GAMMA RADIATION INDUCED POLYGENIC VARIATION IN HOMOZYGOUS AND HETEROZYGOUS GENOTYPES OF SAFFLOWER

S. A. PATIL, R. L. RAVIKUMAR,  T. G. PRABHU  AND  K. G. PARAMESHWARAPPA

Abstract

            The seeds of the genotype A-1 and of the F₁ of the cross 398-9-15   x  420- 24-3 were treated with 30 kr  gamma rays.  A three way cross hybrid (398-9-15 x 420-24-3) x A-1 was also produced. The treated populations and the three way cross hybrids were advanced to their respective M_2, F₂, F₂M₂ and / three way cross F₂. The mean values of treated populations were compared to F₂ and three way cross F₂ populations.  The mean values of the treated populations were reduced compared to F₂ and three way cross F₂ population for the majority of the characters. The magnitude of the induced variation in the pure breeding variety A-1 was lower than the conventional segregation following hybridization for 100 seed weight, head diameter and number of capitula per plant. The variation from the mutation of heterozygous genotypes was found to be more than that in the untreated F₂ population for important characters such as seed weight, number of seeds and yield per plant and vice versa for number of branches, number of capitula and head diameter. The simultaneous introduction of more than two parents in the population also produced increased variability for number of seeds, seed weight and yield per plant..

 Key words:  Safflower, Hybridization, Irradiation, variability.