Abstract:

¹²C heavy ion beam is a kind of new irradiation source. Compared with the physical mutation, such as γ ray and X ray treatments, ¹²C heavy ion beam are much better in physiological, biological and chemical effects with higher mutation rate, wider mutational spectrum and stability easier to be get. It arouses people’s attention in recent years. There are some reports of ¹²C heavy ion beam treatments on paddy, wheat and maize, but a few on rapeseed. Our objectives were to investigate ¹²C heavy ion beam influence on rapeseed morphological characteristics, seed quality, chromosome and DNA molecular aberrations using original Xiangyou 15 (B. napus) seeds with these treatments of 30 Gy, 50 Gy and 80 Gy. The growing period duration was earlier, the rape plants grew luxuriously with larger leaves (Table 1–Table 4) and the agronomic characters were improved in the treatments of 50 Gy and 80 Gy. Some plants were mutated showing tumor-like roots, dwarf stems, light green spoon leaves (Fig.1), multipistil flowers, multi-siliquae (Fig.2) or yellow seed (Table 5). Treatment of 80 Gy ¹²C heavy ion beams irradiation increased oil content in different degrees. The oleic acid content of some plants was more than 70%. There were root tip chromosome aberration and pollen mother cell chromosome aberration under 30 Gy, 50 Gy and 80 Gy ¹²C heavy ion beams irradiation. The aberration type included micronucleus (Fig.3), mininucleus (Fig.4), abnormal tetraspore (Fig.5), chromosome bridge (Fig.6), lagging chromosome (Fig.7-1, Fig.7-2, Fig.7-3) and fragment. Most of aberration cells were with micronucleus. The aberration percentage was increased with increasing irradiation dosage (Table 7, Table 8). RAPD analysis using 40 random primers proved that treatments of 50 Gy and 80 Gy ¹²C heavy ion beams irradiation had some effects on DNA of rapeseed. Forty-three DNA fragments were amplified and showed the polymorphism in a certain degree in different dosage treatments. The relative biological effect (RBE) was higher and the mutation was more difficult to be repaired by the plant with a high and stable mutation percentage. The results suggest that mutation induced by ¹²C heavy ion beam irradiation will be very useful in rapeseed breeding. Our previous studies showed crucifer is insensitive to irradiation because their seeds have propylene mustard oil as a barrier to irradiation. So, ¹²C heavy ion beam irradiation dosage should be increased suitably to rapeseed if we want to get more mutation.

Key words: ¹²C heavy ion beams, Irradiation, Rapeseed