Optimization of culture media for in vitro rooting of Malus domestica Borkh cv Compact Spartan

Shoots of Malus domestica Borkh. cv. Compact Spartan raised in vitro do not root in a single auxin medium. Components of the rooting medium were tested not only for root initiation but also for root elongation. Root emergence and further growth were inhibited by a too prolonged auxin treatment, the presence of NH4NO3 and the lack of substrate aeration. Saccharose was essential to achieve highly reproducible root growth on agar but was not necessary on watered vermiculite. Ca(NO3)(2) stimulated root initiation, emergence and growth and improved their viability.