| Through two years field investigation and laboratorial test, the genetic variation of progeny M4 and M5 colonies of 3 cotton varieties, irradiated by Y -ray were studied by using phenotypic characters and SSR markers analysis for the first time. The results are as follows.1. The average of coefficient variation (CV) and genetic diversity indexes of the phenotypic characters among M4 or M5 colonies derived from 3 cotton varieties were very significant. This clarified that the radiation of different cotton varieties resulted in the different uniformity rate and abundant rate of the variation.2. Correlation analysis indicated that the correlation coefficient of phenotypic characters in the colonies of M4 and M5 were significant at 0.01 levels, and those of lint percentage, boll weight, plant height, fiber length , strength of fiber , fiber micronaire also between M4 and M5 also were very significant. This proved that the genetic variation of the phenotypic characters in the irradiated progenies of cotton variety can inherit, and intend to be stable in the progenies M4 and M5.3. The range of genetic distance of phenotypic characters among the mutagenic progeny M5 of 3 cotton varieties were 1.83—34.68, 1.26 — 34.55, 2.22—17.05 respectively. Moreover, a series of mutants with significant variation were screened. The analysis of phenotypic characters illuminated thatY -ray radiation can result in abundant genetic variation.4. Polymorphic loci of SSR markers which can detected among the mutagenic progeny M5 of 3 cotton varieties accounted for 51.3%, 48.7% and 66.7% to the total respectively. The variance range of genetic similarity coefficient of SSR markers among the mutagenic progeny M5 of 3 cotton varieties were 0.6129—0.9848, 0.6212—1.000, 0.4857—0.9905 respectively. The analysis of molecular markers also indicate abundant genetic variation can result from the Y -ray radiation. This provided detective method and theoretic base for germplasm enhancement by using γ -ray radiation.
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