Production of triploid plants of papaya by endosperm culture

Abstract

Triploid papaya (Carica papaya) plants were obtained by immature endosperm culture. Visible callusing of the endosperm occurred 21 days after initiation of cultures. A continuously growing callus was observed and a maximum of 68.7% of callus induction frequency was obtained when immature endosperm with embryo was cultured on Murashige and Skoog (MS) medium containing 6.0 lM 2,4-dichlorophenoxyacetic acid (2,4-D), 2.5 lM a-naphthaleneacetic acid (NAA) and 4.0 lM 6-furfurylamino purine (Kn). Shoot buds were produced when the callus was subcultured on a medium supplemented with 6-benzyladenine (BA) or thidiazuron (TDZ) along with NAA. Shoots were detached from the callus and transferred to the elongation medium supplemented with indole-3-acetic acid (IAA) and BA. The combination of 3.0 lM IAA and 1.5 lM BA was the best in terms of the number of cultures (93.8%) showing axillary shoot proliferation. The addition of 2.0 lM indole-3-butyric acid (IBA) to the 1/2 MS medium was most effective at inducing root formation with 90% of the shoots developing four to five roots. Healthy rooted plantlets were transferred to pots containing sterilized bed soil and perlite (3:1) mixture in the greenhouse and 78% of the micropropagated plants survived transplantation. The leaves from endosperm-derived plants showed larger stomata and more chloroplasts in guard cells than that from the parent plants. Over 75% of the endosperm-derived plants were triploid with chromosome number 2n = 3x = 27.

Genome-wide transcriptome profiling of Carica papaya L. embryogenic callus

“…The basal media comprised Murashige and Skoog (MS) medium (Murashige and Skoog 1962), 3 g/ L gelrite and 30 g/L sucrose, with pH adjusted to 5.7-5.8. Autoclaved growth media were supplemented with established (Sun et al 2011) concentrations of plant growth regulators: 1.5 mg/L 2,4-dichlorophenoxy acid (2,4-D), 0.5 mg/L a-naphthaleneacetic acid (NAA), 2.25 mg/L benzylaminopurine (BAP) and 1 mg/L kinetin for callus induction. Induction of somatic embryos was performed using regeneration media consist of 0.02 mg/ L NAA and 0.1 mg/L BAP at 25 ± 1°C in the light.…”

“…The availability of completed 372 Mbp papaya genome with various bioinformatics tools and resources accelerates the identification of genes involved in important biological processes (Ming et al 2008). Molecular studies in papaya have been facilitated by the establishment of in vitro culture and transformation system, including numerous studies in callus induction and regeneration from various explants (Ascencio-Cabral et al 2008;Bhattacharya and Khuspe 2001;Chen and Chen 1992;Chen et al 1987;Fitch et al 1993;Conover 1981, 1982;Sun et al 2011;Yu et al 2000).…”

Breeding triploid plants: a review

“…Thammina et al (2011) reported that callus was not induced with Euonymus alatus endosperm on hormone-free MS medium. Sun et al (2011) also reported that all papaya (Carica papaya) explants turned brown and died without any sign of growth on basal medium. Tian et al (2012) reported that high callus formation rates (approx.…”

“…Embryo rescue was utilized by plant breeders to rescue inherently weak, immature and/ or abortive embryos, breeding seedless crosses and triploid plants, and distant hybridization between different species (Sharma 1995). Thus far, embryo rescue was extentively applied in rescuing many fruit crops, including apple (Dantas et al 2006), banana (Uma et al 2011), citrus (Viloria & Grosser 2005;Aleza et al 2012), grape (Sun et al 2011), etc. Li et al (2015 provided an overview of the factors that affect its efficiency, including genotype, the time point of removing ovules, medium, culture method and condition, plant growth regulators, etc.…”

“…Ploidy levels, however, have been found to be relatively stable in some endosperm-generated plantlets and these kinds of endosperm cells often can maintain a long-term ability to differentiate organs. Sun et al (2011) reported that over 75% of endospermderived papaya plants were triploid with chromosome number 2n = 3x = 27. Tiku et al (2014) analyzed the chromosome number of 80 Phlox drummondii plants derived from endosperm cultures.…”