Line the inside of a cardboard box with aluminum foil. Bring a bottle of alcohol 70 to spray the inside of the box. Carry an alcohol burner to burn the tweezers. Spray with alcohol the culture flasks containing sterile culture medium.  The beakers, Petri dishes and water , etc. must be sterile and open once the inside of the box is sterile.  The box can be used to carry everything.  Work very carefully.  

Thank you very much! Could you tell me why" The beakers, Petri dishes and water , etc. must be sterile and open once the inside of the box is sterile"?Although the box was steriled, if open the beakers or others,will they be polluted again?

You should tried to keep the contamination as low as possible in the field to establish the explant under in vitro, even though the explant must be sterilezed again at the lab. The addition of antibiotics and fungicides to the culture medium taken to the field is recommended.  Look for the book "In vitro collecting techniques for germplasm conservation" fron IPGRI, for more information.  Best regards.