Analysis of in-vitro explants mineral contents to modify medium mineral composition for enhancing growth of Persian walnut (Juglans regia L.).

摘要

Micropropagation of Persian walnut (Juglans regia L.) still needs more study to be used consistently in various cultivars. Due to slow growth and yellow appearance of Persian walnut explants in DKW medium, a trial was conducted to refine the DKW medium composition. The method consists of adding the mineral composition that the walnut explants contain in the period of maximum growth to the DKW medium. The mineral composition of the explants of two walnut cultivars (Sunland and Chandler) were determined by ICP-OES technique. Two modified media (mDKW) were formulated based on the walnut explant mineral contents. Because of inappropriate concentration of nitrogen and calcium, media with two ranges of calcium and nitrogen were formulated; (1) mDKW₁ (DKW with 6 modified macronutrient concentrations) and (2) mDKW₂ (DKW with 4 modified macronutrient concentrations). Other minerals were formulated based on explant mineral concentrations. The growth rate of explants cultured on mDKW was compared to those cultured on DKW medium. There were no deficiency symptoms in explants in mDKW. Among the cultivars, Chandler had the maximum stem length and auxiliary bud number. Explants grown on mDKW₂ produced the maximum stem length and auxiliary bud number. Also the explants grown on mDKW₂ showed no deficiency and yellow color leaves after 30 days. The results suggested that micropropagation in a medium containing mineral balance similar to that in explants may hold a hypertonic concentration of minerals for them to move from medium to explant and therefore will obtain better growth and proliferation conditions for explants.