CHANGES OF THE PHENOLIC METABOLISM EXPRES SION IN WALNUT MICROSHOOTS AND REACTIVITY IN TISSUE-CULTURE

Antisense CHS gene strategy was developed in walnut to study the invol vement of flavonoids in rhizogenesis processes. A 400 bp sequence from a walnut CHS gene in antisense position was introduced in walnut soma tic embryos by Agrobacterium tumefaciens. Using secondary embryogenesi s, in vitro culture of embryonic axes and micropropagation, 13 transfo rmed lines by the antisense CHS gene were produced in tissue culture ( microshoots). Six of them strongly under-expressed the CHS genes and l ost their capacity to accumulate flavonoids (flavonols and flavanols) in their tissues. These explants formed large calli in their base and showed dramatic apical necroses after the root induction phase. The ro oting tests would indicate that a strong decrease of the endogenous co ntent in flavonoids is associated to an increase of rooting capacity i n walnut microcuttings.