Abstract: 【Objective】 The purpose of this project was to identify a new early cotton virescent mutant for explanation of the mechanism of the space mutagenesis and application of virescent mutant. 【Method】 Reciprocal crosses were made between the virescent mutant and wild type and 17 virescent materials came from the medium term warehouse of cotton germplasm resource in China. The characters were compared between the virescent mutant and wild type by genetic analysis, chloroplast ultrastructure, and antioxidation enzymes. 【Result】 Leaves color proportion of F2 progeny was 3:1 between green and yellow. The results of reciprocal crosses were same between the virescent mutant and wild type. Therefor, the virescent trait was controlled by a recessive genes. Leaves color of F1 progeny was green between the virescent mutant and 17 virescent materials except several yellow plants. These were proved that genes of the virescent trait was nonallelic with 17 virescent materials. The results of chloroplast ultrastructure showed that chloroplast development of the virescent mutant was deficiency and slowly, less grana and stroma and chaos. Chloroplast structure was gradually recovered to normal level as leaves development. Plant  height, branch fruit numbers, bolls, little bolls, yield and fiber quality of the virescent mutant were significantly lower than wild type. SOD and CAT activities of the virescent mutant were lower than wild type, but tha activity of POD was higher. 【Conclusion】 The new stable genetic virescent mutant was identified which is controlled by a recessive allele and different with 17 virescent materials by space. Many characters of the virescent mutant, such as the activity of antioxidation enzymes, pigment content, the materials of chloroplast synthesis and chloroplast ultrastructure, were affected, by space mutagenesis.

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