| Natural colored cotton becomes more and more attractive to textile industry because of their unique non-fading and environmentally friendly properties. But colored cotton is still not very popular in farming because of their lower lint yield and inferior fiber quality than white cotton. So, improvement of the colored cotton fiber yield and quality becomes an urgent need, which can directly influence its further development. Heterosis utilization is still a powerful way in cotton fiber yield and quality improvement. Because Sea Island cotton (Gossypium barbadense L.) has better fiber quality and Upland cotton (G hiesutum L.) has higher yield, its interspecific hybrid can combinate advantages of the parents in productivity and quality properties and reach the aim of simultaneous improvement of hybrid yield and fiber quality. Therefore, we used Upland and Sea Island cotton with different colored fibers as materials, and studied the characteristics of colored cotton fiber developmnt and their heterosis in hybrid colored cotton. The main results were showed as below:1 Development of colored cotton fiber and white cotton fiber in planta and in vitroThere were significant differences between colored fiber cotton and white fiber cotton in fiber cellulose, pigment, and carbohydrate conten during fiber development.1) Cellulose content in mature fiber of colored cotton (750mg/g) was much lower than white cotton (910mg/g); 2) Total flavoid content in 5DPA brown fiber cotton (8.4mg/g) and green fiber cotton (6.9mg/g) was much higher than that of white fiber cotton (3.1mg/g); 3) Carbohydrate content in colored cotton fiber was lower than white cotton fiber at early stage of fiber development. The content of sucrose, glucose, and fructose in 5DPA fiber of brown cotton and green cotton fiber were 20% and 25%, 16.7% and 28.6%,9.6% and 6.4% lower than that of white cotton fiber. These resules were coinsistance with the study in ovule culture of colored cotton. The study showed that no sugars were added in ovule culure medium, no fiber was produced. Sucrose was the most effective C source for fiber development in vitro, followed by glucose and fructose. The pigment synthesis and depositon in colored fiber cotton may be responsible for the lower cellulose content and inferior fiber quality traits of colored cotton fiber.2 Impact of exogenous respiratory inhibitors on colored cotton fiber development in vitro Ovule and fiber development would be inhibited by both rotenone and thiourea (exogenous respiratory inhibitors) causing ovule fresh weight reduction and fiber shortening. But rotenone was more harmful to ovule and fiber development. The ovule weight and fiber length of brown cotton and green cotton cultured in medium with high concentration of rotenone was 65% and 55% lower than CK. There was no effect on coloration of brown and green fiber cotton while treated by rotenone. Rotenone also had significant influence on coloration of colored cotton and advanced color display for 6 days in green cotton fiber. Although thiourea had less effect on ovule and fiber development, it could result in no color display in green cotton fiber indicating pigment metabolism was inhibited by thiourea (600μM). Moreover, cytochrome coxidase activity rapidly decreased in fiber cells after rotenone treatment and polyphenoloxidase activity reduced by more than 80% in green cotton fiber after thiourea treatment.3 Improvements of yield and quality through inter-and intra-specific hybridization in brown fiber cottonZZ2 produced the highest lint yield for two years among the intra-specific hybrids, which was 57.5% higher than G008 (CK1, a brown pure line) and almost near to the ZM29 (CK2, a commercial hybrid). The average boll numbers of three inter-specific hybrids exceeded G008 and ZM29 by 40.5% and 60.3%, respectively. More boll numbers per plant in ZZ3 produced the highest seed cotton yield, which exceed G008 by 30%. ZZ2 had better yield performance than ZZ1 because of the high yield performance of their male parents. Interspecific hybrids ZZ3 produced the best fiber quality traits. The mean fiber length of inter-specific hybrid increased by 33.9% and 11.2% compared with G008 and ZM29. The mean fiber strength of inter-specific hybrid lines increased almost by 40% and 10% compared with G008 and ZM29. The cellulose contents in mature fiber of ZZ2 (897mg/g) and ZZ3 (906mg/g) was much higher than G008 (746mg/g).4 Relationship between leaf photosynthetic, fiber physiological, yield and quality properties in brown cotton hybridsThe changes in levels of leaf hlorophyll concentration, net photosynthesis rate, sucrose, glucose, and fructose content during fiber development were observed for brown hybrids. ZZ3 had the highest leaf chlorophyll concentrations, which were 22%,12%, and 57% higher than that of ZZ1, ZZ2 and G008, respecitivelly. The higher leaf hlorophyll concentration in ZZ3 indicated its active photosynthesis. High photosynthesis rate in ZZ3 didn't produce the high lint yield, which might be mainly caused by the excessively nutritional plant growth, less bolls per plant, and lighter boll mass. G008 had the lowest leaf chlorophyll concentration and other photosynthetic indexes, leading to a lower amount of photosynthetic product, yield and quality. There were significant differences among all materials in their fiber physiological characteristics. At the early stage of fiber development, the fiber of interspecific hybrids had the higher carbohydrate content and lower pH value than that of intraspecific hybrids.5 Relationship between genes expression level and fiber quality in brown fiber cotton hybridsThe functional genes related to cotton fiber expansion and fiber secondary cell wall synthesis were selected to analyses heir expression level in different type (interspecific hybrid, G. barbadense and G. hirsutum) of brown cotton fibers at the key stage of fiber development by real-time quantitative technology. Five genes, one cell wall extensibility related genes (endo-xyloglucan transferase gene(EXT)), three cell turgor related genes (sucrose synthase gene (SuSy), H+-pyrophosphatase gene (VPP) and Plasma membrane H+-ATPase gene (PMA)) and one cytoskeleton related gene (ACTIN1 (ACT1)), were selected to evaluate their expression level in different type cotton fibers at 10 DPA. And one cell wall synthesis related gene cellulose synthase 1 gene (celAl) was also studied at 24 DPA. The results showed that H8714R (G. barbadense) and interspecific hybrid of brown fiber cotton Z11A×H8714R had the higher expression leves of all six genes than other materials. The expression levels of EXT and ACT1 in Z11A×H8714R were 1.5 times higher than G008. SuSy expressed higher level in interspecific hybrid and G. barbadense than in G. hirsutum. The correlation between genes expression level and related fiber quality of mature cotton fiber was calculated. The expression level was positively associated with the fiber quality traits in different type cotton. It refered that the cell wall extensibility related genes played an important role in fiber length and fiber strength formation. |
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