S04 - Session O2 - Optimizing embryo rescue for coconuts; an essential step for clonal propagation

Authors: Hannes Wilms *, Kevin Longin, Bart Panis

The coconut palm industry is worth about $11.5 Billion, with an annual production of 62.5 M tons of coconuts worldwide. Coconuts are mainly produced on small-scale plantations. However, the palms on these plantations are often grown well past their economic lifespan and are in dire need of replacement. Recently, many coconut growers have been growing hybrid palms (often hybrids of tall and dwarf varieties) as planting material. However, the pollination of coconut palms that leads to the preferred hybrids is, due to their tall size and monoecious nature, difficult and expensive. Recent advances, however, make it possible to clonally propagate individual seedlings on large scale through a new apical shoot micropropagation system. Starting materials for this propagation method are in vitro shoots grown from zygotic embryos. Efficient in vitro germination using embryo rescue is thus an important step in this procedure. While rescuing embryos from coconuts from the supermarket, we encountered several problems such as contamination, poor quality and unknown origin of the coconuts. Therefore, we proceeded with embryos provided to us by the Philippine Coconut Authority and compared different sterilization methods and culture media on the Malayan Yellow Dwarf cultivar. The most promising medium and sterilization method were then applied to 6 different coconut cultivars, representing coconut diversity, while testing embryo placement. The embryos were placed, either horizontally or vertically, on the culture medium, after which their growth was monitored. After 3 months, the horizontally placed embryos grew the largest and developed the strongest root system. However, differences between the cultivars were observed: the embryos of the Markham Valley Tall cultivar showed pink hues during germination and the resulting plantlets were reddish/brownish. Moreover, different growth rates were observed, as the West African Tall germinated significantly slower. Subsequent experiments showed that germination rate and proliferation rate, during the new micropropagation system, were not linked.