Somatic embryogenesis in Carica papaya as affected by auxins and explants, and morphoanatomical-related aspects

Abstract

The aim of this study was to evaluate somatic embryogenesis in juvenile explants of the THB papaya cultivar. Apical shoots and cotyledonary leaves were inoculated in an induction medium composed of different concentrations of 2,4-D (6, 9, 12, 15 and 18 µM) or 4-CPA (19, 22, 25, 28 and 31 µM). The embryogenic calluses were transferred to a maturation medium for 30 days. Histological analysis were done during the induction and scanning electron microscopy after maturing. For both types of auxin, embryogenesis was achieved at higher frequencies with cotyledonary leaves incubated in induction medium than with apical shoots; except for callogenesis. The early-stage embryos (e.g., globular or heartshape) predominated. Among the auxins, best results were observed in cotyledonary leaves induced with 4-CPA (25 µM). Histological analyses of the cotyledonary leaf-derived calluses confirmed that the somatic embryos (SEs) formed from parenchyma cells, predominantly differentiated via indirect and multicellular origin and infrequently via synchronized embryogenesis. The secondary embryogenesis was observed during induction and maturation phases in papaya THB cultivar. The combination of ABA (0.5 µM) and AC (15 g L -1 ) in maturation medium resulted in the highest somatic embryogenesis induction frequency (70 SEs callus -1 ) and the lowest percentage of early germination (4%).

Somatic embryogenesis in the commercial papaya hybrid UENF/Caliman 01 relying on plantlet production from sexed adult hermaphrodite donor plants

“…The results obtained in the present work are in agreement with those reported by Cipriano et al (2018), allowing to infer that papaya cv. golden THB shows greater sensitivity and responsiveness to 4-CPA, as compared to 2,4-D.…”

“…The induction of cotyledonary leaves of papaya cv. golden THB with 2,4-D presented low efficiency, unlike 4-CPA (25 μM), which provided high percentages of embryogenic calli (91.67%) and average number of embryos (65.75) (Cipriano et al 2018). However, using 2,4-D (9.04 or 45.…”

“…reports on the use of 4-CPA in somatic embryogenesis in papaya are still scarce. Nonetheless, Cipriano et al (2018) have successfully reported the induction of cotyledonary leaves in papaya cv. golden THB.…”

“…Considering AC supplementation, its effect is associated with the adsorption of toxic substances, such as phenolic compounds, among other metabolites, which are responsible for the inhibition of morphogenesis, a process that results from cell division and differentiation (Fridborg et al 1978, Martínez et al 2015). According to Cipriano et al (2018), embryogenic calli of papaya cv. golden THB in medium supplemented with ABA (0.5 μM) + AC (15 g L -1 ) showed a higher frequency of SE callus -1 and inhibition of early germination.…”

Differential Influence of Growth Regulators during Somatic Embryogenesis of Gynodioecious Papaya Varieties‘CO.7’ and ‘Red Lady

“…Hence, the induced embryogenic calli were transferred on to somatic embryo maturation medium containing MS medium fortified with different concentrations of ABA and in combination with varying levels of BAP to find out the best combination for hastening maturity. It was earlier reported that ABA allows embryogenesis induction, improves embryo maturation and prevents early germination in papaya [26]. The results revealed that in 'CO.7' and 'Red Lady', the maturation of globular embryos to cotyledonary embryos was 58.33 & 56.67 percentage respectively on MS media fortified with 1.5 mg/L ABA in combination with 0.4 mg/L BAP ( Table 2).…”