GRAFTING PAPAYAS (CARICA PAPAYA L.)

Abstract

Papaya is one of the few fruit crops still propagated by seed. Vegetative propagation by leafy cuttings has been practiced successfully in South Africa for over 40 years, because Papaya ringspot virus has not been a problem. Grafting has been done in various places but problems have arisen locally with bacterial infection of the scions. Several approaches were made to try to help overcome the problem viz. (i) application of soluble silicon to the parent stock and rootstock plants, (ii) spraying scions and rootstocks with Eco-77 ® , a suspension of Trichoderma spores, or a Bacillus broth culture, at the time of grafting, (iii) surface sterilization of rootstock and scion with (a) 5 or 10% household bleach (containing 3.5% sodium hypochlorite) or (b) 10% hydrogen peroxide. Parent stock plants have been repeatedly cut back to ensure the production of many thinner (10-20 mm diameter) side shoots suitable for use as scions. Seedling rootstocks were grown in a composted pine bark medium in plastic bags in a greenhouse. Results showed that household bleach was the significantly best method of surface sterilization. Success rate was 81%, after 15 weeks, when side grafted onto well fertilized and vigorous rootstocks. The biological treatments were not beneficial.