EFFECT OF EXOGENOUS INDOLE BUTYRIC ACID (IBA) ON ROOTING AND LEAF GROWTH OF SMALL DATE PALM OFFSHOOTS (PHOENIX DACTYLIFERA L.) DERIVED FROM ADULT VITROPLANTS OF 'NAJDA' CULTIVAR

‘Najda’ (INRA-3014) is one of the interesting date palm genotypes that were selected for several highly desirable characters, micro-propagated and distributed as vitroplants to date palm growers in Morocco. However, it has been frequently found that adult vitroplants of this cultivar produce lots of offshoots, most of which are high offshoots. Removal of these offshoots is essential for the mother plant and the removed offshoots can be used as an additional source of high quality planting material for the intensification of date palm cultivation in Morocco. Promoting root formation on these offshoots weighing less than 8 kg is therefore essential. The present study was conducted to evaluate the effect of exogenous indole butyric acid (IBA) on root formation and leaf growth of ‘Najda’ small offshoots. Removed offshoots from adult ‘Najda’ vitroplants grown in the Zagora Date Palm Experimental Station were separated in 4 weight groups (0-2, 2-4, 4-6 and 6-8 kg). Prior to planting in pots, offshoots were dipped for 15 min in 4 IBA solutions (2, 5, 10 and 15 mg L^-1). Results showed that exogenous IBA induced significant rooting of ‘Najda’ offshoots. More than 96% of offshoots rooted if treated with 10 or 15 mg L^-1 IBA solutions, while only 50% rooting was obtained with 2 mg L^-1 IBA treated and control offshoots. These rooted offshoots produced an average of 12 visible roots per offshoot. Furthermore, 90% of offshoots of less than 2 kg rooted well if treated with 10 or 15 mg L^-1 IBA solutions. Offshoots’ rooting was also accompanied by a good leaf growth. During this 8-months experiment, offshoots treated with 10 or 15 mg L^-1 IBA solutions produced an average of 4 new leaves, and an increment of 9 cm in the central leaf length. Based on these results, it seems reasonable to conclude that treatment with 10 or 15 mg L^-1 IBA solutions, allows a good rooting of small high offshoots of ‘Najda’.