Better Rooting Procedure to Enhance Survival Rate of Field Grown Malaysian Eksotika Papaya Transformed with 1-Aminocyclopropane-1-Carboxylic Acid Oxidase Gene

Abstract

A high survival rate for transformed papaya plants when transferred to the field is useful in the quest for improving the commercial quality traits. We report in this paper an improved rooting method for the production of transformed Malaysian Eksotika papaya with high survival rate when transferred to the field. Shoots were regenerated from embryogenic calli transformed with antisense and RNAi constructs of 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) genes using the Agrobacterium tumefaciens-mediated transformation method. Regenerated transformed shoots, each measuring approximately 3-4 cm in height, were cultured in liquid half-strength Murashige and Skoog (MS) medium or sterile distilled water, and with either perlite or vermiculite supplementation. All the culturing processes were conducted either under sterile or nonsterile condition. The results showed that rooting under sterile condition was better. Shoots cultured in half-strength MS medium supplemented with vermiculite exhibited a 92.5% rooting efficiency while perlite showed 77.5%. The survival rate of the vermiculite-grown transformed papaya plantlets after transfer into soil, contained in polybags, was 94%, and the rate after transfer into the ground was 92%. Morpho-histological analyses revealed that the tap roots were more compact, which might have contributed to the high survival rates of the plantlets.

Regeneration of highland papaya (Vasconcellea pubescens) from anther culture

“…The phenomenon of callus formation at the base of the shoots is very common in papayas, and it inhibits the complete germination of somatic embryos. Indeed, it has been previously reported in babaco (Vega de Rojas and Kitto, ) and C. papaya (Ascencio‐Cabral et al., ; Sekeli et al., ; Dhekney et al., ; Posada‐Pérez et al., ). Recently, Posada‐Pérez et al.…”

Advances observed in papaya tree propagation

“…Thus, different hormonal combinations are fundamental to find the most adequate conditions to promote efficient rhizogenesis and, consequently, to allow better performance of regenerated plants in the acclimatization phase. In this scenario, several authors observed the superior effect of IBA in relation to the other auxins used in the in vitro rooting of papaya buds (TEIXEIRA DA SILVA et al, 2007, KUMAR et al, 2012, NZILANI et al, 2013SEKELI Et al., 2013). In this context, in addition to the hormonal stimuli and other components of the culture medium, an alternative to increase efficiency in the acclimatization conditions is to allow in vitro gas exchanges, promoting greater ventilation of gases produced during the stretching and rooting phases (LAI et al ., 1998).…”

Effects of different culture conditions (photoautotrophic, photomixotrophic) and the auxin indole-butyric acid on the in vitro acclimatization of papaya (Carica papaya L. var. Red Maradol) plants using zeolite as support

“…This behaviour is good evidence of the effectiveness of the culture conditions and zeolite as a substrate, ventilation of the culture vessels, IBA as a rooting inducer, and the absence of sucrose probably favored the source-demand effect so that photoautotroph would enhance the rooting stimulus of auxin. Several authors note the superior effect that IBA has with respect to other auxins for rooting of in vitro shoots in papaya (Yu et al, 2000;Teixeira da Silva et al, 2007;Kumar et al, 2012;Nzilani et al, 2013;Sekeli et al, 2013). These last authors reported that the best results in the rooting of in vitro shoots of transgenic papaya, Eksotika variety were achieved when first placing the shoots in culture medium with 9.8 µM IBA and in darkness for 4 days and thereafter were subcultured on MS culture medium at 50% of salt concentration, 10 µM of riboflavin and vermiculite as support.…”

“…(Afreen- Zobayed et al, 1999); Eucalyptus sp. (Zobayed et al, 2001); four Australian papaya varieties (Kaity et al, 2009) and in the variety Eksotika (Sekeli et al, 2013); Orchid (Doritaenopsis sp.) (Shin et al, 2013) using different types of porous materials (vermiculite, perlite and mixtures of both).…”

“…In addition, it is sown in other countries in the Caribbean and Central America. Regeneration of papaya plants via somatic embryogenesis has been successful; however, the somatic embryos in germination have problems with root development due to the presence of a basal callus, which prevents the formation of roots or its connection to the stem, besides the low percentage of acclimatization of rooted plants (Fitch and Manchardt, 1990;Dhekney et al, 2007;Sekeli et al, 2013). Another critical aspect has been the adaptation to environmental conditions because of the high relative humidity that this species need to achieve high survival rates (Chen et al, 1991).…”