Influence of different factors on in vitro multiplication and rooting of three local Juglans regia L. genotypes in Uzbekistan

The Persian walnut (Juglans regia L.) is one of the most lucrative and widely distributed nut crops. It is appreciated as a forestry and ornamental tree in addition to its benefits as a fruit crop. Although Central Asian countries, especially Uzbekistan, are among the origins of the Persian walnut; they are not considered as top industrial producers of walnuts. Uzbekistan possesses a wide range of walnut genetic resources and as a result of conducted research, several promising, fruitful, early -harvesting varieties and forms have been selected. The aim of this study is to optimize microclonal in vitro propagation of selected Uzbekistan local varieties and forms by evaluating concentrations of different plant growth regulators and genotype on multiplication and rooting stages. As mother plants, 2 forms and one variety were selected: the Ideal variety, 'Form PDM23' and 'Form 202YaKT'. On the proliferation stage, the growth rate of walnut microshoots on basal medium Driver and Kuniyuki Walnut Medium (DKW) with different concentrations of 6-benzylaminopurine (BAP) and Indole-3-butyric acid (IBA) (0.01 mg/L) was studied. The rooting stage was assessed in half strength macronutrient DKW medium containing different IBA concentrations (0.0, 2.0, 4.0 and 6.0 mg/L). The Ideal variety and 'Form PDM23' performed best in DKW medium supplied with 1.5 mg/L BAP and 0.01 mg/L IBA, whereas 'Form 202YaKT' performed best in DKW medium supplemented with 1.0 mg/L BAP and 0.01 mg/ L IBA for the proliferation stage. For all genotypes, 6.0 mg/L IBA provided the best rooting results.