Showing papers on "Mutation breeding published in 1984"

Mutation breeding of grain legumes

Abstract: Genetic variation among existing cultivars and in germplasm collections is the outcome of selection during evolution and plant breeding. Mutagenesis offers the plant breeder a chance to tackle unconventional objectives, particularly those that were at a selection disadvantage in the past. Effective mutagens are available, but the bottleneck is the effective selection of rare desired variants from large mutagenized populations. Selection methods must be non-destructive. Grain legume mutation breeding has already led to improved cultivars with higher yield, better grain quality, or stronger resistance to pathogens. Many mutations affecting nitrogen fixation related traits have also been reported. Some could be useful in breeding better cultivars, but the majority are being used to study the factors interacting in the complex process of symbiotic nitrogen fixation and to improve the strategy for producing cultivars with better fixation capacity.

Mutagenic response of Rhodes grass (Chloris gayana Kunth.) to gamma rays. II. Studies on second (M2) generation parameters.

Abstract: The effect of gamma rays on parameters such as chlorophyll mutation frequency and spectrum, mutagenic effectiveness and efficiency and viable mutation frequency and spectrum were studied in M2 generation of Rhodes grass employing nine doses of gamma rays. The chlorophyll mutation frequency increased in a linear fashion at low and medium doses and was erratic at higher doses. The chlorophyll mutant spectrum ineluded albina, xantha, chlorina, viridis, tigrina, striata, albo-xantha and albo-viridis. The frequency of these mutants varied with treatments. A dose rate of 60 krad was found to be effective as well as efficient both on M1 and M2 plant basis in inducing chlorophyll mutations. The highest frequency of viable mutations was found in 50 krad treatment. Viable mutants found were: nodal variant, peduncle variant, lax ears, coxcomb ears, earhead proliferation, level of fingers, incurved fingers, gappy ears, apical sterility, partial sterility and high sterility.

Effects of Repeated and Alternate Mutagenic Treatments with Gamma-Rays and Ethyleneimine in Successive Generations on the Genetic Variability in Rice : Studies on the Utility of Artificial Mutations in Plant Breeding XIV.

Abstract: In order to evaluate whether the recurrent mutagenic treatment in successive generations would be a useful tool for mutation breeding or not, seeds of a rice variety Gimbozu were subjected to repeated treatments with 10 and 20 kR ofL gamma-rays and 0.3 and (O. 5% solution of ethyleneimine (EI), and also to alternate treatments with lOkR gammarays and 0.3% EI, then seed fertility, chlorophyll mutation frequency and genetic variations of four agronomic traits were examined in the M1, M2 and M3 generation following the final treatment, respectively. In this report, the n th generation after m th treatment was represented by mRn. Seed fertlllty mR1:In the repeated treatments the mR1 seed fertility monotonously, decreased as the number of times of treatment advanced. This tendency was more remarkable in gamma-rays than in EI and at higher dosages than at lower dosages. In the alternate treatments, the change of the seed fertility clearly depended on the kind of mutagen used in the final treatment.

Mutagenic Effectiveness and Efficiency of Hydrazine and Ethyl Methanesulphonate in Sorghum Bicolor

Abstract: Mutagenic effectiveness and efficiency of hydrazine (HZ) and ethyl mcthanesul phonate(EMS) were studied with a local sorghum variety of Texas, TX-414, based on M1 seedling injury, sterility and chlorophyll and morphological mutations in the M2 generation, HZ was found to be highly efficient mutagen based on low seedling injury and seed sterility, in the M1 generation, than that of EMS. HZ induced a broader spectrum of chlorophyll and morphological mutations in the M2 generation compared to EMS. The 0.015 M concentration was the most efficient mutagenic treatment for both HZ and EMS, when M1 seedling injury and M2 mutation frequency was considered. Relative toxicity, uptake of the mutagen by the seeds and mutagen concentration seem to be important factors to be considered in the use of chemical mutagens for mutation breeding programmes. Recent advances in sorghum improvement are mainly due to spontaneous mutations followed by selection and hybridization. Induced mutagenesis as a tool for amending and rectifying the characters has made only a beginning in sorghum. The basic information on mutagenic sensitivity, effectiveness and efficiency of the mutagens, methods of handling the material and treatment procedures required to maximize the induction of mutations is essential for successful mutation breeding programme in sorghum. With this view, the present study was undertaken to assess the relative mutagenecity of hydrazine, a structural isomer of nucleic acid thymidine and ethyl methanesulphonate, an alkylating agent, by measuring their effect on various M1 biological characters and chlorophyll and morphological mutations in M2 generation of grain sorghum.