THE BEHAVIOUR OF QUINCE SELECTIONS AS PEAR ROOTSTOCKS FOR 'ABBÉ FÉTEL' AND 'CONFERENCE' PEAR CULTIVARS IN THE RIO NEGRO VALLEY, ARGENTINA

Non traditional pear cultivars, such as 'Abbe Fetel' and 'Conference', are of interest for Argentinean growers. Pyrus communis is the main pear rootstock used due to the lack of compatibility of quince with the main cultivars ('Bartlett', 'Beurre d'Anjou' and 'Packham's Triumph'). For high density orchards it is a must to reduce their vigour and increase precocity. From 1991, Abbe Fetel and Conference cultivars were studied when grafted on three virus free quince selections (BA 29, Provence and MA), using Pyrus communis as check. Results show that during the first five years the quince combinations have reduced vegetative growth and increased precocity through a higher yield efficiency. During the first five years no incompatibility problems were shown. However, during the four following years, the combinations on quince showed an increasing and striking reduction in their vegetative growth and a lower fruit production in comparison with Pyrus communis. Other symptoms of incompatibility such as reddish colour and an earlier senescence of the foliage in autumn, and a black line in the junction between the pear stock and quince were observed. Due to the ecological conditions of the Rio Negro Valley, the cvs. Abbe Fetel and Conference cannot be grafted directly on the quince selections available at present. In the future, it will be necessary to evaluate the use of other interstocks to overcome this incompatibility, or else, to select new rootstocks of the Pyrus genus with the capacity to reduce the vigour of trees and increase their precocity.