MORPHOGENIC STUDIES IN TISSUE CULTURES OF PAPAYA (CARICA PAPAYA LINN.)

The commonly grown papaya (Carica papaya L.) cultivars in India are dioecious. Natural seedlings develop either into male, female or intersex plants. Identification of the sex of the plant takes about a year which is the normal period of flowering. Therefore one remains uncertain about the sex of the plant till the onset of flowering. If the seedling turns out to be a male plant, the labour and investment for about a year goes waste. Earlier tissue culture works had been done on foreign hermaphrodite cultivars. In the present work tissue cultures of known female plants of dioecious cultivars "Washington', 'Honey dew' and "Ranchi Local' of papaya (Carica papaya L.) were raised on different nutrient media with a view to induce organogenesis or embryogenesis. White's modified medium (WM) or Murashige & Skoog's medium (MS) served as the basal media, while several auxins (2,4-D, IAA, IBA, NAA), cytokinins (KN, BAP) and growth adjuvants (coconut water, casein hydrolysate) at various concentrations and combinations served as supplements. The maximum callusing was obtained from the mesocarp cultures. Differentiation of shoot buds was obtained from the callus raised from young mesocarp, shoot apex and leaf tissues in decreasing order. Highest percentage (40%) of shoot bud formation was achieved on MS containing NAA (2.0 ppm) and BAP (5 ppm). For root formation in 70% cultures, a higher concentration of IAA (5 ppm) and a low concentration of KN (0.5 ppm) was suitable. Both root and shoot bud formation was observed in about 25% cultures on MS containing NAA (1.5 ppm), BAP (2.0 ppm) IAA (2.5 ppm) and glutamine (200 ppm). Embryogenesis could not be initiated.