**4. Factors that influence the occurrence of somatic embryogenesis**

The control of the occurrence of somatic embryogenesis in *Coffea* is not yet completely identified. Some authors relate the genetic pattern of the species with the absence or low responsiveness [87]. Knowing the factors that control the occurrence of somatic embryogenesis in *C. arabica* will allow to optimize its application and especially the direct pathway. The high or low capacity of somatic embryogenesis of a species is related to the presence of competent cells or not in the explant, inherent to their totipotency [88]. The maintenance of somatic embryogenesis capacity requires the use of conditions that maintain the proliferation of determined and competent cells [86].

Somatic embryogenesis regeneration capacity is also associated with other factors such as explant donor plant developmental stage, explant donor plant physiological conditions, explant position relative to the plant [89], *in vitro* culture conditions and mainly of plant growth regulators. The seasons influenced the indirect somatic embryogenesis response of plant explants to eight *C. arabica* genotypes in the field [56]. Explants formed more somatic embryos in the fall-winter season than in the spring-summer season.

**11**

*Observations on Somatic Embryogenesis in* Coffea arabica *L.*

each month, and can reach sizes up to 30 mm.

size and shape in the presence or absence of light.

*4.1.2 Cultivation temperature*

**4.2 Plant growth regulation**

induction in *C. arabica* explants [91].

the 2.5 and 5 μM doses [95].

In indirect somatic embryogenesis of *C. arabica*, calli are induced and initiated in the absence or presence of light, but they reach a larger size only if maintained in the absence of light [45, 86]. The size of these callus increases gradually

On the direct pathway, *C. arabica* explants also have difficulty responding in the presence of light. In this way, at the edge of the explants, small structures are formed, which are called embryogenic structures, which remain without change in

Cultivation temperature is another factor that may influence the somatic embryogenesis response. Leaf explants of cultivar Catuaí and two hybrids showed

Several studies indicate that phytoregulators play a decisive role in controlling the formation of somatic embryos in *Coffea* leaf explants, which is the most explored aspect on this subject. For the induction of the indirect pathway in *C*. *arabica*, the auxin/cytokine combination, which is already well established for this species, is generally used. In this pathway, auxin 2,4 D has been the most used to induce callogenesis in *C. arabica* leaf explants. This auxin is considered strong and

For induction of the direct pathway, most studies use cytokine without auxin because it tends to inhibit its occurrence. However, the efficiency of the direct pathway response may vary depending on the type and concentration of cytokine employed. A pioneer study showed that 6-BA at 5 μM dose matched direct pathway

The formation of somatic embryos was also obtained from *C. canephora* explants

inoculated in MS medium only with addition of different cytokines being 2-iP, ZE, Ki and 6-BA, all at a concentration of 5 μM [92]. Explants formed somatic embryos in the presence of all cytokines, but responses varied according to cytokine type. The 2-iP was more efficient than the ZE, Kin and 6-BA. In this study, it was also found that auxins used at different concentrations inhibited the direct somatic embryogenesis of these genotypes. In another study, Zeatin caused the direct pathway response in *C. canephora* explants [87]. Cytokine 2-iP also caused direct pathway induction in *Coffea* [93, 94]. In another study, it was found that 2-iP concentrations of 7.5 and 10 μM favored a greater number of somatic embryos than

Synthetic cytokine 6-benzylaminopurine also has the ability to induce the direct pathway in *C. arabica* explants [69, 91, 96–98]. The 6-BA used at 30 μM concentration caused higher production of somatic embryos than the 10 and 20 μM doses in leaf explants of the cultivar Mundo Novo de *C. arabica* [46]. But although the 6-BA concentration was high, embryo production was reduced and the process also took place over a long time. However, this result is interesting because it favors the cost reduction of clonal seedling formation since 6-BA is a cheaper and available synthetic cytokine than zeatin and 2-iP. Cytokine TDZ

higher formation of somatic embryos at 30°C compared to 25°C [90].

is also used for the induction of anthers [39, 40] and roots [47, 48].

*DOI: http://dx.doi.org/10.5772/intechopen.90853*

**4.1 In vitro culture condition factors**

*4.1.1 Lighting*
