An efficient in vitro regeneration protocol for Tagetes minuta

Tagetes minuta is a source of secondary products which are used as pharmace uticals, pesticides and as flavour components in the food industry. Cotyled ons and hypocotyls of T. minuta were cultured on MS medium with combination s of IAA or NAA and BA. Hypocotyl-derived callus developed adventitious sho ots which failed to develop further. Cotyledon-derived callus, cultured on medium with IAA, regenerated adventitious shoots which developed into plant lets on MS medium or half-strength MS with 2.85 mu M IAA. Cotyledons cultur ed on medium with 5.71 mu M IAA + 44.4 mu M BA and transferred to MS medium for shoot growth yielded the highest number of shoots. Nodal segments from developing shoots were micropropagated on half-strength MS medium with 2.5 8 mu M IAA and 95% of plantlets produced adapted successfully to greenhouse conditions. In vitro plants micropropagated from nodes had many shoots whe reas plants regenerated from shoot tips had only a single main stem. This d ifference in morphology was retained after two months growth in a greenhous e. There were no significant differences in leaf and shoot fresh and dry we ights among the regenerated plants after two months growth. After six subcu ltures of cotyledon-derived callus on medium with IAA and BA all explants l ost their ability to regenerate except those cultured on medium with 17.23 mu M IAA and 44.4 mu M BA. The methods of regeneration developed will facil itate selection of T. minuta plants more tolerant of environmental stress, their micropropagation, and the in vitro production of secondary products.