In Vitro Screening of Cucmis Melo L. Against Drought Mediated By PEG and Sorbitol

Abstract

Water deficit in first growth stages of melon (Cucumis melo L.) in formation of first true leaves after germination can be a factor limiting production. The first step for resolve the problem is genotypes evaluation and identification of drought tolerant melons. An effective method to achieve the goal is use of osmotic solution in tissue culture. Responses of Iranian melon landraces to drought was evaluated using sorbitol at 0.1, 0.2 and 0.4 M or polyethyleneglycol (PEG 6000) at 0.009, 0.012 and 0.015 M concentrations, and MS medium without treatment as the control. Coleoptile length, fresh and dry weight of shoots and roots, photosynthetic pigments, protein, proline, malondialdehyde (MDA) and antioxidant enzymes superoxide dismutase, guaiacol peroxidase and ascorbate peroxidase were measured. The PEG or sorbitol decreased coleoptile length, fresh weight and photosynthetic pigments, and led to enhancement of proline and MDA. Contents of protein and antioxidant enzymes was completely dependent on genotype and type and concentration of osmotic material. The in vitro culture for screening and identification of tolerant and sensitive drought genotypes could be rapid, useful and effective, with sorbitol mimicing drought better than PEG. After in vitro evaluation, the genotype responses to induced water deficit need to be confirmed under field conditions.

Tissue Culture—A Sustainable Approach to Explore Plant Stresses

“…Under abiotic stress, plants accumulate solutes or osmolytes within the cell due to less water availability. Therefore, high molecular weight solutes such as sucrose, sorbitol, mannitol, and poly-ethylene glycol (PEG) are suitable candidates to impose physiological drought under in vitro conditions [ 28 , 29 , 30 , 31 , 32 ]. In addition, these osmolytes stabilize proteins and cell membranes’ structure during dehydration stress conditions [ 33 , 34 ].…”

“…PEG, sucrose, mannitol, and sorbitol have been the main chemicals for imposing osmotic pressure in vitro. PEG has reportedly been used to impose physiological drought in plants [ 28 , 29 , 39 , 40 ]. This high molecular weight chemical is an inert, non-penetrating osmoticum that decreases the water potential of nutritional solutions without being taken up by the plant or phytotoxic.…”

“…Therefore, PEG solutions resemble dry soil more closely than low molecular weight chemicals, which permeate the cell wall with solute. PEG is not used in the cellular metabolism of plants, but it does induce water stress by lowering the water potential of nutrient solutions, hence inhibiting plant development in vitro [ 28 , 39 , 41 ]. It has no harmful or toxic effects on the plant; nonetheless, it restricts plant development by lowering the water potential of the culture medium, such as water deficit soil, preventing cultured explants from absorbing water [ 42 ].…”