| Foxtail millet (Setaria italica L.), having a long history of cultivation, is an important grain crop in Northern China. In this study we used Jingu21, which has been bred as a quality millet variety in Shanxi for many years. But it also has some disadvantages such as poor lodging resistance and disease resistance, low rates of grain production. Although Jingu21 has been cultivated in many areas, there are still lots of degradation. We identified some leaf color mutants from the Jingu21 EMS mutant library and made a preliminary research. Because the phenotypes of leaf color mutants are easy to identify and the mutants have important value in the theoretical research and practical application, we expect this study can be foundation to help us enrich the resources of millet leaf color mutants.In this study, we screened leaf color mutants from mutant library and planted their seeds in the next year for physiological indexes and molecular verification. The results were as follows:1. Research of phenotype characteristics and agronomic traits:We observed the phenotype characteristics and measured the main agronomic traits on 7 leaf color mutants. All these mutants showed different degrees of etiolation at seedling stage. Mutant 28 and 29 turned back to green gradually from jointing stage and the leaf widths of these two mutants were wider than wild type (WT) during the whole growth period. The veins of mutant 17 were more obvious than WT. The plant height, stem diameter, aboveground internode number, the first internode length, the second internode length, leaf number, flag leaf length, panicle weight,1000-grain weight and above-ground biomass of these leaf color mutants were all lower than WT.2. Research of photosynthetic characteristics:Photosynthetic characteristics of seven mutants were analyzed. The results of photosynthetic pigments content showed that the content of chlorophyll a, chlorophyll b, total chlorophyll and carotenoids was lower than WT during the whole growth period; The results of starch accumulation showed that the trend between mutants and WT were different; The results of vein density showed that the vein density of mutant 17 was more than WT, while mutant 3,28 and 29 were less than WT; The results of stomata density results showed that mutant stomata densities of flag leaf and top second leaf were less than WT; The results of photosynthetic indexes showed that net photosynthetic rate of mutant 2,3,8,10 and 17 were lower than WT, while the mutant 28 and 29 were higher than WT at jointing stage, and net photosynthetic rate of all the mutants were higher than WT at heading stage; The results of chlorophyll fluorescence kinetics showed that Fo, Fm and Fv/Fm of most mutants were significantly lower than WT.3. Research of leaf cell morphology and chloroplast ultrastructure:We observed cell morphology and chloroplast ultrastructure of mutants leaves. The results showed that the structures of C4 plants were obvious and the number of bundle sheath cells was large and bundle sheath cells were deep dyeing in WT, while the mutants were on the contrary. The chloroplast stroma and granum-thylakoid structure were thick and closely packed, the membrane of chloroplast was smooth, the number of starch granules were lagre but the number of osmiophilic bodies were small in WT, whereas the mutants were on the contrary.4. Verification of two mutants by SSR:The analysis of SSR verification on mutant 28 and 29 showed that the variety of these two mutant were all from Jingu21,In this article, we researched the foxtail millet leaf color mutants on physiological and molecular level, then we analyzed their phenotype characteristics, agronomic traits, photosynthetic characteristics, leaf cell morphology and chloroplast ultrastructure, and finally we verified the variety of two mutants. These researches could not only provide new materials for functional genomics research and breeding but also lay the foundation for enriching leaf color mutation mechanism and developing the following work on foxtail millet. |
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