The Effect of Helium Plasma-Treatment during Pollination of Brassica Species

The trait of self-incompatibility (SI), which is inability of a fertile hermaphrodite plant to produce zygotes after self-pollination, is important for F₁ hybrid seed production in Brassica crops. However, for production of pure line seeds, this trait is not fitted. In order to overcoming SI in Brassica crops, 5% CO₂ treatment was established in 1970s in Japan, and was generally used in pure line seed production in seed companies. In addition to this method, electrical stimuli to pistil and anther was also developed, however, this electrical method was not used in breeding field. Recently, plasma-treatment was applied to life science and agricultural fields. In this study, we surveyed the effect of helium plasma-treatment during pollination process of Brassica rapa. In order to determine the effect of plasma-treatment, pollen tube behavior on the stigma was observed with fluorescence microscopy and microcopy with time-lapse system.

When treating the plasma to self- and cross-pollination, two different treatment time, 1 min and 5 min, was used. In the case of 5 min treatment, morphological change was observed in most of papilla cells, before pollination. This changed phenotype was looked like “scald”. When this scald papilla cells by 5 min plasma-treatment were used to self and cross-pollination, most of pollen grains were not responded. In contrast, in the case of 1 min treatment, a part of papilla cells was looked like “scald”. In this 1 min treatment, the ratio of germination phenotype was upped.