Breeding new corn species using ion beam irradiation, a project jointly undertaken by CAS

Institute of Modern Physics and Gansu Jinxiang Seed, has recently achieved a major

progress, thanks to more than two-year efforts. Researchers treated a wide range of corn

seeds, including Jinxiang-4C, Zheng-58, Lu-9801, and CSR-24001, using 12C6 and

36Ar18, plus the ion beams in different dosages provided by the heavy ion accelerator at

the Institute. They induced expected mutations in inbred corn lines through field growing,

and created an advanced technical means for producing novel species.

Study results show that the treated seeds have a germination potential and rate that goes

down along with an increased irradiation dosage. Researchers determined the right dosage

of both 12C6 and ion beam irradiation, through measuring the response a species would

have to such treatment. M1 corn species showed an apparently changed leave form, while

M2 species saw changes in more aspects, including plant height, ear height, ear number

per plant, color of male gametophytes, corn grain quality, row number per ear, grain

weight, and resistance to diseases. Some mutations, including an increased plant height, a

reduced ear height, increased number of ears at the same height, increased row number

per ear and grain weight, changed grain quality from soft to hard, and an enhanced

resistance to rust and red leave diseases, have secured a preferred mutation rate ranging

between 7.0% and 17.9%. M3 species has registered a steady passing of preferred genetic

mutations, with an enhanced photosynthesis, from which researchers have screened out

98 desirable mutated species. In 2007, researchers grew M4 species in experimental plots

for further observation. An experimental growing of M5 species in Sanya, Hainan has

resulted in 16 hybrid combinations with an increased yield by 17.1%-35.9%, a better

resistance to diseases, and improved field performance, compared with the control

group. In 2008, researchers have been working on DNA part of the mutations using

molecular marker technology, in an attempt to understand the changed quality of 16

combinations that have recorded a yield increase.