Insight into the In vitro Olive Response to Boron Stress

The present research was conducted to investigate the response of two in vitro growing olive cultivars to deficiency and toxicity of B in the culture medium. The in vitro evaluation system is a quick technique for studying plant response to stress conditions; it ensures consistency of methodology and the credibility of the results obtained. Boron (B) is a micronutrient element that is required for normal plant growth. To date, nothing is known about the response of in vitro growing olive shoots to B deficiency and toxicity. The current research was carried out at tissue culture laboratory of Pomology Department, Faculty of Agriculture, Cairo University, Egypt. Olive shoots of ‘Aggezi Shami’ and ‘Picual’ cultivars were grown on Rugini Olive Media (ROM) supplemented with five B concentrations (0, 12.6 (control), 50, 100 and 150 mg L-1 of boric acid). Our results indicated that B deficiency and toxicity had a negative effect on in vitro growing olive shoots of both cultivars. Control and 50 mg L-1 of B produced higher values of olive shoot growth parameters. Olive shoots exhibited a moderate chlorotic appearance and high shoots mortality with 0 and 150 mg L-1 B. By increasing B concentration of the culture medium B contents in explant increased as well as chlorophyll contents declined in response to increased B concentration in the culture medium. Shoots grown on boron-free medium also showed a significant reduction when compared to control treatments. To boron, the 'Aggezi Shami' cv. was more stress tolerant than the 'Picual' cv.