Study On High Frequency Of Plant Regeneration From The Mature Embryos Of Indica Rice (Oryza Sativa L.)

The effects of different phytohormones mixture ratio, ABA concentration, subculture passages,, incubation time and partial desiccation of callus on plant regeneration capacity from mature embryo-derived callus of six indica rice cultivars were investigated in this paper. The results were dedicated as following. (1) The induction rate of embryogenic callus derived from mature embryos was significantly different (P<0.05) in indica rice genotypes. The induction rate of all the tested cultivars reached above percent 90 in basal medium NB supplemented with 2 mg/L 2,4-D. (2) The difference of shoot regeneration in genotypes was extremely significant (P<0. 01). There were higher regeneration rate of MingHui 81, N175, and Hang 1 cultivars in regeneration medium with phytohormones ratio of 3.0~3.5 mg/L KT, 0.5~1.0 mg/L NAA and 5.0 mg/L ABA, ranging from 70% to 80%. (3) Effect of different ABA concentration on plant regeneration frequency of embryogenic callus was significant in different genotypes. The addition of 3.0~5.0 mg/L ABA in regeneration medium contributed to embryogenesis and organogenesis, then enhanced significantly the regenerating frequency by q-test. (4) The difference of plant regeneration frequency in different subculture passages was extremely significant. There was higher frequency of plant regeneration up to 76% after callus had been subcultured for 3-5 passages. The plant regenerating frequency, however, would reduced step by step when subculture passages of callus went up. (5) Incubation time in the subculture medium influenced apparently shoot regeneration. High frequency of plant regeneration appeared when embryogenic callus had been incubated for 20~30 days, then decreased gradually with incubation days prolonging. (6) Embryogenic callus had been desiccated before transferring to the regeneration medium benefited to shoot regeneration. The difference in genotypes responding to partial desiccation of callus was clear. Plant regeneration frequency was increased by 1.1 to 5.7 folds in the cultivars owning inferior regenerating capacity, and only went up by 10.7%~21.2% ?in the cultivars with superior regeneration capacity. Plant regeneration rate came to 69%~80% after callus with green-spot that did not regenerated to shoot had been desiccated properly, and increased by 21.8%~118.5% comparing to control callus that had not desiccated before transferring to 1/2 MS medium. In conclusion, Plant regeneration frequency increased to a certain degreeby selecting embryogenic callus, supplementing with moderate plant hormones mixtures ratio in regeneration medium and partially desiccating before callus transferring to regeneration medium. Plant regeneration frequency raised a great when these factors were incorporated. Our experiments had established the plant regeneration system of callus derived from mature embryos of indica rice cultivars MingHui 81, You 99, R527, N175, and Hang 1. The frequency of induction, regeneration and plantlet survival of the five cultivars accounted for above 90%, 85%, and 95%, respectively. The high efficiency and stability of plant regeneration system were well prepared for further studying on genetic transformation of rice.