In vitro culture of immature embryos may assist mango breeding in the production of hybrid plant material. However, zygotic embryo culture techniques have not been successfully developed for mango. To recover in vitro zygotic plants through embryo culture, ‘Lippens’ and ‘Keitt’ were used as a source of model immature embryos. Excised embryos were incubated in a liquid maturation medium to test different culture systems and media composition. Subsequent germination allowed for the recovery of complete in vitro plantlets. Variables included during artificial embryo maturation, independently or through paired interactions, significantly affected all the parameters measured for embryo development and characterization of the plantlets. Main effects of culture system (i.e., static versus agitation) and coconut water supply (20%) were responsible for up to 85.5% of total treatment variation. Direct and inverse interactions observed between culture system and either coconut water supplement or sucrose content (45 or 60 g·L−1) contributed to define the best combination of factors to improve embryo growth and plant formation. Complete plantlets could be obtained at a frequency above 83% for both cultivars at the end of the in vitro phase at a developmental stage that allowed acclimatization to greenhouse conditions.
Juan Bernardo Pérez-Hernández and María José Grajal-Martín
Víctor Galán Saúco, María José Grajal Martín, Domingo Fernández Galván, Águeda Coello Torres, José Juárez and Luis Navarro
A putative polyploid seedling tree appeared among the polyembryonic mango (Mangifera indica L.) `Gomera-1', widely used as a rootstock in the Canary Islands. Initially detected because of its wider and more coriaceous leaves, further studies showed that fruit from this seedling are considerably larger than normal, although all other fruit characteristics (including polyembryony) were similar to those of standard `Gomera-1' (G-1) fruit. The progeny of this plant has, to date, proved to be morphologically identical to the mother plant. Studies of seedlings from normal G-1 trees growing in the same orchard showed that 10% of the plants had morphological characteristics similar to those of the putative polyploid seedling. Flow cytometry and chromosome count analyses confirmed that G-1 is diploid, whereas the putative polyploid is a stable tetraploid. The study also showed that the morphologically abnormal seedlings from diploid parent trees were spontaneous tetraploids.