Somatic Embryogenesis in Cocos nucifera L.

Abstract

In our coconut laboratory micropropagation has been the subject of research for nearly three decades, as this plant species is highly recalcitrant for in vitro regeneration and so far only achieved through somatic embryogenesis as the sole path for coconut regeneration. Of all the explants tested, plumules have proved to be the most responsive and the process efficiency has been improved by indirect embryogenesis and thereafter secondary embryogenesis and callus multiplication, this strategy is currently applied in floral explants. Two different approaches have been used to find ways to have a more efficient protocol. The first one, a direct and practical method, included plant hormones and activated charcoal. On the other hand, the indirect approach consisted in basic studies on: morphohistological development, biochemical and physiological aspects such as uptake of exogenous auxin, levels of endogenous auxin; shoot apical meristem formation and maintenance (KNOX gene family); the occurrence and expression of genes related to the cell cycle control (Cyclin-Dependent Kinase), and somatic embryogenesis (Somatic Embryogenesis-Related Kinase); and the establishment of a transformation protocol. A better understanding of the somatic embryogenesis of coconut was achieved by these approaches. This way, in the short term there is no doubt that we will have mass propagation options based not only in plumule explants but also on rachillae, unfertilized ovary, and leaf explants.

Cloning Coconut via Somatic Embryogenesis: A Review of the Current Status and Future Prospects

“…In coconut, the type and stage of explant development can significantly affect the responsiveness of the explant to tissue culture [28]. Somatic tissues, such as rachilla segments from immature explants, were commonly used in the early studies of coconut tissue culture because true-to-type clones could be produced from such tissues [7]. However, it is challenging to use these types of coconut tissues.…”

“…This may be because the central tissue contains much of the embryo axis. The callus induction rate was shown to be dramatically decreased when the surrounding, cotyledonary tissue was used [7,34].…”

“…In such Tall types, controlled pollination is required to produce true-totype palms, and this is difficult to achieve on a large scale due to the height these palms can attain at maturity. In addition, when disease-resistant plants are identified, they are usually few in number and therefore unable to produce sufficient seednuts [7] to meet the high demand for disease-resistant seedlings. Similarly, some elite varieties cannot be grown from seed, such as the makapuno and aromatics [8][9][10].…”

“…by Rabechault et al in 1970 [17], and later in coconut by Eeuwens and Blake, in 1977 [18]. To date, these techniques have been considerably improved to be able to produce coconut plantlets in vitro on a large scale [7,19].…”

Response of haustorium tissues and coconut water in somatic embryos induction for the coconut palm (Cocos nucifera L.) variety PB121

“…Coconut palm (Cocos nucifera L.) is a fruit plant cultivated in many countries worldwide that generates important economic value to producers [1]. It contributes significantly for food security, employment generation, and household incomes [2]. In the last 15 years, the commercial importance of coconut has grown rapidly due to its high-value products such as packaged coconut water, coconut oil, coconut milk, coir-biodiesel, fibber derivatives for the automotive industry and horticulture ( [3,4].…”