Optimized protocol for high-frequency papaya propagation: morpho-stereomicroscopic analysis and genetic fidelity assessment.

Papaya is an important crop with a short juvenile phase among the fruit crops. Direct and indirect regeneration protocols were developed for papaya cultivar Red Lady 786, by using apical, nodal, petiole, leaf and root segments. For direct regeneration, plant growth regulators (PGRs) i.e. BAP, Zeatin and NAA and indirect regeneration BAP, Kinetin, TDZ and NAA were investigated. The study showed that apical and nodal segments can undergo direct regeneration with distinct shoot differentiation without the callus phase, resulting in a high success rate of shoot development (65–88%). The indirect method involves the initiation of callus tissues, followed by morphogenesis of somatic embryogenesis significantly influenced by PGRs. A high success rate of somatic embryogenesis (ranging from 75–85%) was observed in cultures derived from multiple explants. The presence of somatic embryogenesis at specific differential stages, namely globular, heart, torpedo and cotyledonary had confirmed through stereo-microscopic analysis. The result significantly indicated that the supplementation of MS media with TDZ (0.3 mg/l), BAP (1.0 mg/l), NAA (0.10 mg/l), and 30 mg/l sucrose as the most efficient medium for somatic embryogenesis. Somatic embryos were sub-cultured on BAP, Kinetin and NAA resulted in a high frequency (75–80%) of complete plantlet regeneration except for root segment explant derived somatic embryos. The in-vitro regenerated plants via direct and indirect regeneration were successfully acclimatized in greenhouse with 88.89% survival rate. The genetic fidelity was checked by using 22 RAPD and 18 ISSR markers. This developed protocol may be utilized for commercial production of ‘Red Lady 786’ papaya plantlets. [ABSTRACT FROM AUTHOR]