Studies On High Efficient In Vitro Shoot Regeneration System From Explants Of Chinese Cabbage

This paper studied the effects of genotypes and different hormone combinations on in vitro shoot regeneration from cotyledons of six excellent quality cultivars of Chinese cabbage, three cultivars were from Japan and the others from China. The effects of explant types, the seedling age, AgNO3 and agar concentration were investigated in Aichi Hakusai (C1) from Japan and Qingyan No. 1 (H1) from China. At the same tune, the change of cotyledons from C1, was observed in the course of culture. With the addition of AgNO3 to the medium, the effects were also studied on physiological and biochemical mechanism. The regenerated plants were compared to the seeding plants in morphological characteristics, chromosome number and biochemical traits. The results were as follows.Genotype was the key factor to shoot regeneration. The cotyledons were in vitro induced from six cultivars, which all could regenerate shoot. The highest frequency of shoot regeneration was C1, a Japanese cultivar, reaching 44.2%. The domestic cultivar, H1 took the second place, reaching 38.3%. Among three cytokinins (TDZ, 6-BA and KT), 1 mg'L-1 TDZ was the best to induce shoot regeneration, leading C1 to reach 75%. 0.5 mg L-1 NAA and 1 mg'L-1 TDZ were proved to be the best combination to induce shoot.Among three kinds of explants (cotyledon segment, hypocotyl and petiole with cotyledon) from C1 and H1, petiole with cotyledon possessed the highest capability for plant regeneration, seedling age from 5 to 8 days was the best, with the addition of AgNO3 5 mg'L-1 and agar 0.8% to the medium MS + NAA 0.5 mg'L-1 + TDZ 1 mg'L-1, the shoot regeneration percentage from cotyledon of the two cultivars reached 98.3% and 84.5% respectively. The quality of regenerated plants was the better.IBA was more suitable for the rooting of Chinese cabbage than NAA, which could achieve remarkable results.The small shoot could be observed 8 days after inoculation and shoots were formed directly. This paper reported the changes of soluble protein content, POD, SOD and CAT activities during shoot differentiation in Chinese cabbage C1. Except CAT tended to decline,soluble protein content, POD, SOD activities, and isozyme bands tended to increase, which indicated that there was a close correlation between morphological change and physiological change. Additionally, the addition of AgNO3 to the medium was found to stimulate isozyme activities and promote shoot differentiation.Compared with regenerated plants and seeding plants of C1, their outward appearance and chromosome number were the same. In their leaves, C/N ratio varied with the course of growth. Content of soluble protein increased at first. The number of leaves increased during the growth period, the metabolic intensity of protein increased with the stages of the growth period, content of soluble sugar also increased, it was better to growth.The range of genotype was expanded by in vitro shoot regeneration of Chinese cabbage introduced from Japan. Compared with 6-BA popularly used in the past, TDZ was proved to be more effective to induce shoot regeneration. Through cytological observation and physiological and biochemical measurement, a correlation between morphological change and physiological and biochemical change was discussed, genetic stability of regenerated plants were also studied.