Gustavo Mack Teló

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%.

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.

População de plantas, dose de nitrogênio e aplicação de fungicida na produção de arroz irrigado: I-características agronômicas

A field experiment was aimed at evaluating the effects of plant densities, nitrogen rates and chemical disease control on agronomic characteristics that affect grain yield of irrigated rice. The study was conducted during 2003/2004, in the Departamento de Fitotecnia of Universidade Federal de Santa Maria. The experiment was arranged in randomized blocks with sub-plots and four replicates, in Santa Maria-RS, Brazil and the treatments were: three plant densities (150, 260 and 380plants m-2), five nitrogen rates (0, 40, 80, 120 and 160kg ha-1) with and without chemical foliar disease control. The nitrogen was dressing was twice split at initial tillering and panicle differentiation. Grain yield increased in a quadratic fashion in response to nitrogen rates to up to 97kg ha-1. The use of fungicides to control foliar diseases resulted in higher grain yelds regardless of plant population or nitrogen fertilizer rates. Irrigated rice can compensate yield components between 150 and 380plants m-2. The most efficient rate of nitrogen was 97kg ha-1. Chemical foliar diseases control increases irrigated rice productivity even at low disease incidence.

Produção integrada de arroz irrigado e peixes

This work was developed aiming to determine the quantity of fish and the time of entry of fingerlings in areas that provide the best productivities in the combination of irrigate rice and fish. The experiments were carried out on growing seasons 2001/02 and 2002/03, in the experimental design of randomized complete block with three replications, in trifactorial scheme (year x quantity x time), with three quantities of fish: D0= without fingerlings, D1=3000 fingerlings ha-1 and D2=6000 fingerlings ha-1 and three times of entry of fish: E1= seeding, E2= 20 days after seeding and E3= after harvest. The species utilized were: common, grass, silver, big head carps and silver catfish, in rates of 60, 20, 5, 5 and 10%, respectively. Rice in pre-germinate system and IRGA 419 cultivar, was utilized with the quantity of 120kg ha-1 of seeds. The productivity of grains in this experiment was 6372kg ha-1, and it was not affected by the presence of fishes. The productivity of fishes was not influenced by the quantities neither by the times of entry of fingerlings in the area, with a production of 404kg ha-1 of fishes. It was possible to verify that the greatest taxes of survival occurred when the entry of fishes was after harvest.

INFLUÊNCIA DA APLICAÇÃO DE NITROGÊNIO E FUNGICIDA NO ESTÁDIO DE EMBORRACHAMENTO SOBRE O DESEMPENHO AGRONÔMICO DO ARROZ IRRIGADO ( 1 )

Factors limiting rice plant growing and development caused by nutritional deficiency, especially by lack of nitrogen and diseases, affect the photosynthetic capacity and rice yield. The objective of this experiment was to evaluate the effect of the nitrogen and fungicide application on booting stage in order to verify photosynthetic area and rice yield. This work was conducted in 2005/2006 in lowland area in Santa Maria, RS, Brazil. The treatments were nitrogen rates (50, 100, and 150 kg ha-1), composing the factor A, and management practices during the booting stage (supplementary application of 30 kg ha-1 nitrogen, fungicide application, and the combination of the previous treatments, besides check treatment), composing the factor D. The treatments were arranged in a randomized experimental block design, in a factorial scheme with four replications. The nitrogen rates promoted differentiated effects in the evaluated characteristics until booting stage (number of stem m-2, leaf area index and SPAD reading). However, there was not verified interaction among the treatments during rice grains filling. The management practices carried out on booting stage did not affect foliar area and senescence, yield and components of rice yield. The low occurrence of diseases, the efficiency of nitrogen utilization and the suitable climatic conditions for rice yield can explain the lack response to the management practices.

População de plantas, dose de nitrogênio e aplicação de fungicida na produção de arroz irrigado: II. Qualidade de grãos e sementes

This study was aimed at evaluating the effect of plant densities, nitrogen rates and foliar diseases control on the physical, physiological and sanitary qualities of rice seeds. The experiment was conducted during 2003/2004 growing seasons in Santa Maria-RS, Brazil. The treatments were: three plant densities (150, 260 and 380 plants m-2), five nitrogen rates (0, 40, 80, 120 and 160kg ha-1), and control or no control of foliage diseases. The nitrogen fertilizer was top-dressed, and split in two times. There was no triple interaction among the parameters evaluated. Increasing nitrogen rates resulted in higher seed protein content. The chemical control of diseases contributed for better physiological and sanitary qualities such as better germination and vigor and lower incidence of pathogens associated with seeds.

Cytogenotoxicity of rice crop water after application of the tricyclazole fungicide

Tricyclazole is currently one of the fungicides recommended for the treatment of diseases in irrigated rice. However, there is relatively little information on its cytotoxic and genotoxic potential. The objective of this study was to evaluate the cytotoxicity and genotoxicity of rice crop water after apllication of the tricyclazole fungicide through the Allium cepa L. test. The rice crop water samplings were collected before and 1, 15 and 30 days after application of the fungicide in rice plant shoots. The Allium cepa roots were placed in contact with the rice crop water to check for possible chromosomal abnormalities and mitotic index of the bioindicators meristematic cells. The data obtained by the Allium cepa test indicates that the application of the tricyclazole fungicide leads to an increase in the genotoxic activity in the rice crop water, through the appearance of chromosomal abnormalities, without, however, causing significant effects on the mitotic index. The major chromosomal alterations observed were anaphasic and telophasic bridges and laggard chromosomes.

Aplicação de fungicida em plantas de arroz irrigado e seu efeito na qualidade de sementes durante o armazenamento

The storage of irrigated rice seeds consists of the preservation of seed physiological quality for new crops and may involve fungicide applications to the plant canopy in order to maintain this. The objective of this study was to evaluate the effect of the fungicide mixture of propiconazole+trifloxystrobin applied to the plant canopy at different developmental stages of irrigated rice, on the physiological and sanitary quality of seeds produced and stored in two locations, for six months. The experimental design was randomized blocks with four replications in a factorial scheme (4x2x4), with the factors being: application of the fungicide mixture propiconale+trifloxystrobin on plant canopy at stages R2, R3, R2+R4 and plants with no fungicide applications during the growing cycle; two storage locations (cold and dry chamber and warehouse) and 0, 2, 4, and 6 months of storage. We conclude that the use of two applications of the fungicide mixture (propiconazole +trifloxystrobin) benefits germination and seed vigor, as well as reducing the incidence of fungi associated with seeds; the increase of storage time reduces seed vigor and germination, independent of the storage conditions, but the incidence of fungi associated with seeds in a cold and dry chamber is smaller.

Aplicação de fungicida em cultivares de arroz irrigado e seu efeito na qualidade de sementes

The objective of the present study was to verify the effect of aerial fungicide application on irrigated rice seeds, planted after the recommended period and harvested with different moisture contents. The experiment was conducted during the 2008/09 season, using an experimental design of randomized blocks in a factorial scheme, with strip plots and four replications. The main factor, in strip plots, was composed of four irrigated rice cultivars: BR-IRGA 409, IRGA 417, IRGA 422CL and IRGA 423. In the sub-plot, the fungicide was applied to the plant canopy at different development stages (T1- untreated check, T2- application in R2 stage, T3- application in R3 stage and T4- application in R2+R4 stages). Each strip in the sub-subplot was harvested with an average moisture content of 24, 22, 20, 18, 16 and 14%. Fungicide application of a formulated mixture of propiconazole+trifloxystrobin maintains the physiological quality of the rice seeds high, especially with two applications (at the stage R2+R4). There is a reduction in rice seed germination and vigor with delayed harvest, which was more evident when the average moisture content at harvest was below 22%.

Accelerated Solvent Extraction of Insecticides from Rice Hulls, Rice Bran, and Polished Rice Grains.

Analysis of pesticide residues in irrigated rice grains is important for food security. In this study, we analyzed accelerated solvent extraction (ASE) conditions for the extraction of thiamethoxam and chlorantraniliprole insecticides from rice hulls, rice bran, and polished rice grains. Several variables, including extraction solvent, extraction temperature, extraction pressure, cell size, static extraction time, and sample concentration, were investigated. The average recoveries of the three matrixes were between 89.7 and 109.7% at the fortification level of 0.75 mg/kg. The optimum ASE operating conditions were acetonitrile (100%) as extraction solvent, extraction temperature of 75°C for rice hulls and 100°C for rice bran and polished rice grains, extraction cell pressure of 10.3 MPa, 22 mL cell size, and two extraction cycles. The total extraction time was approximately 25 min. The extracted volume was evaporated to dryness and the residues were redissolved in 2 mL acetonitrile after 1 min of vortex-shaking. Thiamethoxam and chlorantraniliprole were analyzed by ultra-HPLC with tandem MS. In conclusion, ASE in rice hulls, rice bran, and polished rice grains offers the possibility of a fast and simple method for obtaining a quantitative extraction of the studied pesticides.