OPTIMIZATION OF ROOTING OF IN VITRO PROPAGATED MALUS X DOMESTICA ¿PINOVA¿

Abstract

Following Agrobacterium-mediated transformation of apple, it is rather difficult to achieve rooting of new shoots. Therefore in vitro rooting of micropropagated 'Pinova'apple shoots was tested in different media in order to carry out rooting of transformed shoots. Following a four-day pretreatment in liquid or agar-solidified half strength MS medium containing 0, 1, 2 and 3 mg L -1 IBA, shoots were placed in hormone free agar-solidified or vermiculite-supplemented half strength MS medium. The highest rooting efficiency was achieved when plantlets were pretreated in liquid medium without any hormone. When no IBA was added the efficiency of rooting was 73% in vermiculite and 46.7% in agar. With 1 mg L -1 IBA the efficiency was reduced to 53.3% in vermiculite and increased to 67% in agar-solidified medium. Generally, in medium containing vermiculite a higher number of roots developed. Furthermore, in vermiculite numerous roots were branched and displayed a firm and brown appearance. It was concluded that medium with vermiculite following a pretreatment without hormone promotes rooting of apple. Therefore, the use of vermiculite in the rooting of transformed shoots is suggested.