اثر پيش تيمارهاي دمايي، هورموني و سطح تماس لپه بر باززايي درون شيشه اي آفتابگردان

Effect of pretreatments of temperature of ormone and cotyledon surface on in vitro plaLt regeneration in sunflower (Heliunthus annum L.)

Sunflower is one of the most important oilseed crops in the world that genetic im provement of this crop through biotechnological tools is necessary. A study in three in dependent experiments was set up to determine the organogenesis ability of cotyledon er /lants of sunflower. The experimental designs were randomize i complete block with tt ?e repli ations. Seeds were surface sterilized and subsequently germinated on he mone free half strength MS medium. Cotyledons taken froi i two day old seedlings were splits J in half and the four explants of each seed were transferred to regeneration medium consisted of full strength MS medium with 4.4 juM BAP and 5.4 //MNAA, and solidified with 0.7% agar. In first experiment effect of six temperature treatments on organogenesis parameters was studied that statistical analysis showed highly significant differences among 4, 25 and 30°C temperature as well as incubation period effects on all studied parameters. Increasing cold treatment period (T4, T5) reduced the average number of shoots per explants plated. So, the pretreatment of explants at 25°C demonstrated the most percentage of explants forming shoots (57%). Furthermore, results indicated that darkness induce positive effect on all studied parameters. In the second experiment, effect of four cotyledon surface treatments on organogenesis parameters was studied; results showed that the explants that their adaxial surface was in contact with medium for 28 days gave the best results for all studied traits. In the third experiment, effect of three hormone pretreatment on organogenesis parameters was studied; Results showed hormonal pretreatment hasnʹt positive effect on plant regeneration.