الشد المائي باستعمال المانيتول و دوره في الإكثار الدقيق و الأقلمة لصنفين من الرز (Oryza sativa L.)‎ المستزرع في العراق

الملخص EN

The study was conducted in order to investigate the effects of water stress induced by theaddition of mannitol at four levels (-0.112,-0.224,-0.336 and -0.448 MPa) to the nutrient medium, on callus induction and development, number and germination percent of somatic embryos, percent of successfully acclimated plants in two Iraqi rice cultivars named Ambar33 and Mushkhab1.The explants (mature seeds of the mentioned rice cultivars) were cultured on MS nutrient medium with the addition of: B5 vitamins (1mg.l-1), sucrose (30g.l-1), agar (5g.l-1) and the growth regulators used were 2,4-Dichlorophenoxyacetic acid (2,4-D) and Benzyl adenine (BA).The results showed that water stress induced by mannitol at -0.112, -0.224, -0.336 MPa has no significant effect onthe embryogenic callus fresh weight, while there was a significant decrease at -0.448 MPa when compared with the control treatment (mannitol-free nutrient medium).

Numbers and germination percent of somatic embryos and percent ofsuccessfullyacclimated plants where increased significantlyat -0.112 MPa while the higher levels of water stress caused a significant decrease in all the previous growth parameters,with no significant differences between the two cultivars.

Results reveled that high levels of water stress by mannitol caused a significant increase in proline accumulation and sodium ion concentration, while there was a significant decrease in potassium ion concentration in the embryogenic callus of the two rice cultivars studied.

No significant difference were observed between the cultivars regarding to those biochemical parameters.We can conclude from our study that the addition of mannitol at -0.112 MPa to the nutrient medium has a positive effect on embryogenic callus fresh weight, number and germination percent of somatic embryos and on percent of acclimated plants, so we recommend its addition to the nutrient medium used for rice micropropagation.