Influence of FeSO4.7H2O, Indole-3-Butyric Acid and Different Nutrient Medium on In Vitro Sapling Propagation and Micrografting of Walnut (Juglans Regia L.)

Walnuts are considered a functional food and play a significant role worldwide in people's regular diets. The cultivation and trade of walnut rootstocks and saplings are crucial agricultural activities globally and in Türkiye. Rootstocks are used for grafting and propagating different walnut varieties, and they are essential for tree development, fruit yield, product quantity, and most importantly, their ability to adapt to various ecological conditions and resist diseases and pests. Fruit growing and production of fruit rootstocks of deep-rooted plants in horticulture is given high importance in many countries. However, poor rooting and slow-growing sapling prevent establishing high-yield clonal production. Especially walnut sapling propagation is more complicated and time-consuming than other woody plants. Our research aims to grow high-quality saplings by using biotechnological techniques. This study used modifications to the current in vitro basal medium and evaluated the effects on in vitro rooting and micrografting of walnut species. The optimal medium for shoots induction (2.93±0.90) of the plant was determined as 4 number medium (Murashige and Skoog (MS) nutrient medium with 5.4 µM NAA + 6.9 µM TDZ + 0.6 µM GA3 and solidified with 0.7% agar). In trials to develop sapling, the 10.33 and 6 rooted (2.5cm root length) shoots were obtained from MS nutrient medium with 14.7 and 19.6 µM of IBA and 348.42 µM of FeSO4. 7H2O, and two micrografted plants in MS medium with 19.6 µM of IBA and 348.42 µM of FeSO4.7H2O survived. After three months in the growth chamber, six saplings were ready for transfer to the field. Our findings suggested that FeSO4.7H2O and high dose IBA treatment in MS medium is efficient for in vitro rooting and obtaining in vitro micrografted saplings.