Abstract
In general, the current industrial somatic embryogenesis (SE) propagation processes for coffee are costlybecause they are not productive enough. We show that SE-derived plantlets from C. arabica hybrids weretemporarily − between 10 and 25 weeks of development in nursery − able to root with a high success rate(up to 90%) whatever the genotype tested, before gradually losing that capacity. We took advantage ofthis transient rooting capacity, probably due to the rejuvenation process occurring during SE, to establisha new propagation system based on the continuous culture of rejuvenated SE plants and on the serialrooting of cuttings under nursery conditions, known as horticultural rooted mini-cutting (HRMC). Theexcessively low SE efficiency with an embryo-to-plantlet conversion rate of only 37% can be greatly offsetby the much higher HRMC multiplication rate (14 in six months) and better overall quality. Fifteen week-old rooted mini-cuttings proved to be more uniform (2–4.5 vs.1–5.5 cm for plant height distribution) andvigorous (1.41 vs. 0.81 mm for stem diameter) than same-age somatic seedlings. This effect persistedfor five years after field planting, mainly through a slightly greater collar diameter (43.3 vs 40.6 mm),whereas at root level no differences were found. The HRMC method is expected to dramatically reducearabica hybrid production costs (by up to 50% at US$ 0.27/plant ready for field planting) and thus topromote the mass utilization of genetically superior hybrid clones of coffee.