Mutagenic Effectiveness of Gamma Rays in Inducing Polygenic Variability in Maize (Zea mays L.)

Abstract

The present investigation was carried out to assess the mutagenic effectiveness in inducing favorable genetic variability for maize population improvement. Gamma rays were used to induce mutation in maize variety Sultan with four irradiation doses (20 Gray, 40 Gray, 60 Gray and 80 Gray). Data were collected for various agronomic traits including p lant height (cm), number of days to silking, number o f days to tasseling, number of grain rows per cob, cob length (cm), number of cobs per plant, diameter of the cob (cm), number of grains per row, number of grains per cob, grain weight per cob (g), 100 grain weight (g) and grain yield per plant (g). The results showed a positive respons e to mutagenic changes at the specific dose; plant height inc reased to 192 cm, cob length increased to 23 cm, grain weight per cob improved to 160 g and 100 grains weight showed 1 g increase at the dose of 20 gray as compared to respective traits at normal conditions. Number of grain rows per cob increased up to 22 rows per cob and number of cobs per plant increased up to 8 at the dose of 40 gray compared to the normal treat ment. Days taken to silking reduced to 57 days from 62 days and days taken to tasse ling showed early development in 53 days at the dose of 60 gray which showed positive mutation. On the other hand, some traits showed negative response owing to mutagenic treatments . Most of the cobs were unfertile, diameter of the cob, number of grains per row and number of grains per cob were reduced as compared to control (untreated). Principal component analysis conducted in the present study , showed a high level of positive associations among cob diameter, cob length, grains per row, grains per cob, gra in weight per cob and grain yield under untreated control conditions. While plant height , days to tasseling and number of cobs per plant showed high mean performance and positive associations under 60 gray treatments. It has been concluded that gamma radia tion induced effective mutations in some of the agronomic traits at specific dose especially 60 gray which could be further utilize d to induce effective mutation s in future maize breeding programs.

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