Abstract

Aseptic cultures of pineapple ‘smooth cayenne’ were established from shoot tip explants. They were initiated on Murashige and Skoog (MS) basal medium with vitamins supplemented with various combinations of 6-benzylaminopurine (BAP) (0, 0.1, 0.2, 0.3 and 0.4 mg L^-1) and Gelrite [1.0 g L^-1 (semi-liquid), 1.5 g L^-1 (semi-solid) and 2.0 g L^-1 (solid)]. Explants were transferred five weeks after in vitro initiation to semi-liquid medium containing higher concentrations of BAP (0, 0.5, 1.0, 1.5 and 2.0 mg L^-1) for proliferation. Four sub-cultures were made at five weeks interval for twenty weeks in the proliferation medium. Established shoots were introduced into rooting medium containing either full (4.4 g L^-1) or half (2.2 g L^-1) strength MS basal medium with vitamins supplemented with 0, 0.5 mg L^-1 BAP alone or in combination with 0, 0.9 and 1.8 mg L^-1 α-naphthaleneacetic acid (NAA). Semi-liquid MS basal medium supplemented with 0.1 and 0.3 mg L^-1 BAP gave the best regeneration results, producing the highest average shoot length (34.6 mm) and average number of shoot buds (2.4) per explants. Significant difference (p≤0.05) in average shoot number per explant was observed with semi-liquid MS basal medium supplemented with 1.5 mg L^-1 BAP, producing the highest average shoot number (6.1) per explant at 5 weeks and this increased to 167.7 after 20 weeks. The half-strength MS basal medium without growth regulators or with 0.9 mg L^-1 NAA gave the highest average root length (29.3 mm) and root number per shoot (7.9). The semi-liquid MS basal medium supplemented with low BAP (1.5 mg L^-1) is a cost-effective method for in vitro propagation of pineapple. Half strength MS basal medium without hormones or with low NAA are also cost-effective methods for inducing roots in pineapple.

Key words: Gelrite, growth regulators, medium type, pineapple, propagation.