Regeneration of plantlets from cultured morphactin-induced barren capitula of African marigold (Tagetes erecta L.)

Abstract

Foliar application of morphactin caused high floricidal effects in African marigold plants. In extreme cases only 'barren capitula' which had a bulged receptacle and a suppressed rim were formed. When these capitula were cultured on B5 medium + BAP, they gave rise to small protuberances on the receptacular surface which developed into shoot buds. When these buds were excised and grown on B5 + 10^-5 or 10^-6 M 6-benzylaminopurine (BAP), more callusing ensued and fresh shoot buds were differentiated. The latter developed into green vegetative shoots or strap-shaped, yellow to orange-coloured structures that were midway between leaves and ray florets. On further subculture on B5 + BAP or naphthaleneacetic acid (NAA) or B5 + BAP + NAA, rooting was induced. After 2 months growth, these plants produced miniature terminal capitula. Thus over 115 plants could be raised from a single barren capitulum in 3 months. The present work has demonstrated that the morphactin-induced inhibition of the capitula can be partially overcome and that entire flowering plants can be recovered from their tissues.