The Expression Conditions And Inheritance Of Zebra-leaf Trait In Rice (Oryza Sativa L.)

The rice B411 is a mutant with zebra-leaf trait identified by our lab. The further study on the formation mechanism of zebra-leaf trait has not been engaged. In the thesis, the expression conditions of zebra-leaf trait were studied by transplantation with root cutting at different stages, and by different light intensity and temperature treatment. The trait formation causes were discussed by analysis of the photosynthetic pigment content of stripes with different leaf color and ultra structure of chloroplasts. The main results were as follows:1. The seedlings transplanted with root cutting and non-transplanted were treated with different light intensity, photoperiod and photoinductive cycles. The results showed that both transplantation with root cutting and more than 300μmol·m^-2s^-1 light intensity were the necessary expression conditions of zebra-leaf trait. The critical day length for the expression of zebra-leaf trait was 3 h with light intensity of 1000μmol·m^-2s^-1 and light/dark temperature 32℃/22℃. The minimum photoinductive cycles for the zebra-leaf trait expression was 2 with photoperiod of 12 h/12 h treatments.2. The results of different temperature treatments showed that, under 1000μmol·m^-2s^-1 light intensity condition, the temperature above 26℃was beneficial to the expression of zebra-leaf trait, and the degree of chlorosis reduced when the temperature was below 26℃. The zebra-leaf trait did not express at 22℃, neither did it when the temperature was between 22℃and 35℃under 200μmol·m^-2s^-1 light intensity condition.3. The rice B411 had the potential to express zebra-leaf from first leaves to flag leaves. The zebra-leaf trait was only expressed on the newborn leaves transplanted with root cutting. Taking the rice transplanted with root cutting at trileaf stage for example, it were the forth and fifth leaves that developed into zebra-leaves. The expression of zebra-leaf trait stopped when the new root formed and recovered the normal physiological functions, and the yellow stripes of the zebra-leaves regreened gradually.4. The results of photosynthetic pigment content of B411 indicated that, the photosynthetic pigment content of yellow stripes was lower than that of green stripes, and the decreased degree of chlorophyll content was larger than that of carotenoid content. Therefore, it was supposed that the decrease of chlorophyll content of yellow stripes would be one of the causes leading to the appearance of zebra-leaf trait. The photosynthetic pigment content of green stripes decreased compared with that of normal green leaf. The zebra-leaf has a process of regreen gradually, and the photosynthetic pigment content of green stripes could approach that of normal green leaves, while the photosynthetic pigment content of yellow stripes could recover to 65.6% of that of normal green leaves.5. Ultrastructural observations on chloroplasts of the zebra-leaf revealed that the chloroplasts in green stripes developed normally, while the shape of chloroplasts in yellow stripes was abnormal with incomplete membrane systems and contained some osmiophilic bodies, which renewed the normal structure when the yellow stripes regreened. However, some yellow stripes could not recover green, which there were not any chloroplast in mesophyll cells.6. The combinations of B411 hybridized with normal green varieties were used in genetic analysis. The result showed that the leaf color of each F₁ progenies represented normal green, which suggested that the trait was controlled by recessive nuclear gene. Segregation ratio of normal green plants to zebra-leaf plants fitted the expected value 3:1 in each F₂ population, which suggested that the zebra-leaf trait of B411 was controlled by one pair of gene.