Different Methods for Overcoming Integumental Dormancy during in vitro Germination of Red Araza Seeds

Red Araza, or Red Strawberry Guava (Psidium cattleianum Sabine) is a native Brazilian Atlantic Forest species of the Myrtaceae family, whose seeds exhibit integumental dormancy. Due to its importance to different industries worldwide, recent research efforts are seeking to expand this species’ micropropagation processes using in vitro seedling germination, especially since in vitro micropropagation of adult plant material has, so far, been limited. This research effort evaluated different methods of overcoming integumental dormancy during in vitro germination of the Red Araza, so as to allow future micropropagation of the species. The seeds’ emergence and vigor were evaluated based on mechanical and acid scarification, using different substrates and immersions in solutions with different levels of gibberellic acid (GA3), and on the influence of the pre-immersion of seeds in water and sulfuric acid. The mechanical and acid scarification of the seeds, combined or separate, resulted in higher in vitro germination percentages and a higher germination rate index (GRI). Pre-immersion in distilled water (20 hours) also proved to be efficient for the germination of the Red Araza seed, with 76.2% of the seeds germinating and a higher speed of emergence (GRI = 0.18). When compared to a Murashige and Skoog (MS-zero) medium, sowing in a hydrophilic cotton substrate showed greater emergence and vigor, with approximately 70% of the seeds germinating. Treating the seeds by pre-immersing them in GA3 turned out to be unnecessary. The methods used for overcoming integumental dormancy during in vitro germination of Red Araza seeds proved to be efficient, and could be used to develop micropropagation protocols of seminal origin for this species.