Evaluation of root-to-shoot de novo organogenesis in wild guava species, Psidium schenckianum and P. guineense (Myrtaceae)

We aimed to evaluate the organogenic responses of root explants of Psidium schenckianum and P. guineense inoculated onto JADS liquid culture medium containing different concentrations (0.00, 2.22, and 4.44 µM) of 6-benzyladenine (BA) alone or in combination with 0.054 µM α-naphthaleneacetic acid (NAA). After 60 days of culture, the percentage of explants with shoots (PES) and number of shoots (NS) were recorded. Root explant samples were collected and analyzed under light and scanning electron microscopes. Elongated shoots were rooted and acclimatized. After acclimatization, the genetic stability of regenerated plants was characterized by flow cytometry. Shoot regeneration of P. guineense occurred at all treatments. On the other hand, the P. schenckianum did not respond at any conditions. The P. guineense species had the highest NS and PES at 2.22 and 0.00 µM BA, respectively, with no difference between these treatments. Shoots were formed via direct organogenesis from cells associated to the vascular tissues. Regenerated plants were acclimatized, yielding 100% survival rate. These regenerated plants kept the same ploidy as that of seed-germinated counterparts. This is the first report of P. guineense regeneration from root explants, which is a promising alternative for the micropropagation of this species.