‫ إيمان إبراهيم محمود الضبعاوى‬-4
‫دراسات بيوتكنولوجية ووراثية على نبات االستيفيا المعامل بأشعة جاما‬
Eman Ebrahim Mahmoud El-Dabaawy
BIOTECHNOLOGICAL AND GENETICAL STUDIES ON GAMMA IRRADIATED STEVIA (Stevia
rebaudiana) PLANT
ABSTRACT
This study was carried out at the Department of genetics, Faculty of Agriculture, Kafrelsheikh University, Egypt, using
Plant Tissue Culture Laboratory in Biotechnology Unit, Plant Research Department, Division of Isotopes Applications, Nuclear
Research Centre, Atomic Energy Authority, Egypt.
This work aimed to induced artificially new genetic variation in Stevia rebaudiana Brtoni by using somaclonal variants and
gamma rays, which might be useful for increasing the bioactive components and tolerant to abiotic stresses such as salinity. The
micropropagated plants (six weeks old) were treated with 0,750,1500 and 2250 doses of gamma rays according to Mathius et al.
(1995) to obtain the suitable explants. Then explants were cultured to callus induction media, after that calli were transferred to
regeneration media supplemented with 0, 2000, 4000 and 6000 ppm 0f NaCl. Some plants were relatively tolerant to salt stress.
The plants which showed tolerance to salt stress were examined by using RAPD-PCR technique.
Eight random primers were used to identify the effect of four gamma ray doses ( 0.0, 750.0, 1500.0 and 2250.0 rad ) on
micropropagated plants and to identify the genetic variations between four somaclonal variants under salinity concentrations. Four
primers only gave polymorphism under these studies.
HPLC analysis was done to evaluate the percentage of the bioactive component (stevioside) in the plants which produced
from somaclonal variants, micropropagated plants and gamma irradiated plants. Stevia leaves which obtained from somaclonal
variants gave nearly double the amount of stevioside (505.51 Mg/100g with 0.5 %), compared with that obtained from
micropropagated plants (278.94 Mg/100g with 0.28 %) under laboratory conditions with six weeks age.
Key words: Stevia rebaudiana, somaclonal variation, gamma rays, salinity, RAPD-PCR, HPLC analysis.