Micropropagation of apple proliferation-resistant apomictic Malus sieboldii genotypes
¹ IASMA Research Centre - Plant Protection Department, Via E.Mach,I-38010 San Michele all’Adige (TN) – Italy
² AlPlanta – Institute for Plant Research, RLP AgroScience, Breitenweg 71,D-67435 Neustadt/W. – Germany,
*corresponding author: firstname.lastname@example.org
Apple proliferation (AP) is a serious disease of apple in Europe. Natural resistance was found in apomictic Malus sieboldii-derived genotypes which can be used as rootstocks and whose agronomic value is actually improved in ongoing breeding programs. As these genotypes are difficult to propagate by standard procedures micropropagation was established and validated in this study to multiply the material in larger scale. A propagation protocol was developed for in vitro establishment, multiplication and rooting of eleven interesting AP-resistant genotypes. For the optimisation of the multiplication medium, four different macro and micro element formulations were tested: MS, QL, WPM and DKW. Phytohormones (0.25 µM IBA, 4.44 µM BAP and 0.28 µM GA3) and vitamins (MS modified for thiamine at 2.96 µM), established for the propagation of M. domestica, were also suitable for the propagation of M. sieboldii-genotypes. The MS medium yielded in general the highest proliferation rates and the best shoot growth. Significantly better growth with the MS medium was also favoured by replacing Fe-EDTA by Fe-EDDHA as the iron source. By comparing four different rooting treatments a significantly higher percentage of rooting was observed when the induction was carried out in the dark with 25 µM IBA either in liquid or agarised medium. The time required for root formation on hormone-free medium varied among the different genotypes and three classes, low, medium and high rooting efficiency could be defined. The acclimatisation method adopted for the ex vitro plants in the greenhouse yielded survival rates between 90-100% for most of the genotypes.