Studies on induced chloroplast mutation in rice

Studies on induced chloroplast mutation following treatment with different mutagens like gamma rays, EMS and NMU on rice cultivar namely Saturn. Ch.45 and Ratna were made. The study led to the realisation that for screening chloroplast mutants employing Gustafsson's classification it is desirable to grow the M2 seedlings in both dry and wet seasons for proper estimation of the frequency and spectrum of chloroplast mutation since seasonal variation leading to change in environmental conditions like light and temperature and state of growth of mutants may result in either under-estimation or over estimation of one or few classes of chlorophyll deficient phenotypes. Most of these mutants are due to changes in nuclear genes and for each phenotype one or more number of loci are involved. Very few of these mutants exhibited chromosome structural changes and biochemical analysis revealed quantitative reduction of different chlorophyll fractions in most of these mutants. (author)