Materials and Methods
Plant material and explant preparation
Newly developed young shoots were collected from Thomson navel
sweet orange (Citrus sinensis (L.) Osbeck) trees from citrus groves in
Mazandaran province, Iran. After removing the leaves, shoots were
washed thoroughly under running tap water and nodal segments
and shoot tips were cut (approximately one cm in length). The ex-
plants were then surface sterilized with 70% ethanol for 30 to 45 sec-
onds, then rinsed with 0.1 % solution of mercuric chloride for 5 min-
utes and rinsed with distilled water twice. A final step of 8 minute
disinfection with 1% sodium hypochlorite solution containing 0.05 %
Tween-20 was performed, and the explants were blotted on sterile
filter paper after rinsing 5 times with sterilized distilled water. Af-
terwards, Internodal segments were cut either longitudinal radially
or transversely and placed horizontally on shoot induction media.