Basal Salt Requirements Differ According to Culture Stage and Cultivar in Date Palm Somatic Embryogenesis

Abstract

Problem statement: Various media formulations differing in basal salt composition are arbitrary selected to provide essential nutrients for plant in vitro cultures. Evidence suggests that in vitro response to various media formulations varies among genotypes and depends on the culture stage. This study examined the efficacy of five basal salt formulations on callus growth and somatic embryogenesis in date palm Phoenix dactylifera L. using three commercial cultivars, Khusab, Berny and Barhee. Approach: Callus from shoot tip explants maintained on MS medium was introduced to various media formulations including SH, W, MS, WPM and NN media containing 53.7 μM NAA and 7.4 μM 2iP. To assess the effect on callus growth, fresh callus weight was measured 4 and 8 weak later. To evaluate embryogenesis response, callus was transferred to hormone-free media corresponding to those during callus growth stage. Results: The optimum medium formulation varied according to cultivar and culture stage. Extending callus growth to 8 weak allowed for greater discernment of differences as compared to 4 weak because of the inherent slow growth nature of date palm callus. The best callus growth was achieved in cv. Khusab using W and WPM media, cv. Berny using SH and NN medium and cv. Barhee using SH, W and MS media. An optimal medium for callus growth was not necessarily the best for somatic embryogenesis. The highest regeneration percentage in cv. Berny occurred on WPM medium, cv. Khusab on W medium and cv. Barhee using W and WPM media. The highest number of resultant embryos was achieved in cv. Khusab using W and SH media, cv. Berny on WPM and MS media and cv. Barhee using W and SH media. Conclusion: This study provides important information to optimize medium formulation in micropropagation protocols of various date palm cultivars, particularly recalcitrant genotypes. It showed that the best basal salt formulation differed among date palm genotypes and suggested culture stage-specific requirement.