ISHS Acta Horticulturae 410: II International Cherry Symposium
CHERRY HYBRID ROOTSTOCKS DEVELOPED AT GIESSEN: NEW EXPERIENCES AND EVALUATION |
| Author: | S. Franken-Bembenek |
| Abstract:
In 1965, Prof. Gruppe initiated a program for breeding dwarfing rootstocks for cherries at Giessen university (Gruppe, 1985). Crosses between more than 10 different Prunus species resulted in about 6000 hybrids. Many of them were tested in rootstock trials at Heldenbergen near Giessen (Schmidt and Gruppe, 1988) and later on at Witzenhausen, Ahrensburg and Hattersheim. From this material 25 clones (GI-clones) have so far been selected (Table 1). All of them are hybrids between the Eucerasus species P. avium, P. cerasus, and P. fruticosa, as well as P. canescens, a shrub with spreading branches, pubescent leaves, small pinkish flowers and (although classified as Pseudocerasus species (Rehder, 1962), showing very good crossing and grafting compatibility with P. avium. Some hybrids with P. canescens as one parent and P. cerasus as the other are very promising as rootstocks for P. avium. GI-clones are under investigation in rootstock trials at several places in Germany, Europe, the United States (Perry, 1990) and Canada. Clone 148/2 has been introduced to the market in Germany as "Gisela 5". Data on GI-clones were collected from many places, entered into a data base and used for a comprehensive evaluation. Because of different scions, status of plant material, soil and climatic conditions, planting year, spacing, and varying cultural conditions, measurements of growth and yield were transformed into percentages of the respective standard rootstocks budded with the same cultivars. Trunk cross-sectional area in the fourth or fifth leaf was used as a measure of vigour. Fig. 1 gives a comparison of vigour of GI-clones in relation to Colt, Mazzard and F 12/1. These standards are marked by a line at the 100% level. Most GI-clones clearly induce weaker growth than the standards. Clones 148/1, 195/1 and 196/4 are the most vigorous of the GI-clones; 154/5, 172/7, and 172/9 are most growth-reducing. The broad range of variation points to an important influence of environmental conditions. Because of the enormous ranges, it is impossible to state that a given rootstock reduces vigour by a certain percentage. The values for 148/1, for example, range from 37% to 96% of Colt, for 148/8 from 32 to 82%, and for 172/9 from 7 to 47%. Statements about yield potential are even more difficult. The variability is probably due to the influence of climatic conditions, which are more important for reproductive than for vegetative characters. Early yields of trees on GI-clones are often, but not always, higher than on Colt, Mazzard or F 12/1. Clones 148/1, 195/1, 107/1, 148/13, 196/13 and 195/20 were outstanding in precocity and yield in some | |
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