A multi-site pear-interstem trial in the Netherlands and Belgium

An interstem trial was planted in the spring of 1989 with two pear cultivar s 'Conference' and 'Doyenne du Comice' on the tender Quince MC rootstock wi th six interstem cultivars, viz 'Beurre d'Anjou: 'Beurre Hardy'(standard), 'Doyenne du Comice,' 'Nouveau Poiteau,' 'Old Home' and 'Flemish Beauty' to determine the influence of the interstems on winter hardiness and growth co ntrol. Two-year-old trees budded directly on Quince MC served as controls. The trees were planted at two sites in The Netherlands and one in Belgium i n single rows at distances ranging from 3.00m x 1.30m to 3.50m x 1.50m and trained as slender spindles. The trial was evaluated until 1998. No damaging freezes occurred during the experimental period, therefore no c onclusions could be drawn with regard to the winter hardiness of the inters tem cultivars involved. Vigor control was obtained with 'Beurre d'Anjou' an d 'Flemish Beauty, probably as a result of incompatibility of these two int erstem cultivars with the Quince MC rootstock. The interstems compatible wi th the Quince MC rootstock did not provide vigor control, or promoted it, a s was the case with 'Old Home.' The 'Old Home' interstem reduced cropping. 'Nouveau Poiteau' had a small negative effect on the fruit size of 'Confere nce.' 'Beurre Hardy' and 'Doyenne du Comice' are useful interstems for Conf erence, but do not reduce vigour. For 'Doyenne du Comice: with the exceptio n of the poorly compatible interstems, none of the other interstems studied reduced vigor.