Macropropagation of macadamia nut (Macadamia integrifolia Maiden & Betche) through shoot cuttings

Abstract

Macadamia integrifolia, locally known as Macadamia, is a tree species native to
Queensland, Australia. The species is also recognized as an appropriate option for
land rehabilitation in Indonesia, with one location being the Lake Toba catchment
area in North Sumatra. This species is planted on a large scale because of its
adaptability and relatively short harvesting time. The high demand for macadamia
seeds cannot be supported by the species' ability to regenerate, as natural
regeneration is slow due to the thick and hard seed coat. As a result, a short-term,
quality propagation technique that the community can easily use, such as shoot
cuttings, is required. This study aimed to determine the success of the shoot cutting
technique and the adventitious roots development on macadamia cuttings. The
cutting material was obtained from a healthy mother tree from the Sipiso-piso
garden, North Sumatra. The research was designed by using the factorial complete
block design with two factors randomized design with two factors namely cutting
media (A) and auxin application (B). The media treatment consisted of sand and
topsoil mixture (A1: 1/1 v/v), pure sand (A2), and pure topsoil (A3), while the
auxin application consisted of 0 g (B1), 200 ppm (B2), and 600 ppm (B3). All
treatments were carried out with 3 replications, each consisting of 5 individual
cuttings. The results showed that macadamia shoot cuttings varied survival rate
ranging from 33.33 % to 86.66% with the rooting percentage ranging from 6.66%-
40%. The highest survival rate was found in the top soil mixture: sand and without
auxin treatment (88.66%) while the lowest was found in sand and without auxin
(33.33 %). The cutting media and auxin application did not significantly affect all
the observed parameters. Based on histological root observations, the adventitious
roots of Macadamia form from the wound-induced root with a process that begins
with callus formation and ends with the advent of adventitious roots. This research
found that the juvenile level of the cutting material used is considered a very
important factor in the success of macadamia shoot cuttings.