Abstract:
A study was carried out to investigate the effect of culture medium factors that influence the shoot
regenerative potential of Macadamia nodal segments in vitro. Explants were obtained from shoots of
current growth flush of Macadamia integrifolia and inoculated onto different test media. Woody plant
medium (WPM) gave results comparable to MS medium whose macronutrients had been reduced to half
rate. Explants cultured on media gelled with Biotec agar No. 1 and Purified agar had significantly higher
bud breaking frequency and shoot number per explant than Phytagel and Gelrite. Optimum culture
performance was obtained on MS medium enriched with 30 g/L sucrose. Highest bud breaking
frequency (98%), shoot number per explant (8.1) and shoot length (3.3 cm) were obtained when WPM
was supplemented with 2 mg/L BAP, 1 mg/L IBA and 1 mg/L GA3. When elongated shoots were cultured
on to medium supplemented with cytokinins for rooting, only excessive callusing was obtained but no
roots were formed within the culture period. The results of this study indicate that M. integrifolia is
amenable to tissue culture but further studies are required to obtain rooting of in vitro shoots to come
up with an optimized commercially feasible protocol for Macadamia tissue culture.
