Morphogenetic potential of native passion fruit (Passiflora gibertii N. E. Brown.) calli

Some species of non-cultivated passion fruit plant have important contributions to genetic improvement. However, there are few studies concerning about embryogenic and organogenic calli mainly related with structural alterations during their development. The objective of this work was to characterize, structurally the callogenesis on leaf explants of Passiflora gibertii N. E. Brown. The cotyledons were inoculated in MS culture medium, containing half salt concentration, supplemented with sucrose (3 %), and picloram+kinetin for the calli formation. Different calli colors were obtained and used for structural analyses. The calli colors were translucent, white, dark-yellow, white-brown, light-yellow, and white-yellow. After 30 days of cultivation, the calli were fixed in Karnovsky and prepared for the visualization under the scanning and transmission electron microscope and optic microscope. Translucent and light-yellow calli did not present morphogenic characteristics. The cells had different shapes forming non-organized cellular system and the absence or reduced starch content. On the other hand, white and dark-yellow calli manifested embryogenic characteristics such as small isodiametric cells, an organized cellular, dense cytoplasm rich in mitochondria and endoplasmic reticulum, small vacuole and significant starch contend. The culture medium supplemented with 4.14 μM of picloram +0.46 μM of kinetin is the most suitable to induce embryogenic cells.