500, 1000, and 2000 mg L-1. The extract, in which the phenolic compounds gallic acid, gallocatechin, catechin, epicatechin, ellagic acid, and salicylic acid were identified at a concentration of 2000 mg L-1, in average, increased mortality rates by 150% in the larval stage, duration of larval stages by 60%, and pupal by 17%, and decreased amount of females by 55%. On the other hand, the extract at 1000 mg L-1 only increased duration of larval period by 24%. It was concluded that the extract is harmful to this insect, probably due to the presence of phenolic compounds. <![CDATA[<b>Productive and metabolic response to two levels of corn silage supplementation in grazing dairy cows in early lactation during autumn</b>]]> Corn (Zea mays L.) silage (CS) is a nutritious food that can be used as a supplement in dairy cows. The aim of this study was to determine the effect of supplementation with two amounts of CS on milk production and composition, live weight and body condition, as well as on some blood indicators for energy and protein metabolism on dairy cows in early lactation and grazing low mass pasture during autumn. The study was carried out in 40 Holstein Friesian cows over 57 d. Prior to experimental treatment, milk production and days of lactation averaged 24.1 ± 2.8 kg d-1 and 62 ± 14 d, respectively. The dietary treatments consisted of two levels of supplementation with CS; 4.5 and 9 kg DM cow-1 d-1 (treatments LCS and HCS, respectively). Additionally, all the cows received a pasture allowance of 21 and 3 kg DM cow-1 d-1 of concentrate. Milk composition was determined using infrared spectrophotometry, while blood indicators were obtained using an autoanalyzer. There were not differences between treatments regarding milk production or composition, total DM or energy intake. Herbage and protein intake was higher for LCS treatment (P < 0.001). Increasing supplementation decreased (P < 0.001) daily weight gain but did not affect body condition. Plasma concentrations of βOH-butyrate were lower (P = 0.038) for the LCS treatment; while urea concentrations were higher (P = 0.003), with no differences for non-esterified fatty acids (NEFA) concentrations. Supplementation with 4.5 kg d-1 of CS was sufficient to meet the production requirements of the cows. <![CDATA[<b>Estimation of water requirements and Kc values of 'Thompson Seedless' table grapes grown in the overhead trellis system, using the Eddy covariance method</b>]]> Crop evapotranspiration (ETc) is essential for irrigation scheduling. The amount of water consumed can be estimated by multiplying the reference evapotranspiration (ET0) by a crop coefficient (Kc); the value of Kc is usually obtained from FAO Paper nr 56. In table grapes (Vitis vinifera L.), Kc are obtained from experiments in vines trained on trellis systems; however in Chile, the most used is the overhead trellis system (parronal). Therefore, the objective was to determine water requirements and Kc values of a table grape orchard cv. Thompson Seedless trained on an overhead trellis system in Calle Larga (32°52'40" S, 70°37'45" W, 795 m a.s.l.), Aconcagua Valley, Chile, using the Eddy covariance method. During the 2008/2009 and 2009/2010 seasons, the instruments required for ET0 and ETc measurement were installed on a 4 m tower above the soil (2 m above vine canopy). The ET0 was estimated according to the FAO Penman-Monteith equation and ETc by the Eddy covariance method. The Kc was obtained by ratio between ETc and ET0. The maximum ETc was 7 mm d-1 and total water consumption was 810 mm. The season maximum Kc value of 1.2 was obtained near harvest during the first season, and 20 d before veraison in the second season. The Kc increased linearly with the percentage of intercepted solar radiation (IRS) by the vine canopy at noon, suggesting that an equation to convert the IRS to Kc is more useful than Kc tabulated according to phenology. The equation obtained in this experiment was Kc = 0.012 IRS - 0.1029, R² = 0.85. <![CDATA[<b>Assessment of current and potential yield of hand-dug wells in a semi-arid zone in south-central Chile using an analytical methodology</b>]]> The semi-arid interior dryland region in south-central Chile is characterized by shrink-swell granitic soils and a semi-arid Mediterranean climate, which together cause scarce dry-season surface water supplies. Historically, the lack of easily accessible water has limited the region's economic development. In most of the region's rural communities, the only local water supplies for drinking and small-scale irrigation are shallow, hand-dug wells. The objectives of this study, conducted in the San José catchment in the Biobío Region (36°24' S, 72°30' W), were to demonstrate the usefulness of a simple aquifer characterization methodology to assess the likelihood of additional extraction of groundwater in this area with existing wells, estimate potential increases in productivity through increases in well depth, and present the spatial distribution of aquifer properties in this area. Hydraulic conductivity values (Ks) were measured from analyses of recovery rates of hand-dug wells. Values of Ks ranged between 0.04 and 5.1 m d-1 (mean = 1.07 m d-1; standard deviation = 1.36 m d-1), which resulted in a low yield from the shallow wells. These Ks values were used to estimate the potential groundwater yield which could be extracted from hand-dug wells in the region in their current condition with increased pumping and, where feasible, if wells were deepened by 0.5 m. Results suggested that existing wells could produce up to 0.008 m yr-1 and up to 0.02 m yr-1 by deepening them. Since current water usage has been estimated as 0.002 m yr-1, these results suggest that additional groundwater supplies could be exploited. <![CDATA[<b>Influence of breed and feeding on the main quality characteristics of sheep carcass and meat</b>: <b>A review</b>]]> This paper reviews two factors (breed and feed) affecting the carcass and meat quality of sheep. The quality of livestock products has acquired greater importance from the distinct perspectives of the different participants in the agricultural food chain. Consumers, producers and the industry give different levels of importance to the parameters of meat and carcass quality. Nevertheless, all the participants in the meat production chain must ensure quality to improve their competitiveness. The quality of the carcass and meat can be influenced by different factors such as breed and type of feed. The breed can influence weight, yields, and the conformation of the carcass, among other variables, as well as the pH level and the fatty acid composition of the meat, whereas the feed mainly affects carcass conformation and several physicochemical and organoleptic parameters of meat quality such as proximal composition, the fatty acid profile, tenderness and color. Consequently, the effects of breed and feed type should be considered to obtain a quality product that satisfies consumer demand. <![CDATA[<b>Toxicity of some insecticides used in maize crop on <i>Trichogramma pretiosum</i> (Hymenoptera, Trichogrammatidae) immature stages</b>]]> Fall armyworm Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) is an important pest of maize (Zea mays L.) crops in Brazil. The effects of beta-cypermethrin, chlorfenapyr, chlorpyrifos, spinosad, etofenprox, triflumuron, alpha-cypermethrin/teflubenzuron, and lambda-cyhalothrin/thiamethoxam on Trichogramma pretiosum Riley, 1879 (Hymenoptera: Trichogrammatidae) immature stages were evaluated. Eggs of Anagasta kuehniella (Zeller, 1879) (Lepidoptera: Pyralidae), containing immature stages of the parasitoid were dipped in water solution pesticides, to evaluate their effects on emergence and sex ratio of F1 parasitoids. For F2 parasitoids, emergence, parasitism capacity, and sex ratio were evaluated. Beta-cypermethrin, chlorfenapyr, chlorpyrifos, and spinosad affected the emergence success of F1 T. pretiosum. Insects exposed to etofenprox and alpha-cypermethrin/teflubenzuron during the egg-larval period and to lambda-cyhalothrin/thiamethoxam during the pupal stage also suffered reduction in the emergence. Beta-cypermethrin affected the sex ratio of F1 T. pretiosum from host eggs treated during the egg-larval period; spinosad affected it during the egg-larval period and the pupal stage, whereas chlorpyrifos did the same when applied during the pupal stage. Chlorpyrifos also affected the sex ratio of F2 parasitoids, but only when applied during the egg-larval period, whereas chlorfenapyr reduced this trait when applied during the pre-pupal phase. Chlorpyrifos and alpha-cypermethrin/teflubenzuron affected the parasitism capacity of F1 females from eggs treated during the egg-larval period. Considering the overall effects, only etofenprox and triflumuron were selective on T. pretiosum when applied on parasitized A. kuehniella eggs. Further studies need to be carried out to verify the toxicity of the other pesticides under semi-field and field conditions. <![CDATA[<b>Effect of different day and night nutrient solution concentrations on growth, photosynthesis, and leaf NO<sub>3</sub><sup>-</sup> content of aeroponically grown lettuce</b>]]> Nitrate content in leafy green vegetables has raised concerns among consumers and policy makers worldwide. Several cultural practices have been evaluated to manipulate NO3- content in fresh leaves with varying degrees of success. The present study was conducted to evaluate different concentrations of the nutrient solution applied during the day (D) and night (N) to aeroponically grown lettuce (Lactuca sativa L.) in Davis, California, USA, in the spring of 2012 with the objective of assessing the effect on growth, leaf photosynthesis, and nitrate accumulation in leaves. Two different treatments in the nighttime solution concentration (D25/N75, EC: 1.8 dS m-1; and D25/N50, EC: 1.2 dS m-1), a day nutrient solution of EC 0.6 dS m-1, plus a day and night treatment with constant EC (D50/N50, EC: 1.2 dS m-1) were applied. Plant growth, leaf photosynthesis, and leaf nutrient content were evaluated after 3 wk of growth. Mean shoot weight was 106.3 g with no differences among treatments. Root biomass was lower with D25/N75 (0.14 vs. 0.85 g in the other treatments). The maximum rate of leaf photosynthesis was 66% lower with D25/N75 than in the other treatments. Nitrogen, P, K, Ca, and Mg were lower in leaf tissue in the treatments with different solution concentrations where leaf NO3- content was reduced by approximately 75%. Switching nutrient solution concentration between day and night is a viable practice to reduce NO3- in lettuce leaves with no detriment to leaf production.