Embryo rescue of Spondias tuberosa and exogenous application of gibberellic acid

Abstract

The umbuzeiro (Spondias tuberosa Arruda) is a native fruit tree of Caatinga and has great economic importance. Its fruits are collected extractivistically due to lack of commercial plantations. Furthermore, the seeds have physical dormancy, which reduces germination rates. However, tissue culture can be used to overcome such problems by excision and in vitro culture of embryos with gibberellin. The objective of this study was to evaluate different disinfection times of zygotic embryos in sodium hypochlorite (NaOCl) and the effect of gibberellic acid (GA(3)) in the in vitro establishment of excised embryos. For aseptic test, zygotic embryos (15 replicates/treatment) were excised and immersed in NaOCl (1.25% active chlorine) for different times (5, 10, and 15 min) and rinsed three times with distilled and sterilized water. The explants were cultured on Murashige and Skoog medium (MS) supplemented with 2.88 µM GA(3). After 30 days we evaluated the contamination and germination percentages. The influence of different concentrations of GA(3) was also tested. Zygotic embryos (24 replicates/treatment) were inoculated onto MS medium with different concentrations of GA(3) (0.0, 0.72, 1.44, and 2.88 µM). After 30 days the germination and normal seedlings percentage, height, number of leaves, fresh and dry weight of shoot and root were evaluated. The experimental design of both trials was completely randomized. The immersion in NaOCl for more than 10 min reduced contamination as well as the germination percentage (p=0.0281). The effect of GA(3) was significant (p=0.0346) in stem elongation in a concentration of 2.88 µM compared to control without gibberellin. The 10-min time was effective in disinfection and gibberellic acid promotes increased height of seedlings.