Relationship between Induction of Novel Somaclonal Variants and Types of Organogenesis in Muskmelon (Cucumis melo L.)

A comparative study on induction of somaclonal variation in muskmelon (Cucumis melo L.) cv. Birdie regenerants obtained through direct and indirect organogenesis was carried out. Two types of non-meristematic explants (e.g. cotyledon and petiole) were used for this study. A significantly lower (p<0.05) frequency of variation was observed in muskmelon somaclones regenerated via direct organogenesis (MS medium with BAP) compared to indirect (MS medium with BAP and 2,4-D). Morphological study revealed that the somaclones regenerated from proximal cotyledon, petiole and distal cotyledon explants through direct organogenesis did not show any variation in elongation medium at the concentrations of BAP 0.1, 0.3 and 0.5 mg-l, respectively. In contrast, higher number of morphologically somaclonal variants was obtained from these explants at the same concentration of BAP obtained through indirect organogenesis. Other concentrations of BAP, on the other hand, added to the elongation medium showed higher percentage of somaclones with different types of novel variations, e.g. early flowering including higher number of flowers, slow growth of shoots with variant shape of leaves having long and thick petioles, and stubby shoot apices including flattened stem. These variations could be the prime genetic materials to develop new varieties of muskmelon, e.g. high yielding variety, early, late variety, dwarf variety, and variety with desirable body configurations. The results suggest that specific concentrations of BAP or combinations of BAP and 2,4-D have a significant (p<0.05) influence on the induction of novel somaclonal variations in muskmelon regenerants. Future cytogenetic and molecular studies reveal that the novel genetic variations at the chromosome level in somaclonal variants can exist.