Scielo RSS <![CDATA[Chilean journal of agricultural research]]> vol. 76 num. 4 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<b>Quantitative assessment of <i>indica</i> rice germination to hydropriming, hormonal priming and polyethylene glycol priming</b>]]> Seed priming is a useful technique which improves seed germination parameters. The present investigation was conducted to evaluate some of the most important germination parameters such as total germination, germination rate, mean germination time, average speed, germination percentage (GP), germination vigor index (GVI), relative frequency, plumule fresh and dry weight, radical fresh and dry weight, plumule and radical length, leaf and root proline content of six indica rice (Oryza sativa L.) varieties, including MR219, MR219-4, MR219-9, MR220, MR159, and MR 211 under hydro-, hormonal- and polyethylen glycol (PEG)- priming conditions. The highest germination parameters were achieved under the hydro-priming treatment, at 18 h (100%), 6 h (100%), 18 h (90.3%), 12 h (91.6%), 18 h (86.6%), and 18 h (78.3%) for the genotypes MR219, MR219A MR219-9, MR220, MR159, and MR211, respectively. The best germination feedback of the rice varieties under the hormonal priming were observed in 50 mg L-1 abscisic acid (ABA), 10 mg L-1 gibberellic acid-3 (GA3), 50 mg L-1 indole-3-acetic acid (IAA), 50 mg L-1 GA3, 100 mg L-1 ABA, and 10 mg L-1 GA3 for the genotypes MR219, MR219A MR219-9, MR220, MR159 and MR211, respectively. The rice varieties showed different responses to various levels of PEG in which MR219, MR219-4 and MR219-9 responded positively to higher PEG levels, while MR220, MR159 and MR211 showed better feedback under lower PEG concentrations. These outcomes comply with the higher tolerance of MR219, MR219-9 and MR219-4 varieties to drought stress. <![CDATA[<b>Jupiter-INIA</b>: <b>A new oat variety with improved </b><b>β</b><b>-glucan and protein contents</b>]]> Jupiter-INIA is a new oat (Avena sativa L.) cultivar selected in preliminary field trials for higher β-glucan and protein content, resistance to disease and lodging, and similar yield than the other cultivated oat varieties. The objective of the present research was to compare agronomic, industrial performance and groat nutritional quality of 'Jupiter-INIA' with the widespread commercial 'Supernova-INIA' in southern Chile. Field trials were conducted at four different locations during four seasons in a randomized complete block design with three replicates. 'Jupiter-INIA' had about 20% more β-glucan (4.25 vs. 3.31 g 100 g¹, P < 0.0001) and protein (16.14 vs. 12.78 g 100 g-1, P < 0.0001) contents than 'Supernova-INIA'. The overall plant height, lodging, and disease reaction to crown rust were lower in 'Jupiter-INIA' than in 'Supernova-INIA'. Grain yield, 1000-grain weight, and hectoliter weight, were lower in 'Jupiter-INIA' than in 'Supernova-INIA'; however, its mean values were within the range for oat cultivars. Dehulled-grain yield and stained grains were similar to 'Supernova-INIA'. This results point out that 'Jupiter-INIA' groat had superior nutritional quality than 'Supernova-INIA', and thus it could be an important contribution to be included in the development of healthy oats-containing food products. <![CDATA[<b><i>Bacillus spp.</i></b><b> inoculation improves photosystem II efficiency and enhances photosynthesis in pepper plants</b>]]> Bacillus is one of the main rhizobacteria to have been used as a study model for understanding many processes. However, their impact on photosynthetic metabolism has been poorly studied. The aim of this study was to evaluate the physiological parameters of pepper (Capsicum chinense Jacq.) plants inoculated with Bacillus spp. strains. Pepper seeds were inoculated with Bacillus cereus (K46 strain) and Bacillus spp. (M9 strain; a mixture of B. subtilis and B. amyloliquefaciens), chlorophyll fluorescence and gas exchange were evaluated. The ANOVA (P ≤ 0.05) showed that the maximum photochemical quantum yield of photosystem II (PSII) (Fv/Fm) in plants inoculated with the M9 strain (0.784) increased with respect to other treatments (K46: 0.744 and Control: 0.739). Inoculated plants with M9 and K46 strains exhibited an increase of both photochemical quenching (qP) (by 27% and 24%, respectively) and CO2 assimilation rate (photosynthesis) (by 20% and 16%, respectively), when compared with non-inoculated plants. Furthermore, plants inoculated with M9 and K46 showed decreased transpiration (61% and 57%, respectively) with respect to controls. Likewise, both electron transport rate of PSII (ETR) and PSII operating efficiency (ΦPSII) increased in inoculated plants. However, only plants inoculated with the M9 strain showed enhancements on all growth characteristics. Our results therefore show that inoculating plants with M9 strain positively influenced the performance of the photosynthetic mechanism in pepper plants to increase chlorophyll fluorescence and gas exchange parameters. promotion of photosynthetic capacity in pepper was due to increased ETR in the thylakoid membranes, which was promoted by the bacteria. M9 strain could even be used in sustainable agriculture programs. <![CDATA[<b>AUPOV morphological versus molecular markers for maize inbred lines variability determination</b>]]> In maize (Zea mays L.) breeding programs, it is very important to define a genetic distance of inbred lines and to establish criteria and biometric methods for the satisfactory germplasm classification. A total of 29 inbred lines from Maize Research Institute "Zemun Polje" (MRIZP) breeding program, Belgrade, Serbia, were used to compare similarities obtained by morphological (according to UPOV - Union Internationale pour la Protection des Obtentions Vegetales) and molecular (simple sequence repeats, SSR) markers. The aim was to assess discriminative power of applied markers in the separation of related lines, and to determine the possibility of their application in choosing parental lines for breeding programs. Application of different marker types resulted in adequate separation of inbreds into divergent groups, which facilitates the choice of parental lines. However, there were still many inconsistencies between the field and laboratory results. The quality of information from morphological markers was improved by the application of the appropriate descriptor, measurement scale and the biometric method. According to the correspondence analysis, increased number of SSR markers will enable more reliable results. Regression analysis of morphological visual assessment (MVG) and SSR similarity of individual inbreds pointed out that in some cases morphological, and in others molecular markers more accurately reflected known pedigree information of tested maize lines. In the early generations of maize inbred lines testing, we propose utilization of information resulting from morphological markers, according to UPOV descriptor. However, application of adequate number of molecular (SSR) markers has an economic justification on a smaller number of elite lines in the later generations of line testing. <![CDATA[<b>Mixed models and multivariate analysis for selection of superior maize genotypes</b>]]> Selections via the mixed model and the multivariate analysis approach can be powerful tools for selecting cultivars in plant breeding programs. Therefore, this study aimed to compare the use of mixed models, multivariate analysis and traditional phenotypic selection to identify superior maize (Zea mays L.) genotypes. Seventy-one (71) maize Topcrosses and three commercial cultivars were evaluated using these three methods. Plant height, ear height, ear placement, stalk lodging and breakage, and grain yield were evaluated. There was a difference between selection methods, as the selection with mixed models and the selection based on the average phenotypic afforded the inclusion of genotypes with high productivity, which did not occur for the multivariate analysis. The selection by multivariate analysis allowed the inclusion of genotypes with better agronomic and other desirable traits, not only those with highest productivity, in a maize breeding program. <![CDATA[<b>Control of weeds in glasshouse and rice field conditions by phytotoxic effects of <i>Tinospora</i> crispa (L.) Hook. f. & Thomson leaves</b>]]> Phytotoxic potential of powder and methanol extract of Tinospora crispa (L.) Hook. f. & Thomson leaves as pre- and post-emergence applications on the growth of transplanted rice (Oryza sativa L.) and associated weeds were evaluated under glasshouse and field conditions to determine its herbicidal activity as soil additive material in rice fields. In glasshouse study, utilization of leaf powder and leaf extract of T. crispa as pre-emergence application provided a satisfactory weed control, inhibiting seed germination and reducing the growth of germinated seedlings with an increase in the yield of transplanted rice. The magnitude of the phytotoxic effects at the same concentration levels in the test plants was dependent on the application methods (powder and extract), time of application (pre-and post-emergence), concentration and the recipient species. Field experiment consisted of T. crispa leaf powder (1, 2 and 4 t ha¹), chemical herbicide (pretilachlor + pyribenzoxim at 1 L ha-1) as positive control and a negative control (no treatment). There was nonsignificant difference between leaf powder-treated plots (2 and 4 t ha-1 doses) and plots that received herbicidal treatment in terms of percentage reduction of emergence and weed DM. In plots amended with 1, 2 and 4 t ha-1 leaf powder, weed dry weight was reduced by nearly 80%, 97% and 99% and total weed seedling density was inhibited by 73%, 94% and 99%, respectively, compared to untreated plots. There was a significant promotion on grain yield, straw dry weight and number of seed per panicle of rice, when treated with leaf powders and chemical herbicide compared with negative control. These results suggest that T. crispa has a significant phytotoxic activity on the germination and growth of weed species in rice fields. <![CDATA[<b>Density effect and economic threshold of Japanese brome (<i>Bromus japonicus</i> Houtt.) in wheat</b>]]> Japanese brome (Bromus japonicus Houtt.) is a winter annual weed commonly found in the wheat (Triticum aestivum L.) fields of China. It is prevalent in northern China and produces obvious wheat yield losses. Information on the interference of Japanese brome on wheat density and its economic threshold (ET) is unknown; this information is useful to manage Japanese brome. Two-year field experiments were designed to determine the ET of Japanese brome in wheat. The dry weight of Japanese brome with a density of 320 plants m-2 was similar to the 'natural weeds including Japanese brome' treatments and higher than other Japanese brome densities, except for the 640 plants m-2 density which had the highest weed dry weight and yield loss. In the absence of Japanese brome, natural weed infestation was less competitive. The ET of Japanese brome in wheat was between 4 and 5 plants m-2 with 80% efficiency for the herbicide flucarbazone. It predicted that 4 plants m-2 of Japanese brome can cause 2.11% to 2.24% yield losses. This information can contribute to decision making for Japanese brome management. Given several production factors, this ET is more precise and reliable than the ET determined with only yield losses and can be used to develop better control strategies. <![CDATA[<b>Conditions to optimize mass production of <i>Metarhizium anisopliae</i> (Metschn.) Sorokin 1883 in different substrates</b>]]> One of the best alternatives to reduce the amount of chemical insecticides released into the environment is biological agents. Metarhizium anisopliae (Metschn.) Sorokin 1883 (Hypocreales: Clavicipitaceae) is an entomopathogenic fungus with great potential as a biological pesticide to biologically control pests. However, the relatively high cost of the substrate needed for its mass production system increases product price and discourages its use. The objective of this study was to optimize the mass production conditions of M. anisopliae for use as a biological control agent using two solid substrates, new parboiled rice (NPR) and recycled parboiled rice (RPR). Conidial production was optimized by the response surface methodology (RSM). The effects of the temperature, time, and molasses variables and the interactions between them (conidia g-1) were determined. For the NPR substrate, it was determined that the significant variables were time and temperature, and the interactions were temperature x molasses and temperature x time. For the RPR substrate, the significant variables were temperature and time, and the interactions were time x molasses and temperature x time. Both substrates obtained the highest industrial yields at 25 °C for a period of 20 d. Given that the percentage of molasses was not critical for yields, it is recommended that it be set at 5% to reduce costs. Finally, it was possible to use the RPR substrate from the M. anisopliae produ9ction itself as an alternative to solid substrate; mean industrial performance (conidia g-1) was higher than values obtained with NPR and at a lower cost. <![CDATA[<b>Changes in physiological and antioxidant activity of <i>indica</i> rice seedlings in response to mannitol-induced osmotic stress</b>]]> Morphological, physiological, and biochemical plant responses were studied in unstressed and stressed seedlings of indica rice (Oryza sativa L.) genotypes. The effect of NB medium supplemented with a 100 mM mannitol treatment, which induced drought stress conditions, was measured for relative growth rate, cell membrane stability, antioxidant enzyme activity (superoxide dismutase [SOD], catalase [CAT], and peroxidase [POD]), and total antioxidant capacity by DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2'-azino-bis[3-ethylbenzothiazoline-6-sulfonic acid] diammonium salt) assays. Results of morphological and physiological factors showed two contrasting rice groups, drought-sensitive and drought-tolerant genotypes. After drought stress, the increased rate of SOD activity was lower in drought-tolerant than in drought-sensitive genotypes, but the increased rate of CAT and POD activity and total antioxidant capacity was higher in drought-tolerant than in drought-sensitive genotypes. Increasing changes in activity levels of antioxidant enzymes and total antioxidant capacity indicated more rapid free radical scavenging compared with relative growth and cell membrane stability in drought-tolerant genotypes under short-term treatment. The trend toward change in CAT and POD antioxidant enzyme activity and total antioxidant capacity of stressed seedlings, as well as the correlation between these changes, and the morphological and physiological responses (0.96 correlation coefficient [R²] between relative growth rate and CAT; 0.93 R² between relative growth rate and POD enzyme activity; 0.96 R² between relative growth rate and Trolox equivalent antioxidant capacity values) coincided with the degree of drought tolerance. <![CDATA[<b>Yield of beet cultivars under fertigation management and salinity control in a protected environment</b>]]> In a protected environment, applying excess fertilizer and using water with soluble salts cause soil salinization due to the absence of lixiviation by precipitation. Among commercial vegetables, beets (Beta vulgaris L.) have good tolerance to soil salinity, being a good option for growth under these conditions. An experimental study was carried out in the municipality of Botucatu, São Paulo, Brazil. The treatment consisted of a combination of the following factors: initial soil salinity (1, 3, 6, 9, and 12 dS m-1), fertigation management (traditional vs. control of ion concentration of the soil solution) and two beet cultivars ('Early Wonder' and 'Itapua') in a 5 x 2 x 2 factorial design. A randomized block design with four replicates was adopted, totaling 80 experimental plots. The total fresh weight of aerial part and root, total dry weight of aerial part and root, and water use efficiency (WUE) were assessed. Significant differences were found between fertigation management practices and salinity levels proposed. 'Itapua' showed better yield and WUE for electrical conductivity (EC) below 6 dS m-1. Under traditional fertigation, root yield response fits a linear model with a decrease of 11.365 g ('Early Wonder') and 11.025 g ('Itapua') for each unit increase in EC. Under controlled fertigation, the best-fit model was quadratic, with maximum estimates of 248.83 g for 'Early Wonder' and 258.52 g for 'Itapua'. Controlling EC of the soil solution had a positive effect, while salinity levels above 6 dS m-1 must be avoided. <![CDATA[<b>Evaluation of induced pitting damage of late season cherries 'Regina' and 'Sweetheart' using an impact energy method</b>]]> Late season cherry (Prunus avium [L.] L.) cultivars have turned of important relevance in production systems of the south of Chile with a continuous increase in exports. Cherries reach final markets after long distance ocean shipping and pitting damage continues to be the main postharvest detrimental quality loss during this period. Different factors affect pitting expression responses during harvest and postharvest fruit management. The aim of this study was to determine the influence of postharvest factors in pitting development of two late cherry 'Regina' and 'Sweetheart' using an impact energy method. Maturity stage (red and dark red), impact energy (0.00342 and 0.0107 J) and storage time (0, 7, 14, 21, 28 d) were evaluated. Fruit composition (soluble solids, pH, and titratable acidity), weight loss (%) and firmness were measured. Induced pitting was determined after allocating a known impact energy level and obtaining an imprint of the damaged area. Pit diameter, depth and volume were determined by light microscopy techniques and image analysis. Pitting damage that occurred naturally on fruit picked at commercial maturity stage was determined at harvest and during cold storage. The induced pitting device allowed for the application of a mechanical injury of known impact energy, useful to determine pitting susceptibility differences among cultivars. The coefficient of variation of the method was 0.18 for pit diameter, 0.37 for pit depth and 0.6 for pit volume, indicating repeatability of results independent of the impact energy applied or the variety studied. 'Sweetheart' showed higher incidence of induced pitting during storage, with an average 2.8 pit volume increase compared to a 2.2 increase in 'Regina' during the same period. Naturally occurring damage of commercial fruit verified results obtained with the induced pitting device, with 'Sweetheart' more susceptible than 'Regina' (P < 0.05). <![CDATA[<b>Characterization of chemical compositions and bioactive compounds in juices from pomegranates ('Wonderful', 'Chaca' and 'Codpa') at different maturity stages</b>]]> In recent years, pomegranate (Punica granatum L.) fruit has gained popularity due to its functional properties. In this study, the effects of maturity on the chemical composition (pH, acidity and total soluble solids), total phenolic contents, anthocyanin contents and antioxidant capacities of pomegranate juices from three varieties (Wonderful, Chaca and Codpa) were assessed. The fruits were collected manually at three maturity stages (M1: unripe, M2: medium ripe, and M3: full ripe) from the Region de Coquimbo (Chile). Pomegranate juice was obtained from squeezed arils of fresh fruit. Results showed that chemical composition did not significantly differ according to the variety or maturity stage. Phenolic contents decreased during the final stage (M3) for 'Wonderful' and 'Codpa' (8% and 29%, respectively, from M2). Six main anthocyanin compounds (cyanidin 3,5-diglucoside, delphinidin 3,5-diglucoside, pelargonidin 3,5-diglucoside, cyanidin 3-glucoside, delphinidin 3-glucoside, and pelargonidin 3-glucoside) were detected in the three varieties. Significant differences in the anthocyanin content and antioxidant capacity were determined among different varieties and maturity stages. 'Codpa' pomegranate juice can be considered a good potential source of anthocyanin compounds (total content 715 mg L-1) with a high antioxidant capacity (15.83 mmol Trolox L-1); the highest values for both parameters were observed in juice from fruits collected at the M2 stage. Principal component analysis allowed for differentiation of the pomegranate juices according to variety but not according to maturity stage. <![CDATA[<b>Long term climatic trends in Chile and effects on soil moisture and temperature regimes</b>]]> Climate change could potentially affect agricultural and forest production in Chile through changes in soil moisture and temperature regimes. In Soil Taxonomy the Soil Moisture Regime (SMR) is used to classify soils at the Suborder, Great Group and Subgroup levels, whereas Soil Temperature Regime (STR) is mainly used at the Family level. Both SMR and STR can be calculated using climatic data input to the Newhall model. Therefore, the objective of this research was to test the hypothesis that long term climate change has already affected the SMR and STR in different locations of the country. Historical values (1912-2015) of monthly precipitation and temperature were input to the model, with the available soil water set to 180 mm, and the offset of air to soil temperature set to 2 °C. The climatic records indicated a general trend of less precipitation in central and south central Chile whereby the SMR changed in Concepción from Ustic-Udic Tropustic to Ustic-Typic Tropustic; in Puerto Montt from Perudic to Udic-Typic Udic; and in Punta Arenas from Aridic-Typic Aridic to Xeric-Typic Xeric. In general, the recent period had more frequent extreme dry years. There was also a general tendency for slightly cooler temperatures mainly along the coast, and warming in Santiago, but the dominant STRs did not change between periods. Additionally, in south central Chile there was a decrease of annual moist days when the soil temperature is > 5 °C, which suggests that in some areas soil temperature and moisture conditions have become somewhat more limiting over time, and, if continued, will likely result in a southerly expansion of the Xeric SMR, and increased need for supplemental irrigation of crops.