REVIEW OF RESEARCH ON USE OF RADIATION-INDUCED MUTATIONS IN CROP BREEDING IN JAPAN
Radiation treatment has been used to improve the grain yield, stiffness of straw, earliness, disease resistance, seed quality, and other agronomic characters. In wheat and tobacco, radiation has been utilized for transmitting disease-resistant genes from wild species to cultivated ones by means of chromosomal translocations. Radiophosphorus (P/sup 32/) and x rays were used in earlier studies on rice, the most intensively investigated plant in Japan, while later experiments have also employed gamma radiation from Co/sup 60/ and Cs/sup 137/) neutrons, and S/sup 35/. Among the characters that have been observed as mutated in rice, chlorophyll deficiency, heading time, culm length, and grain weight are most easily obtained. Some of the induced mutants showed the same or higher productivity as compared to the parent variety. A table is provided showing the principle irradiation variants obtained in Japan, and lists the kind of plant, the irradiated component, period of radiation and dosages applied, changes induced, and where experiments were conducted. General conclusion of interest in radiation botany, gained from these investigations, are summarized. The most effective doses for mutation breeding are estimated for dry seed treatment in various crop plants as ranging from 20 to 60 r of x or gamma radiation. Effect of moisture content, protective chemicals, and other external factors on radiosensitivity of seeds is discussed. Fractional x irradiation of rice seeds produces more sterility than single irradiation, and increase of the test period elapsing between the first irradiation and the next gives more sterile panicles. The frequency of chlorophyll mutation shows no difference between fractional dosages and single ones. Maximum frequency of chlorophyll mutation in rice is higher for thermal neutrons than for x rays, but the relative frequency of various kinds of chlorophyll mutations produced by x rays and thermal neutrons seems to be similar. From experiments using rice seeds, the 1-r equvalent effects produced by thermal neutrons were calculated. For fast neutron irradiation of rice seeds, it is estimated that approximately 6 x 10/sup 6/ n/cm/ sup 2/ are equivalent to 1 r from x radiation for the production of chlorophyll mutation. Treatment of rice seeds with P/sup 32/ results in a very high frequency of morphologic mutations, 2 to 3 times higher than that with x rays, in terms of the mutation frequency per X/sub 1/ plant. The mutagenic effects of 0.2 mC/g P/sup 32/ and 0.8 mC/g I/sup 131/ solutions correspond roughly to those of 2.5 kr gamma radiation in experiments using dormant seeds of Einkorn wheat. Repeated irradiation of rice seeds in successive generations is more effective than single irradiation. Screening techniques for selection of mutants are discussed. In general the pedigree method of screening X/sub 1/ spike (or panicle) strains has been used; however, it has been proposed that bulk handling of X/sub 2/ progenies using one seed from each X/sub 1/ individual might be more efficient for screening mutants. The majority of mutations in cereals are those concerned with chlorophyll production. Earliness or lateness of heading time of radioinduced mutant strains in rice as compared to the parent variety is mainly attributable to the decrease or the increase of photoperiodic sensibility, and is connected with the minimum heading duration. The earliness of mutant strains in rice may be ascribed to the recessive mutation of a single independent gene. Some accompanying changes of morphologic or physiologic characters in these early strains are also attributable to the recessive mutation of one gene which is independent of the genes related to heading time. It is concluded that although methods of plant breeding utilizing ionizing radiation have not been perfected yet, radiations readily induce mutants which prove useful in crop improvement. (BBB)
- Research Organization:
- Tokyo Univ.
- NSA Number:
- NSA-18-013484
- OSTI ID:
- 4087937
- Journal Information:
- Euphytica. Netherlands Journal of Plant Breeding (Netherlands), Vol. Vol: 11; Other Information: Orig. Receipt Date: 31-DEC-64
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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Related Subjects
CEREALS
CESIUM 137
CHLOROPHYLL
CHROMOSOMES
COBALT 60
CROPS
GAMMA RADIATION
GAMMA SOURCES
GENES
HUMIDITY
IRRADIATION
LABELLED COMPOUNDS
MUTATIONS
NEUTRON BEAMS
NICOTIANA
PHOSPHORUS 32
PLANTS
RADIATION DOSES
RADIATION EFFECTS
RADIOSENSITIVITY
RICE
SEEDS
SULFUR 35
THERMAL NEUTRONS
TRACER TECHNIQUES
WHEAT
X RADIATION