Establishment of an in vitro propagation and transformation system of Balanites aegyptiaca

Abstract

Balanites aegyptiaca (Balanitaceae) is a drought-tolerant but salt-sensitive tree species distributed in the tropical and arid lands in Africa and Asia. The tree contains many secondary metabolites and a high percentage of oil in the kernels that can be used for biodiesel production. This study aimed to establish an in vitro propagation system of two B. aegyptiaca provenances (El-Kharga and Wadi El-Alaqi) from nodal and cotyledon explants. The explants were placed on Murashige and Skoog medium supplemented with different concentrations of 6-benzyladenine (BA) and thidiazuron (TDZ) for shoot induction. BA was significantly more effective in shoot induction from nodal explants and treatment with BA also resulted in higher regeneration rates of about 40–60 % of adventitious shoots on cotyledon explants, whereas on TDZ-containing medium slightly higher shoot numbers per explant but a negative effect on shoot length were recorded. Rooting was achieved in 40–60 % of the shoots on medium containing between 1.2 and 4.8 µM indole-3-butyric acid. Three different Agrobacterium tumefaciens strains (EHA105, GV3101, and LBA4404) harboring the plasmid pCAMBIA2301 containing the nptII marker and gus reporter genes were used to establish a transformation system in B. aegyptiaca. Strain GV3101 resulted in the highest survival rates and highest number of explants positive in the GUS assay. This selected A. tumefaciens strain was used to introduce pBinAR containing the sequence encoding ERD10 (early responsive to dehydration 10) to produce salt-tolerant B. aegyptiaca plants. The presence of the ERD10 and the nptII gene were detected by PCR in transformed B. aegyptiaca plants.