Rice lodging is still a problem in many countries, as all rice-growing countries have some varieties that get lodged. Direct evaluation of lodging resistance requires visual estimates in plots, but is not feasible in early generations of breeding programs, where genetic variability is too high. The aim of this study was to compare two methods for indirect evaluation of lodging resistance, especially in field conditions: the recovery ability after bending (measured as the tiller angle difference before and after bending); and, to test the sturdiness of the lower part of the plant, we have measured its resistance to pulling. Sixteen rice varieties and two F 5 breeding lines were grown in plots and rows; 20 additional F 5 breeding lines were only tested in rows. Visual estimates of plot lodging were significantly correlated with their tiller angle difference (r = 0.56*), but not with plant height or pulling resistance, although the latter was also correlated with visual lodging when only susceptible accessions were considered (r = -0.72*). Tiller angle difference was not significantly correlated with pulling strength, but it correlates with plant height (r = 0.56*). The scoring of tiller angle difference is simpler and less dependent on the evaluator than pulling resistance. It is concluded that it can be a valuable trait to select for resistance to lodging in early segregating generations of a pedigree breeding program.Additional key words: culm elasticity; lodging resistance; Oryza sativa; plant height; pulling strength; tiller angle. Resumen Comunicación corta. Evaluación de la resistencia al encamado en arroz: comparación de dos ensayos indirectosEl encamado del arroz sigue siendo un problema en muchos países, ya que todos los países cultivadores tienen algunas variedades que se encaman. La evaluación directa de la resistencia al encamado requiere estimas visuales en parcelas, pero no es posible en las primeras generaciones de un programa de mejora, cuya variabilidad genética es demasiado grande. El objetivo de este estudio fue comparar dos métodos de evaluación indirecta de resistencia al encamado en campo: la capacidad de recuperación tras doblado (medida como la diferencia angular de un tallo antes y después del doblado); y para probar la fortaleza de la parte inferior de la planta, se midió su resistencia a la tracción. Se cultivaron 16 variedades y dos líneas de mejora (F 5 ) en parcelas y líneas; 20 líneas de mejora adicionales (F 5 ) fueron sólo ensayadas en filas. Las estimas visuales de encamado en parcelas estuvieron significativamente correlacionadas con la diferencia del ángulo de sus tallos (r = 0,56*), pero no con la altura de planta ni con la resistencia a la tracción, aunque esta última también mostró correlación con el encamado visual cuando sólo se consideraron las entradas susceptibles (r = -0,72*). La diferencia del ángulo del tallo no estuvo significativamente correlacionada con la resistencia a la tracción, pero sí con la altura de planta (r = 0,56*). La medida de la diferencia ang...

The cultural practices of the early generations in a pedigree breeding programme may influence its success. The main objective of this study was to compare two selection environments in rice: Widely spaced planting in the field and dense planting in concrete basins. Both methods had yielded commercial varieties in the past. Two F2 populations (J and MS), derived from two crosses sharing the same female parent, were transplanted to both environments. Phenotypic traits were evaluated and their narrow sense heritabilities (h2) estimated in the F3 and in the F4 progenies of selected plants, all grown in the field. Growth potential was more apparent in the field for most traits, especially those related to yield, but broad sense heritabilities were higher in the basins for ten traits, being higher in the field for the other five. In population F2MS, field selection resulted in F3 plants which retained a higher tillering ability than those derived from basins selection. Most traits showed low h2 values: Additive variance was only relevant in panicle length (in both populations), plant height and mean panicle weight (in the J population). However, response to one generation of selection (from F3 to F4) also showed fixable variation in panicle number. In addition, this selection reduced plant height, increased culm diameter and internode length (in both populations), and improved pulling resistance (against lodging) in population J. It may be concluded that both practices can be used for selection in the F2, although different responses might be expected in yield related traits.

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