La certificación de semillas es un sistema de multiplicación con número limitado de generaciones para preservar la pureza e identidad genética de cultivares mejorados. El diagnóstico de la cadena agroindustrial de arroz, Oryza sativa L., en Venezuela realizado en 1996, identificó problemas asociados con la pureza genética y calidad general de la semilla certificada de las variedades comerciales de arroz. El objetivo de este estudio fue determinar y cuantificar la posible contaminación de la pureza genética en las cuatro clases de semillas de arroz: Genética, Fundación, Registrada y Certificada, además de la semilla informal de los cultivares comerciales Araure 4, Cimarrón, FONAIAP 1 y Palmar. También se diseñó y validó un nuevo método para cuantificar contaminantes en muestras de semillas de arroz, cuya aplicación en el estudio demostró que la clase Registrada de la variedad Araure 4, y la semilla pirata de FONAIAP 1, presentaron 28 y 8% de contaminación en relación con el patrón isoenzimático de sus respectivas clases Genéticas. Estos resultados indican que la contaminación detectada responde a mezclas con otras variedades y/o semillas de arroces rojos, ocurridas durante su multiplicación por manejo inadecuado durante las diversas labores de campo, cosecha y post cosecha. Se demostró que la técnica de electroforesis, sola o combinada con evaluaciones morfométricas, representa un método consistente para validar la identidad y pureza genética de las variedades de arroz y sus clases de semilla certificada.

Seed certification is a system based upon a multiplication of a limited number of generations to assure the genetic identity of improved cultivars. The 1996 survey on the Venezuelan rice industry, reported crop limitations associated with the genetic purity and overall quality of certified rice seed utilized at the market place. The objective of this research was to determine and quality contamination of the genetic purity of the four classes of rice seed: Breeder (BS), Foundation (FS), Registered (RS) and Certified (CS), all belonging to the seed certification system of rice, as weel as “non certified seed” (NCS) coming from the illegal rice market. Also a new method was designed and validated to quantify the genetic contamination levels of seeds. This method, applied to all samples of varieties and seed classes, showed 28 and 8% of contamination for RS of Araure 4 and NCS of FONAIAP 1, when compared to their original BS profile. These results demonstrated that the previously reported levels of contamination were associated with red rice weed, due to mismanagement of seed production fields or mechanical mixtures during seed processing, rather than a truly genetic erosion of commercial varieties. Electrophoresis by itself or in combination with morphometric evaluations proved to be a consistent method to validate identity and genetic purity of rice varieties and their classes of certified seed.

La investigación estudió la contribución de la semilla Certificada de maíz (SCM), en la productividad de los sistemas de producción de Portuguesa y Guárico en el año 2000; estimar la influencia de la SCM en la rentabilidad obtenida; y evaluar la participación de las asociaciones de productores (PGM) en las negociaciones con los proveedores de granos, insumos y servicios agrícolas. Se encuestaron 90 PGM de Portuguesa y 40 de Guárico. Las variables cuantitativas se evaluaron con el análisis de los componentes principales (ACP) de la varianza total (VT) y clasificación jerárquica ascendente (CJA); las cualitativas mediante un estudio descriptivo. Los resultados indicaron que en Portuguesa, el mayor porcentaje de semilla sembrada fue de las trasnacionales Pioneer y Cargill, con una productividad mayor de 1.000 kg ha-1 a la obtenida por los híbridos de origen nacional; mientras que en Guárico la Sefloarca e Himeca, fue significativamente superior a Pioneer. La integración de los PGM en Portuguesa en asociaciones gremiales, da más poder de negociación con los proveedores de servicios e insumos, en comparación a los de Guárico, que realizan operaciones individualmente. Así mismo, el ACP para los 130 PGM estudiados, identificó que 6 variables: precio de semilla, fertilizante, costo de labores mecánicas, mano de obra, cosecha y transporte, fueron responsables por el 75% de la VT de los costos de producción, agrupándose en 3 CP, el CPI de fertilizante, labores mecánicas y cosecha, explicó el 35,21% de la VT; El CP2 por mano de obra semilla y cosecha, explicó el 22,16% del VT y el CP3, determinado por transporte y mano de obra, explicó el 17,82%. El CJA, conformó 5 grupos para los 90 PGM de Portuguesa y 2 grupos para los 40 de Guárico, con la particularidad que un PGM individual fue agrupado con los de Portuguesa debido a su patrón tecnológico de trabajo.

The development and use of new maize cultivars have increased the productivity and rentability of corn growers nationwide. The objetives of this research were to: evaluate the contribution of certified maize seed (CMS) to the productivity of corn production systems of Portuguesa and Guarico States during the growing season of the year 2000; estimate the influence of CMS upon crop rentability; and evaluate the roles played by growers’ associations on the negotiations with seed and other inputs suppliers. Ninety maiz growers of Portuguesa and 40 of Guarico were surveyed. Quantitative variables were evaluated by using Principal Components Analisis (PCA) and the Upward Hierarchical Classifications (UHC). For qualitatives variables, descriptive analyses were used. Results showed that in Guarico the largest percentage of planted seed belonged to transnational companies, Pioneer and Cargill, with productivity 1.000 kg ha-1 higher than the obtained by hybrids of national seed companies. In contrast, at Guarico locations, the yields of the hybrids to Seflorca and Himeca national seed companies were significant higher that those of Pioneer. The main role of Portuguesa growers’ associations was to strengthten producers’ negociation power with seed and inputs suppliers, as opposed to individual actions of Guarico maiz growers. The PCA for the 130 growers studied found that six variables: seed price, fertilizer, farming practices, labor, harvesting and transporting, accounted for 75% of the total variance (TV) for production costs. These variables were clustered in three principal components (PC1, 2 and 3), in which the CP1 formed by fertilizer, farming practices, and harvesting, accounted for 35.21.5 of TV; CP2 conformed by labor and harvest accounted for 22.12% of VT; and CP3 represented labor and transporting, accounted for 17.82% of TV. The UHC identified five groups for the 90 Portuguesa growers, and two for the Guarico growers; interestingly, one Guarico grower was included in the Portuguesa groups, because his farming profile fitted that location rather than the Guarico patterns.

La mayor utilización de semilla certificada de arroz (SCA) de óptima calidad mejoraría la competitividad de la cadena de arroz. Los análisis oficiales de germinación y pureza evalúan insuficientemente la calidad integral de la SCA. Esta investigación evaluó el peso específico (PES) y la emergencia en campo (PEC) como indicadores de calidad física y fisiológica de SCA en las variedades Araure 4, Cimarrón, FONAIAP 1 y Palmar. Para determinar la uniformidad de la SCA, las semillas se sumergieron en soluciones de sulfato de amonio (SDA), ajustadas a ocho densidades entre > o = 1,6 y <1 g cc-1. Las evaluaciones entre Variedades, PES, PEC y porcentaje de germinación en laboratorio (PGEL), se realizaron en el laboratorio de semillas y campo de la Facultad de Agronomía-UCV, usando el diseño en bloques al azar, con arreglo factorial para variedades y clases de PES, y separación de medias de tratamientos con rangos múltiples de Duncan. La inmersión en SDA separó ocho clases de PES, confirmando alta desuniformidad de la SCA en las cuatro variedades. La semilla con mayor PES ( > o = 1,6 g cc-1) representó el 90% de la SCA. Su PGEL y PEC superaron estadísticamente al resto de clases de semilla. Las semillas con mayor PES y el testigo SCA tuvieron PEC y PGEL superiores a 80%, lo que avala al PEC como método de apoyo al PGEL para evaluar la calidad fisiológica de la semilla de arroz. Las semillas con PES <=1,6 g cc-1 mostraron inferior calidad física y fisiológica que la SCA.

The production and utilization of high quality certified rice seed (CSR) are important strategies to improve the competitiveness of the Venezuelan rice seed industry. Official germination and purity trials do not completely evaluate overall quality of CRS. This investigation evaluated specific weight of seed (SWS) and percentage of field emergence (PFE) as indicators of physical and physiological quality of CRS of `Araure 4', `Cimarron', `Fonaiap 1' and `Palmar' varieties. In order to determine uniformity, seed samples were immersed in a 96% solution of ammonium sulphate adjusted to six densities ranging from > or = 1.6 to <1 g cc-1 . The associations between varieties, classes of SWS, PFE and percentage of germination in the laboratory (PLG), were evaluated by field and laboratory trials conducted in the facilities of the Agronomy School of the Central University of Venezuela, located at Maracay, Venezuela, using a random blocks (RB) desing and a factorial arrangement for varieties and classes of SWS. Duncan's Multiple Range Test was used for assessment of treatments means. Results indicated the separation of eight classes of SWS confirming high heterogeneity of commercial CRS for all varieties. In all tests performed, always the heaviest seed class ( > or = 1.6 g cc-1) represented more than 90% of total bulk of CSR. Also, it was remarkable that results for PLG and PFE of the heaviest SWS class, were consistently superior than those with SWS <=1.6 g cc-1. The quality of seed belonging to SWS class > or = 1.6 g cc-1 showed a highly deteriorated and weedy profile affecting overall quality of CSR. These findings seem to justify the innovation in processing procedures, by adding equipment for densimetric analysis to up grade the current level of physical and physiological quality of the CSR used by Venezuela farmers.

OBJECTIVE: One of the most exciting potential applications of percutaneous therapy is the treatment of abdominal aneurysms. METHODS: Of 230 patients treated with a self-expanding polyester-lined stent-graft for different aortic pathologies at our institution, we selected 80 abdominal aneurysm cases undergoing treatment (from May 1997 to December 2002). The stent was introduced through the femoral artery, in the hemodynamic laboratory, with the patient under general anesthesia, with systemic heparinization, and induced hypotension. RESULTS: The procedure was successful in 70 (92.9%) cases; 10 patients with exclusion of abdominal aortic aneurysms were documented immediately within the hemodynamic room and 5 patients persisted with a residual leak. Two surgical conversions were necessary. Additional stent-grafts had to be inserted in 3 (3.7%) cases. In the follow-up, 91.4% of patients were alive at a mean follow-up of 15.8 months. CONCLUSION: We believe that stent-grafts are an important tool in improving the treatment of abdominal aneurysms, and this new policy may change the conventional medical management of these patients.