CALLUS INDUCTION FROM FLORAL EXPLANTS OF CUPUASSU

Abstract

There are few studies related to the in vitro cultivation of plants from theTheobroma genus and no effective micropropagation protocols for T.grandiflorum. The aim of this study was to evaluate the calli formation in cupuassu floral explants, targeting their organogenic or embryogenicdevelopment. Experiments were conducted in the Plant Tissue Culture Laboratory of EMBRAPA, Porto Velho, Rondônia, Brazil. Floral parts from unopened immature flower buds taken from seedless cupuassu trees were sterilized and employed as a source of explants. These explants were cultivated in Petri dishes in an induction medium consisting of MS salts and vitamins, supplemented with glycine(3 mg.L-1), lysine (0,4 mg.L-1), leucine (0,4 mg.L-1), arginine (0,4 mg.L-1), tryptophan (0,2 mg.L-1), 2,4-D (1 mg.L-1), kinetin (0,25 mg.L-1), coconut water (50 ml.L-1), sucrose (40 g.L-1), Gelrite (2,2 g.L-1) and pH adjusted to 5,8. Cultures were maintained in the dark for 3 weeks at 27°C and then subcultured for six weeks in medium without growth regulators supplemented with glycine (1 mg.L-1), lysine (0,2 mg.L-1), leucine (0,2 mg.L-1), arginine (0,2 mg.L-1), tryptophan (0,1 mg.L-1), coconut water (100 ml.L-1), sucrose (40 g.L-1), Gelrite (2,2 g.L-1) and pH 5,8. We used a completely randomized design with 10 replications of 5 explants per plate and four different explant sources: staminode, petal, ligule and ovary. As a result, we obtained a highercalli formation in theinduction medium when ovaries were used as source of explants. However, there was no development of somatic embryosor organogenic response in medium without growth regulators and further studies are being conducted.