Sexual Propagation of the Tunisian Spinescent Opuntia ficus-indica (L.) Mill., Morphogenetic Deployment and Polymorphism

Abstract

The most common means of Opuntia ficus-indica (L.) Mill. propagation is through the use of asexually methods without genetic recombination which has been extensively studied for commercial purpose or to reduce erosion and desertification. However, seeds are important units to be considered for maintaining the species genetic variability. With the aim to undrestand the morphogenetic polymorphism deployment of the Tunisian spinescent Opuntia ficus-indica from the juvenile to the advanced stages, we search, firstly, the optimal conditions permetting to ensure the highest germination rate during the shortest period with sulphuric acid scarification in ten levels time of dipping. The best germinated rate (68.0%) is reached within 30 min of treatment exposure. Some germinated seeds showed polyembryony phenomenon. The highest rate (29.3%) was recorded after 25 and 30 min of pretreatment. Occurrence of morphogenetic abnormalities: tricotyledony, dissymmetried, coiled and adhered cotyledons in percentages varying from 12.8 to 20.0% was also reported. Secondly, a morphogenetic tracking of Opuntia ficus-indica young seedlings to adult plants during seven years (2009-2015) from the germination of seeds to the production of seeds was performed. This essay allowed us to report major seedling characteristics, their growth and phenotypic polymorphism: vertical succession of varying numbers of basal cladodes, future plant trunk formation, development and arrangement of secondary cladodes in the space, spinescence polymorphism and the first flowering and fruiting.