Recovering polyploid papaya in vitro regenerants as screened by flow cytometry

Abstract

Several protocols have been proposed for in vitro propagation of papaya, either based on somatic embryogenesis or shoot organogenesis. It is well-known that tissue culture-based approaches are frequently associated with somaclonal variation. Whether on the one hand this phenomenon can preclude further stages of in vitro culture, on the other hand it can generate useful genetic variability for crop improvement. However, somaclonal variation analyses are limited in papaya tissue culture. The DNA ploidy level of 250 papaya somatic embryogenesis-derived plantlets from immature zygotic embryos was analyzed by flow cytometry. In vitrogrown and greenhouse seed-derived plantlets were used as diploid standards. Flow cytometry unambiguously evidenced euploid (diploid, mixoploid, triploid and tetraploid) and aneuploid papaya plantlets, indicating that in vitro culture conditions can lead the occurrence of somaclonal variation. Additionally, the two subsequent flow cytometry analyses showed that the DNA ploidy level remained stable in all cloned papaya plantlets during the successive subcultures in the multiplication medium.

Massal Induction of Carica papaya L. ^|^lsquo;Golden^|^rsquo; Somatic Embryos and Somaclone Screening by Flow Cytometry and Cytogenetic Analysis

“…This observation is consistent with the findings of Clarindo et al (2008) and Anandan et al (2012), who reported asynchronous maturation of C. papaya SE in a medium supplemented with ABA. ABA has been the most indicated PGR for regulating SE maturation in vitro (Chen and Chen 1992, Castillo et al 1998a, Anandan et al 2012.…”

“…Accordingly, Anandan et al (2012) also observed a high rate of pro-embryogenic calli (75.12%) from zygotic embryos of C. papaya Co7 . As reported by Monmarson et al (1995), Clarindo et al (2008) and Anandan et al (2012), zygotic embryos of papaya show high-embryogenic potential and quick response to tissue culture conditions. Comparatively, Fitch (1993) observed a callogenic response from hypocotyl segments between the 10th and 14th weeks, as did Castillo et al (1998a) around the sixth week.…”

“…Using the same detection tool, Clarindo et al (2008) also evidenced this phenomenon in papaya, finding 4.4% of the plantlets to be triploid, 2.0% tetraploid, 5.6% mixoploid and 2.0% aneuploid, in addition to the 86% of diploid ones. Differently from the protocol employed in this study, these authors adopted semi-solid conditions throughout the procedure of SE induction.…”

“…The media M1 and M2 were supplemented with 9.05 μM 2,4-D. This in vitro condition was considered by Clarindo et al (2008) and Anandan et al (2012) as the most suitable for callogenic and embryogenic induction from zygotic embryos of C. papaya. The synthetic PGR 2,4-D is considered the driving force of embryogenic competence for most plant species (Monmarson et al 1995, Jordan and Velozo 1996, Fehér et al 2003, including the papaya crop (Castillo et al 1998b, Almeida et al 2001, Clarindo et al 2008, Anandan et al 2012.…”

Regeneration of Allotriploid <i>Coffea</i> Plants from Tissue Culture: Resolving the Propagation Problems Promoted by Irregular Meiosis

“…1a). This response characterized the somatic embryogenesis process as asynchronous, which is commonly observed in some species such as C. arabica (Quiroz-Figueroa et al 2002), C. papaya (Clarindo et al 2008 and Vitis vinifera L. (Jayasankar et al 1999). Furthermore, emergence of secondary somatic embryos from primary ones was also observed (Fig.…”