Abstract
In countries where spring frost frequently causes damage to pear flowers, cropping is possible through natural and induced parthenocarpy. The tendency to bear parthenocarpic fruit is a genetic feature so it differs between cultivars. The goal of the study was to assess the influence of the cultivar and rootstock on the occurrence of parthenocarpy and to determine the influence of the number of seeds on the quality of fruit and the speed with which it ripens. Pears of five European cultivars were collected from trees planted in 2002 at a distance of 4 × 1.5 m. Each cultivar was grown on three different rootstocks. The experiment was conducted in 2008 and 2011. There was a spring frost during the flowering period and many flowers were killed. Nevertheless, the trees cropped, which was the reason to expect an increased occurrence of parthenocarpy. During harvest, each pear was examined in respect of: firmness, TSS, acidity, skin base colour and starch pat-tern. After the tests, the pears were cut and the number of seeds was counted. The number of seedless pears varied between 2.2% (‘Carola’) and 46.7% (’Amfora‘) in 2008, and be-tween 26.7% (‘Dicolor’) and 84.1% (‘Amfora’) in 2011. The rootstock influenced the number of seedless pears of each cultivar. The largest number of parthenocarpic pears was harvested from trees grown on Quince S1. The number of seeds influenced some quality parameters, like the mass of fruit, firmness and TSS. Parthenocarpy was also found to affect the speed in which fruit ripens, as measured by the starch disintegration and Streif indices. Only acidity and base skin colour were slightly or not at all dependent on the occurrence of parthenocarpy or on the number of seeds.
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