La principal variedad de peral cultivada en España, "Agua de Aranjuez", se caracteriza por una marcada tendencia a los cuajados erráticos. A consecuencia de esto y con el fin de estabilizar producciones, la aplicación de ácido giberélico para la inducción de frutos partenocárpicos se ha convertido en una práctica generalizada. La creciente preocupación por la regularización de hormonas de síntesis en fruticultura puede poner en riesgo la producción de este cultivar. El mal comportamiento productivo de "Agua de Aranjuez", se ha intentado explicar sobre la base de numerosas hipótesis. En este artículo revisamos los últimos resultados obtenidos en este cultivar, determinando la importancia relativa de diferentes factores reproductivos que contribuyen a explicar los cuajados erráticos. En base a estos resultados se propone una alternativa agronómica a su actual sistema de producción, basada en el establecimiento de unas adecuadas condiciones de polinización.

Most pear (Pyrus communis L.) cultivars are impaired to set fruit under self-pollination, because self-fertilization is prevented by a gametophytic self-incompatibility system. However, accumulated information in this species shows that often for a same cultivar, after self-pollination, a variable response in fruit set can be obtained in different years or growing conditions. In this work, we characterize self-incompatibility and self-fruitfulness in 'Agua de Aranjuez', the main Spanish pear cultivar, which also shows a variable response to self-pollination. Two years with a different fruit setting response after self-pollination, one with no fruit set and the other with a moderate fruit set, were compared for parthenocarpic fruit development and for pollen tube performance. Results show that in both years, this cultivar behaves as self-incompatible with absence of parthenocarpy. In selfed flowers, most pollen tubes are arrested in the upper half of the style, although in a small proportion of the styles, a pollen tube can reach the base of the style and eventually effect fertilization. Self-fertilization, although occurring at a low level, can explain the fruit set levels obtained under self-pollination given that flowers with just one fertilized ovule are able to set fruit. This behavior could explain confusing results about self-fruitfulness in 'Agua de Aranjuez' and other pear cultivars.

El ensayo se llevo a cabo en la Estacion Experimental de la Universidad de Concepcion, Campus Chillan. En el se evaluo el efecto de diferentes regimenes hidricos bajo riego por microjet sobre parametros biofisicos, productivos y de calidad, en frutos de perales europeos (Pyrus communis L.), de doce años de edad. Los resultados obtenidos en este estudio permiten establecer que la produccion de frutos aumento a medida que se incremento el agua aplicada. Los parametros biofisicos evaluados fueron sensibles al riego diferencial por microjet, a excepcion de la temperatura foliar. El calibre de los frutos no mostro resultados concluyentes al incrementar el volumen de agua aplicada. Los indices de madurez, tanto presion de pulpa como solidos solubles, no fueron afectados por los tratamientos de riego a la cosecha, ni durante el periodo de almacenaje

A study was carried out, to determine the effects of different water levels on the physiological, vegetative and productive parameters of four year-old pear trees (Beurre Bosc) under drip irrigation. For each treatment the water application rate was determined by the pan evaporation (25, 50, 75 and 100 per cent of replacement). Randomized design with four treatments and four replicates were used as statistical method. Further, means were analyzed by Tukey test. Yield and fruits number -productive parameters- had response by increasing application of water in pear trees. Soluble solids and pressure, were not affected by the levels of water application. The highest values for fruit quality were found in the 50 and 25 per cent replacement treatment. There was no response to different levels of water in volume and mean weight. The highest transpiration rate was found between December 1991 and March 1992 for a 100 per cent of water replacement treatment. However there was no difference in transpiration for all other treatments. It must emphasize that for all treatments, the higher transpiration rate occurs around the 15 hours of the day. Diffusive resistance did not show differences between treatment. Similar values were found between the 100 and 25 per cent of water replacement treatment, and between 75 and 50 per cent of replacement. Leaves temperature results do not agree with those of the literature, The leaves temperatures were slightly higher in 100 per cent of water replacement, and it seems that there are no differences due to the levels of water. There is a positive relation between vegetative parameters and water levels for pear trees, because the highest values in branch length, diameter and stem perimeter were attained in 100 per cent of water replacement treatment. The water volume applied ranged between 1753 and 6846 cubic meter per ha during the irrigation period November 1991 and April 1992.