Gamma Gardens (Atomic Gardens)
What are Gamma Gardens or Atomic Gardens?
Gamma garden or Atomic garden is a concept popularized after the Word War 2 for the peaceful use of atomic energy (atoms for peace) for the crop improvement. Gamma gardens or atomic gardens are a type of induced mutation breeding where radioactive sources particularly gamma rays from cobalt -60 or Caesium-137 are used to induce desirable mutations in crop plants.
Salient features of Gamma Garden
Ø Gamma gardens are “area subjected to gamma irradiation of crop plants”.
Ø They are giant structures, enclosed by thick high wall to protect the plants and animals outside.
Ø The purpose of a gamma garden is to irradiate the whole plants during different stages of development and of varying duration.
Ø The source of radiation used is Cobalt-60.
Ø Rarely Caesium-137 is also used as the source of radiation.
Ø The strength of 60Co is 200 curies.
Ø The source of radiation is located at the centre.
Ø The area is divided into concentric circles with varying intensity of radiation.
Ø Plants to be irradiated are arranged as concentric circles around the radiation source.
Ø The intensity of radiation decrease as one move away from source of the radiation.
Ø The radially arranged plants in gamma garden can be grouped into three sectors.
Sector – I:
o They are plants nearest to the central radiation source.
o Plants in the sector I usually die immediately due to the high dose of radiation.
o They are not used in further experiments.
Sector – II:
o This include plants located next to the sector I.
o These plants develop severe tumors, malformations and other abnormalities.
o These plants are also not used in further experiments.
Sector – III
o They include plants located next to sector III.
o They are the actual plants of interest in Gamma gardens.
o They may have random mutations not severe enough to damage the crop plant.
o The variations obtained in the sector III are used in further breeding experiments.
o They can be used as a source of variation in hybridization or can be directly released as a variety.
Ø The first gamma garden: in Long Island, New York, USA.
Ø First gamma garden in India: Bose Research institute at Calcutta (1959).
Ø Second gamma garden in India: Indian Agricultural Research Institute (1960).
Advantages of Gamma Garden
Ø Gamma gardens can produce large amount of variations within a short time.
Ø Desirable mutants can be released directly as a new variety.
Ø Gamma gardens are good examples of the peaceful use of atomic energy for human welfare.
Disadvantages of Gamma Garden:
Ø High initial investment required.
Ø Other cheapest mutation methods are now available.
Ø Chances of undesirable mutations are very high.
Ø Mutations are random; we cannot predict the effects of mutations.
Ø Loss of many natural good qualities of crops due to recessive mutations.
Ø Mutated characters may not be stable as they segregate in the next generation.