Induced Mutation Tissue Culture
Natural mutation at the gene level and subsequent recombination and selection. Changes in structure level, such as rearrangement within and between chromosomes. Natural mutation rates estimated at 1 in a million. Most natural mutations are recessive and deleterious.
Crossing F 2 F 1 Single plants F 3 Head rows F 4 Head rows F 5 Head rows F 6-7 F 8-9 Cultivar Early yield trials Advanced yield trials
Crossing M 2 F 1 Single plants M 3 Head rows M 4 Head rows M 5 Head rows M 6-7 M 8-9 Cultivar Early yield trials Advanced yield trials
Radiation Gama rays: Gamma rays, now most favors source. Produced by disintegration of radioisotopes. Can be long or short exposure. Cobalt 60 and Cesium 137. Gamma rays are responsible for 66% of the radiation-induced mutant derived cultivars. Applied as a single dose or applied to whole plants in multiple doses.
Radiation X-rays: X-rays used to be most common source. X-rays are electromagnetic radiation produced when high speed electrons strike a metallic target. Short wavelengths (hard x-rays) have greater penetration but less potential for creating molecular changes than ones with longer waves. X-rays have been responsible for only 22% of all reported mutation breeding success.
Radiation Others: Neutrons: an electrically neutral elementary nuclear particles from nuclear fission by Uranium 235 in an atomic reactor. Beta radiation: negatively charged particles that are emitted from radioisotopes such as phosphorus 32 and carbon 14. Ultraviolet radiation: used primarily for induced mutation in pollen grains.
Alkylating agents: Sulphur mustards, nitrogen mustards, epoxides, ethylene-imines, sulphates and sulphones, diazo-alkanes and nitroso-compounds. Most commonly used are Ethylmethane-sulphonate (EMS) and ethylene-imine (EI)
Genome mutation: Changes in chromosome number due to addition or loss of whole chromosomes.
Structural changes in chromosome: Translocations (interchange between non-homologous chromosomes). Inversions, changes in the location of loci but not their number. Deletions and duplications.
Gene mutation (point mutation): Change in a single gene. Often the result of a single base pair change at the DNA level. Extra nuclear mutation: Mutation in one of the cytoplasmic organelles (i.e. plasmids, mitochondria).
Seeds: Chemical and Radiation. Tolerant to wide range of physical conditions. Desiccated, soaked, heated, frozen etc. No mutation, True mutation, Chimera.
Pollen: Usually radiation. Avoids chimera s. Obtaining large quantities. Apical buds and cuttings: Radiation and chemical. Whole plants: Usually radiation.
Rates changes for different species and different genotypes within species. Dose rates. Too high: kills plants. Too low: to few mutation events. Manipulate rate and treatment duration. Often aim for LD 50.
Mutagenic substances kill. Often suitable facilities are not available. Safe storage of chemicals and radiants. Suitable equipment. Control of contamination.
The Manual on Mutation Breeding 1977, Technical Report Series No. 119, International Atomic Energy Agency, Vienna.
Mutagens are indiscriminant agents. Clean up and stabilize mutants. Get rid of undesirable mutants. Selection of desirable mutants. Rapid screen necessary. In vitro screening.
Sinapis alba L. Tilney
Identifier Seed Yield Oil Content Cover Days to Flowers Days to Flower End Tilney 2733 30.1 8.7 54 80 M3-a 700 30.5 3.0 59 86 M3-b 2267 29.2 4.7 58 85 M3-c 1267 30.4 2.0 60 86 M3-I 1700 29.7 4.7 59 86 M3-II 1567 29.7 3.0 60 87 M3-III 967 30.1 2.3 59 86 M3-IV 1867 31.0 3.3 58 86 M3-V 15.33 31.0 5.0 58 86
Semi-dwarf rice is cultivated over millions of hectares. The ert dwarfing gene in spring barley was an EMS mutant of Valticky later used as a parent of Golden Promise perhaps the most successful barley in Scottish history. Low polyunsaturated fats in canola ( Stellar ) and in soybeans were mutation derived.
500 450 400 350 300 250 200 150 100 50 0 Rice Barley Wheat Soybean All fruit Maize Pea Cotton
Mutagenesis is indiscriminant and generates large numbers of undesirable mutations. Desirable mutations are rare. Isolation of desirable mutations is almost impossible in many crop species. It is easier to find a gene than to make one!
Totipotency the ability of a single cell to divide and produce all the differentiated cells in an organism. Plant Tissue Culture
Potato Breeding
Nuclear Stock Potato
Nuclear Stock Potato
Anther or microspore culture. Genotypic dependant. Somatic variation. Non-random recovery of haploids. Cost
Glucosinolate Profiles Type Brassica juncea Sinapis alba Hybrid Allyl ++++++ - ++++++ 4-Pent ++ - ++ OH-Benz - ++++++ ++++++
Interspecific Hybridization
X Hordeum vulgare Hordeum bulbosum Haploid Barley H. vulgare
H. bulbosum pollen is used to fertilize H. vulgare plants. The H. bulbosum chromosomes are eliminated due to the inability of H. bulbosum chromosomes to move to the spindle poles during cell division, leaving a developing haploid H. vulgare embryo. Embryos rarely survive if left to develop in vivo, thus they are rescued 12-18 days after crossing, and are transferred and develop in vitro. When the plants reach a certain growth stage, they are treated with colchicine, which promotes doubling of the chromosome number.
Maintain disease-free plant material (mainly clonal crops). Rapid increase of planting In vitro selection materials.
Plant Transformation