Somatic embryo germination of Psidium guajava L. in the Rita® temporary immersion system and on semisolid medium

Abstract

Germination of somatic embryos and development to plants is recognized as one of the most critical stages in the process of plant propagation via somatic embryogenesis. The objective of the study was to investigate the germination of somatic embryos of Psidium guajava cv. Cuban Red Dwarf EEA 18–40 in the RITA® system and on semisolid medium. Somatic embryos were obtained from immature zygotic embryos which were cultured on the major salts of MS medium at half strength, supplemented with 400 mg l⁻¹ L-glutamine, 100 mg l⁻¹ ascorbic acid, 60 g l⁻¹ sucrose and 1 mg l⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D). Somatic embryos at the heart and torpedo stages were transferred for germination into RITA® vessels containing liquid half strength MS medium of the major salts supplemented with 0.25 mg l⁻¹ 6-benzylaminopurine (6-BAP), 10 µg l⁻¹ Biobras-6 (brassinosteroid analogue) and 20 g l⁻¹ sucrose or to semiliquid medium of the same composition (solidified with 2.5 g l⁻¹ Gellum Gum, Spectrum®) in 250 ml glass vessels. The germination percentage, fresh weight and number of somatic embryos with complete germination were determined. After 10 weeks of culture the highest germination percentage (91%) and fresh weight (1.22 g) were achieved in the temporary immersion system, being statistically superior to those obtained from semisolid culture medium (81.79% and 1.03 g respectively).