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 arearbitrary selected to provide essential nutrients for plant in vitro cultures. Evidence suggests that invitro response to various media formulations varies among genotypes and depends on the culturestage. This study examined the efficacy of five basal salt formulations on callus growth and somaticembryogenesis in date palm Phoenix dactylifera L. using three commercial cultivars, Khusab, Bernyand Barhee. Approach: Callus from shoot tip explants maintained on MS medium was introduced tovarious media formulations including SH, W, MS, WPM and NN media containing 53.7 μM NAA and7.4 μM 2iP. To assess the effect on callus growth, fresh callus weight was measured 4 and 8 weaklater. To evaluate embryogenesis response, callus was transferred to hormone-free mediacorresponding to those during callus growth stage. Results: The optimum medium formulation variedaccording to cultivar and culture stage. Extending callus growth to 8 weak allowed for greaterdiscernment of differences as compared to 4 weak because of the inherent slow growth nature of datepalm callus. The best callus growth was achieved in cv. Khusab using W and WPM media, cv. Bernyusing SH and NN medium and cv. Barhee using SH, W and MS media. An optimal medium for callusgrowth was not necessarily the best for somatic embryogenesis. The highest regeneration percentage incv. Berny occurred on WPM medium, cv. Khusab on W medium and cv. Barhee using W and WPMmedia. 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 studyprovides important information to optimize medium formulation in micropropagation protocols ofvarious date palm cultivars, particularly recalcitrant genotypes. It showed that the best basal saltformulation differed among date palm genotypes and suggested culture stage-specific requirement. © 2010 Science Publications.