Scielo RSS <![CDATA[Chilean journal of agricultural research]]> vol. 75 num. 3 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<b>Genetic diversity, identification, and certification of Chilean rice varieties using</b> <b>molecular markers</b>]]> It takes approximately 14 yr to produce a new rice (Oryza sativa L.) variety, that is, from initial hybridization to its commercial release. Currently, new varieties are identified based on morphological descriptors, which have been efficient over time. However, due to the main constraints on seed type impose to other breeding objectives and the pressure of continuous release of varieties, high degree of parentage, and genetic and morphological uniformity has been observed in the breeding populations. The objectives of this study were: to determine the genetic variability of Chilean and foreign commercial rice varieties, and determine, identify, and certify the genetic relationships among varieties, using simple sequence repeat (SSR) markers. A total of 16 commercial varieties, some of them closely related, were included in the study, which were genétically analyzed using 54 microsatellites. The 54 microsatellite loci allowed the discrimination among the 16 varieties. The number of alleles ranged between 2 and 8 with a mean of 3.54 alleles per locus, while the polymorphism information content (PIC) presented a mean of 0.44. The genetic distance and diversity parameters between pairs of varieties indicate a limited diversity among these genotypes. The cluster analysis indicated that varieties were grouped according to their grain type and pedigree. Results demonstrate that the identification and certification of varieties using microsatellite markers could be a good complement to existing agro-morphological data when varieties are closed related. <![CDATA[<b>Photosynthetic performance index in early stage of growth, water use efficiency, and grain yield of winter barley cultivars</b>]]> Repetitive heat and drought stress conditions have a significant impact on quantity and quality of barley (Hordeum vulgare L.) production in most regions of the world. Objective of this study was to determine the relationships between photosynthetic performance index (PI ABS), water use (WU), grain yield-based water use efficiency (WUE G), and grain yield per pot (GYP) of winter barley cultivars grown in a pot trial under short-term drought stress conditions and grain yield and its stability from the multi-environmental field trials. Ten winter barley cultivars were examined in two water treatments. One treatment was well watered, while the second treatment was subjected to short-term stress caused by deficiency of water in the stages of full tillering, beginning of heading, and grain filling. PI ABS was measured at full tillering stage while WU, WUE G, and GYP of barley cultivars were estimated after the whole vegetative cycle. Also, multi-environmental field trials with the same winter barley cultivars were carried out during 4 yr (2004-2007) and 3 yr (2009-2011) with two sowing densities (300 and 450 seeds m-2) on multiple locations in the lowland part of the Republic of Croatia. ANOVA showed highly significant (P ≤ 0.001) cultivar effect for all of the examined traits in the pot trial. PI ABS of cultivars in both treatments was in a negative nonsignificant correlation with grain yield and grain yield stability (ecovalence) of the same cultivars in multi-environmental field trials. Winter barley cultivars with higher WU and WUE G also had higher values of grain yield, and harvest index observed on the basis of the pot trial. WU, WUE G, and GYP of 10 barley cultivars in pot trial showed highly positive phenotypic correlation with grain yield of all eight and 10 barley cultivars in the multi-environmental field trials. These results suggests that WU and WUE G could be good indicators for preliminary selection of modern, high yielding, and stable winter barley genotypes which have better water management capabilities. <![CDATA[<b>Over fertilization limits lettuce productivity because of osmotic stress</b>]]> It is customary that growers apply high doses of nutrients to the soil in order to achieve high yields, with detrimental consequences for the environment; but no information exists with regards to the crop response to high fertilization levels. To evaluate the physiological response of lettuce (Lactuca sativa L.) to various root zone nutrient concentrations (expressed as electrical conductivity, from 0.6 to 10 dS m-1), a replicated experiment was conducted using increasing concentrations of macronutrients applied to the root zone in an aeroponic system. Leaf photosynthesis and chlorophyll fluorescence were measured using a portable infrared gas analyzer attached with a fluorometer. Leaf nutrient content was analyzed by mass spectrometry and NO3-N was determined by flow injection analysis. Leaf photosynthetic rates increased when the solution concentration was raised from 0.6 to 4.8 dS m-1, but further increases in solution concentration did not result in any differences. The enhancement in photosynthetic rates was related to higher concentrations of N, P, Mg, and S in leaves. Leaf K content was correlated with stomatal conductance. Maximum growth was achieved with solution concentrations between 1.2 and 4.8 dS m-1 while at 10.0 dS m-1 leaf production was reduced by 30%. It is concluded that at high concentration of nutrients supplied in the root zone, yield reduces because of a combination of decreased stomatal conductance and leaf area. <![CDATA[<b>Influence of microclimatic conditions under high tunnels on the physiological and productive responses in blueberry 'O'Neal'</b>]]> Blueberry (Vaccinium corymbosum L.) production under tunnels has spread in recent years. However, there is little information on the productive and physiological responses of blueberry grown under high tunnels. The objective of this research was to evaluate the effect of high tunnel microclimate on the physiological and productive responses of blueberries. A total of 1296 plants of highbush blueberry 'O'Neal' were grown in high tunnels, leaving the same amount of plants under open fields (control). Environmental temperature (T, °C) and relative humidity (RH, %), diffuse and total photosynthetically active radiation (PARdiffuse and PARtotal, /<mol m-2 s-1), stomatal conductance (g s, mmol nr² s-1) and maximum photochemical efficiency of photosystem II (Fv/Fm) of the leaf were measured. Fruit yield, date of harvest initiation and fruit growth rate were also determined. The maximum T was on average 10-12 °C higher inside the high tunnel than the control, whereas the minimum T averaged only 2-5 °C higher. PARtotal decreased an average of 25% under tunnel, while levels of PARdiffuse increased more than 150%. The g s ranged between 42% and 99% higher in the high tunnel compared to the control, and was positive and statistically related (r² = 0.69**) to PARdiffuse variations. Blueberries under high tunnel recorded an accumulated yield 44% higher, while harvest started 14 d earlier compared to control. The results suggest that high tunnels in blueberries increases fruit yield and improves precocity due to higher temperatures during the flowering stage and fruit set. Particular light conditions under tunnels would favor higher leaf stomatal conductance in this crop. <![CDATA[<b>Different aspects of <i>Lactobacillus</i> inoculants on the improvement of quality and safety of alfalfa silage</b>]]> There is a significant range of bacterial inoculants for forage ensiling, but there is still a need for formulations to improve the safety of feed. The objective of the study was to evaluate the usefulness of three lactobacilli strains in alfalfa (Medicago sativa L.) The following bacterial inoculants were used: Lactocacillus plantarum K KKP 593p (LPK), L. plantarum C KKP 788p (LPC), L. buchneri KKP 907p (LB), and mix of all three strains (LPK+LPC+LB). The application of bacterial inoculants in alfalfa ensiling resulted in a reduction of the total number of molds, Clostridium perfringens and Listeria sp. (up to 5, 7, and 5 times respectively for LB inoculant in comparison to untreated silage). Total inhibition of Salmonella sp. and Escherichia coli growth was achieved in silages treated with all inoculants except for LPC. Aerobic stability in the control silage was the lowest (77 h) and doubled under the influence of bacterial inoculants. The most stable according to aerobic stability was silage treated with LB inoculant (175 h), where the highest concentrations of acetic acid (4.8 g kg-1), propionic acid (0.7 g kg-1) and 1,2-propanediol (526 mg kg-1) were reported. The study discussed that it is important to evaluate not only the effect of bacterial inoculants on physicochemical and microbiological silage properties, as the presence and expression of antibiotic resistance genes in lactic acid bacteria have been reported. The results of antimicrobial susceptibility testing of the strains showed that almost all minimum inhibitory concentrations values for eight antibiotics were equal to or below the corresponding breakpoints proposed by the European Food Safety Authority, Additives and Products or Substances used in Animal Feed Panel. <![CDATA[<b>Carcass and non-carcass characteristics of sheep fed on cassava (<i>Manihot pseudoglaziovii</i> Pax & K. Hoffm.)</b>]]> Sheep production systems installed in the semi-arid region of Brazil depend on the forage support the 'caatinga' biome. This study aimed at evaluating the substitution of hybrid 'Tifton 85' (Cynodon spp.) by cassava (Manihotpseudoglaziovii Pax & K. Hoffm.) hay or silage on the components of sheep's' body weight. Twenty-four animals, with no defined breed, were used for the study, with an initial body weight of 19.77 ± 1.95 kg and an average age of 6-mo, being divided into three treatments ('Tifton 85' hay, cassava silage, and cassava hay). The animals were slaughtered at 56 d and all the body parts of the animals were weighed. Data were subjected to ANOVA and mean comparison test (P = 0.05). Means were superior (P < 0.05) for DM intake and contents of the gastrointestinal tract (CGT) with values of 1.17 kg d-1 and 4.84 kg for cassava hay, respectively. There was no significant difference (P &gt; 0.05) for body weight at slaughter and cold carcass weight, which had means of 28.10 and 12.38 kg, respectively. The hot carcass and leg yields showed values of 58% and 34%, respectively, and were not influenced (P &gt; 0.05) by different forages. The constituents that were not components of the carcass, organs, offal, and by-products were not affected by the replacement of 'Tifton 85' hay by cassava hay or silage. Cassava hay or silage can replace 'Tifton 85' hay for feeding sheep in complete diets without compromising their body components' yields and weights. <![CDATA[<b>Effects of <i>Pleurotus sapidus</i> (Schulzer) Sacc. treatment on nutrient composition and ruminal fermentability of barley straw, barley rootless, and a mixture of the two</b>]]> Barley (Hordeum vulgare L.), and its derivatives, ranks fourth in cereal production worldwide, and the Pleurotus species are among the most efficient types of lignocellulolytic white-rot fungi. The objective of this research study was to evaluate the degradation of barley straw and barley rootless with an inoculum of Pleurotus to improve their nutritional availability as a food source for ruminants. Two experiments were conducted; the first was to determine the effects of inoculation of Pleurotus sapidus (Schulzer) Sacc. (PS) in barley straw (BS), barley rootless (BR), and a 75% BS and 25% BR mixture (M). The second experiment was to evaluate the same substrates in vitro ruminal fermentation. Barley rootless had better organic matter (OM) degradability than BS after 24 h incubation with PS. The protein content in BR was higher than in BS (P < 0.01). Enzyme activities had the highest concentration from the start of fermentation, and in vitro dry matter (DM) degradability in BS and BR increased after 8 and 24 d fermentation, respectively (P < 0.05). Propionic acid concentration was enhanced after 16 d fermentation in BR (P < 0.5). The use of BS combined with BR exhibited better fermentation; this result provides relevant information for integrating BR with other substrates and improving the use of straw, which can be more nutritionally available for feeding ruminants. <![CDATA[<b>Identification of virus and nematode resistance genes in the Chilota Potato Genebank of the Universidad Austral de Chile</b>]]> Potato Genebank of the Universidad Austral de Chile (UACh) is an important gene bank in Chile. The accessions collected all over the country possess high genetic diversity, present interesting agronomic and cooking traits, and show resistance to biotic and abiotic stress. A particularly interesting subgroup of the gene bank includes the accessions collected in the South of Chile, the Chilota Potato Genebank. The focus of this study is the identification of virus and nematode resistant genes in potatoes (Solatium tuberosum L.), using the RYSC3 and YES3-3B molecular markers. The Potato virus Y(PVY) resistance genes Ry adg and Ry sto were identified. Furthermore, the CP60 marker was used to assess the Rx resistance gene that confers resistance to Potato virus X (PVX). In addition, the HC and GRO1-4 markers were utilized to identify the GpaVvrn_QTL and Gro1-4, resistance genes of Globodera pallida and Globodera rostochiensis, respectively. Both G. pallida and G. rostochiensis are Potato Cyst Nematodes (PCN). The plant material used in this study included leaves from 271 accessions of the gene bank. These samples were collected in the field where natural pathogen pressure of potential viruses and diseases exists. ELISA assays were run for field detection of PVY and PVX. However, there have been no previous reports of nematode presence in the plant material. The results herein presented indicate presence of virus and nematode resistance genes in accessions of the Chilota Potato Genebank. In terms of virus resistance, 99 accessions out of the 271 tested possess the Ry adg resistance gene and 17 accessions of these 271 tested have the Ry sto resistance gene. Also, 10 accessions showed positive amplification of the Rxl resistant gene marker. As to nematode resistance, 99 accessions have possible resistance to G. pallida and 54 accessions show potential resistance to G. rostochiensis as detected using the available molecular markers. <![CDATA[<b>Modeling climate change impacts on overwintering of <i>Spodoptera exigua</i> Hübner in regions of China</b>]]> Inferential models are usually used to evaluate the effect of winter warming on range expansion of insects. Generally, correlative approaches used to predict changes in the distributions of organisms are based on the assumption that climatic boundaries are fixed. Spodoptera exigua Htibner (Lepidoptera: Noctuidae) overwinters as larvae or pupae in China regions. To understand the climate change impacts on overwintering of this species in regions of China, CLIMEX and Arc-GIS models were used to predict possible changes of distribution based on temperature. The climate change projection clearly indicated that the northern boundary of overwintering for S. exigua will shift northward from current distribution. Thus, the ongoing winter warming is likely to increase the frequency of S. exigua outbreaks. <![CDATA[<b>Bioactivity of <i>Peumus boldus</i> Molina, <i>Laurelia sempervirens</i> (Ruiz & Pav.) Tul. and <i>Laureliopsis philippiana</i> (Looser) Schodde (Monimiacea) essential oils against <i>Sitophilus zeamais</i> Motschulsky</b>]]> The maize weevil (Sitophilus zeamais Motschulsky) is one of most important pest of stored seeds worldwide, but its current control method is based on the use of synthetic insecticides, usually leading to undesirable problems such as insecticide residues on treated food, human intoxications, and insect resistance development. Therefore the search of friendly alternative methods is required. The aim of this study was to assess, under laboratory conditions, the insecticidal properties of Peumus boldus Molina, Laurelia sempervirens (Ruiz & Pav.) Tul., and Laureliopsis philippiana (Looser) Schodde essential oils against S. zeamais. The phytochemical analysis of the three essential oils showed 1,8-cineole, safrole and methyleugenol as the common components; all of them documented with insecticidal activity from essential oils from other plant species. The highest toxicity (100% mortality) of these three oils acting as a contact insecticide was observed at 24 h exposure at 4% concentration. The estimated LC50 values for P. boldus, L. sempervirens, and L. philippiana were 0.37, 1.02, and 0.28 μL g-1, respectively. Peumus boldus exhibited the highest fumigant activity with 100% adult mortality at 30 μL oil L-1 air. At ≥ 0.5% (v/w) concentration, all essential oils showed repellent activity. These three essential oils showed a promissory insecticidal activity against the maize weevil. <![CDATA[<b>Evaluation of three semi-empirical approaches to estimate the net radiation over a drip-irrigated olive orchard</b>]]> The use of actual evapotranspiration (ETα) models requires an appropriate parameterization of the available energy, where the net radiation (Rn) is the most important component. Thus, a study was carried out to calibrate and evaluate three semi-empirical approaches to estimate net radiation (Rn) over a drip-irrigated olive (Olea europaea L. 'Arbequina') orchard during 2009/2010 and 2010/2011 seasons. The orchard was planted in 2005 at high density in the Pencahue Valley, Maule Region, Chile. The evaluated models were calculated using the balance between long and short wave radiation. To achieve this objective it was assumed that Ts = Tα for Model 1, Ts = Tv for Model 2 and Ts = Tr for Model 3 (Ts is surface temperature; Tα is air temperature; and Tv is temperature inside of the tree canopy; Tr is radiometric temperature). For the three models, the Brutsaert's empirical coefficient (Φ) was calibrated using incoming long wave radiation equation with the database of 2009/2010 season. Thus, the calibration indicated that Φ was equal to 1.75. Using the database from 2010/2011 season, the validation indicated that the three models were able to predict the Rn at a 30-min interval with errors lower than 6%, root mean square error (RMSE) between 26 and 39 W m-2 and mean absolute error (MAE) between 20 and 31 W m-2. On daily time intervals, validation indicated that models presented errors, RMSE and MAE between 2% and 3%, 1.22-1.54 and 1.04-1.35 MJ m-2 d-1, respectively. The three R„-Models would be evaluated and used in others Mediterranean conditions according to the availability of data to estimate net radiation over a drip-irrigated olive orchard planted at high density. <![CDATA[<b>Microbiological activity and N transformations in a soil subjected to aggregate extraction amended with pig slurry</b>]]> Pig slurry as a fertilizer source has been extensively used in agriculture; however, in order to reduce the risks of contaminating the water supplies given its high level of N sources, it is important to understand the N transformations occurring in the soil where it is applied. In this study, incubations were performed at 25 °C for a period of 63 to 73 d to evaluate the effect of different doses of pig slurry on the global microbiological activity and the N dynamics in time, with an emphasis on N mineralization and nitrification in a soil subject to aggregate extraction. The slurry was applied in doses equivalent to: 0, 162, 244, and 325 m³ ha-1, constituting four treatments: T0, T50, T75, and T100, respectively. The microbiological activity and the contents of NH4+-N and NO3-- N were measured. Increasing doses of slurry produced an increase in the evolution of the accumulated CO2, with 63.5, 115.0, 112.7, and 125.7 mg 100 g-1 soil for T0, T50, T75, and T100 respectively. A similar situation was observed in the initial contents of NH4+-N, which were 22.4, 30.3, 44.3, and 60.7 mg kg-1 in each treatment, respectively. On the other hand, the increase in NO3-- N contents were only noticed by the end of the incubation period and corresponded to 28.6, 69.0, 95.3, and 109.8 mg kg-1. In addition, the net N mineralization was predominant in all treatments with slurry during the measurement period, being 9.1, 45.4, 58.1, and 52.7 mg kg-1 for T0, T50, T75 and T100, respectively, at the end of the trial. The mineralization rate of the organic C decreased when increasing the dose of slurry and the mineralization rate of the organic N resulted to be low, which would indicate a high contribution of material resistant to degradation by the slurry, which could have a long term effect in the soil. <![CDATA[<b>Relationship of soil physical quality parameters and maize yield in a Brazilian Oxisol</b>]]> In Brazilian agriculture, maize (Tea mays L.) is prominent because of its magnitude of grain production. However, soil compaction changes negatively the soil physical attributes, limiting the crop growth. This study aimed to evaluate physical attributes of a clayey Oxisol (Rhodic Hapludox) under no-tillage, and the relationships between these attributes with maize yield in the Midwest region of Brazil. Besides this, indicators of soil physical quality when subjected to levels of compaction were determined. A randomized complete block design was applied with five replicates. Treatments were induced levels of compaction: a reference condition that reflects 8 yr of no-tillage (NT); no-tillage with additional compaction by tractor traffic in one (NT-1), two (NT-2), four (NT-4), and six passes (NT-6). There was significant correlation (P < 0.01) between all physical attributes of the studied soil. Maize yield was positively correlated to macroporosity (r = 0.41*), and negatively to penetration resistance (r = -0.42*), geometric mean diameter (r = -0.51*), and mean weighted diameter (r = -0.53*). The index of emergence speed, stem diameter, plant height, grain mass, and grain yield decreased as soil compaction increased. The physical attributes evaluated, especially the resistance to penetration and soil macroporosity, reveal the level of soil compaction and can be used as soil physical quality indicators. <![CDATA[<b>Reference evapotranspiration estimates based on minimum meteorological variable requirements of historical weather data</b>]]> Reference evapotranspiration (ET0) is critical for agricultural and urban planning, irrigation scheduling, regional water balance studies, and agroclimatological zoning. The objective of this study was to estimate ET0 based on methods with minimum meteorological variable requirements and on empirical models to predict solar radiation. These alternative methods were compared to the FAO Penman-Monteith method by using more than 80 yr of historical weather data. Alternative methods were adapted from the standard FAO Penman-Monteith or Priestley-Taylor methods, which allow estimating ET0 when fewer meteorological variables are available. The Hargreaves-Samani method was also analyzed. The mean absolute error, index of agreement, correlation coefficient, and confidence index were used to compare the alternative methods. Results showed that alternative methods based on the maximum and minimum temperatures, sunshine hours, and/ or wind speed are appropriate for estimating ET0 in the region under study. <![CDATA[<b>Insecticidal activity of young and mature leaves essential oil from <i>Eucalyptus globulus</i> Labill. against <i>Tribolium confusum</i> Jacquelin du Val (Coleoptera: Tenebrionidae)</b>]]> The confused flour beetle, Tribolium confusum Jaquelin Du Val, 1868, is a common pest insect known for attacking and infesting stored flour and grain. Biodegradable and ecologically natural products such as essential oils are emerging candidates for replacement of usually applied chemical pesticides. This work reported the chemical composition and effects caused by young and mature leaves essential oils (EOs) from Eucalyptus globulus Labill. against T. confusum. For both oils, no significant differences between yields were observed, being 1,8-cineole the main common constituent. Mature leaves extracts were rich in oxygenated mono- and sesquiterpenes, whereas young leaves showed greater content of non-oxygenated compounds. Bioassay was performed using EOs and 1,8-cineole solutions at different concentrations and time intervals. Adult mortality increased according to concentration and exposure time; young leaves extracts exhibited the greater effectiveness, highest mortalities (31.67%) at the minor time (2 h). At the lowest concentrations, 1,8-cineole solutions and mature leaves EOs did not achieve 100% mortality even when the bioassay was concluded (12 h), while at major doses no insects were alive. These results suggested that young and mature EOs from E. globulus constitute an alternative natural product to the control of T. confusum, since young leaves extracts, rich in monoterpene and sesquiterpene hydrocarbons, may be potential eligible candidates considering their noticeable insecticidal effects at low applied concentrations and short times of exposure.