MEAN AND VARIABILITY STUDIES IN M1 AND M2 GENERATIONS OF SUNFLOWER (Helianthus annuus L.)

The experiment was carried out to induce variability in the sunflower varieties Morden and CO 4 (TNAUSUF 7) by a physical mutagen, i.e., gamma rays. The LD50 value was fixed at 15 kR for both varieties based on germina-tion percentage. Progressive decreases in germination and survival with increase in gamma ray dose were recorded in the M1 generation. Stimulatory and inhibitory effects were noticed in quantitative characters with lower and higher doses, respectively. The mean expression and variability in quantitative characters increased considerably in the M2 generation. The different muta-genic treatments showed an inconsistent relationship with respect to mutagen mean and variability. However, considerable increase in variance was observed in traits such as plant height, seed yield per plant and oil content. Regarding seed yield per plant, heritability and genetic advance were maximum at 20 kR and 5 kR in the genotypes Morden and CO 4, respectively. Key words: gamma irradiation, mean, variability, sunflowe