Scielo RSS <![CDATA[Chilean journal of agricultural research]]> vol. 77 num. 2 lang. es <![CDATA[SciELO Logo]]> <![CDATA[Impacts of prolonged high temperature on heavy-panicle rice varieties in the field]]> ABSTRACT Although enhancement of sink capacity with heavy-panicle is an important approach to the improvement of yield potential in super rice (Oryza sativa L.) breeding, environmental fluctuations may greatly affect fertilization and grain filling of heavy-panicle rice. Here, we investigated the response of heavy-panicle rice varieties to high temperature at flowering and grain filling stages under field conditions, with a focus on spikelets positions on the panicle. Six varieties each with four staggered sowings were grown under various climatic conditions, and thus their flowering stages and grain filling stages experienced high or normal temperature weather scenarios. When rice varieties grown under high temperature, spikelet fertilities increased in all tested varieties. Grain weights of varieties CW2221, K106 and R-2 under high temperature stress showed an average of 10.81% increase compared with normal temperature, whereas 'C418', 'J1307' and 'Xianghui210' decreased by 15.21%. Head milled rice rates significantly decreased, but chalky grain rates and chalkiness degrees significantly increased under high temperature. We further demonstrated that the effects of high temperature on spikelet fertility, grain weight and grain qualities were correlated with grain positions. These results indicate that understanding effects of high temperature on grain weight and quality in heavy-panicle rice varieties is a key factor for super rice breeding in the future. <![CDATA[In vivo evaluation of vigor in naked and husked oat cultivars under drought stress conditions]]> ABSTRACT Considering the prevention of crop production, aimed at adaptation to climate changes, searching for or developing genotypes resistant to water deficit is a challenge for modern agriculture and a strategic goal of plant breeding. The objective of the study was to determine the effect of drought stress on the vigor of naked and husked oat (Avena sativa L.) cultivars. The studies concerned eight naked oat cultivars and two husked oat cultivars characterized by high germination capacity (above 95%). Seeds of naked oat cultivars showed susceptibility to varied thermal conditions during drought simulated by the use of polyethylene glycol (PEG) at a concentration of -1.5 MPa. An increase in temperature from 10 to 20 °C resulted in an average 37% increase in the number of normally germinating seeds, and in a more than 40% increase in germination rate, as well as in a 25% decrease in average germination time. A distinct increase in osmotic potential from -1 to -2 MPa during drought stress induction resulted in 15% decrease in vigor of husked cultivars measured by the percentage of normally developed seedlings. The vigor of oat cultivars, evaluated on the basis of electrical conductivity of exudates, was modified by genotypic variability. In naked cultivars, on average, 60% lower values were noted. The coefficients of correlation between electrical conductivity of exudates and germination capacity (r = -0.784**) or frequency of normally developed seedlings (r = -0.919**) confirm the highly significant interrelationship between the methods used for the evaluation of oat seeds under drought conditions. <![CDATA[Seed priming mitigates the effects of saline-alkali stress in soybean seedlings]]> ABSTRACT Soda saline-alkali soil has double adverse effects on growth, morphogenesis and yield of the crops by creating a salinity stress and a high pH value in the rhizosphere surroundings of the plant. Seed priming can be an effective approach to enhance stress adaptation in seedlings growing in salinity stressed conditions. The present study examined the role of hydropriming and comprehensive seed priming with ZnSO4, CaCl2, betaine hydrochloride and GA3 to enhance the soda saline-alkali tolerance in soybeans (Glycine max [L.] Merr.) seedlings. An unprimed control treatment was also maintained for comparison. The results show that two seed priming treatments can effectively mitigate the negative effects of soda saline-alkali stress. Nevertheless, compared with hydropriming, soybean seedlings from the comprehensive seed priming treatment had better growth performance through accumulation of soluble sugar and free proline contents, enhancing the activities of superoxide dismutase (SOD) and catalase (CAT), decreasing the malondialdehyde (MDA) content formed from lipid peroxidation, increasing the photosynthetic pigment contents, maintaining a better membrane integrity of the chloroplasts and mitochondria, and generating more starch grains in the chloroplasts of spongy mesophyll cells under soda saline-alkali stress. In conclusion, our results suggest that soybean seedlings from comprehensive seed priming exhibited a higher tolerance to soda saline-alkali stress than the unprimed control treatment. <![CDATA[Effects of exogenous Ca <strong><sup>2+</sup></strong> on photosynthetic characteristics and fruit quality of pepper under waterlogging stress]]> ABSTRACT Pepper is one of the most important vegetable crops in China. Consumers in China are increasingly demanding high quality pepper (Capsicum annuum L.) fruit. As in flood crops, natural disasters, such as flooding, might not only affect pepper yield, but also significantly impact fruit quality. Thus, it is necessary to study the change in fruit quality under waterlogging stress and seek an improved method. Pepper '5901' was the experimental material; we investigated the effects of spraying exogenous Ca2+ on the photosynthetic characteristics and quality of pepper plants under waterlogging stress. We found that waterlogging significantly reduced the photosynthesis rate (PN), stomatal conductance (g s), fruit length, individual fruit diameter, individual fruit fresh weight, and soluble protein, soluble sugar, free amino acid, P, Fe, vitamin C (Vc), and vitamin E (Ve) contents. It significantly decreased the expression levels of 1-aminocyclopropane-1-carboxylate oxidase 1 (ACO-1), catalase (CAT-2), and pyruvate kinase (PK) genes, and it significantly increased intracellular CO2 concentration, capsaicin content, and the expression level of the alcohol dehydrogenase-1 (ADH-1) gene. The parenchymatous cells in the root system and stem were loosely arranged, the degree of lignification was deepened, leaves became thinner, and palisade tissue thickness was reduced. Exogenous Ca2+ significantly enhanced capsaicin content, alleviated the extent of the reduction in the abovementioned physiological parameters, and maintained epithelial cell shape in the mesophyll layer. It maintained the intactness of the cell wall in the root system, cell membrane, and pulp cavity; it also reduced cell injury and stimulated the expression levels of ACO-1, ADH-1, CAT-2, and PK genes. Compared to the normal control, expression levels of these genes increased by 52.03%, 99.48%, 40.78%, and 125.67%, respectively. The present study indicates that spraying exogenous Ca2+ can effectively alleviate injury to pepper plants caused by waterlogging stress and improve the quality of pepper fruit. <![CDATA[Content of biogenic elements and fatty acid composition of fenugreek seeds cultivated under different conditions]]> ABSTRACT Fenugreek (Trigonella foenum-graecum L.) is a medicinal plant that has been recognized for its numerous health benefits throughout the centuries. The species is a rich source of biogenic elements, and it has a favorable composition of fatty acids. This study evaluated the effect of agrotechnological factors on the chemical composition of fenugreek seeds. The experiments conducted in north-eastern Poland had a fractional factorial design with 54 plots. A total of five agrotechnological factors were tested: seed inoculation with Rhizobium meliloti, sowing date, row spacing, weed control, and protection against fungal pathogens. The chemical composition of fenugreek seeds was influenced mainly by sowing date, row spacing and plant protection. Fenugreek seeds grown in north-eastern Poland contained 26.0% protein and 4.8% oil. Delayed sowing increased N content (9.2%) and decreased the content of P (8.8%), K (5.1%) and Mg (2.8%). An increase in row spacing from 15 cm to 45 cm promoted the accumulation of Fe (31%). Agrotechnological factors induced the greatest variations in the composition of saturated fatty acids (mean difference of up to 14.5%), followed by monounsaturated (up to 9.5%) and polyunsaturated fatty acids (up to 4.5%). Total unsaturated fatty acids accounted for 80% of the fatty acid profile, with a predominance of essential fatty acids in oil: linoleic acid (37.9%) and α-linolenic (28.2%) acid. Sowing date and weed control were responsible for up to 3.1%-4.5% of differences in concentrations of essential fatty acids between treatments. <![CDATA[Effect of herbicide resistance endowing three ACCase mutations on seed germination and viability in American slough grass ( <strong><em>Beckmannia syzigachne</em></strong> Steud. Fernald)]]> ABSTRACT American slough grass (Beckmannia syzigachne Steud. Fernald) is an annual grass which has developed resistance to acetyl-coenzyme A carboxylase (ACCase) inhibitors, and the major mechanism of resistance is target site based. Target site resistance-conferring mutations may confer pleiotropic effects on a weed's life cycle. The effects of three American slough grass spontaneous ACCase mutations (Ile1781Leu, Trp2027Cys and Ile2041Asn) on seed germination and viability under different experimental factors had been investigated in this paper. Seeds containing homozygous 1781Leu/Leu ACCase showed a greater germination under salt and osmotic stress, but no fitness variation in optimal experimental conditions. Homozygous 2027Cys/Cys ACCase caused nonsignificant effects on seed germination in optimal experimental conditions, but caused a greater germination after 16 d incubation at 40 °C and 100% RH. Homozygous 2041Asn/Asn ACCase tended to cause nonsignificant effects on seed germination or seed viability. Finally, an obvious population effects on seed germination was observed between six subpopulations, which indicated that fitness assessing should be measured in resistant and susceptible individuals that share a similar genetic background. These findings suggest that the absence of fitness penalty associated with these three homozygous mutant ACCase alleles may be a contributing factor for resistance spread. <![CDATA[Resistance level and target-site mechanism to fenoxaprop- <strong><em>p</em></strong> -ethyl in <strong><em>Beckmannia syzigachne</em></strong> (Steud.) Fernald populations from China]]> ABSTRACT Beckmannia syzigachne (Steud.) Fernald is one of the main grass weeds severely harming wheat (Triticum aestivum L.) production in rice-wheat areas in China. Fenoxaprop-p-ethyl is the main herbicide used to selectively control grass weed in China. Beckmannia syzigachne has evolved resistance to fenoxaprop-p-ethyl due to continuous application. To investigate fenoxaprop-p-ethyl resistant level and mechanism in B. syzigachne in a portion of the rice-wheat area in China, samples from 31 field populations were collected and treated with fenoxaprop-p-ethyl. The results show that 10 of the 31 tested field populations evolved a high level of resistance to fenoxaprop-p-ethyl. A portion of the acetyl-coenzyme A carboxylase (ACCase) gene was amplified, sequenced and aligned. The known Ile-1781-Leu, Ile-1781-Val, Ile-2041-Asn, Asp-2078-Gly and Gly-2096-Ala mutations were identified in five resistant populations. None of the known resistant substitutions was identified in the other five resistant populations, which means the resistance to fenoxaprop-p-ethyl in these populations is likely endowed by non-target-site resistance mechanism. <![CDATA[Chemical composition and antioxidant activity of leaves of mycorrhized sea-buckthorn ( <strong><em>Hippophae rhamnoides</em></strong> L.)]]> ABSTRACT The leaves of sea-buckthorn (Hippophae rhamnoides L.) can be a rich source of nutrients and biologically active substances. Their levels depend on growing conditions, agricultural technology and climate. The studies however, mainly focus on nutritious value of fruit and seeds and there is shortage of the information regarding to buckthorn leaves. The aim of the experiment was to determine the effect of symbiotic mycorrhizal fungi on the chemical composition and antioxidant activity of sea-buckthorn leaves. The study was conducted in 2014 and 2015 at the Experimental Station in Lipnik, Poland. Mycorrhization improved the nutritional value of leaves of sea-buckthorn by increasing levels of total protein (3%), N free extract (1%), Ca (9%), Na (16%), Fe (18%), Cr (34%), and partially elevating antioxidant activity by increasing the concentration of polyphenols (7%). Leaves of 'Habego' had a higher nutritional value, containing more total protein (4%), crude fat (7%), crude fiber (30%), and all fractions of dietary fiber. 'Hergo' had more beneficial levels of minerals (P-27%, K-67%, Mg-4%, Na-30%, Zn-8%, and Cr-21%), polyphenols (51%), total flavonoids (35%), carotenoids (10%), and L-ascorbic acid (8%), as well as higher antioxidant activity (40%). The results of our study partly confirmed the earlier scientific reports on the impact of mycorrhiza on the chemical composition of plants. However, it is not possible to compare our results with data on berry plants, including sea-buckthorn, due to the lack of information in the literature. <![CDATA[Application of silicon fertilizer affects nutritional quality of rice]]> ABSTRACT To date, information regarding the effects of Si on rice (Oryza sativa L.) nutritional quality is rarely reported. The current study was conducted to evaluate how Si fertilizer impacts the mineral element, protein and amino acid concentrations in brown and milled rice. The experiment was a randomized complete split-plot design, with Si treatments as main plot and two cultivars as subplot. Compared with the control, application of Si fertilizer significantly enhanced the Zn, Ca and Mg concentrations in brown and milled rice but had nonsignificant effects on the Fe, Mn and Cu concentrations. Moreover, application of Si fertilizer resulted in significant increases in the concentrations of protein and most of the amino acids in brown and milled rice. However, the Gly, His, Val, Met and Lys concentrations were unaffected by the application of Si. The responses of the Cys and Phe concentrations to Si fertilizer application were cultivar-dependent. Applying Si significantly increased Zn, Ca, Mg and protein concentrations by 21.77%, 25.77%, 7.25% and 6.19% in milled rice and by 25.18%, 39.81%, 9.24% and 5.52% in brown rice. These results indicate that Si fertilizer could improve rice nutritional quality by increasing concentrations of mineral elements, protein and some amino acids in brown and milled rice. <![CDATA[Effect of water application on wine quality and yield in ‘Carménère’ under the presence of a shallow water table in Central Chile]]> ABSTRACT Chile is the world’s leading producer of ‘Carménère’ (Vitis vinifera L.), which in turn is an important variety in Chile, where vineyards are typically grown under irrigated conditions and a large percentage are located in valleys with similar water table levels to those of the study area. Different irrigation management strategies have been used to improve wine quality, such as water stress and deficit irrigations, but the presence of a water table has not been considered in extant literature. This study analyzes the effects of the irrigation regime on grape yield and wine quality when a shallow water table is located between 1.5 to 2.2 m depth during the irrigation season. Five applied water treatments: 0%, 20%, 40%, 75%, and 100% of estimated vineyard evapotranspiration (ETc) were applied in an own-rooted ‘Carménère’ vineyard located in the Peumo Valley (Chile) during three consecutive seasons (2004-2005 to 2006-2007). Applying 1400 to 9400 m3 ha-1 per season (100% ETc) had no substantial effect on the measured quality parameters, although grape production in the treatment without irrigation (0% ETc) was significantly reduced. Applying water at 20% to 40% ETc produced high yield (13 to 16 t ha-1), double the historical mean production, and high quality wine with the presence of a water table close to the bottom of the root zone. <![CDATA[<strong><em>Tamarixia radiata</em></strong> (Waterston) and <strong><em>Cheilomenes sexmaculata</em></strong> (Fabricius) as biological control agents of <strong><em>Diaphorina citri</em></strong> Kuwayama in Ecuador]]> ABSTRACT Diaphorina citri Kuwayama (Hemiptera: Liviidae) is the main vector of the bacteria that causes Huanglongbing (HLB), the most destructive disease of Citrus. The presence of D. citri was reported in Ecuador in 2013 on branches of citrus, Citrus spp., and orange jessamine, Murraya paniculata (L.) Jack (Rutaceae), but HLB has not been detected so far in this country. This paper reports for the first time the presence of two important natural enemies of D. citri in Ecuador, i.e., its main parasitoid Tamarixia radiata (Waterston, 1922) (Hymenoptera: Eulophidae) and the adventitious ladybird beetle Cheilomenes sexmaculata (Fabricius, 1781) (Coleoptera: Coccinellidae) attacking psyllid nymphs on M. paniculata, in Guayaquil, Guayas province, Ecuador. A short diagnosis of the two natural enemies and their distribution in the New World is presented based on published literature.