Studies On The Cotton Agricultural Character By Space Mutation And Its Virescent Mutants

Different varieties of cotton showed various degrees of sensitivity to space mutation and mutation mechanism. In this study, 10 varieties of cotton including 5 varieties which contained 2 sea island cotton and 5 prematurity varieties were carried by shijian-8 breeding satellite for discussing their sensitivity to space mutation and mutation mechanism. By using the field investigation, the germination of seedlings, plant height, fruit branch number, flowering stage, boll opening stage, boll number, mutation rate were investigated, different varieties of cotton were compared for their degrees of sensitivity to space mutation. Virescent strains were choosed for analysis of morphological and physiological characters of the mutant SP2, as well as cytological and molecular markers. This paper has a preliminary probe into the space mutation mechanism and physiological and biochemical basis of the Virescent strains. The main results were as follows:(1)The investigation results of agricultural characteristics and mutation rate in SP1/SP2 of the 10 different varieties of cotton showed that: Changes of agronomic characters of cotton can be caused by space mutation, different varieties of cotton showed various degrees of sensitivity to space mutation, the physiological damage of sea Island cotton was relatively great, SP1 exhibits a relatively more obviously variation, among which A3023 reached to 1.655%, but most were not heritable. Upland cotton mainly presented variaties of quantitative characters, showed relatively less obviously variation. However, a heritable strain was discovered in upland cotton variety zhong 58. We found that summer cotton has more significant variation than spring cotton.(2) The investigation results of agricultural characteristics of virescent mutants in space mutation in SP2 showed that: Not only true leaf of virescent mutants presented yellow, but also all leaves present yellow and continued to the end of florescence. Variation of plant height, fruit branch number, big bell and small bell reached significant level, among which the average height was 41.36cm, 11.58 cm shorter compared with control; the average of fruit branch number was 11.58, 3.42 less than control. big bell and small bell were 7.37,1.19; reduced 6.42,1.95 compared with control, respectively, presented premature senility.(3) The results of cytological observation and chlorophyll content measurement of virescent mutants showed that: the chloroplast function of new leaves of virescent mutants was presented weaker than the CK, and the chlorophyll content was much lower than the CK; and there was no significant increase of chlorophyll content in top second leaf while the chloroplast functional recovered; But the chlorophyll content of the top 3rd leaf increased significantly when the chloroplast function of the top second leaf recovered. This indicated that virescent mutants caused structure variation of chloroplast first, which leaded to chlorophyll content reduced, thus presented virescent.(4) The study of the antioxidant enzyme systems activity detection and the isozyme analysis showed that: virescent mutants had significant change in physiological and biochemical mechanisms, and SOD, POD and CAT changed differently, among which SOD and POD were positively correlated with virescent mutants, POD was negatively correlated with virescent mutants, suggesting that this be a kind of compensation mechanism of the anti-oxidation in virescent mutants. Isozyme analysis showed that there was a specific POD enzyme zone in the early of the virescent mutants, but no specific SOD isozyme zone, which indicated that virescent was mainly affected by POD isozyme in the early stage.(5)Analysis of SSR markers and genetic analysis of the virescent mutants showed that: by using SSR marker analysis, it showed polymorphism between virescent mutants and the CK, proved that the mutation of virescent was at the DNA level, and indicated that virescent was controlled only by a pair of nuclear recessive genes by orthogonal analysis and reciprocal cross analysis between virescent mutants and the CK.