Rootstock age and grafting season affect graft success and plant growth of papaya ( Carica papaya   L.) in greenhouse

Papaya (Carica papaya L.) is an important fruit crop in many tropical and subtropical countries; it is commercially propagated through seeds, which lead to production of non true-to-type plants. Grafting for mass multiplication of the selected variety is therefore necessary. The objective of this study was to determine the influence of rootstock age and grafting season on the success of cleft grafting and growth of grafted plants under greenhouse conditions. The trial was conducted using an experimental randomized complete block design with 4A × 2B factorial scheme, four blocks, and 15 grafted plants per experimental unit. Factor A represented four rootstock ages (1, 2, 3, and 6 mo) and factor B represented two grafting seasons (summer and autumn). Results showed that rootstock age and grafting season had a significant effect on all the parameters: sprouting time, percentage of graft success, scion sprout length, and number of new leaves per graft. The youngest rootstock age (1 mo) achieved the best results for all the parameters. The best season for grafting was summer. The treatment combination of 1-mo-old rootstocks in summer produced minimum sprouting time (8.40 d), the highest percentage of graft success (93.33%), and graft growth in the greenhouse. Therefore, 1-mo-old rootstocks and grafting in summer or autumn should be used to propagate papaya by cleft grafting.