Scielo RSS <![CDATA[Chilean journal of agricultural research]]> vol. 79 num. 2 lang. en <![CDATA[SciELO Logo]]> <![CDATA[Resistance of lettuce downy mildew’s differential cultivars to root-knot nematodes]]> ABSTRACT Due to the harmful potential and existence of numerous races of lettuce downy mildew (Bremia lactucae Regel), several countries carry out the monitoring of these races through the use of differential cultivars of lettuce (Lactuca sativa L.) The identification of resistance to other important diseases in these cultivars would be of great value for the lettuce’s breeding, allowing the simultaneous selection for diseases. Among soil pathogens, the most important are the root-knot nematodes (Meloidogyne spp.) due their damage and difficulty of control. Thus, the present work evaluated the resistance of these differential cultivars (C-Set) against the two most important nematode species for the crop, M. javanica and M. incognita. The experiment was conducted in a completely randomized design, with eight replicates and initial population of 1000 eggs and juveniles. The evaluations were performed by the criteria of reproduction factor and reproduction index, 75 d after inoculation. Data were submitted to ANOVA and averages were compared by the Scott-Knott test (p &lt; 0.05). All cultivars are considered susceptible to M. incognita by the reproduction factor, ‘Argelès’, ‘Bedford’, ‘Design’ and ‘Grand Rapids’ are considered as slightly resistant by the reproduction index. However, to M. javanica ‘Argelès’, ‘Kibrille’, ‘Balesta’, ‘Colorado’, ‘Design’, ‘Bartoli’, and ‘NunDm15’ are classified as resistant by the reproduction factor and very resistant by the reproduction index, and can be used as resistance source for simultaneous selection to downy mildew and this species of nematode. <![CDATA[Stability and breeding potential of tomato hybrids]]> ABSTRACT Commercial tomato (Solanum lycopersicum L.) hybrids can be a good germplasm for obtaining new tomato inbred lines. The present study was aimed to investigate the stability of commercial F1 hybrids under climatic conditions of highlands, to estimate genetic parameters, and evaluate the breeding potential of F1 hybrids based on the agronomic performance of its F3 progeny. We employed a breeding scheme based on pedigree selection for the obtainment of 49 F3 families. Significant differences were found in most of the traits evaluated in both F1 and F3 generations, while in the F2 population only one variable showed significant differences. Heritability ranged from 0.07 to 0.29 for F1, and from 0.16 to 0.45 for F3. Most of the F1 hybrids exhibited values of stability across seasons in at least one trait. However, ‘Loreto’ and ‘Reserva’ only exhibited a high stability for yield. Genetic gains ranged from -8.40 to 72.95. Yield per plant was the traits with the highest gain. Based on genetic gains obtained by the F3 progeny, we concluded that ‘Cid’, ‘Espartaco’ and ‘Loreto’ have a high breeding potential for yield and other traits, which could be exploited by public tomato breeding programs. <![CDATA[Effects of supplemental irrigation based on soil water content on water consumption, dry matter and yield of wheat]]> ABSTRACT Water-saving cultivation in wheat (Triticum aestivum L.) is an important technique for achieving high yield and high water use eficiency (WUE) in the North China Plain (NCP) where water resources are in shortage. In order to determine the effects of supplemental irrigation based on soil water content on crop evapotranspiration (ET), DM, grain yield and WUE in wheat, treatments were designed to vary the relative soil water content at jointing and anthesis stages: I70 (70%, 70%) and I75 (75%, 75%) with rain-fed (I0) and traditional irrigation (Ick) as contrasts. The results indicated that the irrigation amount of I70 and I75 were significantly lower than that of Ick by 45.1 to 132.4 mm, but soil water depletion increased by 23.5 to 35.4 mm. Although the total ET throughout the growing season (ETt) of I75 was less than that of Ick, the ratio to ETt from anthesis to maturity increased significantly. The DM partitioning ratio was decreased in vegetable organs, but increased in grain for I75 compared with Ick. The grain yield for I75 was significantly higher than that of I0 and I70, whereas nonsignificant difference was observed between I75 and Ick, and the WUE and irrigation water use efficiency of I75 were higher than those of Ick by 11.0% and 87.4% in 2008-2009 and 3.5% and 34.0% in 2009-2010. Thus, I75 can be developed as an optimal water-saving irrigation regimes in the NCP <![CDATA[Effects of different types of fertilizers application on rice grain quality]]> ABSTRACT As expected, applications of organic fertilizer and controlled-release fertilizer are gradually varying traditional fertilization, being considered as important channels for substitution of conventional chemical-fertilizer. However, information regarding their effects on rice (Oryza sativa L.) grain quality remains limited. A field experiment was conducted to investigate the effects of combined application of bio-organic fertilizer and conventional fertilizer (BOF+CF), combined application of organic fertilizer and conventional fertilizer (OF+CF), and application of controlled-release fertilizer (CRF) on rice processing quality, eating quality and nutritional quality with conventional fertilizer (CF) and no fertilizer (NF) as controls. The protein content of OF+CF treatment was increased by 4.67%, 3.29%, 2.61% and 22.66% when compared to BOF+CF, CRF, CF and NF. These results imply that, among all treatments, NF produced the highest rice eating quality followed by CRF and BOF+CF, and OF+CF made the highest nutritional quality followed by CF and CRF. When compared to CF, BOF+CF and NF treatments decreased protein content by 1.96% and 16.34%. Compared to CF, BOF+CF treatment markedly reduced aspartic acid, serine, glutamic acid, glycine, alanine, histidine, arginine, and proline contents in milled rice by 17.31, 14.71%, 16.39%, 16.67%, 20.69%, 11.77%, 18.42%, and 18.75%, respectively. The nutritional quality under NF and BOF+CF was significantly decreased when compared with CF, due to the reductions in protein content of milled rice and most amino acids contents of brown and milled rice. These results suggest that a kind of suitable fertilizer could be chosen from them as alternatives according to desired goal in high-quality rice production. <![CDATA[Preliminary comparisons of early generation individual selection efficiency of a local wheat landrace under different experimental field designs]]> ABSTRACT Wheat (Triticum aestivum L.) landraces are traditional adapted varieties developed and used by farmers but not usually improved by breeders. The objective of our study was to compare the efficiency of three different methods (arrangements) of homogeneity blocks to produce high-yield progenies during the breeding procedure of a local bread wheat landrace. This original genetic material underwent a mass selection scheme in F2 individual plants in three different experimental designs to reduce soil heterogeneity (honeycomb, gridding, double rows); selection was based on individual plant grain weight. In F3 lines, bulk density was the selection criterion in a specific arrangement that divided the experimental field into three plots for 12 subplots to reduce soil heterogeneity. The F4 lines were evaluated in randomized complete block trials for 2 yr based on grain yield, 1000-kernel weight, and bulk density. Progenies from the three different experimental designs were compared. The gridding method seemed more efficient for evaluating sister lines because it maximized yields, provided a greater number of promising lines, and F3/F4 correlations were high and significant. Wheat plants did not perform well under the double row system (mean bulk density 756 g L-1). Heritability was high for all studied traits (0.93) and bulk density was a reliable criterion for selecting promising genetic materials (90.1% genotype contribution in variability) and revealed differences between methods. The local landrace was unstable and exhibited specific adaptability to the cultivated environment. Selected lines (from the most efficient method) improved yield performance by 11% on the average compared with the original population. <![CDATA[<em>Pseudomonas fluorescens</em> affects nutrient dynamics in plant-soil system for melon production]]> ABSTRACT The excessive use of agrochemicals to increase yield and fruit quality can result in soil, freshwater, and groundwater contamination. Designing and using new products based on microorganisms, such as rhizosphere bacteria, could reduce intensive agrochemical application and subsequent potential contamination. Therefore, the effect of a biocontroller (Pseudomonas fluorescens) on the nutrient balance and yield quality of melon (Cucumis melo L.) was evaluated under field conditions. Control and treatment plots without and with a biocontroller applied with an irrigation system were assayed. Soils were monitored by physicochemical and biochemical analysis and plants by nutrient and yield quality analysis during crop development. Pseudomonas fluorescens application significantly promoted salt solubility (416 and 1128 μS cm-1), available Cu concentration (3.8 and 4.3 mg kg-1), P availability (104 and 123 mg kg-1), and microbial C biomass (56 and 93 mg C kg-1) for control and treatment plots, respectively. In addition, biocontroller application did not significantly increase soil total N and exchangeable Na, Mg, and K concentrations. Pseudomonas fluorescens also promoted Mn, N, Zn, and P absorption, which causes competition among nutrients, limiting Cu, Na, Ca, and K absorption by melon plants. The β-glucosidase activity was also responsible for releasing Fe, Zn, Cu, Mn, P, and N in the soil. Finally, P. fluorescens application increased fruit size and weight (3.0 to 3.8 and 3.3 to 4.3 kg for control and biocontroller treatments, respectively); therefore, biofertilization with this bacterium is a sustainable alternative to increase yield and fruit quality without increasing the use of chemical fertilizers and pesticides. <![CDATA[Yield performance and GGE biplot analysis of wheat genotypes under two irrigation treatments at El Bajío, Mexico]]> ABSTRACT In Guanajuato, Mexico, water deficits have dramatically increased in recent years due to over-exploitation of this resource. The objective was to identify high yielding wheat (Triticum spp.) varieties under two irrigation regimes. The experiments were planted at Celaya, Guanajuato, for two consecutive (2013-2014 and 2015-2016) growing seasons (GS). Eleven commercial varieties and nine experimental lines were evaluated under 3 or 4 irrigation regimes; split-plot design with 4 replicates was considered; data on yield performance and its components were measured. There were significant differences between GS and number of irrigation regimes (p ≤ 0.01) for most evaluated traits. ANOVA showed significant differences for all traits in the study, except for the 1000-grains weight. Growing seasons affected yield, grains number m-2 and biomass, mainly; on last cropping season, grain yield was higher (1.8 t ha-1) than first one; strong gluten genotypes were more stable, as compared with the soft gluten genotypes. Some experimental varieties exceeded commercial varieties, which means success in wheat breeding. Genotypes Experimental Line D and control ‘Bárcenas F2002’ under 3 irrigations regime treatment showed the highest grain yield (7.7 and 7.0 t ha-1, respectively). On 4 irrigations regime, the best yielding genotypes were experimental lines D, and H, with 6.5 and 6.1 t ha-1, respectively. Based on regression deviations the most stable and predictable wheat genotypes were strong gluten genotypes. <![CDATA[Biodegradable polymers as floating row covers in field production of radish]]> ABSTRACT Polypropylene (PP) covers are used in radish (Raphanus sativus L. var. sativus) production to provide better microclimate for improving yield and quality, but disposing of non-degradable covers is difficult and expensive. In this work, nonwovens prepared from biodegradable polymers (aliphatic-aromatic copolyesters with and without fatty acid dimers: SB48/11, SB20/13, SB21/13, SB28/13) were tested in the field as substitutes for nonwoven PP. Minimum air temperature under biodegradable covers was higher by 0.6-0.8 °C than under nonwoven PP, but photosynthetically active radiation (PAR) transmission was lower by 4.1% (SB20/13) and 7.1% (SB21/13). We observed a decrease in marketable yield of plants covered with biodegradable fleeces by 1.01 to 2.90 kg m-2 (SB48/11 and SB28/13, respectively) in spring seasons, but similar yields to nonwoven PP were obtained in the autumn seasons. Dry weight, soluble sugars, L-ascorbic acid, pigments content in radish was dependent on a specific set of environmental conditions rather than on the type of cover. However, L-ascorbic acid content in the roots increased significantly by 6.4 and 2.9 mg 100 g-1 FW for SB48/11 and SB20/13 (in one trial), respectively, as compared to nonwoven PP. It is possible to use biodegradable nonwovens as floating covers for radish cultivated in seasons with temperature drops. <![CDATA[Effect of <em>Ecklonia maxima</em> extract on photosynthesis activity and chlorophyll content of <em>Medicago</em> × <em>varia</em> Martyn leaves]]> ABSTRACT Recently, there is a big interest in science to use seaweed extract in agricultural practice. Therefore, the aim of this paper was to determine the effect of foliar application of Ecklonia maxima extract on photosynthetic activity and chlorophyll content of Medicago ×varia Martyn leaves. The experimental factor was a commercial product containing E. maxima extract (Em). The following parameters were determined: maximum photosystem II efficiency (Fv/Fm) in the dark-adapted state, actual photosystem II efficiency in the light-adapted state (∆F/Fm’), the photochemical quenching coefficient (qP), the non-photochemical quenching coefficient (qN), chlorophyll content determination. The Fisher-Snedecor test was used to determine whether the impact of experimental factor was significant, while the value of the HSD0.05 was calculated with Tukey’s test. As a reaction to the particular conditions during the experiment alfalfa treated with Em had a better efficiency of the photosynthetic apparatus in relation to the control. Algae extract used on hybrid alfalfa leaves caused a 12.4% increase of Fv/Fm parameter, from 0.565 on the control to 0.635. The value of the actual efficiency of photosystem II (∆F/Fm) determined under the same conditions turned out to be about 20% higher for plants treated with the extract. Chlorophyll a and b concentration, as a response to the extract, increased by 12% and 16.7%, respectively. The experiment showed that periods of rainfall shortages did not reverse the effect of the extract on plants, with an increase in chlorophyll a and b content during the growing seasons with dry and extremely dry months. <![CDATA[Biodegradation and phytotoxicity of crude oil hydrocarbons in an agricultural soil]]> ABSTRACT Land treatment of crude oil is used by the oil industry, since it has been recognized that hydrocarbons (HC) can be metabolized by the indigenous microbial community of soil. The crude oil biodegradation in agricultural soil was studied for 12-mo to determine the HC biodegradation and leaching, the effect of HC on barley productivity and soil properties, and the potential for HC uptake in the plant. Concentration and composition of HC in the soil were periodically determined at a depth of 0 to 75 cm. The HC concentration decreased over time due mainly to the microbial degradation. At the end, 12% of the primary crude oil amount remained constant in the soil. A vertical migration, leaching and metabolic products of HC into subsoil occurred. The HC have changed soil fertility. Barley has been successfully cultivated in soil but the HC reduced some plant growth parameters. However, HC were not detected in plant seeds. Many of oil-utilizing bacteria and fungi were isolated from soil. The HC biodegradation potential of oil polluted soil (6% to 66%) were higher than of unpolluted one (4% to 53%). The bacteria (22% to 66%) were more active than fungi (4% to 46%) in HC biodegradation. The study demonstrated that agricultural lands with low rates of oil contamination allows the growth of plants. They ensure high efficiency of HC biodegradation. Vertical infiltration plays an important role in HC removing from soil. Alkanes were completely assimilated by microorganisms and polar compounds were more resistant to microbial attack. <![CDATA[Effect of phenological phase of dry grazing pasture on fatty acid composition of cows’ milk]]> ABSTRACT The fatty acid content is a very important feature of the milk that affects the health of consumers. The aim of this study was to estimate cow’s milk fatty acid composition in early vegetative, late vegetative and reproductive phase, with the simultaneous determination of the pasture biomass chemical and botanical composition. The research was conducted on Agrostis castellana semi-natural dry grassland in the vicinity of Podgorica, Montenegro. Cows were put to grazing during the whole experimental period. This pasture was assessed as moderate to good quality and botanically diversified. The chemical composition of the grassland biomass changed with the maturity phase. A significant increase in the content of DM, crude fiber, fat and a decrease in crude protein content were determined throughout three phenological phases (p &lt; 0.05). The content of total milk fat did not show significant variability during first two phases, but it did in the third phase. The content of milk fat and protein was high in all phases, although it is a dry pasture with a poor quality of biomass in the third phase. The content of majority saturated fatty acids (SFAs) increased with grass maturity, while total content of monounsaturated fatty acids (MUFAs) decreased. The polyunsaturated fatty acids (PUFAs) content kept the same level up to the reproductive phase. The phenological phase significantly influenced the content of fatty acids in the third phase (p &lt; 0.05). A notable number of SFAs, MUFAs end PUFAs had the highest content in the second phase <![CDATA[Contribution of seed traits to the genetic diversity of a segregating population of <em>Passiflora</em> spp.]]> ABSTRACT Genetic diversity can be investigated early using seed traits, an important aspect of sexually propagated species. In this context, plant breeders aim at the production of new varieties using seeds with good germination and vigor. The present study was thus designed to examine the genetic diversity of a segregating population from a cross between Passiflora edulis Sims and P. setacea DC. based on seed morphological- and physiological-quality responses. Seventeen seed morphology variables were evaluated via digital image analysis, and a germination test and four vigor tests were applied for the evaluation of physiological quality. Data were interpreted by multivariate analysis for the evaluation of genetic diversity. The parents were allocated to distinct groups by the dendrogram structured using Euclidean distance, based on the morphological- and physiological-quality traits. The unweighted pair group method using arithmetic averages (UPGMA) clustering method formed three groups, the first one represented by backcrossing 32, the second by P. setacea and the third by a larger number of genotypes (P. edulis, hybrids and other backcrosses). The principal component analysis showed that the first two components explained 61.32% of the variation. The clustering methods were efficient in the evaluation of dissimilarity of genotypes from a segregating population of Passiflora <![CDATA[Transcriptome analysis of hot pepper plants identifies waterlogging resistance related genes]]> ABSTRACT Hot pepper (Capsicum annuum L.) is one of the most important vegetable crops in China, but floods bring substantial decreases in production over the past several decades. In order to investigate the mechanisms of waterlogging resistance in mutant hot pepper, we measured the agronomic traits of mutant and wild-type, as well as the activities of root antioxidant enzymes and the contents of osmotic regulation substance. At the same time, we did transcriptome sequencing on the plant roots, and screened for differentially expressed genes between mutant and wild-type. The results showed that, under waterlogging stress, the mutants could grow normally, and the activities of their superoxide dismutase, peroxidase, catalase, and glutathione reductase were significantly increased, as well as the contents of proline and soluble sugar. The accumulation of malondialdehyde and hydroxyl radical in mutants was significantly reduced. Among the 61 differentially expressed genes from transcriptome analysis, 24 genes were up-regulated and 37 genes were down-regulated in mutants. After functional analysis, we found 8 genes related to the metabolism of endogenous hormone and protective enzymes, among which, auxin-induced protein related gene cap.ARATH, ethylene response related gene Cap.RAP2, MYB family related gene Cap.MYB1R1, and the 4 genes related to peroxidase Cap.POD, were significantly up-regulated in mutants, while the Capana01g001329 gene was down-regulated. These results suggest that under waterlogging stress, the mutant could enhance its resistance to waterlogging by regulating the genes involved in metabolism of endogenous hormones and protective enzymes. This study provides the scientific basis for elucidating the gene regulation network of mutant pepper under waterlogging stress <![CDATA[Filamentous fungi in biological control: current status and future perspectives]]> ABSTRACT Agriculture is the largest economic sector in the world. The awareness of the current environmental degradation caused by conventional farming practices has allowed the use of entomopathogenic fungi as a biological control technique to become increasingly widespread. Several studies from the laboratory bench to field trials show that fungi can be directly applied or, more recently, can be carried to the target by other biological vectors (i.e., insects), which increases their potential for dispersal and transmission. In addition, studies on the development of formulations have intensified, with the aim to enable their commercialization and reduce costs for the more sustainable management of crops. This review discusses the positive aspects of the use of filamentous fungi in the biological control of pests, specifically in terms of the use of antagonistic fungal plant pathogens and nematophagous fungi. <![CDATA[Effect of yerba mate ( <em>Ilex paraguariensis</em> A. St.-Hil.) supplementation on oxidative stress in ruminants]]> ABSTRACT Nutrition, especially antioxidant-rich herbal supplementation, is one of the most important factors in the reaction to oxidative stress. Moreover, it influences animal productivity and reproduction. When oxidant production exceeds the capacity of antioxidant defense, this results in oxidative damage to lipids, DNA, and proteins. Oxidative stress, which is described as an imbalance between oxidant and antioxidant levels, is a current field of research in ruminant medicine, and it has been involved in numerous disease processes, including sepsis, mastitis, acidosis, and ketosis. Interest in plant extracts has therefore increased due to the high amount of natural biologically active substances that are potential natural fodder additives. This paper focused on yerba mate tea, an infusion made from the leaves of the Ilex paraguariensis A. St.-Hil. tree, which is a widely consumed traditional beverage in South America. There is growing interest for the properties of yerba mate. Supplementation of I. paraguariensis for large and small ruminants resulted in lower oxidative stress and also improved their productive and reproductive performance <![CDATA[Effect of temperature and scarification on seed germination of <em>Conanthera</em> spp. (Tecophilaeaceae)]]> ABSTRACT The Chilean endemic genus Conanthera is comprised of five species of herbaceous cormous geophytes. They have ornamental value due to their bell-shaped flowers, which are blue, violet or white. Previous germination studies of Conanthera campanulata and Conanthera trimaculata were carried out at 22 °C, and manual mechanical scarification improved germination. Based on these results, it was suggested that physical dormancy is present in the non-scarified seeds. However, an improvement in germination after scarification is not enough evidence to conclude that the seed is non-permeable to water and thus has physical dormancy. The objective of the present study was to assess the testa water permeability via an imbibition test and to identify the optimum germination temperature in C. campanulata and C. trimaculata. Using 6-mo-old seeds, data from the imbibition tests showed that neither the seeds of C. campanulata nor C. trimaculata have physical dormancy. In the germination experiments, the temperature range for achieving high germination percentages was 10 to 15 °C, where germination reached 90% in less than 28 d. Temperature of 20 °C can be considered supra-optimal, while 5 and 25 °C inhibited germination. Manual mechanical scarification did not affect germination results at the range of 10 to 15 °C. However, at the supra-optimal temperature of 20 °C manual mechanical scarification increased germination, although levels were never higher than 25%. <![CDATA[Rootstock affects the blend of biogenic volatile organic compounds emitted by ‘Hass’ avocado]]> ABSTRACT Grafting, using tolerant rootstocks, has been necessary to increase avocado (Persea americana Mill.) production in drought, salinity, pest, and soil disease conditions. The avocado rootstock has shown an influence on scion vigor, nutrient absorption, fruit quality, and disease tolerance. Nevertheless, the avocado rootstock influence on the biogenic volatile organic compounds (BVOCs) emitted from ‘Hass’ shoots has not been reported. Our objective was to study the effect of two avocado rootstocks of the Mexican race on BVOC emitted by avocado ‘Hass’ shoots. We collected BVOCs emitted by ‘Hass’ avocado shoots grafted on ‘Mexicola’ and ‘Zutano’ rootstocks. All volatile collections were made from living plants for 24 h through a dynamic headspace technique. The chemical profiles were analyzed by gas chromatography coupled to a mass spectrometry (GC-MS). BVOC emission rates were highly variable in amount and composition. The monoterpene α-pinene was emitted at 5.06 ± 0.74, 0.73 ± 0.14, and 1.43 ± 0.61 μg mL-1 by graft ‘Hass’/‘Mexicola’, ‘Hass’/‘Zutano’ and ungrafted ‘Mexicola’, respectively. Grafted ‘Hass’ on ‘Mexicola’ emitted a wide variety of monoterpenes as β-pinene, cumene, 3-carene, R-limonene and (Z)-β-ocimene, whereas grafted plants on ‘Zutano’ only released α-pinene and cumene. Estragole was only detected on ungrafted ‘Mexicola’. We found that the chemical profile of volatile compounds released by ‘Hass’ grafted avocado plants was qualitatively and quantitatively influenced by rootstocks