Rhizogenic induction in adult Juglans regia L. cv. Serr tissue induced by indole butyric acid and Agrobacterium rhizogenes

Abstract

The in vitro introduction of adult walnut (Juglans regia L.) tissue represents an opportunity to clone elite genotypes whose selection occurs in advanced ontogenic states. With the purpose of developing a protocol to allow mass propagation of valuable genotypes from adult material, a comparison was made between two root induction systems of walnut microshoots of the fourth subculture of adult walnut tissue of an in vitro introduction program previously reinvigorated through traditional grafting. Rhizogenic induction by indole-3-butyric acid (IBA) and Agrobacterium rhizogenes was used. The rhizogenic process was analyzed in two phases for both auxinic (T1: 3 mg L-1 IBA; T2: 5 mg L-1 IBA) and A. rhizogenes inductions (T3: A-477; T4: A-478). The first phase of root induction was during 3 days in the dark while the second phase, root manifestation, was 27 days. Rooting percentage was evaluated and the induced root systems characterized (number, length, diameter, and root insertion zone) in all the procedures. The best rooting results were obtained in T2, although the response obtained with A. rhizogenes didn't differ from the T1 response. This appears to be an increasingly interesting methodology for adventitious rhizogenesis in this species.