Abstract: The browning and death of calli would reduce the efficiency of cotton plant regeneration and genetic transformation,and it was pivotal to inhibit the two peaks of browning and death of calli during cotton tissue culture to improve plant regeneration and genetic transformation efficiency.In this study, we analyzed subculture time, browning death degree, regeneration time and regeneration efficiency of calli of "Jihe 713"and "Coker 312" cultivars. The results showed that subculture time was able to regulate two peaks of browning and death of calli. To take an extended subculture time during the first PCD peak, subculture time interval 50 d can significantly reduce callus browning and death, increase the rate of callus embryogenesis and shorten the time of embryogenesis. To Take a shortened time of subculture during the second PCD peak, subculture interval 15d can significantly reduce the degree of browning and death, thereby increasing the plant regeneration rate and reducing the regeneration time of the plants. Regulation browning and death by callus subculture time will significantly improve the efficiency of genetic transformation in two cotton varieties, so as to help the gene function and genomics research in cotton.

Key words: Gossypium hirsutum L., calli tissue, program cell death, subculture time