Articles
STUDY OF GROWTH PARAMETERS ON APRICOT SHOOT-TIP GRAFTING IN VITRO (STG)
The technique of STG used in the experiments consists of aseptically grafting a 0.5–1.0 mm long shoot-tip on a rootstock seedling growing in vitro.
Shoot-tips were excised from the following sources: a) dormant buds collected from November to February: b) vegetative flushes from plants normally growing in the field; d) in vitro growing vegetative shoots.
The influence of the following parameters on STG success were studied: rootstock cultivars; position of the shoot tip on the rootstock; shoot-tip size; light and temperature during the culture in vitro of the grafted plants; nutrient composition of the medium to culture the shoot-tip grafted plants; hormone treatments to grafted plants growing in vitro; cold treatments to grafted plants growing in vitro.
Important differences were found among the different sources of shoot-tips.
The best results were obtained when the shoot tips were excised from plants growing in vitro. In the case of shoot-tips excised from dormant buds or growing vegetative flushes a high proportion of the successfully grafted shoot tips remained in a dormant stage and did not grow any further.
Hormone sprays with cytokinins and giberelins and cold treatments stimulated the growth of some dormant shoot-tips.
Several parameters related to the plant material used and the environmental conditions had a strong influence on STG success.
The optimal conditions were the following: the use of 10 to 15-days old Nemaguard peach seedlings as rootstock; the placement of the shoot-tip over the vascular ring of decapitated rootstock seedlings; the use of 0.5–1.0 mm long shoot-tips; the culture of the shoot-tip grafted plants at 25°C and exposed 16 hr dayly to 45 u einsteins.sec-1.m-2 illumination; the culture of the shoot-tip grafted plants in a liquid medium composed of the Murashige and Skoog mineral salt solution, modified White’s vitamins and 3 per cent sucrose.