Interspecific grafting to solve the rootstock shortage in vegetative propagation of Lai-durian (Durio zibethinus x kutejensis) originated from East Kalimantan

Lai-durian (Durio zibethinus x kutejensis) is a durio species derived from a natural crossing between Durio zibethinus (Durian, local name) and Durio kutejensis (Lai, local name) showing high performance of fruit quality and economic value such as golden yellow aril color, sweet and odourless taste, soft and dry texture, long shelf life (7-10 days), high edible portion, and relatively high fruit weight and yield per plant per year. The vegetative propagation of Lai-durian especially using shoot or bud grafting is facing a problem due to the low rootstock availability since Lai-durian seeds show a high percentage of abnormal/undeveloped seeds. This research was performed to evaluate the compatibility and growth performance of the interspecific grafting of two different grafting types, chip budding and cleft grafting using three different rootstock sources, D. zibethinus, D. kutejensis, and D. zibethinus x kutejensis. Three superior national varieties of Lai-durian, i.e., Lai Kayan, Lai Mandong, and Holai Sentawar were used in this research as scion sources. The total number of 180 grafting occasions of chip budding and cleft grafting was conducted using 4–5 months-old seedling plants with 50-60 cm height as rootstocks. The survival rate of the successful grafting and several growth parameters, i.e., plant height, shoot and rootstock diameter, leaf number, and branch number increment were evaluated for two months. The interspecific grafting of Lai-durian on three different rootstock seedlings derived from D. zibethinus, D. kutejensis, and D..zibethinus x kutejensis was compatible and showed a successful graft union using chip budding (94%) or cleft grafting (60%). The use of D. zibethinus and D. kutejensis as rootstocks could replace those of D. zibethinus x kutejensis since there were no significant differences in the grafting compatibility and growth among the three varieties of rootstocks.