Thidiazuron increases fruit size of 'Spadona' and 'Coscia' pear (Pyrus communis L.)

The effect of the synthetic cytokinin thidiazuron (TDZ), derived from phenylurea, on fruit size of the small-fruited 'Spadona' and 'Coscia' pears was examined during five consecutive years (1998-2002) in Israel. TDZ applied at 20-30 ppm, two weeks after full bloom, when the fruitlet diameter was 10 mm, caused an appreciable increase in fruit size of both cultivars. Although slight thinning accompanied the large increase in fruit size, the main TDZ effect was achieved through a direct enhancement of fruit cell division. TDZ increased fruit size without affecting fruit shape, seed number, or return yield in the year following application. Our findings demonstrate the effectiveness of TDZ for both pear cultivars and show that it has a significant potential for improve cropping, apparently without significant negative aspects.