Jean-Paul Ducos

Somatic embryogenesis and vegetative cutting capacity are under distinct genetic control in Coffea canephora Pierre

The purpose of the study was to evaluate the possible genetic effect on vegetative propagation of Coffea canephora. Diversity for somatic embryogenesis (SE) ability was observed not only among two groups of C. canephora Pierre (Congolese and Guinean), but also within these different genetic groups. The results therefore showed that, under given experimental conditions, SE ability is depending on genotype. Furthermore the detection of quantitative trait loci (QTLs) controlling the SE and cutting abilities of C. canephora was performed on a large number of clones including accessions from a core collection, three parental clones and their segregating progenies. On the one hand we detected eight QTLs determining SE. Six positive QTLs for SE ability, whatever the criteria used to quantify this ability, were localized on one single chromosome region of the consensus genetic map. Two negative QTLs for SE ability (frequency of micro calli without somatic embryo) were detected on another linkage group. Deep analysis of the six QTLs detected for SE ability came to the conclusion that they can be assimilated to one single QTL explaining 8.6–12.2% of the observed variation. On the other hand, two QTLs for average length of roots and length of the longest sprouts of cuttings were detected in two linkage groups. These QTLs detected for cutting ability are explaining 12–27% of the observed variation. These observations led to conclude that SE and cutting abilities of C. canephora Pierre appeared to be genetic dependent but through independent mechanisms.

A new approach for automation: Sorting and sowing dehydrated somatic embryos of Daucus and Coffea using seed technologies

Somatic embryos of Daucus carota L. and Coffea canephora L. (var. Robusta) were dehydrated under a 43 % relative humidity then placed in the hopper of a precision seeding system used in the transplant industry. The seeder was adjusted to distribute the embryos onto horticultural trays, each one containing 240 cells filled with soil. As a preliminary result, 72 % and 88 % of the individual cells received a single embryo, in Daucus and Coffea respectively. The embryo-to-plantlet conversion rate was not affected either by the vibration of the hopper or by the nozzles. In carrot 66 % of the embryos germinated after the use of the seeding system (62% germination for the control). Sorting methods traditionally used for the seeds (e.g. air column, vibrating table) can also be used. Such an approach, based on desiccation as a key step, has the potential for a complete automation of the large-scale handling and delivery of somatic embryos.