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Establishment of a highly efficient regeneration system for the mature embryo of wheat will provide a convenient tool for wheat tissue culture and transformation, thereby facilitating the transformation of foreign genes into wheat. By using the mature embryos derived from 20 different wheat lines including Shi 4185, Yumai 66, Lunxuan 987, CB037, Yangmai 6, Xinchun 9, Bobwhite, Han 6172, Zheng 9023, Jimai 20, Ningchun 4, and Jing 411, the effects of some factors including inoculation methods, initiating culture media, organic additives, antioxidants, and auxins on the regeneration from the explants were evaluated. The results indicated that the scraping embryo culture was better than the whole embryo culture, the Aa medium was better than the SD2 medium and dicamba was better than 2,4-D in increasing the regeneration frequency. An Adi medium was established in this study by adding silver nitrate, cysteine, ascorbic acid, dicamba, glutamine into the Aa medium at the concentration of 4 , 40, 100, 2, and 5 mg L-1, respectively. By using the Adi medium and the scraping technique, the regeneration frequencies of the mature embryos of CB037, Lunxuan 987, Han 6172, Yangmai 6, Bobwhite, Zheng 9023, Shi 4185, and Jimai 20 became 85.6, 60.1, 46.0, 42.1, 42.0, 34.0, 33.0, and 32.0%, respectively, which were about 5-8 times higher than that obtained from the conventional culture mediums and techniques. This novel regeneration system could be helpful in wheat transformation.

Resonant self-focusing, which occurs in beat-wave excitation of electron plasma waves, is crucial both for multiline laser fusion and for beat-wave accelerators. In this paper, the resonant self-focusing effect of a dual-frequency laser beam or two laser beams with frequency difference equal to the plasma oscillation frequency in a homogeneous plasma has been studied theoretically, for the first time, by using optical mixing and the self-focusing theory. The nonlinear dielectric constant and the threshold power for resonant self-focusing have been derived analytically. The scaling laws of the threshold power with respect to laser-plasma parameters have been discussed and compared with that of usual ponderomotive self-focusing. Otherwise, the effect of the deviation from the frequency matching condition on the threshold power has also been studied. For typical underdense laser-plasma parameters, our estimation shows that the threshold power of resonant self-focusing is usually ~2 orders of magnitude less than that of normal ponderomotive self-focusing. In addition, it is also shown that a small deviation from resonance will result in a large increase in the threshold power.