Scielo RSS <![CDATA[Chilean journal of agricultural research]]> vol. 80 num. 2 lang. es <![CDATA[SciELO Logo]]> <![CDATA[Additive intercropping of sunflower and soybean to improve yield and land use efficiency: Effect of thinning interval and nitrogen fertilization]]> ABSTRACT An additive intercropping model was adopted to improve land use efficiency and productivity of two prominent oil crops grown in Egypt, that is, sunflower (Helianthus annuus L.) and soybean (Glycine max [L.] Merr.) A 2-yr field trial was conducted in Northern Egypt during the summers of 2017 and 2018. The effects on yield, crop components, and land use efficiency of the system were tested with three N fertilizer rates (70, 105, and 140 kg N ha-1) and three thinning intervals of 15, 30, and 45 d after sowing (DAS) for sunflower and 30, 45, and 60 DAS for soybean. Late thinning increased plant height in both crops, but reduced sunflower stem and head diameters and seed weight per head. The maximum seed yield occurred in the pure stands and reached 4.00 and 1.61 t ha-1 for sunflower and soybean, respectively. Early thinning positively affected seed yield and fresh and dry biological yields, while the effect of N rates was limited. Seed oil content of both crops was slightly affected by the treatments and generally averaged approximately 50% and 20% in sunflower and soybean, respectively. While the land equivalent ratio (LER) indicated the advantage of intercropping sunflower and soybean (LER &gt; 1), the DM equivalent ratio (DMER) provided a more realistic estimate as to the effect of intercropping compared with sole cropping in an additive model. Early and intermediate thinning intervals across all N fertilizer rates resulted in yield gain (DMER &gt; 1), while late thinning reduced yield (DMER &lt; 1). Intercropping sunflower and soybean crops is recommended for low input farming systems, particularly in developing countries. <![CDATA[New polymorphic nuclear microsatellites from <em>Aristotelia chilensis</em> (Mol.) Stuntz (Elaeocarpaceae)]]> ABSTRACT Maqui (Aristotelia chilensis [Molina] Stuntz) is a dioecious small tree native to Chile and southwestern Argentina. This species has gained attention due to its high polyphenol content and anti-oxidant capacity. Nevertheless, genetics studies and information about A. chilensis population genetics are scarce and even contradictory. In fact, the available species-specific simple sequence repeat (SSR) markers are not informative at all, and so we decided to identify and characterize new ones able to trace individual genotypes, a basic tool intended for different genetic studies. We identified and characterized 15 new polymorphic SSR markers for A. chilensis. These markers were evaluated in three populations distributed along 1000 km of Central Chile, exhibiting up to 10 alleles per locus and a combined expected heterozygosity of 0.858. Markers were also informative in two related species, Aristotelia peduncularis (Labill.) Hook. f. and Crinodendron patagua Molina (Elaeocarpaceae), with 13 and six SSRs showing clear amplification patterns, respectively. This new set of SSR markers are highly polymorphic and informative, being the first ones available for the effective fingerprinting of maqui genotypes. A proof of concept of that was the differentiation of six maqui accessions that are under domestication for productive purposes, based on a subset of the polymorphic SSR markers. <![CDATA[Alleviation of cobalt stress by exogenous sodium nitroprusside in iceberg lettuce]]> ABSTRACT Excessive amounts of heavy metals (HMs) in the rooting media affect adversely plant growth, cause loss of yields, and undesirable effects on crops. The aim of this study was to investigate the effects of exogenous sodium nitroprusside (SNP) (200 μM), a nitric oxide (NO) donor, on toxic cobalt (Co) level (200 μM) in iceberg lettuce (Lactuca sativa L. var. capitata). Plants were grown in a hydroponic system (modified Hoagland solution and perlite as inert media) inside a greenhouse under natural light conditions (average temperature 27-18 °C day-night and humidity 63%). Results indicated that excessive Co caused significant reductions in fresh (FW) and dry weights (DW) of the shoots and roots, photosynthetic pigment contents of leaves, and metallic cation concentration of shoots and roots. Also, hydrogen peroxide (H2O2), lipid peroxidation, proline accumulation, catalase (CAT) and ascorbate peroxidase (APX) activities, and total Co accumulation rate (TAR) increased significantly with excessive Co. Compared to Co application, Co+SNP application showed a 48.5% and 31.1% increase in FW and DWs, respectively. Moreover, chlorophyll (Chl) a, Chl b, Chl a+b and carotenoid (Car) content increased 54.5%, 64.4%, 56.6%, and 39.7%, respectively. Similarly, shoot Co uptake (69.7%), shoot and root Fe concentration (21.7% and 149.4%, respectively), root Zn concentration (6.1%), and net accumulation of Fe and Mn via roots (4.5- and 1.6-fold, respectively) were increased. Consequently, the alleviating effect of exogenous NO on Co toxicity in iceberg lettuce could depend on NO-induced increase in antioxidant enzyme activity and its multifunctional role in plant cellular mechanism. <![CDATA[Effect of seeding rate on selected physical parameters and biomass yield of maize]]> ABSTRACT Plant morphology is affected by plant density and uniformity of plant distribution per unit area. This study investigates the effect of seeding rate of two hybrid cultivars of maize (Zea mays L.) harvested for silage on selected physical parameters (stem length, stem diameter, total plant weight and weight of ears with husks), fresh weight yield and ear yield of maize plants. A field experiment was carried out in 2011-2013 on soil of weak rye complex (‘Kosmo’) and a good rye complex (‘Kixxo’). Results were processed by one-way ANOVA, correlation analysis and regression analysis. At constant 0.75 m inter-row spacing, seeding rate (6.5 to 11.9 seeds m-2 for ‘Kosmo’ and 8 to 12 seeds m-2 for ‘Kixxo’) significantly (α = 0.05) influenced evaluated parameters. Higher plant density lowered the weight of plants and ears, and resulted in lower stem diameter. An increase in seeding rate led to a decrease in stem diameter measured at 50, 100 and 150 cm above ground (by ca. 11% to 23% in ‘Kosmo’, and by ca. 3% to 13% in ‘Kixxo’), and an increase in stem length (by 10% to 13% in ‘Kosmo’, and by ca. 8% in ‘Kixxo’). Plants grown with lower seeding rates were larger and heavier. The developed equations are characterized by a good and very good fit to empirical data (multiple correlation coefficient ranged from 0.62 to 0.94 in ‘Kosmo’, and from 0.76 to 0.95 in ‘Kixxo’). This knowledge of the morphological traits of maize is useful to optimize operating parameters of harvesting machines. <![CDATA[Changes in sediment properties and bacterial community in marine sediments after entering the coastal land in Bohai Bay, northern China]]> ABSTRACT In coastal areas of Bohai Bay, China, marine sediments were used for land reclamation. However, vegetation cannot grow well on the reclaimed land because marine sediments have different ecological functions than soil. Changing marine sediment into soil rapidly and accelerating the soil-forming process is key to solving this ecological problem on reclaimed land. Therefore, in this study, we not only measured the chemical properties of marine sediments during an 8 yr soil formation period to explore fertility changes, but we also used MiSeq sequencing to analyze and compare the bacterial community structure and diversity before and after the 8 yr land reclamation. Our results showed: (1) Marine sediment changed from severe to mild salinization during the 8 yr of soil formation, and the sediment salinity decreased significantly to 7.3 g kg-1 (p &lt; 0.05). However, pH of the sediment was always &gt; 8.5 and did not change significantly. In addition, the total fertility of the sediment decreased significantly after 8 yr. Especially, the content of nitrate-N in marine sediment decreased significantly by 86.23% (p &lt; 0.05) after 8 yr of soil formation. Also, the content of available P and soil organic matter decreased significantly by 45.92% and 26.22%, respectively. (2) The total abundance of bacteria increased while the community diversity decreased after the sediments were removed from the ocean environment for 8 yr. The bacterial community composition changed, and results of our redundancy analysis (RDA) indicated that the change was mainly affected by pH, soil contents including, available P, nitrate-N, ammonia-N, Na+, and Cl-, as well as salinity. <![CDATA[Long-term interactions of reduced tillage and different amounts of residue retaining improved soil environment in a semi-arid tropical climate]]> ABSTRACT Soil quality degradation caused by intensification is threatening the sustainability of banana (Musa acuminata Colla) production in South China. Hence comprehensive information about the benefits of conservation management on soil quality is urgently needed. This study aimed to assess the effects of tillage and residue on soil biological properties in a banana plantation for 25 yr. Treatments consisted of three tillage methods (conventional tillage, CT; reduced tillage, RT; no tillage, NT) combined with three residue levels (0, NR; 50%, HR; 100%, TR). Soil samples were taken in 2018-2019 from 0-40 cm depth. Soil moisture, pH, total organic C and total N in NT were 28.8%, 22.4%, 39.9% and 34.3% higher than in CT. However, NT decreased available P by 16.7% compared with CT. HR had higher NH4-N and available K and lower bulk density compared with NR. Microbial biomass C and N were on average 39.2% higher in TR than those in NR. Urease, dehydrogenase and β-glucosidase obtained a mean increase of 34.3% in RT compared to CT. Invertase and catalase were on average 32.9% greater when residue was applied than no residue input plots. CO2 and N2O emissions decreased around 37.6% in different tillage treatments, but increased from 39.9% to 62.6% in all residue input plots. In general, soil biological properties are sensitive characters to changes caused by tillage and residue, and consequently they are well-established as soil physicochemical indicators for soil quality evaluation in conservation tillage systems. <![CDATA[Fitness evaluation of <em>Encarsia sophia</em> parasitizing <em>Aleurocybotus indicus</em> on two rice cultivars]]> ABSTRACT Banker plant system has been widely used to control vegetable pests through the use of different combinations of host plant-alternative host natural enemy. In order to control the destructive pest Bemisia tabaci (Gennadius, 1889) (Hemiptera: Aleyrodidae) with banker plant system, estimating the reproductive potential of parasitoid Encarsia sophia (Girault &amp; Dodd, 1915) (Hymenoptera: Aphelinidae) parasitizing and feeding on alternate host rice whitefly Aleurocybotus indicus (Hymenoptera: Aphelinidae) is critically necessary. Two rice cultivars (‘Changyou’ and ‘Jinjing’) were used as banker plant. Our research showed that the longevity of E. sophia female adult in ‘Changyou’ treatment was significantly longer than that in ‘Jinjing’ treatment. The intrinsic rate of increase (r) and net reproductive rate (R0) of E. sophia parasitizing A. indicus on ‘Changyou’ rice plant were 0.2295 d-1 and 34.6 eggs, respectively, and significantly greater than those on ‘Jinjing’ (0.0.2001 d-1 and 26.4 eggs) rice plant. Additionally, the net host feeding rate (qx) of E. sophia feeding on A. indicus in ‘Changyou’ (36.6 rice whitefly) treatment was significantly greater than that (23.7) in ‘Jinjing’ treatment. In conclusion, between two rice cultivars that were tested in this study, ‘Changyou’ rice plant could serve as a suitable banker plant for rearing E. sophia in biological control programs. The established banker plant system might provide growers with a new option for long-term control of B. tabaci in vegetable production. <![CDATA[Calcium chloride priming increases chilling tolerance in <em>Salvia miltiorrhiza</em> Bunge]]> ABSTRACT Chilling stress inhibits germination and early seedling growth of Salvia miltiorrhiza Bunge. The present study was carried out to investigate the effects of osmopriming with CaCl2 on the germination and early seedling growth of S. miltiorrhiza under chilling stress (10 ℃). Seeds were soaked in different concentrations of CaCl2 solutions (0, 50, 100, and 150 mM) at 20 ℃ for 24 h in darkness, rinsed, and air-dried. The effects of seed priming were evaluated on germination and survival during subsequent exposure to chilling stress (10 ℃) for 14 d. An unprimed control treatment was sown under optimal temperatures (25 ℃). Results indicated that germination percentage, germination potential, and seedling vigor index of unprimed seeds decreased from 69.2%, 12.4, and 0.092 to 28%, 3.6, and 0.022, respectively, when subjected to chilling stress. Higher malondialdehyde (MDA) content and lower chlorophyll contents (including total chlorophyll, chlorophyll a, and chlorophyll b) were detected in S. miltiorrhiza seedlings. Osmopriming with 100 and 150 mM CaCl2 effectively lessened the negative effects of chilling stress. Germination percentage, germination potential, and seedling vigor index of primed seeds reached 42% and 48%, 6.36 and 8.78, and 0.037 and 0.047, respectively. Meanwhile, CaCl2 priming significantly triggered superoxide dismutase, peroxidase, and catalase antioxidant enzyme activity, enhanced the accumulation of osmoregulation substances (soluble protein, accumulation sugars, and proline), increased the photosynthetic pigment content (total chlorophyll, chlorophyll a, chlorophyll b, and carotenoids), and decreased the MDA content. The most effective concentration of CaCl2 priming was 150 mM. <![CDATA[Segregation analysis for bacterial leaf blight disease resistance genes in rice ‘MR219’ using SSR marker]]> ABSTRACT Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae is one of the major hindrances in rice (Oryza sativa L.) production across the world including Malaysia. Therefore, the development of disease-resistant varieties remains a very economical and effective method of controlling BLB in rice. Based on this background, this study was conducted to analyze segregation pattern of simple-sequence repeat (SSR) markers associated with BLB resistance genes in an F2 bulk population derived from a resistant variety (IRBB60) and a susceptible variety (MR219). Out of 129 simple sequence repeat (SSR) markers screened, 18 distinct polymorphism markers including R-gene based markers were used to screen 345 F2 progenies for resistance to BLB. Among the polymorphic markers, the chi-square analyses showed that 15 SSR markers (i.e. RM13 (xa5), RM21 (Xa21), RM122 (xa5), RM153 (xa5), RM164 (Xa13), RM206 (Xa10), RM5509, RM20B, RM25, RM163, RM169, RM218, RM267, RM276, and RM334) had a segregation ratio of 1:2:1 for a single gene model (df = 2.0, p ≤ 0.05). For phenotypic ratio, the F2 population segregated in ratio 3:1 (R:S) for resistant and susceptible plants, respectively. This indicated that resistance to BLB caused by pathotype X. oryzae pv. oryzae (Xoo) in the ‘MR219’ × ‘IRBB60’ F2 population is controlled by single dominant genes. The result presented in this study will help breeders to further breeding research in rice by enabling selection based on the genotype rather than on the phenotype. Similarly, the markers reported in this study will serve as a valuable tool for marker-aided selection for BLB resistance gene. <![CDATA[Effect of a homofermentative lactic acid bacteria additive on the quality of sugar-beet pulp silage and animal response of dairy cows with restricted access to pasture]]> ABSTRACT Sugar-beet (Beta vulgaris L. subsp. vulgaris) pulp is a valuable by-product from the manufacture of beet sugar fresh which is normally preserved in the form of silage. The aim of the present research was to evaluate the effect of adding a homofermentative lactic acid bacteria silage additive during the ensiling period on fermentation and quality of sugar-beet (SB) pulp silage and the animal performance of dairy cows given restricted daily access to pasture. Twelve Holstein × Friesian crossbred cows were assigned to two groups according to milk yield, body weight, days in milk, parity and body condition score. Groups were randomly allocated to two treatments: silage of SB pulp without additive (control diet, SB) and silage of SB pulp with additive (SB+additive). The experiment was carried out in two periods of 28 d each. Once finished each period, cows were crossed for treatments. Chemical composition of SB silage was modified by the additive: Neutral detergent fiber (41.8% vs. 45.7% DM) and metabolizable energy (2.54 vs. 2.55 Mcal kg-1 DM) were greater and butyrate lower (0.34 vs. 4.10 mmol L-1) for SB+additive compared with SB. However, milk production (24.6 and 25.2 kg d-1) and composition were not affected (P &gt; 0.05) by treatments. Similarly, rumen volatile fatty acids were similar between treatments. In conclusion, the use of homofermentative lactic acid additive on SB silage modified the chemical composition of silage and reduced the pasture intake, however, no changes in milk production and composition were detected. <![CDATA[Physiological and biochemical analyses of novel drought-tolerant maize lines reveal osmoprotectant accumulation at silking stage]]> ABSTRACT Drought is one of the most limiting factors in agricultural production worldwide. The aim of this work was to evaluate the per se response to drought stress of three maize (Zea mays L.) semi-inbred lines (CHIH, COAH, and ARZM) during the anthesis and grain filling stages. These semi-inbred lines (BC1S1) are S1 offspring of crosses between drought-tolerant maize and a high-yield line bred by the Centro Internacional de Mejoramiento de Maíz y Trigo (CIMMYT). Materials were evaluated during a 15-d controlled drought and post-drought irrigation reestablishment period. The photosynthetic rate decreased by 50% in CHIH during drought and it recovered after stress was removed. Proline levels increased 2.3 times in COAH during stress and nonsignificant increases were observed in ARZM or CHIH. However, glycine betaine accumulated at 1061-1133 ng mg-1 fresh weight (FW) before stress, but decreased to 879-1000 ng mg-1 FW during drought stress. The trehalose concentration increased 1.8 times in ARZM (5.60 ng mg-1 FW) under drought stress and remained at similar levels in CHIH (6.48 ng mg-1 FW) and COAH (8.63 ng mg-1 FW) before and during drought stress. In contrast, trehalose-6-phosphate decreased 33% to 38% under drought stress in all three BC1S1 entries and recovered its initial levels after irrigation. Grain biomass loss under drought stress was 54% for ARZM, 48.2% for COAH, and only 26.5% for CHIH. These results showed that CHIH, COAH, and ARZM are drought-tolerant and suggest that osmoprotectant accumulation might play a key role in their physiological performance and grain biomass trait. <![CDATA[Reproductive phenology of the arborescent cactus <em>Eulychnia acida</em> Phil. under three agroecological conditions in the Coquimbo Region, Chile]]> ABSTRACT Eulychnia acida Phil. is an arborescent cactus species endemic to Chile, and widespread in the Coquimbo Region, Chile. Wild populations are found on north facing slopes and vary morphologically in fruit shape and color. We conducted a study on reproductive phenology at three locations in the region: Quebrada Honda in the coastal area, Gualliguaica in the Elqui Valley, and La Coipa in the Limarí Valley. A total of 120 stems from 30 selected plants of wild populations were monitored weekly and the phenological stages were evaluated over a season. Through multivariate analysis was determined if climatic factors affected the number of individual and/or reproductive organs observed. The presence of reproductive phenophases is asynchronous, beginning in late autumn with the appearance of flower buds, which bloom mainly in spring and set at the end of the season. Flowering has a unimodal pattern. The variable fruits by stems is strongly correlated (p &lt; 0.05) with the relative humidity (negative) and the degree days (positive). Locations show differences in the duration of the phenological events, which appear to be related to plant size and abundance of reproductive structures. Flowering synchrony among individuals is low when compared with other cacti; this means less overlap of the flowering periods among individuals, which could be a strategy to ensure insect visitation and pollination. Longer term studies are necessary to establish how weather conditions, rainfall and temperature influence the generation of flower buds, since production is affected in periods of drought. <![CDATA[Response of direct seeded rice to increasing rates of nitrogen, phosphorus, and potassium in two paddy rice soils]]> ABSTRACT The rice (Oryza sativa L.) crop is very important worldwide for its contribution to human nutrition. Rice grain yield depends on several agronomic management factors that must also be adjusted to the cropping system such as permanent inundation (anaerobic conditions) or direct seeding (aerobic and anaerobic conditions) mainly in response to the application of nutrients such as N. In Chile, the cropping system with direct seeding has limited agronomic and scientific development. The objective was to determine the effect of increasing N (0, 40, 80, 120, and 160 kg ha-1), P (0, 30, 60, and 120 kg P2O5 ha-1), and K (0, 30, 60, and 120 kg K2O ha-1) rates on grain yield and N agronomic efficiency (NAE) (kg grain produced per kg N applied) in two paddy rice soils for two consecutive seasons. Grain yield had a positive response to increasing N rates in the two evaluated soils (grain yield increased from 6.7 to 8.9 Mg ha-1 in the Vertisol and from 7.4 to 11.0 Mg ha-1 in the Alfisol) and a low response to P rates in the Vertisol. The Alfisol showed no response to increasing P rates, and both soils had no response to K application. The N rates that obtained the highest rice grain yield were 120 and 160 kg ha-1 for Alfisol and Vertisol, respectively. The P rate that obtained the highest rice yield in the Vertisol was 30 kg ha-1 P2O5. In addition, NAE values associated to those N rates were 74 and 61, respectively. In conclusion, direct seeding in rice cropping had a response to high rates of applied N, low response to P, and no response to K. <![CDATA[Strategies for production, characterization and application of protein-based biostimulants in agriculture: A review]]> ABSTRACT Nowadays agriculture is facing constantly challenges to produce more and better food for a growing population under a changing climate scenery. To afford this demand, agricultural practices must innovate in new methods for crop production, nutrition management, and plant health. In addition, the development of new compounds or biological agents able to improve plant yield (regulating plant physiology, metabolism, crop performance), and agro-product quality, are also necessary. In the last decade, agents with these characteristics have been proposed for a sustainable agriculture. These agents, defined as biostimulants, have showed to improve plant nutrition, quality, yield and abiotic tolerance in different agricultural crops. In particular, the use of protein hydrolysates as biostimulants offers promising results to reduce the use of agrochemicals and improve productivity parameters in a variety of cultivars, in agree with the modern agricultural production challenges. The present review is focused in the use of protein hydrolysates as plant biostimulants, describing typical and potential agro industrial by-products as sources substrates for protein-based biostimulants formulation, and commercial or experimental proteolytic enzymes used for hydrolysate production. Moreover, critical aspects during protein biostimulants manufacture, functional profiling and its applications are discussed. Finally, recent advances for the evaluation of protein hydrolysates on plant physiology and metabolism under experimental and commercial scale are also documented. Concluding in the necessity to conduct structural studies, in order to identify and produce bioactive peptides with agricultural applications. <![CDATA[Quinoa (<em>Chenopodium quinoa</em> Willd.) and its relationship with agroclimatic characteristics: A Colombian perspective]]> ABSTRACT A diversity of crops of agri-food interest are produced in the Colombian highlands, including quinoa (Chenopodium quinoa Willd.), an annual herbaceous plant with white, yellow, red or black seeds, containing between 12% and 21% protein. It is an important source of lysine and methionine. Historically, this plant has played a fundamental role in human nutrition, due to its multiple benefits for disease prevention and treatment. Salinity is the abiotic stress most studied in quinoa; however, the development of this crop on all continents has led to the study of other factors, such as cold and heat, resulted by the increase in weather patterns. This review describes the progress in the temperature effects, photoperiod, atmospheric CO2 concentration and agronomic aspects on the growth and development of quinoa, as well as compositional characteristics of the seeds and their prospective related to the agroclimatic diversity of Colombia. <![CDATA[Temperate <em>japonica</em> rice (<em>Oryza sativa</em> L.) breeding: History, present and future challenges]]> ABSTRACT Rice is a staple food mainly cultivated in the tropics, however ~20% of global production originates from temperate regions. The japonica rice (tropical and temperate), is the unique rice type adapted to the temperate conditions through evolution. Nevertheless, at present, there is limited information regarding to breeding of temperate japonica rice because most of the global research and production has been focused on indica rice, which is the most cultivated type (~80% of global production). However, there are many countries where rice is grown under temperate conditions, such as Japan, Russia, Australia, USA, Chile, South Korea, Uzbekistan, Hungary, among others. More information and collaboration between these countries are required to develop better japonica rice cultivars to meet the current agricultural challenges. Here, the japonica rice breeding history, current status and future challenges are compiled to be available to japonica rice breeders, researchers and growers.