Morphogenetic variation in the multiplication and rooting in vitro of wild clones of chocolate cosmos (Cosmos atrosanguineus)
The chocolate cosmos (Cosmos atrosanguineus Sherff) is an ornamental species endemic from Mexico, which has the capacity to produce tuberous roots. The species is reported almost extinct from its natural environment. In 2015, a wild population of chocolate cosmos was collected. In order to study the in vitro morphogenetic response in this species, five wild clones and a cultivated one were evaluated. Nodal and leaf segments were established to obtain callus in two clones. For direct organogenesis, nodal segments of the five wild clones were used. In a cultivated and a wild clone, the response to the photoperiod and its effect on multiplication, in addition to the effect of sucrose and photoperiod on rooting, were evaluated. The response to phloroglucinol during rooting in the cultivated clone was also assessed. The results show that the response to callus formation with 2,4-D was observed in only 50% of leaf segments. The best BA response was in nodal segments with 100% callus formation. In the direct organogenesis stage, the effect of BA was different for all the clones, originating from one to 12.6 shoots. No clear effect was observed in the photoperiods tested. Phloroglucinol doubled the root number per shoot from 11.1 to 24.2. Root length decreased as sucrose concentration increased. It is concluded that all the clones evaluated showed different responses during in vitro morphogenesis and that specific protocols are needed for their efficient micropropagation.
Gómez-Pedraza, D.E., Mejía-Muñoz, J.M., Martínez-Solís, J. and Morales-Vázquez, B. (2019). Morphogenetic variation in the multiplication and rooting in vitro of wild clones of chocolate cosmos (Cosmos atrosanguineus). Acta Hortic. 1237, 243-250
micropropagation, morphogenesis, organogenesis, photoperiod, sucrose