Fusarium oxysporum f.sp. radicis-lycopersici (Forl) is one of the most destructive necrotrophic pathogens affecting tomato crops, causing considerable field and greenhouse yield losses. The use of resistant cultivars is a safe, non-contaminating and reliable control method to eradicate or mitigate this disease. However, it is still necessary to determine the best inoculum density, sufficient to induce levels of resistance or susceptibility. In this study, inoculum concentrations of 3, 5 and 8 x 10 6 microconidia per mL of Forl were evaluated by root immersion and seed spraying in twenty tomato genotypes (Solanum spp.) in a completely randomized design. The germplasm was mainly introduced tomato species from the Genetic Resources Program of the University of California at Davis, USA. The inoculation was done by immersion of roots and by sprinkling of seeds at the time of sowing. For the inoculation by immersion of roots, tomato seedlings of 15 days emergence were used. The wounds were created in root tips then they submerged into the each conidial suspension. Finally, they transplanted into the plastic pots in a greenhouse. Regarding the inoculation by sprinkling of the seed, 20 seeds of each genotype were placed in plastic pots then sprayed with the corresponding conidial suspension. In both cases, the disease index was calculated. This allowed classifying the genotypes as resistant and susceptible. With the root immersion method all the genotypes evaluated showed susceptible. Significant differences were observed (p≤0.01) between genetic materials at different inoculum doses with the inoculation of seeds. This allowed classification of genotypes Solanum parviflorum LA 1326, Solanum chesmanii f. minor LA1401, Solanum chmielewskii LA1306, Solanum pimpinellifolium LA722, Solanum pimpinellifolium LA2184 as resistant to Forl with disease index of 3, 4, 5, 8 and 12% respectively, at a inoculum concentration of 3x10 6 microconidia per mL. These genotypes could be included in a genetic breeding program for resistance to crown and root rot caused by Forl.

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Introducción: El manejo forestal sustentable se enfoca en la obtención de servicios ambientales, a la par que se mantiene la acumulación de biomasa aérea (BA).Objetivo: Estimar la BA a lo largo de una cronosecuencia de bosque templado y examinar el papel del manejo forestal para la producción maderable sobre los patrones de fijación, incremento y asignación de BA.Materiales y métodos: Se seleccionó una cronosecuencia de rodales dominados por Pinus patula Schiede ex Schltdl. & Cham. en un rango de 7 a 30 años. La BA se estimó con modelos alométricos y parametrizados para inferir la edad a la cual el bosque manejado alcanza su producción máxima. Se calculó la producción de BA, la productividad primaria neta aérea (PPNA), los incrementos en BA y su asignación a los componentes estructurales de los árboles, los cuales se compararon con los de un área natural sin manejo forestal (BSM).Resultados y discusión: La BA y PPNA aumentaron con la edad del rodal a lo largo de la cronosecuencia. El rodal de 30 años presentó 79 % de la BA contenida en el BSM. Estos dos sitios tuvieron una producción alta de BA, la cual correspondió a una PNNA elevada con 87 % de similitud. El fuste fue el componente estructural con mayor asignación de BA (70 %), debido principalmente a las prácticas silviculturales como el aclareo, que forma parte del programa de manejo forestal.Conclusion: Los bosques de P. patula con manejo forestal aceleraron la acumulación de BA en rodales de bosques templados a lo largo de la cronosecuencia estudiada, alcanzando niveles similares a los de un BSM en un periodo más corto.

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In the context of the mutants, polyembryony in maize (PEm) has agronomic potential; therefore, the inclusion of the PEm in new varieties may be useful when considering the ascending demand for food. The objective of this study was to develop new genotypes with high productivity potential, superior to in local area, and useful for family and extensive agriculture. In this work, single crosses were carried out between three pure lines and the high frequency polyembryonic populations. The resulting F1 were advanced to the third generation (G3) and the genotypes obtained from this last generation were used as progenitors of a mating plan, according to the Griffing method 4. The resulting crosses were evaluated in a yield test measuring common characteristics of economic importance (Days to Male Flowering (MF), Plant Height (PH), Cob Height (CH), Fusarium Rotten cobs, Cobs (CFUS), Yield (YLD), and analyzed with the computer routine DIALLEL-SAS05. The results allowed to indicate that both the source of variation Genotypes as additive effects (GCA) presented significance for all variables, while non-additive (SCA) were significant only in the variables of cob sanity (p≤0.01) and productivity (p≤0.05). In this regard, most of the variables showed a greater contribution of the effects of General Combining Ability (GCA) compared to Specific Combining Ability (SCA). In addition, it was observed that the crosses were superior in all the variables evaluated with respect to BAP and NAP, and statistically similar in some cases with respect to hybrids. This means that this type of segregant polyembryony crosses can compete with other materials evaluated in the region. The estimation of GCA and SCA generated information on the potential of the studied parents and their crosses and are worthy of being taken into account in the formation of varieties.