The effects of an osmoregulator, carbohydrates and polyol on maturation and germination of ‘Golden THB’ papaya somatic embryos

Abstract

This study evaluated the effect of osmoregulators and carbohydrates on the maturation and germination of somatic embryos of papaya 'Golden THB'. Cotyledon explants from papaya seedlings germinated in vitro on basal MS medium were cultured on somatic embryogenesis induction medium (IM) containing MS salts, myo-inositol, sucrose, agar and p-chlorophenoxyacetic acid. After 50 days, embryogenic calli were transferred onto maturation media (MM) for 45 additional days. For experiment 1, a MS-based medium supplemented with abscisic acid, activated charcoal and concentrations of PEG 6000 (0; 40; 50; 60 and 70 g L-1) was used, whereas for experiment 2 malt extract concentrations (0; 0.1; 0.2; 0.3 and 0.4 g L-1) were assessed. The normal cotyledonary somatic embryos produced in experiment 2 were transferred to the germination medium (GM). The GM consisted of full-strength MS medium, sucrose, agar and was supplemented with myo-inositol at varying concentrations (0; 0.275; 0.55 and 0.825 mM). The PEG concentrations tested impaired the maturation of 'Golden THB' papaya somatic embryos. The MM, supplemented with malt extract at 0.153 g L-1 , promoted the greatest development of normal somatic embryos (18.28 SE calli-1), that is, two cotyledonary leaves produced 36.56 SE calli-1. The supplementation with 0.45 mM myo-inositol provided the highest germination percentage (47.42%) and conversion to emblings.

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

“…Vale et al 2014, adding PEG (6%) to the maturation medium, obtained 40 cotyledonary somatic embryos per callus in the hybrid UeNF/ Caliman 01, in which the proteins in the range of 34-87 KDa were more abundant, suggesting that these proteins can be fundamental in the maturation process, acting as biochemical markers. Chagas et al (2018) found that the increase in Peg 6000 concentrations reduced the normality of somatic embryos of papaya cv. golden THB by approximately 54% to the maximum concentration tested (70 g L -1 ), when compared to its absence.…”