ROOTING RESPONSE OF P.S. B2 AND G.F. 677 ROOTSTOCK CUTTINGS

Trials were carried out on the rooting ability of cuttings of P.S. B2 and G.F. 677 rootstocks using mist and bottom heat techniques. The cuttings, taken at monthly intervals during the year, were treated with IBA at 0, 1 000 ppm, 2 000 ppm and 3 000 ppm. At the various collecting times the growth phases of mother plants were recorded, in an attempt to establish a parameter associated with the rooting potential of cuttings; shoot growth, natural leaf drop and flower bud swelling were thus considered. For both rootstocks, natural rooting potential resulted highest firstly in October, when leaf drop was 80% and 50% in P.S. B2 and G.F. 677 respectively, and secondly during the Winter rest period.

The rooting of P.S. B2 cuttings was improved with IBA at 1 000 ppm concentration and, to a lesser extent, at 2 000 ppm; on G.F. 677 the doses at 1 000 ppm and 2 000 ppm showed a similar effect. The 3 000 ppm concentration often gave a much lower rooting in both the rootstocks. Generally, hardwood cuttings propagated by bottom heat gave the best results. In P.S. B2, the highest rooting percentages induced by IBA (95%) were observed at 80% leaf drop, corresponding to the period of highest natural rooting potential and towards the end of flower bud rest period. G.F. 677 behaved similarly; the best rooting responses (85–95%) were obtained in December, when flower buds were still dormant but about to begin of swelling.