Agrobacterium-mediated transformation of Persian walnut usingBADHgene for salt and drought tolerance

Transgenic walnuts (Juglans regiaL.) were produced in the presence of theAgrobacteriumstrain LBA4404 and the plasmid pBI121. This plasmid contains aBADHgene driven by a CaMV 35S promoter. It further includes anNPTIIgene as a selectable marker which, in turn, is driven by a NOS promoter. Somatic embryos of the walnut cultivar 'Chandler' were inoculated using anAgrobacteriumsuspension. Secondary embryos that developed on a selection medium were driven towards germination so as to develop micro-shoot cultures. The regeneration rate was 5.5%. PCRand southern blot analysis were used for confirming that theBADHtransgene is successfully integrated into the plant genome. Transgenic and wild-type plants raised from somatic embryos were exposed to four osmotic stress levels (i.e. 0%, 2%, 4%, and 8% PEG) and four salinity levels (i.e. 0, 50, 100, and 200 mM NaCl). After 21 days, the transgenic plants grew almost vigorously in saline and drought-stress conditions, whereas the wild-type ones showed retarded levels of growth and did not survive after the cradle stage. These results show that theBADHgene can be expressed effectively in transgenic plantlets of walnut and can be used for breeding walnuts against drought and salinity.