[Harvesting date, physical damage and physiological quality in bean seeds] | Oportunidad de cosecha, dano fisico y calidad fisiologica en semillas de frijol.

Inglés. The experiment was conducted in order to measure the extent of physical damage and its effect on the physiological quality of bean seeds harvested during different development stages. Bean seeds of Bayomex, Flor de Mayo de Mata and Pinto Texcoco cultivars were used. Samplings were taken 101 days after planting until completing six harvesting dates. After harvesting the treatment was applied and consisted in the free-fall dropping of seeds on a hard concrete surface from different heights of drop, 2, 4 and 6 m. The physical quality of the seed was measured in terms of moisture content and physical damage (sodium hypochloride immersion), while the physiological quality was assessed in terms of germination and vigour (accelerated ageing). By delaying the harvest the physical damage increases mainly due to the decrease of the seed moisture content. Physical and physiological qualities are significantly affected when the seeds are exposed to free-fall dropping from higher heights. The highest physical and physiological quality was obtained in the seeds not exposed to damage (control treatment). Varietal differences were observed on the susceptibility to physical damage and on the effect of this on the physiological quality. Key words: Bean seed, Phaseolus vulgaris L., harvesting date, physical damage, physiological quality.

Español; castellano. Se estudio el dano fisico en semillas de frijol en manejo postcosecha para determinar su magnitud y su efecto sobre la calidad fisiologica de semillas cosechadas en distinto estado de desarrollo. Se usaron variedades Bayomex, Flor de Mayo de Mata y Pinto Texcoco y a los 101 dias de siembra se iniciaron muestreos hata completar 6 oportunidades de cosecha. Despues de la cosecha se dejaron caer las semillas sobre una superficie solida de concreto a caida libre de 2, 4 y 6 m de altura. La calidad fisica se midio con base a contenido de humedad y dano fisico (inmersion en hipoclorito de sodio) y la calidad fisiologica se evaluo en terminos de la germinacion y del vigor (envejecimiento acelerado). La demora en la cosecha aumenta el dano fisico por reduccion de humedad. Se afecta significativamente la calidad fisica y fisiologica cuando las semillas se exponen a caidas de mayor altura. La mas alta calidad fisica y fisiologica se obtuvo en semillas que no se expusieron al dano (testigo). Hubo diferencias varietales en la susceptibilidad al dano fisico y en el efecto de este sobre la calidad fisiologica. Palabras clave: Semilla de frijol, Phaseolus vulgaris L., oportunidad de cosecha, dano fisico, calidad fisiologica.