Associação de glyphosate e imidazolinonas no controle de arroz-vermelho em arroz Clearfield® / Association of glyphosate and imidazolinones on red rice control in Clearfield™ rice

O objetivo do presente trabalho foi o de avaliar os efeitos da utilização de glyphosate e herbicidas imidazolinonas, em aplicações isoladas ou associadas, sobre o controle de arroz-vermelho (Oryza sativa) e produtividade de grãos de arroz Clearfield®. O experimento foi conduzido a campo na safra 2007/08, em Cachoeirinha, RS, Brasil, com delineamento em blocos ao acaso e tratamentos dispostos em arranjo fatorial (2x6), usando-se quatro repetições. O fator A constou de dois níveis do herbicida glyphosate, aplicados no subperíodo semeadura-emergência da cultura por ocasião do início da emissão do coleóptilo do arroz (ponto de agulha); o fator B constou de seis tratamentos com imazethapyr+imazapic, aplicados em associação ao glyphosate ou quando a cultura atingiu o estádio de três folhas expandidas. As três variáveis explicativas analisadas foram a população de plantas de arroz e arroz-vermelho, a eficácia do controle de arroz-vermelho e a produtividade de grãos da cultura. O uso de glyphosate no ponto de agulha reduziu em 75% a população do arroz-vermelho e aumentou em 40% a produtividade de grãos de arroz, em relação à testemunha. O uso isolado de herbicidas imidazolinonas e sua associação com o dessecante proporcionou controle eficaz do arroz-vermelho e incrementou a produtividade de grãos, em comparação à situação sem controle da infestante, independente da dose e do sistema de aplicação.

The objective of this research was to evaluate the effects of the utilization of glyphosate and imidazolinones herbicides, in isolated or associated applications, on the effectiveness of red rice (Oryza sativa) control and grain yield of Clearfield-rice. The experiment was conducted under field conditions in 2007/08, in Cachoeirinha, RS, Brazil, using a randomized block design in a two-factorial design 2x6, with four replicates. The factor A was composed by two levels of glyphosate, applied during the subperiod between sowing and crop emergence at the early coleoptile stage of the rice plants; and the factor B consisted of six treatments with imazethapyr+imazapic, applied in association with glyphosate or when the rice crop plants had three expanded leaves. The crop and weed populations, red rice control and grain yield of crop were evaluated. The results show that the glyphosate application at the early coleoptile stage of the crop reduced 75% the red rice population and increased 40% the grain yield, in relation to the situation without weed control. The use of imidazolinones and their association with glyphosate provided effective control of red rice and increased the grain yield, independent of rates and application system.

Indica rice cultivar IRGA 424, transformed with cry genes of B. thuringiensis, provided high resistance against Spodoptera frugiperda (Lepidoptera: Noctuidae).

Plant expression of the entomopathogenic bacteria Bacillus thuringiensis cry gene has reduced the damage created by insect pests in several economically important cultures. For this study, we have conducted genetic transformation of the indica rice "IRGA 424", via Agrobacterium tumefaciens, using the B. thuringiensis cry1Aa and cry1B genes, with the objective of obtaining rice plants resistant to the insect pests from this culture. The gene constructions harbor the promoters maize proteinase inhibitor and ubiquitin. The results showed that high concentration of the hormone 2,4-dichlorophenoxyacetic acid and agarose as the gelling agent helped the production of embryogenic calli for the analyzed cultivar. More than 80% of the obtained transformed plants revealed the integration, using polymerase chain reaction, of the cry1Aa and cry1B genes. Analysis of the expression of the heterologous protein by Western blotting revealed the expression of the Cry1B delta-endotoxin in IRGA 424 plants transformed with the ubiquitin promoter. Data showed the production and dissemination of a high number of embryogenic calli in addition to obtaining plants transformed with the cry1Aa and cry1B genes until the reproductive phase. The feed bioassays with the transformed plants and Spodoptera frugiperda (JE Smith) larvae indicated high rates of mortality to the insect target. The highest corrected mortality rate achieved under laboratory conditions with Bt-rice plants transformed with the cry1B and cry1Aa genes was 94 and 84%, respectively. Thus, our results demonstrated the great potential of transformed Bt-rice plants in controlling the damage caused by these insect pests in rice paddy fields.

Interferência do arroz vermelho no rendimento de engenho de cultivares de arroz irrigado / Red rice interference on milling yield of irrigated rice cultivars

O arroz vermelho é considerado a planta daninha que mais danos causa a orizicultura gaúcha. A presença dos grãos desta invasora junto aos grãos das cultivares de arroz contribui para a diminuição da qualidade física do arroz, na medida em que diminui o rendimento de engenho, aumenta o número de grãos rojados, com centro branco e gessados. Este trabalho foi desenvolvido com o objetivo de determinar o efeito de diferentes quantidades de arroz vermelho na amostra de arroz sobre a renda do beneficio e sobre o rendimento de grãos inteiros e de quebrados em três cultivares de arroz irrigado (BR-IRGA 410, IRGA 416 e IRGA 417) com classe de grão longo fino. Os tratamentos constaram de diferentes proporções na amostra (0, 5, 10, 15, 20, 25, 50, 75 e 100 por cento) de grãos de arroz vermelho. Os resultados evidenciaram que, para todas as cultivares, à medida que aumentou a presença de grãos de arroz vermelho na amostra no processo de beneficiamento, o rendimento de grãos inteiros e a renda do beneficio diminuíram linearmente, enquanto o rendimento de grãos quebrados aumentou linearmente.

Red rice is considered the weed that cause the most significam damage to rice fields in the State of Rio Grande does Soul, Brazil. The presence of red rice grains associated with the grains of the commercial rice cultivars contribute to reduce the physical quality of the rice because reduce the milling yield and increase the number of grains chalky and with white pearly. This experiment was developed with the purpose of determining the effect of different quantities of retrace in the sample on the milling yield of three cultivars of irrigated rice with grains fine long class. The treatments consisted of different proportions in the samples (0, 5, 10, 15, 20, 25, 50, 75 and 100 percent) of grains red rice and grains of the rice cultivars BR-JRGA 410, IRGA 416 and IRGA 417. As the quantity of grains of red rice increased in the sample in the milling process, the whole grain yield and total milling yield decreased linearly, white the yield of broken grains increased linear fly for all cultivars.