A novel in vitro rooting method employing an aerobic medium

Abstract

The beneficial influence of an aerobic propagation medium for in vitro cultures during the rooting phase was found for 28 Australian species and genotypes from the families Liliaceae, Haemodoraceae, Myrtaceae, Thymelaeaceae, Proteaceae, Goodeniaceae and Rutaceae. Microcuttings from established shoot cultures were pulsed for 7 days in the dark on a high-auxin (40 µM indole-3-butyric acid, IBA), agar-solidified medium. The microcuttings were then transferred either to an agar-solidified medium without plant-growth regulators (M1) or a sterile propagation mix. The protocol utilising propagation mix used is referred to as IVS (in vitro soil-less medium). The pulsed cuttings in agar or IVS were placed in the culture room under standard light and temperature regimes and allowed to root. When compared over two harvest times, the use of IVS as a rooting medium gave consistent improvements over the use of M1 medium for percentage rooting, average total root length and root number per microcutting. In total, 27 of the 28 species tested rooted in IVS medium at equal or better rates than in M1. In three cases, Actinodium cunninghamii, one of the genotypes of Pimelea physodes and one of the genotypes of Eriostemon australasis shoots did not root in M1 but showed good root development in IVS medium. With few exceptions, average root length and root number in microcuttings rooted in IVS were superior to the lengths and numbers recorded in agar medium. The materials handing advantages and the application of IVS are discussed.