S04 - Session P1 - New Tools I - Micrografting on Morus nigra on Morus alba

Authors: Juan Luis Fernández *

In a previous work , t hree clones of Morus alba ( ' Criolla ' , ' Tigrenda ' and ' Illa Verde ' ) and a clon e of M. nigra (Bande) selected for fodder use were tested in the field . M. alba clones showed significantly higher growth rate s than M. nigra . In this work , clone 'Bande' was micrografted on clones 'Illa Verde', ' Criolla ' and 'Tigrenda ' to evaluate graft - take, and rooting percentage of rootstocks in different culture conditions, and to obtain grafted plants for new field trials. In a first experiment , 1.5 cm-long nodal segments of clone 'Bande' were micrografted on 2 cm-long unrooted nodal segments of the M. alba clones. M icrograft s were cultured on WPM supplemented with 0 . 88µM BA . At day 60 , graft - take was between 83 .3 - 91 . 7% (100 % in self-grafting ) , and 77 . 3 - 85 .0 % of microscions developed new shoots (95 . 8% in self-grafting ) . R ooting percentage of the M. alba rootstocks ranged from 27,0- 35,0%, and was 0% in ' Bande' ( self-grafting ) . In a second experiment , the micrograft s were established under three different culture conditions , (a - WPM medium ; b - WPM medium supplemented with 0,88µM BA; c - pretreatment of the micrografts by 30 s- dipping in 5 mM IBA solution , followed by introduction in WPM without PGR ). Graft-take ranged between 87.5-100 %, with no significant differences among rootstocks ( including self-grafting ) or culture conditions . Concerning rooting rate of the rootstocks at day 30 , in clones Illa Verde and Criolla , rooting was higher in medium without BA , both in pretreated and non- pretreated micrograftings . 'Illa Verde' rooted significantly better (73.0-79.1%) than ' Criolla' (45.8-58.0%) , while in 'Bande' rooting never exceeded 8.3% .