A Two-Phase System for the In Vitro Culture of Agave guiengola Gentry

Area of Science:

• * Plant Biotechnology
• * Conservation Biology
• * Plant Physiology

Background:

• * *Agave guiengola* Gentry is a critically endangered ornamental species endemic to Oaxaca, Mexico.
• * Its restricted distribution and human activities pose a significant extinction risk.
• * In vitro propagation is crucial for the conservation of this microendemic species.

Purpose of the Study:

• * To evaluate the efficacy of different culture media and plant growth regulators (PGRs) for *in vitro* propagation of *Agave guiengola*.
• * To assess the impact of medium consistency (semisolid vs. liquid) on growth, hyperhydricity, rooting, and callus formation.
• * To propose an optimized biphasic *in vitro* cultivation strategy for enhanced growth and conservation.

Main Methods:

• * Two culture media were tested: Murashige and Skoog (MS) and a modified MS formulation.
• * Plant growth regulators (PGRs) evaluated included 6-benzylaminopurine (BA) for MS media and a combination of kinetin (KIN) and 3-indoleacetic acid (IAA) for modified media.
• * Shoot clusters were cultured in two consecutive 30-day phases, with medium consistency switched between phases to evaluate synergistic effects.

Main Results:

• * The modified MS medium with KIN + IAA yielded the greatest growth (5.5 and 5.0 cm²) in both semisolid and liquid states.
• * Hyperhydricity was significantly reduced in the modified MS medium (0.0%–6.6%) compared to liquid MS media (up to 100%).
• * Transfer from liquid to semisolid medium decreased hyperhydricity (10.47%) versus the reverse (31.35%).
• * Rooting was frequent in modified media, while callogenesis was prominent in MS + BA media (up to 93.2%).

Conclusions:

• * A synergistic biphasic *in vitro* cultivation strategy is proposed: semisolid MS + BA followed by modified MS liquid + KIN + IAA.
• * This optimized approach enhances *in vitro* growth and development for *Agave guiengola* conservation.
• * The study provides a viable method for mass propagation and ex-situ conservation of this threatened species.