Abstract:

Ion implantation technology is an effective means to create new plant germplasm lines. In order to explore the biological effect on red clover （Trifolium pratense） induced by ion implantation， the seeds of T. pratense cv. ‘Emu 5’ were implanted with N⁺ ions at energies of 30 or 50 keV and doses of 5×10¹⁴ or 5×10¹⁵ ions·cm^-2 （N3014， N3015， N5014 or N5015， respectively） or Ar⁺ ions with energies of 30 or 50 keV and a dose of 5×10¹⁴ ions·cm^-2 （Ar3014 and Ar5014， respectively）. The germination characteristics and biological characteristics of irradiated seeds were studied and the variation in agronomic traits， including plant height， branch number per plant， flower number per plant， flower number per inflorescence， leaf length， leaf width， inflorescence length and inflorescence width， was analyzed. We found that the epidermis of red clover seed displayed an obvious ‘burn’ phenomenon after ion implantation， and the color of seed coat changed from yellowish brown to black-brown. Compared to control （CK）， the Ar3014 treatment numerically increased seed germination， while the N3014 and N3015 treatments numerically decreased seed germination； however， these trends were not statistically significant. The N5014 treatment significantly decreased germination by approximately 10% compared to CK and the N5015 and Ar5014 treatments both significantly decreased germination by more than 30%. Radicle volume and length were both significantly increased， compared to CK， by the two N30 irradiation treatments. The irradiated seeds （M₁ generation） were grown and allowed to set seed， which was also grown to produce an M₂ generation. This cycle was repeated twice more to produce M₃ and M₄ generation seeds. The mean values of measured traits in M₂ generation plants were usually significantly lower than those in CK plants （P<0.05）， but showed greater character variation among mutagenic plants， which provided a basis for further screening of mutant materials. N⁺ and Ar⁺ mutagenic treatments at energies of 50 keV showed greater mutagenic effects than those observed at 30 keV， but the majority of mutations were adverse characters. The mutagenic effect was optimal for red clover in the N3014 and N3015 treatments and after four generations of breeding， eight mutant materials from the M₄ generation with stable characters， potentially usable for breeding purposes， were obtained. Our study provides basic data for mutation breeding in red clover.

Key words: red clover, nitrogen ion, argon ion, mutagenesis, biological effect