Luis Antonio de Avila

Arroz: composição e características nutricionais

Due to the importance of rice in the diet, its composition and nutritional characteristics are related to humans health. This cereal is a source of energy, due to its high starch content, also providing proteins, lipids, vitamins and minerals. The present review aimed at examining rice composition, its nutritional characteristics, and the improvement of these characteristics through genetic modification. Variations in rice composition are observed due to genotype and processing, affecting nutritional characteristics. Rice has a positive effect on the prevention of several chronic diseases due to different constituents, and its composition has been improved through genetic modifications, resulting in grains with more interesting nutritional characteristics.

Rice herbicide monitoring in two Brazilian rivers during the rice growing season

Irrigated rice production can involve environmental contamination with pesticides due to the proximity of the fields to rivers and to management problems. During three years (2000 to 2003) the rice herbicides clomazone, propanil and quinclorac were quantified in water during the rice growing season, in the Vacacai and Vacacai-Mirim Rivers, located in Rio Grande do Sul (RS) State, Brazil. Water samples were taken at several locations in each river, selected by their importance in terms of rice drainage area. The samples were analyzed by HPLC-UV. At least one herbicide was detected in 41% of the samples from the Vacacai River and 33% from the Vacacai-Mirim River. The most frequent herbicide in both rivers and in each year was clomazone. The amount of herbicides in the river water was dependent on the rainfall regime. River water contamination by rice herbicides is probably caused by the rice water management used in the fields. The maintenance of flooded areas makes herbicides prone to contaminate the environment. To reduce the environmental contamination risk it is necessary to adopt measures to avoid overflow of flooded rice fields, keeping paddy water in the field for time enough to reduce the herbicide concentration before its release and enhancing the quality of the levees to reduce the probability of paddy rice overflow.

Toxicological responses of Cyprinus carpio after exposure to a commercial herbicide containing imazethapyr and imazapic

Cyprinus carpio was exposed to imazethapyr and imazapic at laboratory and at field conditions. The laboratory experiment was carried out for 7 days and at rice field for 7, 30 and 90 days. Oxidative stress parameters and antioxidant profile were studied as well as metabolic parameters. After 7 days, brain AChE activity increases in laboratory and field, but in muscle, reduction was observed only in laboratory. At the same period, brain and muscle TBARS and liver CAT increase in the laboratory. Metabolic parameters showed changes in both conditions and exposure periods. After 30 days in rice field, brain AChE activity decreases and in muscle it was enhanced. After 90 days in field, only muscle AChE activity was reduced. The disorders in oxidative stress parameters and metabolism remained, indicating mainly a protein catabolism. This study pointed out short- and long-term effects of rice herbicides at environmentally relevant concentrations on toxicological parameters in tissues of C. carpio.

Arroz tolerante a imidazolinonas: controle do arroz-vermelho, fluxo gênico e efeito residual do herbicida em culturas sucessoras não-tolerantes

After several decades searching for tools to control red rice, imidazolinone tolerant rice was developed to selectively control red rice. To better understand this technology An experiment was conducted in 2004/2005, in Santa Maria, Rio Grande do Sul, Brazil to evaluate: 1) red rice control by imidazolinone herbicides in Clearfield™ rice; 2) evaluate the imidazolinone herbicide carryover effect on rygrass and non-tolerant rice (IRGA 417) and 3) evaluate the outcrossing rates between Clearfield rice and red rice. The experimental design was a randomized block design, with 3 treatments and 12 replications. To determine the outcrossing rates between Clearfield rice and red rice, virtually all the red rice panicle was collected and analyzed in the area. The carryover effect was tested using ryegrass and a non-tolerant rice cultivar (IRGA 417). The herbicides tested controlled red rice. Although injury to Clearfield rice was observed, the herbicide did not affect yield. Herbicide carry-over to non-tolerant rice was observed, reducing plant stand on rice seeded 361 days after herbicide application. Natural out-crossing occurred between Clearfield rice and red rice, at rates of 0.065%.

Commercial formulation containing quinclorac and metsulfuron-methyl herbicides inhibit acetylcholinesterase and induce biochemical alterations in tissues of Leporinus obtusidens.

The effects of commercial formulation containing quinclorac and metsulfuron-methyl herbicides on acetylcholinesterase (AChE), antioxidant profile and metabolic parameters in teleost fish (Leporinus obtusidens) were studied. The fish were exposed during 90 days to commercial formulation containing quinclorac (204 μg L(-1)) and metsulfuron-methyl (5.8 μg L(-1)) herbicides in rice field irrigated condition. AChE activity in the brain and muscle decreased after exposure to both commercial formulations. The same response was observed for the TBARS levels in brain, liver and muscle. Liver catalase activity reduced after exposure to commercial formulation containing quinclorac and metsulfuron-methyl herbicides. Metabolic parameters in the liver and white muscle (glycogen, lactate, protein and glucose) were determined. These parameters showed different changes after exposure to both commercial formulations. This study pointed out long-term effects of exposure to commercial formulations containing herbicides used in rice on metabolic and enzymatic parameters in tissues of L. obtusidens.

Resíduos de agrotóxicos na água de rios da Depressão Central do Estado do Rio Grande do Sul, Brasil

The rice-growing activity is conducted out with intensive use of agrochemicals, which, depending on the management and rainfall can reach rivers. The study aimed to determine the residues of herbicides clomazone, quinclorac, propanil, bentazone, 2,4-D and imazethapyr and insecticides carbofuran and fipronil in the Vacacai and Vacacai-Mirim rivers, located in the Central Depression of Rio Grande do Sul, in the crop of 2003/04 untill 2007/08. Samples were collected from November to February (rice growing season). Analysis of herbicides and carbofuran were performed by HPLC-DAD and fipronil by GC-ECD. During 2003/04, in both rivers, the herbicide clomazone, 2,4-D and propanil were the most frequent in water samples. In 2004/05, the quinclorac was detected in many samples and in 2005/06 and 2006/07 seasons fipronil was the most common pesticide in the samples in Vacacai and Vacacai-Mirim rivers. In the 2007/08 crop, there were less residues of pesticides in Vacacai and Vacacai-Mirim rivers. There is presence of pesticides used in rice farming in the Vacacai and Vacacai-Mirim rivers during the rice crop, especially among those analyzed, the herbicides clomazone and quinclorac and the insecticide fipronil.

Persistência dos herbicidas imazethapyr e clomazone em lâmina de água do arroz irrigado

Herbicides can persist in soil and be transported from the application site to the environment. An experiment was conducted to estimate imazethapyr and clomazone persistence in rice paddy water. The treatments included application of the formulated herbicide mixture (imazethapyr 75xa0gxa0a.i.xa0L-1 + imazapic 25xa0gxa0a.i.xa0L-1) and clomazone (500xa0gxa0a.i.xa0L-1). Imazethapyr and clomazone concentrations in water were evaluated from the 1st to the 62nd day after flooding. The period of herbicide detection in water was longer for imazethapyr. Imazethapyr half-life in paddy water varied between 1.6 and 6.2 days and clomazone half-life was 5xa0days.

Dinâmica do banco de sementes de arroz-vermelho afetado pelo pisoteio bovino e tempo de pousio da área

An experiment was conducted in a commercial lowland rice-producing area, adopting the minimum tillage system of rice production, followed by two years of fallow, managed, during this time, by cattle production, in order to evaluate the influence on red rice seed bank dynamics. The experimental design was randomized complete blocks, with three replications, in a bifactorial design. Factor A consisted of rice post-harvest management of the area: [T1] - fallow with cattle trampling and [T2] - fallow without cattle trampling. Factor B was the sampling time: [A1] - 1999, [A2] 2000 and [A3] - 2001. The red rice seed bank estimation was made using 12 soil samples by plot, in April 1999, April 2000 and April 2001, using a 10 cm diameter cylinder soil sampler. The sampling depths were 0-1 cm, 1-5 cm, 5-10 cm and 10-15 cm. After being extracted from the soil, the grains of red rice were counted and submitted to a tetrazolium test to estimate seed viability. Cattle trampling did not affect seed distribution in the soil profile and the dynamics of the red rice seed bank. Fallow duration affected the seed bank of red rice; the regression equation fit that best explains the correlation between number of viable seeds and fallow duration in months was the exponential equation: y = 1382.15 exp (-0.1988*x) p<0.05, showing a decrease in the number of seeds within 12 months, from 1,448 to 151 (90% reduction), and 38 (98% reduction) viable seeds per square meter in 24 months of fallow. Regarding the red rice seed burial depths, seed bank reduction was greater on the soil surface in 2000, with no difference between the depths in 2001. The seeds located on the soil surface lost their viability rapidly, with an average of 99% within one year fallow with or without cattle trampling. It can be concluded that cattle trampling does not affect red rice seed bank dynamics in fallow areas. Soil fallow, with or without cattle trampling, reduces in the red rice seed bank.

Destino ambiental dos herbicidas do grupo das imidazolinonas: revisão

The herbicides of the imidazolinone group control a wide range of weed species. They are absorbed by weed roots and leaves and transported through the phloem and xylem, accumulating in the plant growing points. They inhibit the enzyme acetolactate synthase (ALS), which synthesizes the branched chain amino acids. When used in the field, a large portion of these herbicides reach the soil, where they can be absorbed by the roots of plants, sorbed into the soil colloids, or dissolved in soil solution, going through photolysis, hydrolysis, microbial degradation or leaching. The sorption of imidazolinone is faster and affects other processes. High contents of clay, organic matter and pH lower than 6.0 contribute to enhance the sorption and persistence of imidazolinones in soil. The most important way of dissipation is by microbial degradation, thus conditions favoring microbial development will also enhance imidazolinone degradation.

Controle de arroz-vermelho em dois genótipos de arroz (Oryza sativa) tolerantes a herbicidas do grupo das imidazolinonas

Red rice (Oryza spp.) is one of the main limiting factors to rice (O. sativa) yield. An experiment was carried out to evaluate red rice control and the behavior of two rice genotypes tolerant to the imidazolinone herbicides in response to imazethapyr (75 g L-1 ) + imazapic (25 g L1 ) application rates and timing. The experiment was conducted in Santa Maria-RS, Brazil in 2004/2005 and was arranged in a factorial scheme, in a randomized block design, with four replications. Factor A included the two rice genotypes tolerant to the imidazolinones, a cultivar (IRGA 422 CL) and a hybrid (Tuno CL); and factor D included the treatments for red rice control, which was a combination of rates and herbicide application timing. The hybrid was found to be more tolerant to the herbicide only than the cultivar. Application rates up to 200% on the hybrid genotype could be done without affecting rice yield. It is important to state that increasing the rate of herbicide application can create carryover problems to non-tolerant crops. Red rice control was total with split application of imazethapyr + imazapic in PRE and POST emergence with the total rate above 125%. The most efficient treatment was application of 75% in PRE followed by 50% in POST, which was the lowest rate promoting 100% control, with relatively low toxicity to the cultivar and without affecting rice yield.