Polyploidy and radiosensitivity in wheat and barley

A comparison of mutagenic effectiveness and efficiency of NMU and MNG in Sorghum

A comparative study of the effectiveness and efficiency of NMU and MNG in relation to the effects in M1 plants and induction of mutations in M2 was made in a cultivated variety ofSorghum. There was a decrease in the values obtained in each of the biological criteria in the M1, namely germination, survival, seedling growth and seed fertility, with an increase in the concentration of NMU and MNG. Of the characters, survival following MNG treatments and seed fertility following NMU treatments showed the maximum reduction. NMU was not only effective in decreasing the mean of various characters in the M1, but also efficient in inducing a high frequency and wide spectrum of chlorophyll mutations in the M2 compared with MNG. Low concentrations were found to be more efficient than higher concentrations of NMU. The treated M2 population showed not only a decrease but also an increase in the mean height of plant and length of ear compared with the untreated control population. NMU caused a greater decrease in the mean of both characters and induced greater variability in the length of ear than did MNG treatment.

RADIO-SENSITIVITY IN RAGI (ELEUSINE CORACANA)

Dry seeds of three varieties of ragi (Eleusine coracana) were subjected to gamma irradiation with acute dosage of 20 Kr and 30 Kr. The mutagenic effects of gamma rays in the M1 generation and the mutation frequency with regard to chlorophyll and viable mutations in the M2 generation were studied.The LD50 appears to be around 30 Kr for ragi, although there are enormous varietal differences. Purna is the least and H22 the most sensitive to gamma irradiation in the M1 generation. There is a direct correlation between the radiation effect produced as measured by seedling growth, pollen fertility and seed fertility with the dosage used. Multivalent formation, lagging chromosomes and stickiness, etc. were observed in meiotic studies in the M1 generation.The frequency of chlorophyll mutations was less in populations irradiated with 30 Kr than with 20 Kr. A wide spectrum and a high frequency of viable mutations were produced in Purna. The mutation frequency (viable + chlorophyll) increased with the dosage. The 200 isolated viable mutations included many agronomic types which are useful either directly or in conventional plant breeding.