| The embryo weight of giant embryo rice (ge-rice) is increased by 2-3 times than that of common rice(ck). Compared with its original rice, ge-rice has an increase in the contents of its brown rice proteins, fats, amino acids, mineral elements and vitamin. In this study, giant embryo mutants were directly obtained by irradiation on common indica rice variety. The mutation frequency, genetic characters, biological characters, nutrition characters and anatomical characters of ge mutants were studied. Moreover, the breeding technology of giant embryo rice was established and developed. The main results were as following:1. The giant embryo mutation frequency in M2 averaged 0.00125%, at range of 0.00029%-0.00285%. The giant embryo mutation frequency in M1 averaged 0.03015% or 0.03911%, depend on the different calculation methods. The ge mutants were detected in 9 M2 populations of 11 induced varieties. Mutation frequency varied with applied dosage and mutated materials. The trait of giant embryo is genetically controlled by a pair of recessive genes. The size of rice embryo is only controlled by the genotype of zygote, and not affected by the genotypes of the female parent plant and the cytoplasm. Hence, it is possible to identify giant embryo mutants directly from seeds of M2 or F2.. Population allelic tests shown that the gene in TgeB, 1813geB, 98-14geB and Mge86 are allelic to the ge gene of Japonica mutant "1137".2. (1)Induced mutants possessing ge gene had close similar to the corresponding original lines in allmost of agronomic traits, including plant types, major yield components (No.of productive panicle, No.of grain per panicle and seed set percent) as well as leeding date. However, ge-rice showed a significant decrease in 1000-grain weight, test weight, theory yield and havest yield; The absolute and relative embryo weight of ge-rice are increased by 1.69-2.04 and 1.97-2.47 times; (2) The absolute embryo weight and relative embryo weight of the ge-rice lines bred by hybridization breeding are increased by 2.06 and 1.57, 2.42 and 2.04 times than that of common rice respectively; (3)The ge-hybrids had similar plant type, major agronomic traits and some yield components traits to corresponding ck without ge gene, but ge-rice showed significant decrease in 1000-grain weight, test weight, theory yield and actual yield, and only the homozygous ge gene showed the significant action; (4)The initial filling power(Ro) the maximum filling rate(Gmax), the mean filling rate(Gmean) and the time reaching the 99% grain weight (t(99%)) of ge-rice under research were lower than those of the corresponding types. The filling rate of the fourth day to the twelfth day of the ge-rice were also lower than that of the corresponding ones. As a result, the grain weight of the ge-rice were lower; (5)In ge-rice, there was close relationship between embryo weight and grain length, grain width, grain thicknessand grain weight. Short and light weight with moderate thick grain shape was conducive to the increase of rice embryo weight; In normal rice(wide type), there was close relationship between embryo weight and grain length, grain width, grain thickness and grain length width ratio. The relationship between embryo weight and grain weight is significant, but not significant between embryo weight and grain length width ratio in gorice, and the contrary as the wide type rice. Genetic improvement and application on breeding of ge-rice and small embryo rice were also discussed in this paper.3. The greatest growing speed of embryo of ge-rice appeared during the six day to the nine day after flower, and the growing speed of ge-rice is higher than that of the wild type; The embryo size of ge-rice is larger than that of ck in all stages, ge-rice have about 1.21-1.37 times longer embryo and 1.37-1.70 times thicker embryo than that of ck; The ge-rice have about 1.12-1.31 times embryo shoot width than ck. and in all stages ge-rice indifferentiate embryo shoot length of ck sizes; The ge-rice have about 1.14-1.22 times embryo radicle length than ck, and the embryo radicle width of the ge-rice and ck are almost the same in most stages; The sizes of scutellum of ge-rice are larger than ck in all stages. The ge-rice have about 2.09 times length and 1.90 times width cells of scutellum than ck: The number of cells in embryo of ge-rice is comparable to that of wide type embryo, the enlargement of embryo is exclusively due to the enlargement of scutellum cells.4. Compared with its original rice, ge-rice has an increase in the contents of its brown proteins, fats, crude fibre and ashs, respectively, by 11.14%, 106.09%, 42.21% and 10.17%. Most of the contents of 17 kinds of amino acids are higher than that of ck, and the essential free amino acid contents increase by 2.52% to 35.62%, the total amino acid increase by 4.77% to 37.09%. The average contents of mineral elements Ca^ F^ Zn^ IVfru Mg> P> K, Na and Cd is showed an increase of 42.89%, 47.96%. 38.08%, 37.75%, 1.75%, 5.51%, 13.88%, 16.13% and 36.69%. The fatty acid composition of the ge-rice and ck are almost the same, and all kinds of fatty acids in ge-rice are higher. The measured contents of vitamin VB1, VB2, VPp, VEand Folic acid rose by 2.50% to 24.81%. The contents of GABA( y -aminobutyric acid) in ge-rice is showed an increase of 286.58%.5. The geB lines(giant embryo maintainer lines) had similar plant types as the corresponding B lines. Compared with its original B lines, geB lines has an increase in the absolute and relative embryo weight of its brown rice, from 0.57mg-0.68mg to 1.10mg-1.37mg and 2.69%-2.98% to 6.09%-6.91% respectively. Giant embryo CMS lines (geA) were developed by backcrossing the geB lines to its corresponding original A lines. The geA lines had similar plant types, pollen fertility and yield components as the corresponding A lines. Giant embryo restorer lines(geR) were obtained in the same way and indica giant... |
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