Construction And Characterization Of Brassica Napus L. Mutant Library Induced By Physical And Chemical Mutagens

Seeds of Brassica napus L. variety Gaoyou 605 were induced by 800Gy ⁶⁰Co γ-ray irradiation and 0.4% EMS (Ethyl Methan Sulfonate) for 8 hours. The mutants with mutative traits for plant type, flower, shape or embryo of seed, cotyledon and root system were screened and identified in field or hothouse with hydroponics culture, respectively. The near infrared reflectance spectroscopy (NIRS) was used to screen the mutants for seed quality traits. The mutant library/population of Brassica napus including many types of mutants with different mutative traits was constructed in present experiment. It will provide the important germplasm for further study of genome functions and breeding in rapeseed. The main results were showed as follows:Through screen and identification of morphology in M₂ and M₃, respectively, the mutants with mutative traits of plant were found. In which, 11 mutations were leaf variations, including light-green leaf, deep-green leaf, durative yellowish leaf, temporary yellowish leaf, inlaid yellowish leaf, wrinkly leaf, smooth-edged curly leaf, splitting-shaped curly leaf, peduncular-shaped leaf, round leaf and larger leaf, 12 were mutations on plant type, including excessive branches, lacking branches, highness, dwarf-like, erect posture, reclinate posture, strong stalk, slender stalk, tufty branches, wrinkled plant, purple stalk and hair-covered plant, 14 were flower variations, including dense flowers, light-yellow petals, white petals, white-mosaic petals, wrinkled petales, back-rolled petals, narrow petals, larger petals, smaller petals, apetalous flowers, variable-numbered petals, fertile pistil protraction, sterile pistil protraction and multi-anther, and 5 were physiologic mutants, including genic male sterile (GMS), cytoplasmic male sterile (CMS), bud-dead, and early and later bloom. The total frequencies of mutation was 19.66%, in which 36.60% were multi-mutants and 63.40% were mono-mutants. For the mutants of leaf, plant, flower and physiology, they were accounted for . about 4.58%, 5.08%, 5.33% and 4.67%, respectively. The morphology of these mutants showed that these mutative treats could be stably inherited. 3 types of mutative treats of seed shape were found, including larger seed, smaller seed and yellow seed. The mutants on seed quality traits were screened through the test of M₃ seeds by NIRS, and mutants with higher quality trait, including high protein, oleic acid, linoleic acid, linolenic acid, eicosenoic acid and low erucic acid, and glueosinolate contents, and mutants with lower quality, including low protein, linolenic acid, and eicosenoic acid and high palmitic acid, and glueosinolate contents were found in present experiment. The frequencies of mutants were 8.66% on seed shape, 49.50% on higher quality and 25.16% on lower quality. The total frequency of seed mutation was 83.32%.The morphology of M2 and M3 was observed in hothouse and mutants on cotyledon and root of seedling, or embryo of seed were identified. The result showed that there were 8 types of mutative treats on cotyledon, including light-yellow cotyledon, yellowish cotyledon, trump-shaped cotyledon, multilobed cotyledon, non-cotyledon, single-cotyledon, tricotyledon and quadrcotyledon. For root traits, 4 types of mutative traits including shorter root, larger root, non-hair root, and gravity-insensitive root were found. In addition, plants with embryo number mutation were screened. The total frequencies in M2 and M3 were 14.35% and 27.75% observed in hothouse, respectively. In which, the frequencies of mutants were 3.75% and 14.33% on cotyledon, 10.40% and 7.50% on root system, and 0.20% and 5.92% on embryo number. These mutants appeared in both M2 and M3 with high frequencies, while none of these mutants was found in WT. In M4, mutants in color and number of cotyledon, root length, and embryo number could be inherited stably. The farther observation and identification are needed for these mutants of seedlings.These mutants with mutative morphology and quality treats in the rapeseed mutant library are important germplasm for the further studies of oil rapeseed breeding, genome functions and relationships of genomes.