Technique to minimize phenolics in walnut in vitro culture initiation

Total phenol content of the walnut genotypes was determined to explore the relationship between total phenols and regeneration response for different walnut genotypes. Walnut leaves from ten genotypes (CITHWalnut-I, CITH-Walnut-II, BBW-8, CITH-Walnut-IV, BP-3, SP-1, LG-11, Hamdan, Suleiman, and Opex Culchery) were used for extraction of total phenols through modified Folin-Ciocalteu method. Total leaf phenolic content ranges from 140 μg g⁻¹ (WGB-1) to 285 μg g⁻¹ (BBW-8). Phenolic interactions expressed as darkening of the explants lead to death. Among different antioxidants used ascorbic acid @ 350 mg/l was found best with almost no phenol exudation in the medium and shoot initiation occurred after 8 days of inoculation. The number of shoots was highest (10), followed by citric acid used @ 350 mg/l showing low degree of exudation where shoot initiation was noted in 15 days and with 15.0 shhots per explant.