SELECTION OF CLONAL ROOTSTOCKS OF PYRUS COMMUNIS (L.)

Although quince rootstocks are mainly used in Italy for their size-controlling and early bearing aptitude, they have the disadvantage of poor compatibility with many cultivars, e.g. Bartlett, and susceptibility to lime soils, which are frequent in typical pear growing areas in our country. It thus would appear important to rely on clones of Pyrus communis rootstocks featuring size control and yield comparable to or higher than quinces. A breeding program was thus started in 1979 at the University of Bologna and focused on: (1) collection of one thousand seeds from open-pollinated trees of two local cultivars, 'Mora' and 'Volpina', often used as seedling rootstocks in the past; (2) selection of 470 clones, on the basis of low seedling vigour, and their propagation by stool-beds; (3) collection of the layers (from 1 to 5 per clone) grown in 1982 and 1983 and their grafting to Bartlett. The clones collected in 1982 and 1983 were planted in two comparative evaluation fields with quince BA 29 in November 1984 (Field A, 132 clones) and March 1986 (Field B, 300 clones), respectively.

Further steps in the two fields included a first selection, at the end of the 4th year, of clones with low and medium vigour: 46 and 55 in field A and B, respectively. At the end of the 7th year, results indicate that 16 selections performed better than others, showing yield efficiency comparable to or higher than quince, lower or medium vigour and tolerance to lime chlorosis.