A novel regeneration system through micrografting for Argania spinosa (L.) Skeels, and confirmation of successful rootstock-scion union by histological analysis

Abstract

A novel regeneration system through micrografting is reported for the endangered Argania spinosa (L.) Skeels. Rootstocks were obtained from in vitro germinated seeds of the argan genotype G27. It was found that the storage time significantly affects the seed germination capacity, and that the seeds cultured immediately after harvest exhibit the highest germination percentage (91.6%). Besides, transferring seedlings to half-strength Murashige and Skoog (½MS) medium supplemented with 1 mg l−1 gibberellic acid (GA3) and 1 mg l−1 6-benzylaminopurine (BAP) resulted in the highest shoot and root lengths (2.05 and 5.73 cm, respectively). Scions were taken from axillary shoots developed in vitro from microcuttings of genotype G41. Micrografting was performed by using the wedge technique. Afterwards, the micrografted plants were transferred to media supplemented with different plant growth regulators (PGRs). After 2 months of culture, 65–100% of the micrografted plants survived, and no difficulties were observed during the formation of the rootstock-scion union. Interestingly, the use of GA3 at concentrations ranging from 0.1 to 1 mg l−1 was essential for successful micrografting (85–100%) and subsequent growth and development of shoots (2.40–2.72 cm length). After micrografting, scions produced one, two or multiple shoots, depending on PGRs. Histological analysis clearly demonstrated the successful union between rootstocks and scions, with active cell division and vascular tissue formation in the grafting region. After transferring the micrografted plants to the glasshouse, a survival rate of 80% was observed, and the plants showed normal growth and development. An efficient micropropagation system through in vitro grafting is reported for the first time ever for Argania spinosa (L.) Skeels, and successful micrografting is confirmed by histological analyses.