In vitro Meristem Culture for Rapid Regeneration of Papaya Plantlets in Liquid Media

Abstract

Papaya (Carica papaya L.) is an important crop in Kenya, produced both for local consumption and export. Papaya propagation via seeds makes it difficult in differentiating gender at seedlings phase. However, in vitro system could offer a solution to this problem. This study was an attempt to determine rapid in vitro methods for regeneration of papaya plantlets using liquid and semi solid/liquid double layer media and different concentration of growth regulators. Shoot meristems were harvested from hermaphrodite 30 cm tall papaya seedlings raised in greenhouse and cultured in Murashige and Skoog basal media supplemented with 30 g-1 sucrose, and different concentrations of hormones which were treatments in liquid medium. The treatments comprised five levels (0, 0.05, 0.1, 0.15, and 0.2) of mg.L-1 2 Chloro 4 Pyridy – N Phenyl-urea (CPPU) in liquid and semi-solid/liquid double layer combination for shoot induction. For root initiation, four levels of Indole-3butyric acid (IBA) (0, 2.0, 2.5 and 3.0 mg.L-1) were used. The experiments were laid out in a completely randomized design with 3 replicates. Number of shoots, shoot length and leaf number were recorded every 2 weeks for 8 weeks. The percentage number of shoots that produced roots was also recorded. There was significant differences between the liquid and semi-solid /liquid media and the level of hormones used on shoot induction. The highest number of shoots (10), shoot length and number of leaves was recorded in the semisolid/ liquid double layer combination with CPPU at 0.15 mg.L-1. The highest root initiation (73.33%) was at 3.0 mg.L-1 of IBA. Results indicated that semi-solid/liquid double layer combination could be used for rapid regeneration of papaya plantlets of known gender.