Heterosis And Physiological And Biochemical Characteristics Of Colored Interspecific Hybrid Cotton

Natural colored cotton is a textile crop with naturally pigmented fiber. It becomes more and more attractive to textile industry because of its unique non-fading and environmentally friendly properties. But colored cotton is still not very popular in farming because of its lower lint yield and inferior fiber quality compared with white cotton, also its singleness color. These problems limit the development of colored cotton production. Heterosis utilization is still a useful way in improving crop yield and quality. Because Sea Island cotton (G barbadense L.) has better fiber quality and Upland cotton (G hiesutum L.) has higher yield, their interspecific hybrid can combinate the advantages of the parents in productivity and quality properties and reach the aim of improvement of cotton yield and fiber quality simultaneously, which is a good way to improve colored cotton. However, there are few reports about colored interspecific hybrid. In this experiment, colored interspecific hybrids between Upland cotton and Sea Island cotton were used as materials to study (1) their heterosis of yield and quality, (2) their photosynthetic physiological characteristics of plant leaf and fiber, and (3) the relationship among yield, quality and photosynthetic physiological characteristics, in order to get a breeding theory for solving the problems related with low yield and inferior quality of colored cotton. The main results can be showed as below:1 Heterosis of colored interspecific hybrid cottonUsing colored Upland cotton and withe Sea Island cotton as parents, we got two kinds of colored hybrids, interspecific and intraspecific hybrid. Compared with the white commercial hybrid cotton (CK), the heterosis of these two kinds of hybrids was studied. As a result, interspecific hybrids had more bolls, fruit branches, fruit nodes, higher dry plant weight and higher plant height than intraspecific hybrids, but lower boll weight and lint percentage than intraspecific hybrids. Interspecific hybrids had the most bolls (27.58 n/plant), while intraspecific hybrids only 19.13 n/plant. For the yield, because of more bolls, a few of interspecific hybrids also presented higher lint yield than intraspecific hybrids. For example, there were 2 blown interspecific hybrids which had higher yield than intraspecific hybrids, even than CK. For the fiber quality trails, except for Micronaire value, interspecific hybrids were better in fiber length, fiber strength, fiber uniformity and elongtion rate than intraspecific hybrids and CK. Especially, the green interspecific hybrids had the longest fiber length (35.00mm), which were even superiorer to the Sea Island cotton, and showed an extremely high heterosis.2 Photosynthetic physiological characteristics of colored interspecific hybrid cotton with high yield and good qualityPhotosythesis is associated with lint yield and fiber quality at different development stages of cotton plant. The outcome of photosythesis is the base of growth and development not only for each plant organs but also for cotton fiber cell, because it provides carbohydrate for all the metabolize activity. At present, there was little research about photosynthetic physiological characteristics of colored interspecific hybrid cotton. Therefore, on the base of analysing yield and quality of colored interspecific hybrids and their parents, we measured several photosynthetic indexes, such as leaf chlorophyll a and b content, net photosynthesis rate and carbohydrate content at different development stages, and pollen fertility. The results showed that the colored interspecific hybrid cotton had a lower plant fructose content, weaker pollen fertility, but they had a higher chlorophyll content when compared with their colored cotton parents and the intraspecific hybrid cotton. We also found that interspecific hybrids had a higher net photosynthesis rate than their colored parents and CK. It was suggested that more sufficient metabolism substrate from photosythesis and more glucose content and starch in cotton might be a possible physiological reason for the higher yield and better fiber quality of interspecific hybrid cotton.3 The relationship between fiber physiologic characteristics and fiber quality traits in colored interspecific hybrid cottonCotton is an economic crop whose main outcome is fiber. Colored fiber growth and development is not only associated with leaf photosynthetic physiological characteristics but also with fiber pigment synthesis. Because fiber pigment synthesis is an additional pathway for colored cotton and needs more energy and matter than white cotton, the formation of fiber yield and quality of colored cotton is more complicated than that of white cotton. Therefore, this experiment studied the physiologic characteristics during colored fiber development at different stages through testing of carbohydrate content, cellulose content, flavonoids (pigments) and pH in fiber cell. The results showed that Sucrose content and fructose content in colored fiber of hybrids were higher than that of their parents on the average of different stages, but was lower in fiber of interspecific hybrid than that of intraspecific hybrid. Comparing the two kinds of colored cotton, green cotton had more sucrose than brown cotton, but brown hybrids had more glucose content than green hybrids. In the mature fiber, the cellulose content of colored intersecific hybrids cotton were significantly higher than therir colored parents, but their colored parents had higher flavonoids and pH. Again, the relationship analysis indicated that colored fiber quality was significantly associated with fiber carbohydrate content, flavonoid content and fiber pH value. Abundant carbohydrate content could accelerate fiber enlogation, while high flavonoid content and pH value were not benefit for fiber elongation and quality formation.