Evaluation of Growth Rate and Phenotypic Traits of Meristem-cultured Papaya Plants

Papaya in vitro-based micropropagation has been attempted for a number of cultivars. This effort has mainly been geared towards production of multiple unisexual planting stocks in large-scale production of papaya. In this study, a comparison was made on growth performance between tissue-culture generated and direct-seeded papaya plants. Key morphological traits ranging from leaf length to days taken to flowering were employed in evaluating the effect of in vitro propagation on papaya compared to conventionally, seeds generated papaya plants. Three papaya lines for each experimental group were selected at 5-leaf stage and transplanted in a greenhouse. These were set in a completely randomized design with three replicates and the plants subjected to the same soil and water treatment. Data on growth characteristics was collected weekly from transplanting to plant flowering. One way ANOVA was used to generate means which were then separated using Student Newman’s Kules test at p≤0.05. The results showed that direct-seeded and the in vitro-generated papaya plants varied slightly in respect to leaf length and width with both falling within the normal range (leaf width; 30 – 60 cm, leaf length; 45 – 90 cm). It was also noted that, the tissue cultured plants had shorter and narrower leaves compared to the seeds generated plants. On average tissue cultured plants took 95 days to flowering compared to 100 days taken by the direct seeded papaya plants. On average, the stem diameter variation (0.6 cm) was not significantly different at 95% confidence interval. In addition, the average internode length of seeds generated papaya was slightly longer than that of the tissue culture generated plants. From the seven criteria used in the comparison, this study did not record a consistent difference between seeds and tissue cultured papaya plants. In conclusion, in vitro regeneration process does not change the genetics of the papaya plant but provides a rapid production of true-to-type planting materials per unit time.