Effect of Water Stress Induced by Polyethylene Glycol 6000 on Somatic Embryogenesis in Cocoa (<i>Theobroma cacao</i> L.)

Abstract

Climate change, coupled with insufficient and irregular rains, led to a decline in the productivity of Ivorian cocoa production. The present study aimed to screen three cocoa (Theobroma cacao L.) genotypes in order to evaluate their response to water stress at callus and somatic embryos induction and proliferation stages. Staminode and petal explants of the genotypes C1, C14 and C16 from the collection of National Center of Agronomic Research (CNRA) of Ivory Coast, were placed on medium DKW (Driver & Kuniyuki Walnut) in the presence of different concentrations of Polyethylene glycol (PEG) 6000 (0, 25, 50, 75, 100 and 125 g/l). This polymer was used as osmoticum to stimulate water stress. Data were recorded for callus induction frequency, callus fresh weight, embryogenic callus percentage and average number of somatic embryos. The results obtained showed that intensity of callus proliferation decreased with increasing concentration of PEG 6000. In all genotypes tested, only the petal explants underwent somatic embryogenesis. The induction rates and average number of somatic embryos per explant were reduced with the increase in the concentration of PEG 6000. Among the tested genotypes, C1 produced somatic embryos with all concentrations of PEG 6000 and expressed highest frequencies of induction (62%) and average number of somatic embryos per explant (6.22). This genotype would be the most tolerant to water stress. Somatic embryos obtained with high concentrations of PEG 6000 in this study provide an important basis for the selection and further production of water stress-tolerant varieties of cocoa.

In Vitro Screening of Sugarcane Cultivars (Saccharum spp. Hybrids) for Tolerance to Polyethylene Glycol-Induced Water Stress

“…The use of PEG has been studied under in vitro conditions in species such as tomato (Lycopersicum esculentum L.) [9], cocoa (Theobroma cacao L.) [10], maize (Zea mays L.) [11], chickpea (Cicer arietinum L.) [12] and mango (Mangifera indica) [13]. In the family Poaceae, it has been studied in species such as rice (Oryza sativa L.) [14], sorghum (Sorghum bicolor) [15] and wheat (Triticum aestivum L.) [16].…”

Arbuscular Mycorrhizal Fungi and Higher Plants

“…The lack of response in glycerol treatment might be related to its role as a soil carbon source rather than as an osmolyte. Polyethylene glycol (PEG) is usually used for this purpose which is not a carbon source for microorganisms and acts as an effective osmolyte in hydroponic plant culture and microbial culture media (Eliane et al 2019).…”

Osmotic potential intensity in the control of direct somatic embryogenesis in coffee tree

“…The response of the somatic embryogenesis of different species is affected by osmotic stress. In tissue in vitro, it can be induced by the polyethyleneglycol 6000 (PEG 6000) osmotic agent through water restriction (Merkle et al, 1995;Elmaghrabi et al, 2017), aiming to select genotypes with drought tolerance (Eliane et al, 2019) and to induce somatic embryos and their maturation, as well as callogenesis (Neofiti et al, 2020;Silveira et al, 2020).…”